using Microsoft.EntityFrameworkCore;
using Microsoft.SelfService.Portal.Core.API.Context;
using Microsoft.SelfService.Portal.Core.API.Interfaces;
using Microsoft.SelfService.Portal.Core.API.Models;
using System.Text.Json;

namespace Microsoft.SelfService.Portal.Core.API.Services
{
    public class QueueJobService : IQueueJobService
    {
        private readonly DataContext _context;

        public QueueJobService(DataContext context)
        {
            _context = context;
        }

        public Guid EnqueueTemplateJsonChanged(Guid templateId, string oldJsonData, string newJsonData)
        {
            var deployments = _context.Deployments
                .AsNoTracking()
                .Include(deployment => deployment.DeploymentGroup)
                .Where(deployment => deployment.DeploymentGroup.TemplateId == templateId)
                .ToList();

            var payload = new
            {
                TemplateId = templateId,
                OldJsonData = oldJsonData,
                NewJsonData = newJsonData,
                TargetCount = deployments.Count,
                Created = DateTime.UtcNow
            };

            var queueJob = new QueueJobModel
            {
                Type = QueueJobType.TemplateJsonChanged,
                Status = QueueJobStatus.Pending,
                PayloadJson = JsonSerializer.Serialize(payload),
                Targets = deployments.Select(deployment => new QueueJobTargetModel
                {
                    VirtualMachineId = deployment.VirtualMachineId,
                    DeploymentGroupId = deployment.DeploymentGroupId,
                    TemplateId = templateId,
                    Status = QueueJobStatus.Pending
                }).ToList()
            };
            queueJob.Steps = BuildDefaultJobSteps();

            _context.QueueJobs.Add(queueJob);
            _context.SaveChanges();

            return queueJob.Id;
        }

        public Guid EnqueueDeploymentRequest(Guid deploymentGroupId, ICollection<Guid> virtualMachineIds, string jsonData)
        {
            var deploymentGroup = _context.DeploymentGroups
                .AsNoTracking()
                .Include(group => group.Template)
                .ThenInclude(template => template.DeploymentRule)
                .ThenInclude(rule => rule.Steps)
                .FirstOrDefault(group => group.Id == deploymentGroupId);

            if (deploymentGroup == null)
            {
                throw new InvalidOperationException("DeploymentGroup does not exist.");
            }

            var templateId = deploymentGroup.TemplateId;
            var resolvedVirtualMachineIds = virtualMachineIds
                .Distinct()
                .ToList();

            if (resolvedVirtualMachineIds.Count == 0)
            {
                throw new InvalidOperationException("No target VirtualMachines provided.");
            }

            var existingVirtualMachines = _context.VirtualMachines
                .AsNoTracking()
                .Where(virtualMachine => resolvedVirtualMachineIds.Contains(virtualMachine.Id))
                .Select(virtualMachine => virtualMachine.Id)
                .ToHashSet();

            var missingVirtualMachines = resolvedVirtualMachineIds
                .Where(virtualMachineId => !existingVirtualMachines.Contains(virtualMachineId))
                .ToList();

            if (missingVirtualMachines.Count > 0)
            {
                throw new InvalidOperationException($"Unknown VirtualMachine IDs: {string.Join(", ", missingVirtualMachines)}");
            }

            foreach (var virtualMachineId in resolvedVirtualMachineIds)
            {
                var deployment = _context.Deployments
                    .FirstOrDefault(existing =>
                        existing.DeploymentGroupId == deploymentGroupId
                        && existing.VirtualMachineId == virtualMachineId);

                if (deployment == null)
                {
                    deployment = new DeploymentModel
                    {
                        DeploymentGroupId = deploymentGroupId,
                        VirtualMachineId = virtualMachineId,
                        Status = QueueJobStatus.Pending,
                        JSONData = jsonData
                    };

                    _context.Deployments.Add(deployment);
                }
                else
                {
                    deployment.Status = QueueJobStatus.Pending;
                    deployment.JSONData = jsonData;
                }
            }

            var payload = new
            {
                DeploymentGroupId = deploymentGroupId,
                TemplateId = templateId,
                VirtualMachineIds = resolvedVirtualMachineIds,
                JsonData = jsonData,
                TargetCount = resolvedVirtualMachineIds.Count,
                Created = DateTime.UtcNow
            };

            var queueJob = new QueueJobModel
            {
                Type = QueueJobType.DeploymentRequested,
                Status = QueueJobStatus.Pending,
                PayloadJson = JsonSerializer.Serialize(payload),
                RuleSnapshotJson = deploymentGroup.Template?.DeploymentRuleId.HasValue == true
                    ? SerializeRuleSnapshot(deploymentGroup.Template!.DeploymentRule)
                    : null,
                Targets = resolvedVirtualMachineIds.Select(virtualMachineId => new QueueJobTargetModel
                {
                    VirtualMachineId = virtualMachineId,
                    DeploymentGroupId = deploymentGroupId,
                    TemplateId = templateId,
                    Status = QueueJobStatus.Pending
                }).ToList()
            };
            queueJob.Steps = BuildDeploymentSteps(deploymentGroup.Template?.DeploymentRule);

