[CmdletBinding()]
param(
    [Alias("WebUrl")]
    [string]$SourceUrl,

    [string]$OutputPath = (Join-Path -Path (Get-Location).Path -ChildPath "SPMigrationOutput"),

    [switch]$IncludeHiddenLibraries,

    [switch]$IncludeHiddenLists,

    [Alias("TargetWebUrl")]
    [string]$TargetUrl,

    [Alias("MappingCsvPath")]
    [string]$MappingTable,

    [switch]$Export,

    [switch]$Import,

    [switch]$ImportFiles,

    [switch]$ImportLists,

    [Alias("OverwriteFiles")]
    [switch]$Overwrite
)

Set-StrictMode -Version Latest
$ErrorActionPreference = "Stop"
$script:SkippedImportFieldWarnings = @{}

function Initialize-SharePointPowerShell {
    if($null -eq $(Get-Module SharePointServer)) {
        Import-Module SharePointServer
    }else{
        Write-Host "SharePoint Server PowerShell-Modul bereits geladen."
    }

    try {
        [void][System.Reflection.Assembly]::Load("Microsoft.SharePoint.Taxonomy")
    }
    catch {
        try {
            Add-Type -AssemblyName "Microsoft.SharePoint.Taxonomy"
        }
        catch {
        }
    }
}

function Ensure-Directory {
    param(
        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    if (-not [System.IO.Directory]::Exists($Path)) {
        [System.IO.Directory]::CreateDirectory($Path) | Out-Null
    }
}

function Invoke-MigrationImport {
    param(
        [Parameter(Mandatory = $true)]
        [string]$InputPath,

        [Parameter(Mandatory = $true)]
        [string]$TargetWebUrl,

        [Parameter(Mandatory = $true)]
        [string]$MappingTablePath,

        [switch]$ImportFiles,

        [switch]$ImportLists,

        [switch]$Overwrite
    )

    $resolvedInputPath = [System.IO.Path]::GetFullPath($InputPath)
    $filesRootPath = [System.IO.Path]::Combine($resolvedInputPath, "Files")
    $listsRootPath = [System.IO.Path]::Combine($resolvedInputPath, "Lists")
    $resolvedMappingTablePath = [System.IO.Path]::GetFullPath($MappingTablePath)
    $migrationMappingTable = Get-MigrationMappingTable -Path $resolvedMappingTablePath

    $shouldImportFiles = $ImportFiles.IsPresent
    $shouldImportLists = $ImportLists.IsPresent

    if (-not $shouldImportFiles -and -not $shouldImportLists) {
        $shouldImportFiles = $true
        $shouldImportLists = $true
    }

    $targetWeb = $null

    try {
        $targetWeb = Get-SPWeb -Identity $TargetWebUrl -ErrorAction Stop

        if ($shouldImportFiles) {
            Import-SPDocumentLibraries -Web $targetWeb -FilesRootPath $filesRootPath -MigrationMappingTable $migrationMappingTable -Overwrite:$Overwrite
        }

        if ($shouldImportLists) {
            Import-SPLists -Web $targetWeb -ListsRootPath $listsRootPath -MigrationMappingTable $migrationMappingTable
        }

        Write-Host ("Import abgeschlossen. Quelle: {0}" -f $resolvedInputPath)
    }
    finally {
        if ($null -ne $targetWeb) {
            $targetWeb.Dispose()
        }
    }
}

function Get-SafePathSegment {
    param(
        [Parameter(Mandatory = $true)]
        [string]$Name
    )

    $invalidChars = [System.IO.Path]::GetInvalidFileNameChars()
    $safeName = $Name

    foreach ($char in $invalidChars) {
        $safeName = $safeName.Replace($char, "_")
    }

    $safeName = $safeName.Trim()

    if ([string]::IsNullOrWhiteSpace($safeName)) {
        return "_"
    }

    return $safeName
}

function Test-IsCatalogList {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List
    )

    try {
        return [bool]$List.IsCatalog
    }
    catch {
        return $false
    }
}

function Get-SafeCollectionCount {
    param(
        $Value
    )

    if ($null -eq $Value) {
        return 0
    }

    try {
        return [int]$Value.Count
    }
    catch {
    }

    try {
        return [int]$Value.Length
    }
    catch {
    }

    return @($Value).Length
}

function Combine-PathSegments {
    param(
        [Parameter(Mandatory = $true)]
        [string]$BasePath,

        [string[]]$Segments = @()
    )

    $combinedPath = $BasePath

    foreach ($segment in $Segments) {
        if (-not [string]::IsNullOrWhiteSpace($segment)) {
            $combinedPath = [System.IO.Path]::Combine($combinedPath, $segment)
        }
    }

    return $combinedPath
}

function Convert-SPFieldValue {
    param(
        [Parameter(ValueFromPipeline = $true)]
        $Value
    )

    if ($null -eq $Value) {
        return $null
    }

    if ($Value -is [System.DateTime]) {
        return $Value.ToString("o")
    }

    if ($Value -is [Microsoft.SharePoint.SPFieldUserValue]) {
        return @{
            LookupId = $Value.LookupId
            LookupValue = $Value.LookupValue
            Email = $Value.User.Email
            LoginName = $Value.User.LoginName
        }
    }

    if ($Value -is [Microsoft.SharePoint.SPFieldUserValueCollection]) {
        return @($Value | ForEach-Object { Convert-SPFieldValue $_ })
    }

    if ($Value -is [Microsoft.SharePoint.SPFieldLookupValue]) {
        return @{
            LookupId = $Value.LookupId
            LookupValue = $Value.LookupValue
        }
    }

    if ($Value -is [Microsoft.SharePoint.SPFieldLookupValueCollection]) {
        return @($Value | ForEach-Object { Convert-SPFieldValue $_ })
    }

    if ($Value -is [Microsoft.SharePoint.SPFieldUrlValue]) {
        return @{
            Url = $Value.Url
            Description = $Value.Description
        }
    }

    if ($Value -is [System.Guid]) {
        return $Value.ToString()
    }

    if ($Value -is [System.Collections.IEnumerable] -and -not ($Value -is [string])) {
        return @($Value | ForEach-Object { Convert-SPFieldValue $_ })
    }

    $typeName = $Value.GetType().FullName
    if ($typeName -like "*TaxonomyFieldValue") {
        return @{
            Label = $Value.Label
            TermGuid = $Value.TermGuid
            WssId = $Value.WssId
        }
    }

    if ($typeName -like "*TaxonomyFieldValueCollection") {
        return @($Value | ForEach-Object {
                @{
                    Label = $_.Label
                    TermGuid = $_.TermGuid
                    WssId = $_.WssId
                }
            })
    }

    return $Value
}

function Get-FieldTextValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field,

        $RawValue
    )

    try {
        return $Field.GetFieldValueAsText($RawValue)
    }
    catch {
        return $null
    }
}

function Get-ItemFieldTextValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [Parameter(Mandatory = $true)]
        [string]$InternalName
    )

    $field = $null

    try {
        $field = $Item.Fields.GetFieldByInternalName($InternalName)
    }
    catch {
        $field = $null
    }

    if ($null -eq $field) {
        try {
            $field = $Item.Fields.GetFieldByStaticName($InternalName)
        }
        catch {
            $field = $null
        }
    }

    if ($null -eq $field) {
        return $null
    }

    $rawValue = $null

    try {
        $rawValue = $Item[$field.InternalName]
    }
    catch {
        try {
            $rawValue = $Item[$field.Id]
        }
        catch {
            $rawValue = $null
        }
    }

    return Get-FieldTextValue -Field $field -RawValue $rawValue
}

function Get-ListItemFieldMetadata {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item
    )

    $fieldMetadata = @()

    foreach ($field in $Item.Fields) {
        $rawValue = $null

        try {
            $rawValue = $Item[$field.InternalName]
        }
        catch {
            try {
                $rawValue = $Item[$field.Id]
            }
            catch {
                $rawValue = $null
            }
        }

        $fieldMetadata += [PSCustomObject]@{
            InternalName = $field.InternalName
            TypeAsString = $field.TypeAsString
            TextValue = Get-FieldTextValue -Field $field -RawValue $rawValue
            Value = Convert-SPFieldValue $rawValue
        }
    }

    return $fieldMetadata
}

function Get-ListItemFieldValueMap {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [switch]$AsText
    )

    $fieldValues = [ordered]@{}

    foreach ($field in $Item.Fields) {
        $rawValue = $null

        try {
            $rawValue = $Item[$field.InternalName]
        }
        catch {
            try {
                $rawValue = $Item[$field.Id]
            }
            catch {
                $rawValue = $null
            }
        }

        if ($AsText) {
            $fieldValues[$field.InternalName] = Get-FieldTextValue -Field $field -RawValue $rawValue
        }
        else {
            $fieldValues[$field.InternalName] = Convert-SPFieldValue $rawValue
        }
    }

    return [PSCustomObject]$fieldValues
}

function Get-ListItemAttachmentMetadata {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item
    )

    $attachments = @()
    $attachmentCollection = $Item.Attachments

    if ((Get-SafeCollectionCount $attachmentCollection) -eq 0) {
        return $attachments
    }

    foreach ($attachmentName in @($attachmentCollection)) {
        $attachments += [PSCustomObject]@{
            FileName = $attachmentName
            Url = $attachmentCollection.UrlPrefix + $attachmentName
        }
    }

    return $attachments
}

function Get-ListItemMetadataObject {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item
    )

    $attachmentCollection = $Item.Attachments

    return [PSCustomObject]@{
        Id = $Item.ID
        UniqueId = $Item.UniqueId.ToString()
        Title = if ($Item.Fields.ContainsField("Title")) { $Item["Title"] } else { $null }
        ContentTypeId = $Item.ContentTypeId.ToString()
        FileSystemObjectType = $Item.FileSystemObjectType.ToString()
        DisplayName = $Item.DisplayName
        Name = if ($Item.Name) { $Item.Name } else { $null }
        Url = if ($Item.Url) { $Item.Url } else { $null }
        ServerRelativeUrl = if ($Item.Folder) { $Item.Folder.ServerRelativeUrl } else { $null }
        Created = if ($null -ne $Item["Created"]) { ([datetime]$Item["Created"]).ToString("o") } else { $null }
        Modified = if ($null -ne $Item["Modified"]) { ([datetime]$Item["Modified"]).ToString("o") } else { $null }
        CreatedBy = Get-ItemFieldTextValue -Item $Item -InternalName "Author"
        ModifiedBy = Get-ItemFieldTextValue -Item $Item -InternalName "Editor"
        HasAttachments = (Get-SafeCollectionCount $attachmentCollection) -gt 0
        Attachments = Get-ListItemAttachmentMetadata -Item $Item
        FieldValues = Get-ListItemFieldValueMap -Item $Item
        FieldTextValues = Get-ListItemFieldValueMap -Item $Item -AsText
        Fields = Get-ListItemFieldMetadata -Item $Item
    }
}

function Get-FileMetadataObject {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFile]$File
    )

