<#
.SYNOPSIS
    Executes the safe half of Scratchpad cleanup. Dry-run unless -Execute.

.DESCRIPTION
    Consumes scan.ps1's classification and performs only the reversible or
    provably-safe actions:

      AutoPurge   delete .log/.err files and empty directories
      Quarantine  MOVE stale files to _trash\<date>\ (never delete)
      PurgeTrash  delete _trash\<date>\ folders past the grace period
      Restore     move a quarantine batch back where it came from

    It deliberately does NOT act on the protected, promoteCandidates,
    supersession, or largeFiles buckets. Those require judgment and belong to
    the scratchpad-cleanup skill's report.

    Scratchpad is not a git repo, so quarantine is the only undo that exists.
    Every batch writes a manifest.json recording original paths.

.EXAMPLE
    .\apply.ps1                                  # dry run, all safe modes
    .\apply.ps1 -Execute
    .\apply.ps1 -Mode Quarantine -Execute
    .\apply.ps1 -Mode Restore -RestoreDate 2026-09-14 -Execute
#>
[CmdletBinding()]
param(
    [string] $Root = 'D:\Repos\Scratchpad',

    [ValidateSet('All', 'AutoPurge', 'Quarantine', 'PurgeTrash', 'Restore')]
    [string] $Mode = 'All',

    # Nothing is written unless this is present. Default is a dry run on purpose.
    [switch] $Execute,

    [int] $QuarantineAfterDays = 45,
    [int] $TrashGraceDays = 30,

    # Safety valve: refuse to quarantine more than this many files in one run.
    # Guards against a threshold change silently sweeping the whole folder.
    [int] $MaxQuarantinePerRun = 60,

    [string] $RestoreDate
)

$ErrorActionPreference = 'Stop'
$Root = (Resolve-Path -LiteralPath $Root).Path
$trashRoot = Join-Path $Root '_trash'
$stamp = (Get-Date).ToString('yyyy-MM-dd')
$batchDir = Join-Path $trashRoot $stamp
$scanScript = Join-Path $PSScriptRoot 'scan.ps1'
if (-not (Test-Path -LiteralPath $scanScript)) { throw "scan.ps1 not found next to apply.ps1 ($scanScript)" }

$actions = [System.Collections.ArrayList]::new()
function Add-Action($kind, $from, $to, $note) {
    [void]$actions.Add([PSCustomObject]@{ kind = $kind; from = $from; to = $to; note = $note })
}

# --- Restore is standalone; it does not need a scan ---------------------------
if ($Mode -eq 'Restore') {
    if (-not $RestoreDate) { throw 'Restore requires -RestoreDate yyyy-MM-dd.' }
    $src = Join-Path $trashRoot $RestoreDate
    if (-not (Test-Path -LiteralPath $src)) { throw "No quarantine batch at $src" }
    $manifestPath = Join-Path $src 'manifest.json'
    if (-not (Test-Path -LiteralPath $manifestPath)) { throw "Batch has no manifest.json; refusing to guess original paths." }

    $manifest = Get-Content -LiteralPath $manifestPath -Raw | ConvertFrom-Json
    foreach ($item in $manifest.items) {
        $from = Join-Path $src $item.rel
        $to = Join-Path $Root $item.rel
        if (-not (Test-Path -LiteralPath $from)) { Add-Action 'restore-skip' $from $to 'missing in batch'; continue }
        if (Test-Path -LiteralPath $to) { Add-Action 'restore-skip' $from $to 'destination already exists'; continue }
        Add-Action 'restore' $from $to ''
        if ($Execute) {
            $parent = Split-Path -Parent $to
            if (-not (Test-Path -LiteralPath $parent)) { New-Item -ItemType Directory -Path $parent -Force | Out-Null }
            Move-Item -LiteralPath $from -Destination $to
        }
    }
    $actions | Format-Table -AutoSize
    if (-not $Execute) { Write-Host 'DRY RUN - nothing moved. Re-run with -Execute.' -ForegroundColor Yellow }
    return
}

