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

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

    [string]$RepositoryRoot,

    [switch]$AllowDirtyTargets
)

$ErrorActionPreference = 'Stop'
if ([string]::IsNullOrWhiteSpace($RepositoryRoot)) {
    $RepositoryRoot = Split-Path -Parent $PSScriptRoot
}
$repositoryRoot = [System.IO.Path]::GetFullPath($RepositoryRoot)
$tfsExportRoot = [System.IO.Path]::GetFullPath($TfsExportRoot)
$statePath = Join-Path $repositoryRoot 'sync\tfs-state.json'

$files = [ordered]@{
    'F4SDM42WebApi\F4SDHelperService.cs' = 'Legacy\F4SDM42WebApi\F4SDHelperService.cs'
    'F4SDM42WebApi\F4SDM42WebApiController.cs' = 'Legacy\F4SDM42WebApi\F4SDM42WebApiController.cs'
    'F4SDM42WebApi\cM42LogEntry.cs' = 'Legacy\F4SDM42WebApi\cM42LogEntry.cs'
    'F4SDM42WebApi\Properties\AssemblyInfo.cs' = 'Legacy\F4SDM42WebApi\Properties\AssemblyInfo.cs'
    'F4SDHelper\Properties\AssemblyInfo.cs' = 'Legacy\F4SDHelper\Properties\AssemblyInfo.cs'
}

if (-not (Test-Path -LiteralPath (Join-Path $repositoryRoot '.git'))) {
    throw "Repository root is not a Git worktree: $repositoryRoot"
}

foreach ($sourceRelative in $files.Keys) {
    $sourcePath = Join-Path $tfsExportRoot $sourceRelative
    if (-not (Test-Path -LiteralPath $sourcePath)) {
        throw "Required TFS source file not found: $sourcePath"
    }
}

if (-not $AllowDirtyTargets) {
    $targetPaths = @($files.Values)
    $status = & git -C $repositoryRoot status --porcelain -- $targetPaths
    if ($LASTEXITCODE -ne 0) {
        throw 'Could not inspect the Git worktree.'
    }
    if ($status) {
        throw "Legacy sync targets contain uncommitted changes. Commit or stash them first:`n$($status -join [Environment]::NewLine)"
    }
}

$utf8WithBom = [System.Text.UTF8Encoding]::new($true)
$hashes = [ordered]@{}
foreach ($entry in $files.GetEnumerator()) {
    $sourcePath = Join-Path $tfsExportRoot $entry.Key
    $targetPath = Join-Path $repositoryRoot $entry.Value
    $content = [System.IO.File]::ReadAllText($sourcePath)
    $content = [regex]::Replace($content, "`r?`n", "`r`n")

    if ($PSCmdlet.ShouldProcess($targetPath, "Import TFS changeset $Changeset")) {
        [System.IO.File]::WriteAllText($targetPath, $content, $utf8WithBom)
    }

    $hashes[$entry.Value.Replace('\', '/')] = (Get-FileHash -LiteralPath $sourcePath -Algorithm SHA256).Hash
}

$baseCommit = (& git -C $repositoryRoot rev-parse HEAD).Trim()
$state = [ordered]@{
    LastImportedChangeset = $Changeset
    ImportedAtUtc = [DateTime]::UtcNow.ToString('o')
    SourceRoot = $tfsExportRoot
    BaseGitCommit = $baseCommit
    Files = $hashes
}

if ($PSCmdlet.ShouldProcess($statePath, 'Update TFS import state')) {
    [System.IO.File]::WriteAllText(
        $statePath,
        ($state | ConvertTo-Json -Depth 5),
        $utf8WithBom)
}

Write-Host "Imported TFS changeset $Changeset into the Legacy sources."
Write-Host 'Review and commit this import on sync/tfs-legacy, then merge it into the development branch.'
Write-Host 'Publishing the final result back to TFS remains a manual Visual Studio step.'