    $item = $File.Item

    return [PSCustomObject]@{
        ExportedAtUtc = [System.DateTime]::UtcNow.ToString("o")
        Web = [PSCustomObject]@{
            Title = $Web.Title
            Url = $Web.Url
            ServerRelativeUrl = $Web.ServerRelativeUrl
            Id = $Web.ID.ToString()
        }
        Library = [PSCustomObject]@{
            Title = $List.Title
            Id = $List.ID.ToString()
            RootFolderUrl = $List.RootFolder.ServerRelativeUrl
            BaseTemplate = [int]$List.BaseTemplate
        }
        File = [PSCustomObject]@{
            Name = $File.Name
            Url = $File.Url
            ServerRelativeUrl = $File.ServerRelativeUrl
            UniqueId = $File.UniqueId.ToString()
            Length = $File.Length
            TimeCreated = $File.TimeCreated.ToString("o")
            TimeLastModified = $File.TimeLastModified.ToString("o")
            CheckOutType = $File.CheckOutType.ToString()
            Level = $File.Level.ToString()
            MajorVersion = $File.MajorVersion
            MinorVersion = $File.MinorVersion
        }
        Item = if ($null -ne $item) {
            Get-ListItemMetadataObject -Item $item
        }
        else {
            $null
        }
    }
}

function Write-MetadataJson {
    param(
        [Parameter(Mandatory = $true)]
        $MetadataObject,

        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    $json = $MetadataObject | ConvertTo-Json -Depth 10
    [System.IO.File]::WriteAllText($Path, $json, [System.Text.Encoding]::UTF8)
}

function Write-ManifestRow {
    param(
        [Parameter(Mandatory = $true)]
        [pscustomobject]$Row,

        [Parameter(Mandatory = $true)]
        [string]$ManifestPath
    )

    $append = [System.IO.File]::Exists($ManifestPath)
    $Row | Export-Csv -Path $ManifestPath -NoTypeInformation -Delimiter ";" -Encoding UTF8 -Append:$append
}

function New-ManifestRow {
    param(
        [string]$RecordType = "",
        [string]$ObjectType = "",
        [string]$SourceWebUrl = "",
        [string]$SourceTitle = "",
        [string]$TargetTitle = "",
        [string]$BaseType = "",
        [string]$BaseTemplate = "",
        [string]$RootFolderUrl = "",
        [string]$SourceServerRelativeUrl = "",
        [string]$FileName = "",
        [string]$FileUniqueId = "",
        [string]$FileLength = "",
        [string]$LocalFilePath = "",
        [string]$LocalMetadataPath = "",
        [string]$ExportedAtUtc = ""
    )

    return [PSCustomObject]@{
        RecordType = $RecordType
        ObjectType = $ObjectType
        SourceWebUrl = $SourceWebUrl
        SourceTitle = $SourceTitle
        TargetTitle = $TargetTitle
        BaseType = $BaseType
        BaseTemplate = $BaseTemplate
        RootFolderUrl = $RootFolderUrl
        SourceServerRelativeUrl = $SourceServerRelativeUrl
        FileName = $FileName
        FileUniqueId = $FileUniqueId
        FileLength = $FileLength
        LocalFilePath = $LocalFilePath
        LocalMetadataPath = $LocalMetadataPath
        ExportedAtUtc = $ExportedAtUtc
    }
}

function Write-ContainerManifestRow {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [string]$ManifestPath
    )

    $objectType = if ($List.BaseType -eq [Microsoft.SharePoint.SPBaseType]::DocumentLibrary) { "DocumentLibrary" } else { "List" }

    $manifestRow = New-ManifestRow `
        -RecordType "Container" `
        -ObjectType $objectType `
        -SourceWebUrl $Web.Url `
        -SourceTitle $List.Title `
        -TargetTitle "" `
        -BaseType $List.BaseType.ToString() `
        -BaseTemplate ([string][int]$List.BaseTemplate) `
        -RootFolderUrl $List.RootFolder.ServerRelativeUrl `
        -SourceServerRelativeUrl $List.RootFolder.ServerRelativeUrl `
        -ExportedAtUtc ([System.DateTime]::UtcNow.ToString("o"))

    Write-ManifestRow -Row $manifestRow -ManifestPath $ManifestPath
}

function Get-RelativeFilePathSegments {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFile]$File
    )

    $rootUrl = $List.RootFolder.ServerRelativeUrl.TrimEnd("/")
    $fileUrl = $File.ServerRelativeUrl
    $relativeUrl = $fileUrl.Substring($rootUrl.Length).TrimStart("/")

    return @($relativeUrl.Split("/") | ForEach-Object { Get-SafePathSegment $_ })
}

function Get-SPListItemsRecursive {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List
    )

    $query = New-Object Microsoft.SharePoint.SPQuery
    $query.Query = ""
    $query.Folder = $List.RootFolder
    $query.ViewAttributes = "Scope='RecursiveAll'"
    $query.RowLimit = 0
    $query.ViewFieldsOnly = $false

    return @($List.GetItems($query))
}

function Export-SPFile {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFile]$File,

        [Parameter(Mandatory = $true)]
        [string]$FilesRootPath,

        [Parameter(Mandatory = $true)]
        [string]$ManifestPath
    )

    $relativeSegments = @(Get-RelativeFilePathSegments -List $List -File $File)
    $relativeDirectorySegments = @()

    if ($relativeSegments.Length -gt 1) {
        $relativeDirectorySegments = $relativeSegments[0..($relativeSegments.Length - 2)]
    }

    $safeLibraryName = Get-SafePathSegment $List.Title
    $fileDirectory = Combine-PathSegments -BasePath ([System.IO.Path]::Combine($FilesRootPath, $safeLibraryName)) -Segments $relativeDirectorySegments

    Ensure-Directory -Path $fileDirectory

    if ($relativeSegments.Length -eq 0) {
        throw ("Konnte keinen relativen Dateipfad fuer '{0}' ermitteln." -f $File.ServerRelativeUrl)
    }

    $fileName = $relativeSegments[-1]
    $localFilePath = [System.IO.Path]::Combine($fileDirectory, $fileName)
    $metadataPath = [System.IO.Path]::Combine($fileDirectory, "$fileName.properties.json")

    [System.IO.File]::WriteAllBytes($localFilePath, $File.OpenBinary())

    $metadata = Get-FileMetadataObject -Web $Web -List $List -File $File
    Write-MetadataJson -MetadataObject $metadata -Path $metadataPath

    $manifestRow = New-ManifestRow `
        -RecordType "File" `
        -ObjectType "DocumentLibrary" `
        -SourceWebUrl $Web.Url `
        -SourceTitle $List.Title `
        -TargetTitle "" `
        -BaseType $List.BaseType.ToString() `
        -BaseTemplate ([string][int]$List.BaseTemplate) `
        -RootFolderUrl $List.RootFolder.ServerRelativeUrl `
        -SourceServerRelativeUrl $File.ServerRelativeUrl `
        -FileName $File.Name `
        -FileUniqueId $File.UniqueId.ToString() `
        -FileLength ([string]$File.Length) `
        -LocalFilePath $localFilePath `
        -LocalMetadataPath $metadataPath `
        -ExportedAtUtc ([System.DateTime]::UtcNow.ToString("o"))

    Write-ManifestRow -Row $manifestRow -ManifestPath $ManifestPath
}

function Export-SPFolder {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFolder]$Folder,

        [Parameter(Mandatory = $true)]
        [string]$FilesRootPath,

        [Parameter(Mandatory = $true)]
        [string]$ManifestPath,

        [ref]$FileCount
    )

    foreach ($file in $Folder.Files) {
        Export-SPFile -Web $Web -List $List -File $file -FilesRootPath $FilesRootPath -ManifestPath $ManifestPath
        $FileCount.Value++
    }

    foreach ($subFolder in $Folder.SubFolders) {
        if ($subFolder.Name -eq "Forms") {
            continue
        }

        Export-SPFolder -Web $Web -List $List -Folder $subFolder -FilesRootPath $FilesRootPath -ManifestPath $ManifestPath -FileCount $FileCount
    }
}

function Export-SPDocumentLibrary {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [string]$FilesRootPath,

        [Parameter(Mandatory = $true)]
        [string]$ManifestPath
    )

    Write-Host ("Exportiere Bibliothek: {0}" -f $List.Title)
    Write-ContainerManifestRow -Web $Web -List $List -ManifestPath $ManifestPath
    $fileCount = 0

    Export-SPFolder -Web $Web -List $List -Folder $List.RootFolder -FilesRootPath $FilesRootPath -ManifestPath $ManifestPath -FileCount ([ref]$fileCount)

    Write-Host ("  Dateien exportiert: {0}" -f $fileCount)
}

function Export-SPList {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [Parameter(Mandatory = $true)]
        [string]$ListsRootPath,

        [Parameter(Mandatory = $true)]
        [string]$ManifestPath
    )

    Write-Host ("Exportiere Liste: {0}" -f $List.Title)
    Write-ContainerManifestRow -Web $Web -List $List -ManifestPath $ManifestPath

    $safeListName = Get-SafePathSegment $List.Title
    $listPath = [System.IO.Path]::Combine($ListsRootPath, "$safeListName.json")
    $items = @()

    foreach ($item in @(Get-SPListItemsRecursive -List $List)) {
        $items += Get-ListItemMetadataObject -Item $item
    }

    $listExport = [PSCustomObject]@{
        ExportedAtUtc = [System.DateTime]::UtcNow.ToString("o")
        Web = [PSCustomObject]@{
            Title = $Web.Title
            Url = $Web.Url
            ServerRelativeUrl = $Web.ServerRelativeUrl
            Id = $Web.ID.ToString()
        }
        List = [PSCustomObject]@{
            Title = $List.Title
            Id = $List.ID.ToString()
            BaseType = $List.BaseType.ToString()
            BaseTemplate = [int]$List.BaseTemplate
            DefaultViewUrl = $List.DefaultViewUrl
            RootFolderUrl = $List.RootFolder.ServerRelativeUrl
            ItemCount = $List.ItemCount
            Hidden = $List.Hidden
        }
        Items = $items
    }