# --- everything else is scan-driven -------------------------------------------
$scanRaw = & powershell.exe -NoProfile -ExecutionPolicy Bypass -File $scanScript -Root $Root -QuarantineAfterDays $QuarantineAfterDays -TrashGraceDays $TrashGraceDays
$scan = ($scanRaw -join "`n") | ConvertFrom-Json

if ($Mode -in 'All', 'AutoPurge') {
    foreach ($e in @($scan.buckets.autoPurgeFiles)) {
        $p = Join-Path $Root $e.rel
        Add-Action 'delete-file' $p '' $e.reason
        if ($Execute -and (Test-Path -LiteralPath $p)) { Remove-Item -LiteralPath $p -Force }
    }
    # Deepest-first so nested empties collapse correctly.
    foreach ($e in (@($scan.buckets.emptyDirs) | Sort-Object { ($_.rel -split '\\').Count } -Descending)) {
        $p = Join-Path $Root $e.rel
        Add-Action 'delete-dir' $p '' $e.reason
        if ($Execute -and (Test-Path -LiteralPath $p)) {
            # Re-check emptiness at execution time; scan data may be seconds stale.
            if (-not (Get-ChildItem -LiteralPath $p -Recurse -Force -ErrorAction SilentlyContinue | Select-Object -First 1)) {
                Remove-Item -LiteralPath $p -Force
            }
        }
    }
}

if ($Mode -in 'All', 'Quarantine') {
    $q = @($scan.buckets.quarantine)
    if ($q.Count -gt $MaxQuarantinePerRun) {
        throw ("Refusing to quarantine {0} files in one run (cap {1}). This usually means QuarantineAfterDays was lowered. Review with scan.ps1 -ReportOnlyAges, then raise -MaxQuarantinePerRun deliberately." -f $q.Count, $MaxQuarantinePerRun)
    }
    $manifestItems = [System.Collections.ArrayList]::new()
    foreach ($e in $q) {
        $from = Join-Path $Root $e.rel
        $to = Join-Path $batchDir $e.rel
        Add-Action 'quarantine' $from $to $e.reason
        [void]$manifestItems.Add([PSCustomObject]@{ rel = $e.rel; ageDays = $e.ageDays; kb = $e.kb; reason = $e.reason })
        if ($Execute -and (Test-Path -LiteralPath $from)) {
            $parent = Split-Path -Parent $to
            if (-not (Test-Path -LiteralPath $parent)) { New-Item -ItemType Directory -Path $parent -Force | Out-Null }
            Move-Item -LiteralPath $from -Destination $to -Force
        }
    }
    if ($Execute -and $manifestItems.Count -gt 0) {
        if (-not (Test-Path -LiteralPath $batchDir)) { New-Item -ItemType Directory -Path $batchDir -Force | Out-Null }
        [PSCustomObject]@{
            batch          = $stamp
            createdAt      = (Get-Date).ToString('o')
            root           = $Root
            purgeEligibleOn = (Get-Date).AddDays($TrashGraceDays).ToString('yyyy-MM-dd')
            items          = @($manifestItems)
        } | ConvertTo-Json -Depth 6 | Set-Content -LiteralPath (Join-Path $batchDir 'manifest.json') -Encoding UTF8
    }
}

if ($Mode -in 'All', 'PurgeTrash') {
    foreach ($e in @($scan.buckets.trashExpired)) {
        $p = Join-Path $Root $e.rel
        Add-Action 'purge-trash' $p '' ("{0}d old, grace {1}d, {2} files" -f $e.ageDays, $TrashGraceDays, $e.files)
        if ($Execute -and (Test-Path -LiteralPath $p)) { Remove-Item -LiteralPath $p -Recurse -Force }
    }
}

if ($actions.Count -eq 0) {
    Write-Host 'Nothing to do.' -ForegroundColor Green
}
else {
    $actions | Group-Object kind | Sort-Object Name | ForEach-Object { '{0,-14} {1}' -f $_.Name, $_.Count }
    Write-Host ''
    $actions | Format-Table -AutoSize kind, from, note
}
if (-not $Execute) { Write-Host 'DRY RUN - nothing changed. Re-run with -Execute.' -ForegroundColor Yellow }