            _context.QueueJobs.Add(queueJob);
            _context.SaveChanges();

            return queueJob.Id;
        }

        public bool RetryQueueJob(Guid queueJobId)
        {
            var queueJob = _context.QueueJobs
                .Include(job => job.Targets)
                .FirstOrDefault(job => job.Id == queueJobId);

            if (queueJob == null)
            {
                return false;
            }

            queueJob.Status = QueueJobStatus.Pending;
            queueJob.ErrorMessage = null;
            queueJob.Finished = null;
            queueJob.LockedUntil = null;
            queueJob.LockedBy = null;
            queueJob.Steps ??= new List<QueueJobStepModel>();

            foreach (var target in queueJob.Targets)
            {
                if (target.Status == QueueJobStatus.Failed || target.Status == QueueJobStatus.Cancelled)
                {
                    target.Status = QueueJobStatus.Pending;
                    target.ErrorMessage = null;
                }
            }
            foreach (var step in queueJob.Steps)
            {
                if (step.Status == QueueJobStatus.Failed
                    || step.Status == QueueJobStatus.Cancelled
                    || step.Status == QueueJobStatus.WaitingForApproval
                    || step.Status == QueueJobStatus.Rejected)
                {
                    step.Status = QueueJobStatus.Pending;
                    step.ApprovedAt = null;
                    step.ApprovedBy = null;
                    step.ApprovalComment = null;
                }
            }

            return _context.SaveChanges() > 0;
        }

        public bool ApproveQueueJobStep(Guid queueJobStepId, string approvedBy, string? comment)
        {
            var step = _context.QueueJobSteps
                .Include(existing => existing.QueueJob)
                .FirstOrDefault(existing => existing.Id == queueJobStepId);

            if (step == null || step.StepType != QueueJobStepType.Approval)
            {
                return false;
            }

            step.Status = QueueJobStatus.Succeeded;
            step.ApprovedAt = DateTime.UtcNow;
            step.ApprovedBy = approvedBy;
            step.ApprovalComment = comment;
            step.QueueJob.Status = QueueJobStatus.Pending;
            step.QueueJob.LockedUntil = null;
            step.QueueJob.LockedBy = null;
            step.QueueJob.ErrorMessage = null;

            return _context.SaveChanges() > 0;
        }

        public bool RejectQueueJobStep(Guid queueJobStepId, string approvedBy, string? comment)
        {
            var step = _context.QueueJobSteps
                .Include(existing => existing.QueueJob)
                .FirstOrDefault(existing => existing.Id == queueJobStepId);

            if (step == null || step.StepType != QueueJobStepType.Approval)
            {
                return false;
            }

            step.Status = QueueJobStatus.Rejected;
            step.ApprovedAt = DateTime.UtcNow;
            step.ApprovedBy = approvedBy;
            step.ApprovalComment = comment;
            step.QueueJob.Status = QueueJobStatus.Rejected;
            step.QueueJob.Finished = DateTime.UtcNow;
            step.QueueJob.LockedUntil = null;
            step.QueueJob.LockedBy = null;
            step.QueueJob.ErrorMessage = comment ?? "Deployment step rejected.";

            return _context.SaveChanges() > 0;
        }

        private static List<QueueJobStepModel> BuildDefaultJobSteps()
        {
            return new List<QueueJobStepModel>
            {
                new()
                {
                    Id = Guid.NewGuid(),
                    SortOrder = 1,
                    Name = "Provision",
                    StepType = QueueJobStepType.Provision,
                    Status = QueueJobStatus.Pending
                }
            };
        }

        private static List<QueueJobStepModel> BuildDeploymentSteps(DeploymentRuleModel? deploymentRule)
        {
            if (deploymentRule?.Steps == null || deploymentRule.Steps.Count == 0)
            {
                return BuildDefaultJobSteps();
            }

            var steps = deploymentRule.Steps
                .OrderBy(step => step.SortOrder)
                .Select(step => new QueueJobStepModel
                {
                    Id = Guid.NewGuid(),
                    SortOrder = step.SortOrder,
                    Name = step.Name,
                    StepType = step.RequiresApproval ? QueueJobStepType.Approval : step.StepType,
                    Status = QueueJobStatus.Pending,
                    MetadataJson = step.MetadataJson
                })
                .ToList();

            for (var i = 1; i < steps.Count; i++)
            {
                steps[i].DependsOnQueueJobStepId = steps[i - 1].Id;
            }

            return steps;
        }

        private static string? SerializeRuleSnapshot(DeploymentRuleModel? rule)
        {
            if (rule == null)
            {
                return null;
            }

            var snapshot = new
            {
                rule.Id,
                rule.Name,
                Steps = rule.Steps
                    .OrderBy(step => step.SortOrder)
                    .Select(step => new
                    {
                        step.Id,
                        step.SortOrder,
                        step.Name,
                        step.StepType,
                        step.RequiresApproval,
                        step.MetadataJson
                    })
            };

            return JsonSerializer.Serialize(snapshot);
        }
    }
}