    Write-MetadataJson -MetadataObject $listExport -Path $listPath

    Write-Host ("  Listeneintraege exportiert: {0}" -f $items.Length)
}

function Get-ObjectPropertyValue {
    param(
        $Object,

        [Parameter(Mandatory = $true)]
        [string]$PropertyName,

        $DefaultValue = $null
    )

    if ($null -eq $Object) {
        return $DefaultValue
    }

    $property = $Object.PSObject.Properties[$PropertyName]
    if ($null -eq $property) {
        return $DefaultValue
    }

    return $property.Value
}

function Read-ManifestRows {
    param(
        [Parameter(Mandatory = $true)]
        [string]$ManifestPath
    )

    if (-not [System.IO.File]::Exists($ManifestPath)) {
        return @()
    }

    return @(Import-Csv -Path $ManifestPath -Delimiter ";")
}

function New-MigrationContainerMappingEntry {
    param(
        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List
    )

    return [PSCustomObject]@{
        ObjectType = $ObjectType
        SourceTitle = $List.Title
        TargetTitle = $List.Title
        BaseType = $List.BaseType.ToString()
        BaseTemplate = [int]$List.BaseTemplate
        RootFolderUrl = $List.RootFolder.ServerRelativeUrl
        Hidden = [bool]$List.Hidden
    }
}

function Test-SPFieldSupportedForImport {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field
    )

    $unsupportedInternalNames = @(
        "AccessPolicy",
        "AppAuthor",
        "AppEditor",
        "Attachments",
        "BannerUrl",
        "BaseName",
        "Author",
        "ComplianceAssetId",
        "ContentType",
        "ContentTypeId",
        "ContentVersion",
        "Created",
        "Created_x0020_Date",
        "DocIcon",
        "Duration",
        "Edit",
        "Editor",
        "EncodedAbsUrl",
        "EventCanceled",
        "EventType",
        "FileDirRef",
        "File_x0020_Type",
        "FileLeafRef",
        "FileRef",
        "FolderChildCount",
        "FreeBusy",
        "FSObjType",
        "Geolocation",
        "GUID",
        "HTML_x0020_File_x0020_Type",
        "ID",
        "InstanceID",
        "ItemChildCount",
        "Last_x0020_Modified",
        "LinkFilename",
        "LinkFilename2",
        "LinkFilenameNoMenu",
        "LinkTitle",
        "LinkTitle2",
        "LinkTitleNoMenu",
        "MasterSeriesItemID",
        "MetaInfo",
        "Modified",
        "NoExecute",
        "Order",
        "OriginatorId",
        "Overbook",
        "owshiddenversion",
        "Participants",
        "PermMask",
        "ProgId",
        "RecurrenceData",
        "RecurrenceID",
        "Restricted",
        "ScopeId",
        "SelectTitle",
        "ServerUrl",
        "SMLastModifiedDate",
        "SMTotalFileCount",
        "SMTotalFileStreamSize",
        "SMTotalSize",
        "SortBehavior",
        "SyncClientId",
        "TimeZone",
        "UID",
        "UniqueId",
        "webPartRteVersion",
        "WorkflowInstanceID",
        "WorkflowVersion",
        "Workspace",
        "WorkspaceLink",
        "XMLTZone",
        "_Level",
        "_ModerationStatus",
        "_UIVersion",
        "_UIVersionString"
    )

    $unsupportedFieldTypes = @(
        "Attachments",
        "Computed"
    )

    if ($Field.ReadOnlyField) {
        return $false
    }

    if ([string]$Field.InternalName -like "_*") {
        return $false
    }

    if ($unsupportedFieldTypes -contains [string]$Field.TypeAsString) {
        return $false
    }

    return -not ($unsupportedInternalNames -contains [string]$Field.InternalName)
}

function Resolve-SPFieldById {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFieldCollection]$Fields,

        [Parameter(Mandatory = $true)]
        [Guid]$FieldId
    )

    try {
        return $Fields[$FieldId]
    }
    catch {
    }

    foreach ($candidateField in $Fields) {
        if ($candidateField.Id -eq $FieldId) {
            return $candidateField
        }
    }

    return $null
}

function Get-SPFieldSupportingInternalNames {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFieldCollection]$Fields
    )

    $supportingInternalNames = @()

    $typeName = [string]$Field.GetType().FullName
    if ($typeName -like "*TaxonomyField*") {
        try {
            $textFieldId = [Guid]$Field.TextField
            if ($textFieldId -ne [Guid]::Empty) {
                $supportingField = Resolve-SPFieldById -Fields $Fields -FieldId $textFieldId
                if ($null -ne $supportingField -and -not [string]::IsNullOrWhiteSpace([string]$supportingField.InternalName)) {
                    $supportingInternalNames += [string]$supportingField.InternalName
                }
            }
        }
        catch {
        }
    }

    $internalNamePrefix = "{0}_" -f $Field.InternalName
    foreach ($candidateField in $Fields) {
        if ($candidateField.Id -eq $Field.Id) {
            continue
        }

        if (-not [bool]$candidateField.Hidden) {
            continue
        }

        if ([string]$candidateField.InternalName -like ($internalNamePrefix + "*")) {
            $supportingInternalNames += [string]$candidateField.InternalName
        }
    }

    return @($supportingInternalNames | Sort-Object -Unique)
}

function Test-SPFieldShownInMappingTable {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field,

        [hashtable]$SupportingFieldLookup = @{}
    )

    $fieldKey = ([string]$Field.InternalName).ToLowerInvariant()
    if ($SupportingFieldLookup.ContainsKey($fieldKey)) {
        return $false
    }

    return $true
}

function Test-SPFieldIsSystemColumn {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field
    )

    try {
        if ([bool]$Field.FromBaseType) {
            return $true
        }
    }
    catch {
    }

    try {
        if (-not [bool]$Field.CanBeDeleted) {
            return $true
        }
    }
    catch {
    }

    if ([bool]$Field.Hidden) {
        return $true
    }

    if ([string]$Field.InternalName -like "_*") {
        return $true
    }

    if (-not (Test-SPFieldSupportedForImport -Field $Field)) {
        return $true
    }

    return $false
}

function Write-SkippedImportFieldWarning {
    param(
        [Parameter(Mandatory = $true)]
        [string]$FieldInternalName,

        [Parameter(Mandatory = $true)]
        [string]$Message
    )

    $warningKey = $FieldInternalName.ToLowerInvariant()
    if ($script:SkippedImportFieldWarnings.ContainsKey($warningKey)) {
        return
    }

    $script:SkippedImportFieldWarnings[$warningKey] = $true
    Write-Warning $Message
}

function New-MigrationFieldMappingEntries {
    param(
        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List
    )

    $rows = @()
    $supportingFieldLookup = @{}

    foreach ($field in @($List.Fields)) {
        foreach ($supportingInternalName in @(Get-SPFieldSupportingInternalNames -Field $field -Fields $List.Fields)) {
            if (-not [string]::IsNullOrWhiteSpace([string]$supportingInternalName)) {
                $supportingFieldLookup[[string]$supportingInternalName.ToLowerInvariant()] = $true
            }
        }
    }

    foreach ($field in @($List.Fields | Sort-Object -Property InternalName)) {
        if (-not (Test-SPFieldShownInMappingTable -Field $field -SupportingFieldLookup $supportingFieldLookup)) {
            continue
        }

        $rows += [PSCustomObject]@{
            ObjectType = $ObjectType
            ContainerSourceTitle = $List.Title
            SourceInternalName = $field.InternalName
            SourceCanonicalInternalName = $field.InternalName
            SourceSupportingInternalNames = @(Get-SPFieldSupportingInternalNames -Field $field -Fields $List.Fields)
            TargetInternalName = $field.InternalName
            DisplayName = $field.Title
            TypeAsString = $field.TypeAsString
            Hidden = [bool]$field.Hidden
            ReadOnly = [bool]$field.ReadOnlyField
            Sealed = [bool]$field.Sealed
            IsSystemColumn = (Test-SPFieldIsSystemColumn -Field $field)
            ImportSupported = (Test-SPFieldSupportedForImport -Field $field)
        }
    }

    return $rows
}

function New-MigrationMappingTable {
    param(
        [Parameter(Mandatory = $true)]
        [string]$SourceWebUrl,

        [Microsoft.SharePoint.SPList[]]$DocumentLibraries = @(),

        [Microsoft.SharePoint.SPList[]]$Lists = @()
    )

    $libraryMappings = @()
    $listMappings = @()
    $systemColumnMappings = @()
    $customColumnMappings = @()

    foreach ($library in @($DocumentLibraries)) {
        $libraryMappings += New-MigrationContainerMappingEntry -ObjectType "DocumentLibrary" -List $library
        $fieldMappings = @(New-MigrationFieldMappingEntries -ObjectType "DocumentLibrary" -List $library)
        $systemColumnMappings += @($fieldMappings | Where-Object { [bool](Get-ObjectPropertyValue -Object $_ -PropertyName "IsSystemColumn" -DefaultValue $false) })
        $customColumnMappings += @($fieldMappings | Where-Object { -not [bool](Get-ObjectPropertyValue -Object $_ -PropertyName "IsSystemColumn" -DefaultValue $false) })
    }

    foreach ($list in @($Lists)) {
        $listMappings += New-MigrationContainerMappingEntry -ObjectType "List" -List $list
        $fieldMappings = @(New-MigrationFieldMappingEntries -ObjectType "List" -List $list)
        $systemColumnMappings += @($fieldMappings | Where-Object { [bool](Get-ObjectPropertyValue -Object $_ -PropertyName "IsSystemColumn" -DefaultValue $false) })
        $customColumnMappings += @($fieldMappings | Where-Object { -not [bool](Get-ObjectPropertyValue -Object $_ -PropertyName "IsSystemColumn" -DefaultValue $false) })
    }

    return [PSCustomObject]@{
        SchemaVersion = 1
        GeneratedAtUtc = [System.DateTime]::UtcNow.ToString("o")
        SourceWebUrl = $SourceWebUrl
        LibraryMappings = $libraryMappings
        ListMappings = $listMappings
        MetadataColumnMappings = [PSCustomObject]@{
            SystemColumns = $systemColumnMappings
            CustomColumns = $customColumnMappings
        }
    }
}

function Write-MigrationMappingTable {
    param(
        [Parameter(Mandatory = $true)]
        $MappingTable,

