[CmdletBinding()]
param(
    [Parameter(Mandatory = $true)]
    [string]$SiteUrl,

    [string]$PollListTitle = 'Polls',

    [string]$AnswerListTitle = 'Poll Answers'
)

$ErrorActionPreference = 'Stop'

function Ensure-Field {
    param(
        [Microsoft.SharePoint.SPList]$List,
        [string]$InternalName,
        [string]$SchemaXml
    )

    if (-not $List.Fields.ContainsField($InternalName)) {
        [void]$List.Fields.AddFieldAsXml($SchemaXml, $true, [Microsoft.SharePoint.SPAddFieldOptions]::AddFieldInternalNameHint)
        $List.Update()
    }
}

$web = Get-SPWeb -Identity $SiteUrl
try {
    $polls = $web.Lists.TryGetList($PollListTitle)
    if (-not $polls) {
        $listId = $web.Lists.Add($PollListTitle, 'Questions and options for the Dynamic Poll web part.', [Microsoft.SharePoint.SPListTemplateType]::GenericList)
        $polls = $web.Lists[$listId]
        $polls.OnQuickLaunch = $true
        $polls.Update()
    }

    Ensure-Field -List $polls -InternalName 'Question' -SchemaXml '<Field Type="Text" DisplayName="Question" Name="Question" StaticName="Question" Required="TRUE" />'

    $legacyOptionsField = $null
    try { $legacyOptionsField = $polls.Fields.GetFieldByInternalName('Options') } catch { }
    if ($legacyOptionsField) {
        $legacyOptionsField.Title = 'Options (legacy)'
        $legacyOptionsField.Required = $false
        $legacyOptionsField.ShowInNewForm = $false
        $legacyOptionsField.ShowInEditForm = $false
        $legacyOptionsField.ShowInDisplayForm = $false
        $legacyOptionsField.Update()
    }

    Ensure-Field -List $polls -InternalName 'OptionsText' -SchemaXml '<Field Type="Note" DisplayName="Options" Name="OptionsText" StaticName="OptionsText" Required="FALSE" NumLines="8" RichText="FALSE" AppendOnly="FALSE" />'

    if ($legacyOptionsField) {
        foreach ($item in $polls.Items) {
            if (-not [string]::IsNullOrWhiteSpace([string]$item['OptionsText']) -or $null -eq $item[$legacyOptionsField.Id]) { continue }
            $legacyValue = $legacyOptionsField.GetFieldValue([string]$item[$legacyOptionsField.Id])
            $optionLines = New-Object System.Collections.Generic.List[string]
            if ($legacyValue -is [Microsoft.SharePoint.SPFieldMultiChoiceValue]) {
                for ($choiceIndex = 0; $choiceIndex -lt $legacyValue.Count; $choiceIndex++) {
                    if (-not [string]::IsNullOrWhiteSpace($legacyValue[$choiceIndex])) { $optionLines.Add($legacyValue[$choiceIndex]) }
                }
            }
            elseif (-not [string]::IsNullOrWhiteSpace([string]$legacyValue)) {
                $optionLines.Add([string]$legacyValue)
            }
            if ($optionLines.Count -gt 0) {
                $item['OptionsText'] = ($optionLines -join [Environment]::NewLine)
                $item.SystemUpdate($false)
            }
        }
    }
    Ensure-Field -List $polls -InternalName 'StartDate' -SchemaXml '<Field Type="DateTime" DisplayName="Start date" Name="StartDate" StaticName="StartDate" Format="DateTime" />'
    Ensure-Field -List $polls -InternalName 'EndDate' -SchemaXml '<Field Type="DateTime" DisplayName="End date" Name="EndDate" StaticName="EndDate" Format="DateTime" />'
    Ensure-Field -List $polls -InternalName 'IsActive' -SchemaXml '<Field Type="Boolean" DisplayName="Active" Name="IsActive" StaticName="IsActive"><Default>0</Default></Field>'

    $answers = $web.Lists.TryGetList($AnswerListTitle)
    if (-not $answers) {
        $listId = $web.Lists.Add($AnswerListTitle, 'Votes submitted through the Dynamic Poll web part.', [Microsoft.SharePoint.SPListTemplateType]::GenericList)
        $answers = $web.Lists[$listId]
        $answers.OnQuickLaunch = $false
        $answers.Update()
    }

    $pollListId = $polls.ID.ToString('B')
    Ensure-Field -List $answers -InternalName 'Poll' -SchemaXml (('<Field Type="Lookup" DisplayName="Poll" Name="Poll" StaticName="Poll" List="{0}" ShowField="Title" Required="TRUE" />' -f $pollListId))
    Ensure-Field -List $answers -InternalName 'Answer' -SchemaXml '<Field Type="Text" DisplayName="Answer" Name="Answer" StaticName="Answer" Required="TRUE" MaxLength="255" />'

    Write-Host ('Dynamic Poll lists are ready at {0}' -f $web.Url) -ForegroundColor Green
    Write-Host ('Poll list: {0} ({1})' -f $polls.Title, $polls.ID)
    Write-Host ('Answer list: {0} ({1})' -f $answers.Title, $answers.ID)
}
finally {
    if ($web) { $web.Dispose() }
}