        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    $json = $MappingTable | ConvertTo-Json -Depth 10
    [System.IO.File]::WriteAllText($Path, $json, [System.Text.Encoding]::UTF8)
}

function Get-ContainerManifestEntryKey {
    param(
        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    return ("{0}|{1}" -f $ObjectType.Trim(), $SourceTitle.Trim()).ToLowerInvariant()
}

function Get-ContainerManifestMap {
    param(
        [Parameter(Mandatory = $true)]
        [object[]]$ManifestRows
    )

    $containerMap = @{}

    foreach ($row in $ManifestRows) {
        $recordType = [string](Get-ObjectPropertyValue -Object $row -PropertyName "RecordType")
        $sourceTitle = [string](Get-ObjectPropertyValue -Object $row -PropertyName "SourceTitle")
        $objectType = [string](Get-ObjectPropertyValue -Object $row -PropertyName "ObjectType")

        if ($recordType -ne "Container" -or [string]::IsNullOrWhiteSpace($sourceTitle) -or [string]::IsNullOrWhiteSpace($objectType)) {
            continue
        }

        $key = Get-ContainerManifestEntryKey -ObjectType $objectType -SourceTitle $sourceTitle
        $containerMap[$key] = $row
    }

    return $containerMap
}

function Get-TargetContainerTitle {
    param(
        [Parameter(Mandatory = $true)]
        [hashtable]$ContainerManifestMap,

        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    $key = Get-ContainerManifestEntryKey -ObjectType $ObjectType -SourceTitle $SourceTitle
    $manifestEntry = $ContainerManifestMap[$key]

    if ($null -eq $manifestEntry) {
        return $SourceTitle
    }

    $targetTitle = [string](Get-ObjectPropertyValue -Object $manifestEntry -PropertyName "TargetTitle")
    if ([string]::IsNullOrWhiteSpace($targetTitle)) {
        return $SourceTitle
    }

    return $targetTitle.Trim()
}

function Test-ContainerHasExplicitTargetMapping {
    param(
        [Parameter(Mandatory = $true)]
        [hashtable]$ContainerManifestMap,

        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    $key = Get-ContainerManifestEntryKey -ObjectType $ObjectType -SourceTitle $SourceTitle
    $manifestEntry = $ContainerManifestMap[$key]

    if ($null -eq $manifestEntry) {
        return $false
    }

    $targetTitle = [string](Get-ObjectPropertyValue -Object $manifestEntry -PropertyName "TargetTitle")
    return -not [string]::IsNullOrWhiteSpace($targetTitle)
}

function Test-ObjectHasProperty {
    param(
        $Object,

        [Parameter(Mandatory = $true)]
        [string]$PropertyName
    )

    if ($null -eq $Object) {
        return $false
    }

    return $null -ne $Object.PSObject.Properties[$PropertyName]
}

function Read-JsonFile {
    param(
        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    return Get-Content -Path $Path -Raw -Encoding UTF8 | ConvertFrom-Json
}

function Get-MigrationMappingTable {
    param(
        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    if (-not [System.IO.File]::Exists($Path)) {
        throw ("MappingTable nicht gefunden: {0}" -f $Path)
    }

    $extension = [System.IO.Path]::GetExtension($Path)
    if ($extension -ieq ".json") {
        $mappingTable = Read-JsonFile -Path $Path
    }
    elseif ($extension -ieq ".csv") {
        $fieldMapping = Get-FieldMapping -Path $Path
        $metadataColumnMappings = @()

        foreach ($sourceInternalName in $fieldMapping.Keys) {
            $metadataColumnMappings += [PSCustomObject]@{
                ObjectType = "*"
                ContainerSourceTitle = "*"
                SourceInternalName = [string]$sourceInternalName
                SourceCanonicalInternalName = [string]$sourceInternalName
                SourceSupportingInternalNames = @()
                TargetInternalName = [string]$fieldMapping[$sourceInternalName]
                DisplayName = ""
                TypeAsString = ""
                Hidden = $false
                ReadOnly = $false
                Sealed = $false
                IsSystemColumn = $false
                ImportSupported = $true
            }
        }

        $mappingTable = [PSCustomObject]@{
            SchemaVersion = 1
            GeneratedAtUtc = [System.DateTime]::UtcNow.ToString("o")
            SourceWebUrl = ""
            LibraryMappings = @()
            ListMappings = @()
            MetadataColumnMappings = [PSCustomObject]@{
                SystemColumns = @()
                CustomColumns = $metadataColumnMappings
            }
        }
    }
    else {
        throw "MappingTable muss eine JSON- oder CSV-Datei sein."
    }

    if ($null -eq $mappingTable) {
        throw "MappingTable konnte nicht gelesen werden."
    }

    return $mappingTable
}

function Get-ContainerMappingTableEntryKey {
    param(
        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    return ("{0}|{1}" -f $ObjectType.Trim(), $SourceTitle.Trim()).ToLowerInvariant()
}

function Get-MetadataColumnMappingRows {
    param(
        [Parameter(Mandatory = $true)]
        $MigrationMappingTable
    )

    $metadataColumnMappings = Get-ObjectPropertyValue -Object $MigrationMappingTable -PropertyName "MetadataColumnMappings" -DefaultValue @()
    if ($null -eq $metadataColumnMappings) {
        return @()
    }

    if ($null -ne $metadataColumnMappings.PSObject.Properties["SystemColumns"] -or $null -ne $metadataColumnMappings.PSObject.Properties["CustomColumns"]) {
        return @(
            @(Get-ObjectPropertyValue -Object $metadataColumnMappings -PropertyName "SystemColumns" -DefaultValue @()) +
            @(Get-ObjectPropertyValue -Object $metadataColumnMappings -PropertyName "CustomColumns" -DefaultValue @())
        )
    }

    return @($metadataColumnMappings)
}

function Test-MetadataColumnMappingRowImportSupported {
    param(
        [Parameter(Mandatory = $true)]
        $Row
    )

    if (Test-ObjectHasProperty -Object $Row -PropertyName "ImportSupported") {
        return [bool](Get-ObjectPropertyValue -Object $Row -PropertyName "ImportSupported" -DefaultValue $false)
    }

    $sourceInternalName = [string](Get-ObjectPropertyValue -Object $Row -PropertyName "SourceInternalName")
    $typeAsString = [string](Get-ObjectPropertyValue -Object $Row -PropertyName "TypeAsString")
    $readOnly = [bool](Get-ObjectPropertyValue -Object $Row -PropertyName "ReadOnly" -DefaultValue $false)

    $unsupportedInternalNames = @(
        "AccessPolicy",
        "AppAuthor",
        "AppEditor",
        "Attachments",
        "BannerUrl",
        "BaseName",
        "Author",
        "ComplianceAssetId",
        "ContentType",
        "ContentTypeId",
        "ContentVersion",
        "Created",
        "Created_x0020_Date",
        "DocIcon",
        "Duration",
        "Edit",
        "Editor",
        "EncodedAbsUrl",
        "EventCanceled",
        "EventType",
        "FileDirRef",
        "File_x0020_Type",
        "FileLeafRef",
        "FileRef",
        "FolderChildCount",
        "FreeBusy",
        "FSObjType",
        "Geolocation",
        "GUID",
        "HTML_x0020_File_x0020_Type",
        "ID",
        "InstanceID",
        "ItemChildCount",
        "Last_x0020_Modified",
        "LinkFilename",
        "LinkFilename2",
        "LinkFilenameNoMenu",
        "LinkTitle",
        "LinkTitle2",
        "LinkTitleNoMenu",
        "MasterSeriesItemID",
        "MetaInfo",
        "Modified",
        "NoExecute",
        "Order",
        "OriginatorId",
        "Overbook",
        "owshiddenversion",
        "Participants",
        "PermMask",
        "ProgId",
        "RecurrenceData",
        "RecurrenceID",
        "Restricted",
        "ScopeId",
        "SelectTitle",
        "ServerUrl",
        "SMLastModifiedDate",
        "SMTotalFileCount",
        "SMTotalFileStreamSize",
        "SMTotalSize",
        "SortBehavior",
        "SyncClientId",
        "TimeZone",
        "UID",
        "UniqueId",
        "webPartRteVersion",
        "WorkflowInstanceID",
        "WorkflowVersion",
        "Workspace",
        "WorkspaceLink",
        "XMLTZone",
        "_Level",
        "_ModerationStatus",
        "_UIVersion",
        "_UIVersionString"
    )

    if ($readOnly) {
        return $false
    }

    if ([string]::IsNullOrWhiteSpace($sourceInternalName)) {
        return $false
    }

    if ([string]$sourceInternalName -like "_*") {
        return $false
    }

    if ($typeAsString -in @("Attachments", "Computed")) {
        return $false
    }

    return -not ($unsupportedInternalNames -contains $sourceInternalName)
}

function Get-ContainerMappingMap {
    param(
        [Parameter(Mandatory = $true)]
        $MigrationMappingTable
    )

    $containerMap = @{}
    $rows = @(
        @(Get-ObjectPropertyValue -Object $MigrationMappingTable -PropertyName "LibraryMappings" -DefaultValue @()) +
        @(Get-ObjectPropertyValue -Object $MigrationMappingTable -PropertyName "ListMappings" -DefaultValue @())
    )

    foreach ($row in $rows) {
        $objectType = [string](Get-ObjectPropertyValue -Object $row -PropertyName "ObjectType")
        $sourceTitle = [string](Get-ObjectPropertyValue -Object $row -PropertyName "SourceTitle")

        if ([string]::IsNullOrWhiteSpace($objectType) -or [string]::IsNullOrWhiteSpace($sourceTitle)) {
            continue
        }

        $key = Get-ContainerMappingTableEntryKey -ObjectType $objectType -SourceTitle $sourceTitle
        $containerMap[$key] = $row
    }

    return $containerMap
}

function Get-TargetContainerTitleFromMappingTable {
    param(
        [Parameter(Mandatory = $true)]
        [hashtable]$ContainerMappingMap,

        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    $key = Get-ContainerMappingTableEntryKey -ObjectType $ObjectType -SourceTitle $SourceTitle
    $entry = $ContainerMappingMap[$key]

    if ($null -eq $entry) {
        return $SourceTitle
    }

    $targetTitle = [string](Get-ObjectPropertyValue -Object $entry -PropertyName "TargetTitle")
    if ([string]::IsNullOrWhiteSpace($targetTitle)) {
        return $SourceTitle
    }

    return $targetTitle.Trim()
}

function Test-ContainerHasExplicitTargetMappingInTable {
    param(
        [Parameter(Mandatory = $true)]
        [hashtable]$ContainerMappingMap,

        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    $key = Get-ContainerMappingTableEntryKey -ObjectType $ObjectType -SourceTitle $SourceTitle
    $entry = $ContainerMappingMap[$key]

    if ($null -eq $entry) {
        return $false
    }

    $targetTitle = [string](Get-ObjectPropertyValue -Object $entry -PropertyName "TargetTitle")
    return -not [string]::IsNullOrWhiteSpace($targetTitle)
}

function Get-FieldMappingForContainer {
    param(
        [Parameter(Mandatory = $true)]
        $MigrationMappingTable,

        [Parameter(Mandatory = $true)]
        [string]$ObjectType,

        [Parameter(Mandatory = $true)]
        [string]$SourceTitle
    )

    $rows = @(Get-MetadataColumnMappingRows -MigrationMappingTable $MigrationMappingTable)
    $mapping = [ordered]@{}
    $mappingPriority = @{}

    foreach ($row in $rows) {
        $rowObjectType = [string](Get-ObjectPropertyValue -Object $row -PropertyName "ObjectType")
        $rowContainerSourceTitle = [string](Get-ObjectPropertyValue -Object $row -PropertyName "ContainerSourceTitle")
        $sourceInternalName = [string](Get-ObjectPropertyValue -Object $row -PropertyName "SourceInternalName")
        $sourceCanonicalInternalName = [string](Get-ObjectPropertyValue -Object $row -PropertyName "SourceCanonicalInternalName")
        $targetInternalName = [string](Get-ObjectPropertyValue -Object $row -PropertyName "TargetInternalName")
        $isHiddenRow = [bool](Get-ObjectPropertyValue -Object $row -PropertyName "Hidden" -DefaultValue $false)

        if ([string]::IsNullOrWhiteSpace($sourceInternalName) -or [string]::IsNullOrWhiteSpace($targetInternalName)) {
            continue
        }

        $objectTypeMatches = ($rowObjectType -eq "*") -or ($rowObjectType -eq $ObjectType)
        $containerMatches = [string]::IsNullOrWhiteSpace($rowContainerSourceTitle) -or ($rowContainerSourceTitle -eq "*") -or ($rowContainerSourceTitle -eq $SourceTitle)

        if (-not $objectTypeMatches -or -not $containerMatches) {
            continue
        }

        if (-not (Test-MetadataColumnMappingRowImportSupported -Row $row)) {
            continue
        }

        $normalizedSourceInternalName = $sourceCanonicalInternalName
        if ([string]::IsNullOrWhiteSpace($normalizedSourceInternalName)) {
            $normalizedSourceInternalName = $sourceInternalName
        }

        if ($isHiddenRow -and $sourceInternalName -match "^(.*)_\d+$") {
            $normalizedSourceInternalName = $matches[1]
        }

        if ([string]::IsNullOrWhiteSpace($normalizedSourceInternalName)) {
            continue
        }

        $priority = if ($isHiddenRow) { 1 } else { 2 }
        $normalizedSourceInternalName = $normalizedSourceInternalName.Trim()

        if ($mappingPriority.ContainsKey($normalizedSourceInternalName) -and $mappingPriority[$normalizedSourceInternalName] -gt $priority) {
            continue
        }

        $mapping[$normalizedSourceInternalName] = $targetInternalName.Trim()
        $mappingPriority[$normalizedSourceInternalName] = $priority
    }

    return $mapping
}

function Resolve-SPField {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFieldCollection]$Fields,

        [Parameter(Mandatory = $true)]
        [string]$InternalName
    )

    try {
        return $Fields.GetFieldByInternalName($InternalName)
    }
    catch {
    }

    try {
        return $Fields.GetFieldByStaticName($InternalName)
    }
    catch {
    }

    foreach ($field in $Fields) {
        if ($field.InternalName -eq $InternalName -or $field.StaticName -eq $InternalName) {
            return $field
        }
    }

    return $null
}

function Get-FieldMapping {
    param(
        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    $rows = Import-Csv -Path $Path -Delimiter ";"
    $mapping = [ordered]@{}

    foreach ($row in $rows) {
        $sourceInternalName = [string](Get-ObjectPropertyValue -Object $row -PropertyName "SourceInternalName")
        $targetInternalName = [string](Get-ObjectPropertyValue -Object $row -PropertyName "TargetInternalName")

        if ([string]::IsNullOrWhiteSpace($sourceInternalName) -or [string]::IsNullOrWhiteSpace($targetInternalName)) {
            continue
        }

        $mapping[$sourceInternalName.Trim()] = $targetInternalName.Trim()
    }

    return $mapping
}

function Convert-ToBoolean {
    param(
        $RawValue,
        $TextValue
    )

    if ($RawValue -is [bool]) {
        return $RawValue
    }

    $candidate = $RawValue
    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        $candidate = $TextValue
    }

    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        return $null
    }

    return [System.Convert]::ToBoolean($candidate)
}

function Convert-ToInt32 {
    param(
        $RawValue,
        $TextValue
    )

    $candidate = $RawValue
    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        $candidate = $TextValue
    }

    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        return $null
    }

    return [int]$candidate
}

function Convert-ToDouble {
    param(
        $RawValue,
        $TextValue
    )

    $candidate = $RawValue
    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        $candidate = $TextValue
    }

    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        return $null
    }

    return [double]::Parse(
        [string]$candidate,
        [System.Globalization.NumberStyles]::Any,
        [System.Globalization.CultureInfo]::InvariantCulture
    )
}

function Convert-ToDateTimeValue {
    param(
        $RawValue,
        $TextValue
    )

    $candidate = $RawValue
    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        $candidate = $TextValue
    }

    if ($null -eq $candidate -or [string]::IsNullOrWhiteSpace([string]$candidate)) {
        return $null
    }

    return [datetime]::Parse(
        [string]$candidate,
        [System.Globalization.CultureInfo]::InvariantCulture,
        [System.Globalization.DateTimeStyles]::RoundtripKind
    )
}

function Resolve-SPUser {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        $RawUserValue,

        [string]$TextValue
    )

    $candidates = @()

    if ($null -ne $RawUserValue) {
        $loginName = Get-ObjectPropertyValue -Object $RawUserValue -PropertyName "LoginName"
        $email = Get-ObjectPropertyValue -Object $RawUserValue -PropertyName "Email"
        $lookupValue = Get-ObjectPropertyValue -Object $RawUserValue -PropertyName "LookupValue"

        if (-not [string]::IsNullOrWhiteSpace([string]$loginName)) {
            $candidates += [string]$loginName
        }

        if (-not [string]::IsNullOrWhiteSpace([string]$email)) {
            $candidates += [string]$email
        }

        if (-not [string]::IsNullOrWhiteSpace([string]$lookupValue)) {
            $candidates += [string]$lookupValue
        }
    }

    if (-not [string]::IsNullOrWhiteSpace([string]$TextValue)) {
        $candidates += [string]$TextValue
    }

    foreach ($candidate in $candidates | Select-Object -Unique) {
        try {
            return $Web.EnsureUser($candidate)
        }
        catch {
        }
    }

    return $null
}

function Convert-ToUserFieldValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        $RawValue,

        [string]$TextValue
    )

    $user = Resolve-SPUser -Web $Item.Web -RawUserValue $RawValue -TextValue $TextValue
    if ($null -eq $user) {
        return $null
    }

    return New-Object Microsoft.SharePoint.SPFieldUserValue($Item.Web, $user.ID, $user.LoginName)
}

function Convert-ToUserMultiFieldValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        $RawValue,

        [string]$TextValue
    )

    $collection = New-Object Microsoft.SharePoint.SPFieldUserValueCollection
    $rawUsers = @($RawValue)

    if (($rawUsers.Length -eq 1) -and $null -eq $rawUsers[0] -and -not [string]::IsNullOrWhiteSpace($TextValue)) {
        $rawUsers = @($TextValue.Split(";", [System.StringSplitOptions]::RemoveEmptyEntries))
    }

    foreach ($rawUser in $rawUsers) {
        $userValue = Convert-ToUserFieldValue -Item $Item -RawValue $rawUser -TextValue ([string]$rawUser)
        if ($null -ne $userValue) {
            [void]$collection.Add($userValue)
        }
    }

    return $collection
}

function Convert-ToUrlFieldValue {
    param(
        $RawValue,

        [string]$TextValue
    )

    $url = Get-ObjectPropertyValue -Object $RawValue -PropertyName "Url"
    $description = Get-ObjectPropertyValue -Object $RawValue -PropertyName "Description"

    if (-not [string]::IsNullOrWhiteSpace([string]$url)) {
        $fieldValue = New-Object Microsoft.SharePoint.SPFieldUrlValue
        $fieldValue.Url = [string]$url
        $fieldValue.Description = [string]$description
        return $fieldValue
    }

    if (-not [string]::IsNullOrWhiteSpace([string]$TextValue)) {
        $fieldValue = New-Object Microsoft.SharePoint.SPFieldUrlValue
        try {
            $fieldValue.FromString([string]$TextValue)
            return $fieldValue
        }
        catch {
        }
    }

    return $null
}

function Convert-ToTaxonomyTermEntries {
    param(
        $RawValue,

        [string]$TextValue
    )

    $termEntries = @()
    $rawTerms = @($RawValue)

    if (($rawTerms.Length -eq 1) -and $null -eq $rawTerms[0]) {
        $rawTerms = @()
    }

    foreach ($rawTerm in $rawTerms) {
        $termGuid = [string](Get-ObjectPropertyValue -Object $rawTerm -PropertyName "TermGuid")
        $label = [string](Get-ObjectPropertyValue -Object $rawTerm -PropertyName "Label")

        if ([string]::IsNullOrWhiteSpace($termGuid) -and ($rawTerm -is [string])) {
            $rawTermString = [string]$rawTerm

            if ($rawTermString -match "^(.*)\|([0-9a-fA-F-]{36})$") {
                $label = $matches[1]
                $termGuid = $matches[2]
            }
            else {
                $parsedGuid = [Guid]::Empty
                if ([guid]::TryParse($rawTermString, [ref]$parsedGuid)) {
                    $termGuid = $rawTermString
                }
            }
        }

        if ([string]::IsNullOrWhiteSpace($label) -and -not [string]::IsNullOrWhiteSpace($TextValue) -and $rawTerms.Length -le 1) {
            $label = $TextValue
        }

        if ([string]::IsNullOrWhiteSpace($termGuid)) {
            continue
        }

        if ([string]::IsNullOrWhiteSpace($label)) {
            $label = $termGuid
        }

        $termEntries += [PSCustomObject]@{
            Label = $label
            TermGuid = $termGuid
        }
    }

    if ($termEntries.Count -eq 0 -and -not [string]::IsNullOrWhiteSpace($TextValue)) {
        $segments = @($TextValue -split ";#")

        foreach ($segment in $segments) {
            if ([string]::IsNullOrWhiteSpace([string]$segment)) {
                continue
            }

            if ([string]$segment -match "^(.*)\|([0-9a-fA-F-]{36})$") {
                $termEntries += [PSCustomObject]@{
                    Label = $matches[1]
                    TermGuid = $matches[2]
                }
            }
        }
    }

    return @($termEntries)
}

function New-TaxonomyFieldValueObject {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field,

        [Parameter(Mandatory = $true)]
        $TermEntry
    )

    $label = [string](Get-ObjectPropertyValue -Object $TermEntry -PropertyName "Label")
    $termGuid = [string](Get-ObjectPropertyValue -Object $TermEntry -PropertyName "TermGuid")
    $labelGuidPair = "{0}|{1}" -f $label, $termGuid

    $taxonomyField = [Microsoft.SharePoint.Taxonomy.TaxonomyField]$Field
    $taxonomyValue = $null

    try {
        $taxonomyValue = New-Object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValue($taxonomyField)
    }
    catch {
    }

    if ($null -eq $taxonomyValue) {
        try {
            $taxonomyValue = New-Object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValue
        }
        catch {
        }
    }

    if ($null -eq $taxonomyValue) {
        throw ("Konnte kein TaxonomyFieldValue fuer Feld '{0}' erstellen." -f $Field.InternalName)
    }

    $isPopulated = $false

    try {
        $taxonomyValue.PopulateFromLabelGuidPair($labelGuidPair)
        $isPopulated = $true
    }
    catch {
    }

    if (-not $isPopulated) {
        try {
            $taxonomyValue.Label = $label
            $taxonomyValue.TermGuid = $termGuid
            $taxonomyValue.WssId = -1
            $isPopulated = $true
        }
        catch {
        }
    }

    if (-not $isPopulated) {
        throw ("Konnte TaxonomyFieldValue fuer Feld '{0}' nicht befuellen." -f $Field.InternalName)
    }

    return $taxonomyValue
}

function Set-SPTaxonomyFieldValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field,

        $RawValue,

        [string]$TextValue
    )

    $taxonomyField = [Microsoft.SharePoint.Taxonomy.TaxonomyField]$Field
    $termEntries = @(Convert-ToTaxonomyTermEntries -RawValue $RawValue -TextValue $TextValue)

    if ($termEntries.Count -eq 0) {
        $Item[$Field.InternalName] = $null
        return
    }

    if ([string]$Field.TypeAsString -eq "TaxonomyFieldTypeMulti") {
        $labelGuidPairs = @()

        foreach ($termEntry in $termEntries) {
            $label = [string](Get-ObjectPropertyValue -Object $termEntry -PropertyName "Label")
            $termGuid = [string](Get-ObjectPropertyValue -Object $termEntry -PropertyName "TermGuid")
            $labelGuidPairs += ("{0}|{1}" -f $label, $termGuid)
        }

        $pairString = $labelGuidPairs -join ";#"
        $taxonomyCollection = $null

        try {
            $taxonomyCollection = New-Object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValueCollection($Item.Web, "", $taxonomyField)
        }
        catch {
        }

        if ($null -eq $taxonomyCollection) {
            try {
                $taxonomyCollection = New-Object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValueCollection($Item.Web, $pairString, $taxonomyField)
            }
            catch {
            }
        }

        if ($null -eq $taxonomyCollection) {
            throw ("Konnte keine TaxonomyFieldValueCollection fuer Feld '{0}' erstellen." -f $Field.InternalName)
        }

        $collectionIsPopulated = $false

        try {
            $taxonomyCollection.PopulateFromLabelGuidPairs($pairString)
            $collectionIsPopulated = $true
        }
        catch {
        }

        if (-not $collectionIsPopulated) {
            try {
                foreach ($termEntry in $termEntries) {
                    [void]$taxonomyCollection.Add((New-TaxonomyFieldValueObject -Field $Field -TermEntry $termEntry))
                }
                $collectionIsPopulated = $true
            }
            catch {
            }
        }

        if (-not $collectionIsPopulated) {
            throw ("Konnte die TaxonomyFieldValueCollection fuer Feld '{0}' nicht befuellen." -f $Field.InternalName)
        }

        try {
            $taxonomyField.SetFieldValueByValueCollection($Item, $taxonomyCollection)
            return
        }
        catch {
        }

        try {
            $taxonomyField.SetFieldValue($Item, $taxonomyCollection)
            return
        }
        catch {
        }

        $Item[$Field.InternalName] = $taxonomyCollection
        return
    }

    $taxonomyValue = New-TaxonomyFieldValueObject -Field $Field -TermEntry $termEntries[0]

    try {
        $taxonomyField.SetFieldValueByValue($Item, $taxonomyValue)
        return
    }
    catch {
    }

    try {
        $taxonomyField.SetFieldValue($Item, $taxonomyValue)
        return
    }
    catch {
    }

    $Item[$Field.InternalName] = $taxonomyValue
}

function Set-SPItemFieldValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [Parameter(Mandatory = $true)]
        [string]$TargetInternalName,

        $RawValue,

        [string]$TextValue
    )

    $field = Resolve-SPField -Fields $Item.Fields -InternalName $TargetInternalName
    if ($null -eq $field) {
        Write-SkippedImportFieldWarning -FieldInternalName $TargetInternalName -Message ("Zielfeld nicht gefunden: {0}" -f $TargetInternalName)
        return
    }

    if (-not (Test-SPFieldSupportedForImport -Field $field)) {
        Write-SkippedImportFieldWarning -FieldInternalName $TargetInternalName -Message ("Zielfeld wird nicht importiert und wird uebersprungen: {0}" -f $TargetInternalName)
        return
    }

    try {
        switch ($field.TypeAsString) {
            "TaxonomyFieldType" {
                Set-SPTaxonomyFieldValue -Item $Item -Field $field -RawValue $RawValue -TextValue $TextValue
                return
            }
            "TaxonomyFieldTypeMulti" {
                Set-SPTaxonomyFieldValue -Item $Item -Field $field -RawValue $RawValue -TextValue $TextValue
                return
            }
            "Boolean" {
                $Item[$field.InternalName] = Convert-ToBoolean -RawValue $RawValue -TextValue $TextValue
                return
            }
            "Integer" {
                $Item[$field.InternalName] = Convert-ToInt32 -RawValue $RawValue -TextValue $TextValue
                return
            }
            "Counter" {
                return
            }
            "Number" {
                $Item[$field.InternalName] = Convert-ToDouble -RawValue $RawValue -TextValue $TextValue
                return
            }
            "Currency" {
                $Item[$field.InternalName] = Convert-ToDouble -RawValue $RawValue -TextValue $TextValue
                return
            }
            "DateTime" {
                $Item[$field.InternalName] = Convert-ToDateTimeValue -RawValue $RawValue -TextValue $TextValue
                return
            }
            "URL" {
                $Item[$field.InternalName] = Convert-ToUrlFieldValue -RawValue $RawValue -TextValue $TextValue
                return
            }
            "User" {
                $Item[$field.InternalName] = Convert-ToUserFieldValue -Item $Item -RawValue $RawValue -TextValue $TextValue
                return
            }
            "UserMulti" {
                $Item[$field.InternalName] = Convert-ToUserMultiFieldValue -Item $Item -RawValue $RawValue -TextValue $TextValue
                return
            }
            default {
                if ($null -eq $RawValue) {
                    $Item[$field.InternalName] = $TextValue
                }
                else {
                    $Item[$field.InternalName] = $RawValue
                }

                return
            }
        }
    }
    catch {
        if (-not [string]::IsNullOrWhiteSpace($TextValue)) {
            try {
                $field.ParseAndSetValue($Item, $TextValue)
                return
            }
            catch {
            }
        }

        Write-SkippedImportFieldWarning -FieldInternalName $TargetInternalName -Message ("Konnte Feld '{0}' nicht setzen und ueberspringe es. {1}" -f $TargetInternalName, $_.Exception.Message)
        return
    }
}

function Apply-FieldMappingToItem {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [Parameter(Mandatory = $true)]
        [System.Collections.IDictionary]$FieldMapping,

        $SourceFieldValues,

        $SourceFieldTextValues
    )

    foreach ($sourceInternalName in $FieldMapping.Keys) {
        $targetInternalName = [string]$FieldMapping[$sourceInternalName]

        $hasRawValue = Test-ObjectHasProperty -Object $SourceFieldValues -PropertyName $sourceInternalName
        $hasTextValue = Test-ObjectHasProperty -Object $SourceFieldTextValues -PropertyName $sourceInternalName

        if (-not $hasRawValue -and -not $hasTextValue -and $sourceInternalName -match "^(.*)_\d+$") {
            $canonicalSourceInternalName = $matches[1]
            $hasRawValue = Test-ObjectHasProperty -Object $SourceFieldValues -PropertyName $canonicalSourceInternalName
            $hasTextValue = Test-ObjectHasProperty -Object $SourceFieldTextValues -PropertyName $canonicalSourceInternalName

            if ($hasRawValue -or $hasTextValue) {
                $sourceInternalName = $canonicalSourceInternalName
            }
        }

        if (-not $hasRawValue -and -not $hasTextValue) {
            continue
        }

        $rawValue = if ($hasRawValue) {
            Get-ObjectPropertyValue -Object $SourceFieldValues -PropertyName $sourceInternalName
        }
        else {
            $null
        }

        $textValue = if ($hasTextValue) {
            [string](Get-ObjectPropertyValue -Object $SourceFieldTextValues -PropertyName $sourceInternalName)
        }
        else {
            $null
        }

        Set-SPItemFieldValue -Item $Item -TargetInternalName $targetInternalName -RawValue $rawValue -TextValue $textValue
    }
}

function Get-SPItemFieldRawValue {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPField]$Field
    )

    try {
        return $Item[$Field.InternalName]
    }
    catch {
        try {
            return $Item[$Field.Id]
        }
        catch {
            return $null
        }
    }
}

function Test-SPValuePresent {
    param(
        $Value
    )

    if ($null -eq $Value) {
        return $false
    }

    if ($Value -is [string]) {
        return -not [string]::IsNullOrWhiteSpace($Value)
    }

    if ($Value -is [System.Collections.IEnumerable] -and -not ($Value -is [string])) {
        return @($Value).Count -gt 0
    }

    return $true
}

function Get-SPItemMissingRequiredFields {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item
    )

    $missingFields = @()

    foreach ($field in $Item.Fields) {
        if (-not $field.Required) {
            continue
        }

        if ($field.TypeAsString -eq "Computed" -or $field.TypeAsString -eq "Attachments") {
            continue
        }

        $rawValue = Get-SPItemFieldRawValue -Item $Item -Field $field
        if (-not (Test-SPValuePresent -Value $rawValue)) {
            $missingFields += $field.InternalName
        }
    }

    return $missingFields
}

function Save-SPListItem {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPListItem]$Item,

        [string]$Context = ""
    )

    $missingRequiredFields = @(Get-SPItemMissingRequiredFields -Item $Item)
    if ($missingRequiredFields.Count -gt 0) {
        $message = "Pflichtfelder ohne Wert: {0}" -f ($missingRequiredFields -join ", ")
        if (-not [string]::IsNullOrWhiteSpace($Context)) {
            $message = "{0}. {1}" -f $Context, $message
        }

        throw $message
    }

    $saveErrors = @()

    try {
        $Item.UpdateOverwriteVersion()
        return
    }
    catch {
        $saveErrors += ("UpdateOverwriteVersion: {0}" -f $_.Exception.Message)
    }

    try {
        $Item.SystemUpdate($false)
        return
    }
    catch {
        $saveErrors += ("SystemUpdate(false): {0}" -f $_.Exception.Message)
    }

    try {
        $Item.Update()
        return
    }
    catch {
        $saveErrors += ("Update: {0}" -f $_.Exception.Message)
    }

    $missingRequiredFields = @(Get-SPItemMissingRequiredFields -Item $Item)
    $messageParts = @()

    if (-not [string]::IsNullOrWhiteSpace($Context)) {
        $messageParts += $Context
    }

    if ($missingRequiredFields.Count -gt 0) {
        $messageParts += ("Pflichtfelder ohne Wert: {0}" -f ($missingRequiredFields -join ", "))
    }

    if ($saveErrors.Count -gt 0) {
        $messageParts += ("Save-Versuche fehlgeschlagen: {0}" -f ($saveErrors -join " | "))
    }

    throw ("Konnte Listenelement nicht speichern. {0}" -f ($messageParts -join ". "))
}

function Get-RelativeSegmentsFromMetadataPath {
    param(
        [Parameter(Mandatory = $true)]
        [string]$MetadataFilePath,

        [Parameter(Mandatory = $true)]
        [string]$FilesRootPath
    )

    $relativePath = $MetadataFilePath.Substring($FilesRootPath.Length).TrimStart("\")
    return @($relativePath.Split("\") | Where-Object { -not [string]::IsNullOrWhiteSpace($_) })
}

function Ensure-SPFolderHierarchy {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$List,

        [string[]]$FolderSegments = @()
    )

    $currentFolder = $List.RootFolder

    foreach ($folderSegment in $FolderSegments) {
        $nextFolder = $null

        foreach ($existingFolder in $currentFolder.SubFolders) {
            if ($existingFolder.Name -eq $folderSegment) {
                $nextFolder = $existingFolder
                break
            }
        }

        if ($null -eq $nextFolder) {
            $nextFolder = $currentFolder.SubFolders.Add($folderSegment)
        }

        $currentFolder = $nextFolder
    }

    return $currentFolder
}

function Get-SPFolderFileByName {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFolder]$Folder,

        [Parameter(Mandatory = $true)]
        [string]$FileName
    )

    foreach ($existingFile in $Folder.Files) {
        if ($existingFile.Name -eq $FileName) {
            return $existingFile
        }
    }

    return $null
}

function Update-SPExistingFileAsNewVersion {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFile]$ExistingFile,

        [Parameter(Mandatory = $true)]
        [byte[]]$FileBytes
    )

    $requiresCheckout = $false

    try {
        $requiresCheckout = [bool]$ExistingFile.ParentFolder.DocumentLibrary.ForceCheckout
    }
    catch {
        $requiresCheckout = $false
    }

    if ($requiresCheckout -and $ExistingFile.CheckOutType -eq [Microsoft.SharePoint.SPFile+SPCheckOutType]::None) {
        $ExistingFile.CheckOut()
    }

    $existingFile.SaveBinary($FileBytes)

    if ($ExistingFile.CheckOutType -ne [Microsoft.SharePoint.SPFile+SPCheckOutType]::None) {
        $checkInType = [Microsoft.SharePoint.SPCheckinType]::MajorCheckIn

        try {
            if ([bool]$ExistingFile.ParentFolder.DocumentLibrary.EnableMinorVersions) {
                $checkInType = [Microsoft.SharePoint.SPCheckinType]::MinorCheckIn
            }
        }
        catch {
        }

        $ExistingFile.CheckIn("Imported by Start-SPMigration", $checkInType)
    }

    return $ExistingFile
}

function Import-SPFileToFolder {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPFolder]$TargetFolder,

        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPList]$TargetLibrary,

        [Parameter(Mandatory = $true)]
        [string]$FileName,

        [Parameter(Mandatory = $true)]
        [byte[]]$FileBytes,

        [switch]$Overwrite
    )

    $existingFile = Get-SPFolderFileByName -Folder $TargetFolder -FileName $FileName

    if ($null -eq $existingFile) {
        return $TargetFolder.Files.Add($FileName, $FileBytes, $false)
    }

    if ($Overwrite.IsPresent) {
        return $TargetFolder.Files.Add($FileName, $FileBytes, $true)
    }

    if (-not [bool]$TargetLibrary.EnableVersioning) {
        Write-Warning ("Datei uebersprungen, da sie bereits existiert und in der Zielbibliothek keine Versionierung aktiv ist: {0}/{1}" -f $TargetLibrary.Title, $FileName)
        return $null
    }

    Write-Host ("Datei existiert bereits. Erzeuge neue Version: {0}/{1}" -f $TargetLibrary.Title, $FileName)
    return Update-SPExistingFileAsNewVersion -ExistingFile $existingFile -FileBytes $FileBytes
}

function Import-SPDocumentLibraries {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [string]$FilesRootPath,

        [Parameter(Mandatory = $true)]
        $MigrationMappingTable,

        [switch]$Overwrite
    )

    if (-not [System.IO.Directory]::Exists($FilesRootPath)) {
        Write-Warning ("Kein Files-Ordner gefunden: {0}" -f $FilesRootPath)
        return
    }

    $containerMappingMap = Get-ContainerMappingMap -MigrationMappingTable $MigrationMappingTable
    $metadataFiles = @(Get-ChildItem -Path $FilesRootPath -Recurse -File -Filter *.properties.json)
    Write-Host ("Gefundene Datei-Metadaten: {0}" -f $metadataFiles.Length)

    foreach ($metadataFile in $metadataFiles) {
        $sourceFilePath = $metadataFile.FullName.Substring(0, $metadataFile.FullName.Length - ".properties.json".Length)
        if (-not [System.IO.File]::Exists($sourceFilePath)) {
            Write-Warning ("Quelldatei zur Metadatei nicht gefunden: {0}" -f $metadataFile.FullName)
            continue
        }

        $metadata = Read-JsonFile -Path $metadataFile.FullName
        $libraryMetadata = Get-ObjectPropertyValue -Object $metadata -PropertyName "Library"
        $itemMetadata = Get-ObjectPropertyValue -Object $metadata -PropertyName "Item"
        $sourceLibraryTitle = [string](Get-ObjectPropertyValue -Object $libraryMetadata -PropertyName "Title")

        if ([string]::IsNullOrWhiteSpace($sourceLibraryTitle)) {
            Write-Warning ("Bibliothekstitel fehlt in: {0}" -f $metadataFile.FullName)
            continue
        }

        $targetLibraryTitle = Get-TargetContainerTitleFromMappingTable -ContainerMappingMap $containerMappingMap -ObjectType "DocumentLibrary" -SourceTitle $sourceLibraryTitle
        $targetLibrary = $Web.Lists.TryGetList($targetLibraryTitle)
        if ($null -eq $targetLibrary) {
            if (Test-ContainerHasExplicitTargetMappingInTable -ContainerMappingMap $containerMappingMap -ObjectType "DocumentLibrary" -SourceTitle $sourceLibraryTitle) {
                Write-Warning ("Zielbibliothek '{0}' fuer Quellbibliothek '{1}' nicht gefunden. Bitte diese Bibliothek im Ziel manuell anlegen." -f $targetLibraryTitle, $sourceLibraryTitle)
            }
            else {
                Write-Warning ("Zielbibliothek '{0}' nicht gefunden und kein TargetTitle in der MappingTable gepflegt. Bitte Bibliothek manuell anlegen oder TargetTitle in der MappingTable setzen." -f $sourceLibraryTitle)
            }
            continue
        }

        if ($targetLibrary.BaseType -ne [Microsoft.SharePoint.SPBaseType]::DocumentLibrary) {
            Write-Warning ("Zielliste ist keine Dokumentbibliothek: {0}" -f $targetLibraryTitle)
            continue
        }

        $relativeSegments = @(Get-RelativeSegmentsFromMetadataPath -MetadataFilePath $metadataFile.FullName -FilesRootPath $FilesRootPath)
        if ($relativeSegments.Length -lt 2) {
            Write-Warning ("Dateipfad konnte nicht relativ zur Bibliothek ermittelt werden: {0}" -f $metadataFile.FullName)
            continue
        }

        $folderSegments = @()
        if ($relativeSegments.Length -gt 2) {
            $folderSegments = $relativeSegments[1..($relativeSegments.Length - 2)]
        }

        $targetFolder = Ensure-SPFolderHierarchy -List $targetLibrary -FolderSegments $folderSegments
        $fileName = [System.IO.Path]::GetFileName($sourceFilePath)
        $fileBytes = [System.IO.File]::ReadAllBytes($sourceFilePath)

        Write-Host ("Importiere Datei: {0} -> {1}" -f $sourceFilePath, $targetLibrary.Title)

        $spFile = Import-SPFileToFolder -TargetFolder $targetFolder -TargetLibrary $targetLibrary -FileName $fileName -FileBytes $fileBytes -Overwrite:$Overwrite
        if ($null -eq $spFile) {
            continue
        }

        $spItem = $spFile.Item

        if ($null -ne $itemMetadata) {
            try {
                $fieldMapping = Get-FieldMappingForContainer -MigrationMappingTable $MigrationMappingTable -ObjectType "DocumentLibrary" -SourceTitle $sourceLibraryTitle
                Apply-FieldMappingToItem -Item $spItem -FieldMapping $fieldMapping -SourceFieldValues (Get-ObjectPropertyValue -Object $itemMetadata -PropertyName "FieldValues") -SourceFieldTextValues (Get-ObjectPropertyValue -Object $itemMetadata -PropertyName "FieldTextValues")
                Save-SPListItem -Item $spItem -Context ("Bibliothek '{0}', Datei '{1}'" -f $targetLibrary.Title, $fileName)
            }
            catch {
                Write-Warning ("Metadaten fuer Datei konnten nicht gespeichert werden: {0}" -f $_.Exception.Message)
            }
        }
    }
}

function Import-SPLists {
    param(
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.SPWeb]$Web,

        [Parameter(Mandatory = $true)]
        [string]$ListsRootPath,

        [Parameter(Mandatory = $true)]
        $MigrationMappingTable
    )

    if (-not [System.IO.Directory]::Exists($ListsRootPath)) {
        Write-Warning ("Kein Lists-Ordner gefunden: {0}" -f $ListsRootPath)
        return
    }

    $containerMappingMap = Get-ContainerMappingMap -MigrationMappingTable $MigrationMappingTable
    $listFiles = @(Get-ChildItem -Path $ListsRootPath -File -Filter *.json)
    Write-Host ("Gefundene Listen-JSONs: {0}" -f $listFiles.Length)

    foreach ($listFile in $listFiles) {
        $listExport = Read-JsonFile -Path $listFile.FullName
        $listMetadata = Get-ObjectPropertyValue -Object $listExport -PropertyName "List"
        $items = @(Get-ObjectPropertyValue -Object $listExport -PropertyName "Items" -DefaultValue @())
        $sourceListTitle = [string](Get-ObjectPropertyValue -Object $listMetadata -PropertyName "Title")

        if ([string]::IsNullOrWhiteSpace($sourceListTitle)) {
            Write-Warning ("Listentitel fehlt in: {0}" -f $listFile.FullName)
            continue
        }

        $targetListTitle = Get-TargetContainerTitleFromMappingTable -ContainerMappingMap $containerMappingMap -ObjectType "List" -SourceTitle $sourceListTitle
        $targetList = $Web.Lists.TryGetList($targetListTitle)
        if ($null -eq $targetList) {
            if (Test-ContainerHasExplicitTargetMappingInTable -ContainerMappingMap $containerMappingMap -ObjectType "List" -SourceTitle $sourceListTitle) {
                Write-Warning ("Zielliste '{0}' fuer Quellliste '{1}' nicht gefunden. Bitte diese Liste im Ziel manuell anlegen." -f $targetListTitle, $sourceListTitle)
            }
            else {
                Write-Warning ("Zielliste '{0}' nicht gefunden und kein TargetTitle in der MappingTable gepflegt. Bitte Liste manuell anlegen oder TargetTitle in der MappingTable setzen." -f $sourceListTitle)
            }
            continue
        }

        if ($targetList.BaseType -eq [Microsoft.SharePoint.SPBaseType]::DocumentLibrary) {
            Write-Warning ("Liste ist eine Dokumentbibliothek und wird im Listenimport uebersprungen: {0}" -f $targetListTitle)
            continue
        }

        Write-Host ("Importiere Liste: {0}" -f $targetListTitle)
        $fieldMapping = Get-FieldMappingForContainer -MigrationMappingTable $MigrationMappingTable -ObjectType "List" -SourceTitle $sourceListTitle

        foreach ($sourceItem in $items) {
            $sourceItemId = [string](Get-ObjectPropertyValue -Object $sourceItem -PropertyName "Id")
            $sourceItemTitle = [string](Get-ObjectPropertyValue -Object $sourceItem -PropertyName "Title")
            $fileSystemObjectType = [string](Get-ObjectPropertyValue -Object $sourceItem -PropertyName "FileSystemObjectType")
            if ($fileSystemObjectType -eq "Folder") {
                Write-Warning ("Ordner in normalen Listen werden in dieser Version uebersprungen: {0}" -f $targetListTitle)
                continue
            }

            if ((Get-ObjectPropertyValue -Object $sourceItem -PropertyName "HasAttachments" -DefaultValue $false)) {
                Write-Warning ("Listenanlagen wurden im Export nicht physisch gesichert und werden uebersprungen. Liste: {0}, ItemId: {1}" -f $targetListTitle, (Get-ObjectPropertyValue -Object $sourceItem -PropertyName "Id"))
            }

            try {
                $targetItem = $targetList.Items.Add()
                Apply-FieldMappingToItem -Item $targetItem -FieldMapping $fieldMapping -SourceFieldValues (Get-ObjectPropertyValue -Object $sourceItem -PropertyName "FieldValues") -SourceFieldTextValues (Get-ObjectPropertyValue -Object $sourceItem -PropertyName "FieldTextValues")
                Save-SPListItem -Item $targetItem -Context ("Liste '{0}', Quell-ItemId '{1}', Titel '{2}'" -f $targetListTitle, $sourceItemId, $sourceItemTitle)
            }
            catch {
                Write-Warning ("Listenelement wurde uebersprungen: {0}" -f $_.Exception.Message)
                continue
            }
        }
    }
}

Initialize-SharePointPowerShell

$resolvedOutputPath = [System.IO.Path]::GetFullPath($OutputPath)
$filesRootPath = [System.IO.Path]::Combine($resolvedOutputPath, "Files")
$listsRootPath = [System.IO.Path]::Combine($resolvedOutputPath, "Lists")
$manifestPath = [System.IO.Path]::Combine($resolvedOutputPath, "manifest.csv")
$mappingTablePath = if ([string]::IsNullOrWhiteSpace($MappingTable)) {
    [System.IO.Path]::Combine($resolvedOutputPath, "MappingTable.json")
}
else {
    [System.IO.Path]::GetFullPath($MappingTable)
}

$shouldExport = $Export.IsPresent
$shouldImport = $Import.IsPresent

if (-not $shouldExport -and -not $shouldImport) {
    $shouldExport = -not [string]::IsNullOrWhiteSpace($SourceUrl)
    $shouldImport = -not [string]::IsNullOrWhiteSpace($TargetUrl)
}

if (-not $shouldExport -and -not $shouldImport) {
    throw "Bitte mindestens -Export oder -Import angeben."
}

if ($shouldImport -and [string]::IsNullOrWhiteSpace($TargetUrl)) {
    throw "Fuer den Import muss TargetUrl angegeben werden."
}

if ($shouldImport -and -not $shouldExport) {
    if (-not [System.IO.File]::Exists($mappingTablePath)) {
        throw ("MappingTable nicht gefunden: {0}" -f $mappingTablePath)
    }

    Invoke-MigrationImport -InputPath $resolvedOutputPath -TargetWebUrl $TargetUrl -MappingTablePath $mappingTablePath -ImportFiles:$ImportFiles -ImportLists:$ImportLists -Overwrite:$Overwrite
    return
}

if ([string]::IsNullOrWhiteSpace($SourceUrl)) {
    throw "Fuer den Export muss SourceUrl angegeben werden."
}

Ensure-Directory -Path $resolvedOutputPath
Ensure-Directory -Path $filesRootPath
Ensure-Directory -Path $listsRootPath

if ([System.IO.File]::Exists($manifestPath)) {
    [System.IO.File]::Delete($manifestPath)
}

$web = $null

try {
    $web = Get-SPWeb -Identity $SourceUrl -ErrorAction Stop

    $documentLibraries = @(
        $web.Lists | Where-Object {
            $_.BaseType -eq [Microsoft.SharePoint.SPBaseType]::DocumentLibrary -and
            ($IncludeHiddenLibraries -or -not $_.Hidden) -and
            -not (Test-IsCatalogList -List $_)
        }
    )

    $lists = @(
        $web.Lists | Where-Object {
            $_.BaseType -ne [Microsoft.SharePoint.SPBaseType]::DocumentLibrary -and
            ($IncludeHiddenLists -or -not $_.Hidden) -and
            -not (Test-IsCatalogList -List $_)
        }
    )

    Write-Host ("Gefundene Bibliotheken: {0}" -f $documentLibraries.Length)
    Write-Host ("Gefundene Listen: {0}" -f $lists.Length)

    $migrationMappingTable = New-MigrationMappingTable -SourceWebUrl $web.Url -DocumentLibraries $documentLibraries -Lists $lists
    Write-MigrationMappingTable -MappingTable $migrationMappingTable -Path $mappingTablePath
    Write-Host ("MappingTable geschrieben: {0}" -f $mappingTablePath)

    foreach ($library in $documentLibraries) {
        Export-SPDocumentLibrary -Web $web -List $library -FilesRootPath $filesRootPath -ManifestPath $manifestPath
    }

    foreach ($list in $lists) {
        Export-SPList -Web $web -List $list -ListsRootPath $listsRootPath -ManifestPath $manifestPath
    }

    if ($documentLibraries.Length -eq 0 -and $lists.Length -eq 0) {
        Write-Warning ("Keine exportierbaren Bibliotheken oder Listen im Web gefunden: {0}" -f $SourceUrl)
        return
    }

    Write-Host ("Export abgeschlossen. Ausgabe: {0}" -f $resolvedOutputPath)

    if (-not $shouldImport) {
        Write-Host "Import wurde nicht angefordert. Export ist abgeschlossen."
        return
    }

    Write-Host ("Starte Import nach Export. Zielweb: {0}" -f $TargetUrl)
    Invoke-MigrationImport -InputPath $resolvedOutputPath -TargetWebUrl $TargetUrl -MappingTablePath $mappingTablePath -ImportFiles:$ImportFiles -ImportLists:$ImportLists -Overwrite:$Overwrite
}
finally {
    if ($null -ne $web) {
        $web.Dispose()
    }
}