<#
.SYNOPSIS
    Campaign V self-differential pixel gate. Captures deterministic offline
    screenshots and optionally compares them against a baseline capture.

.DESCRIPTION
    Every Campaign V renderer-port slice must prove it changed no pixels. The
    connected lifecycle gate needs a live ACE server and the user's attention;
    this gate needs neither. The client is launched WITHOUT ACDREAM_LIVE, so it
    renders the world straight from the DATs, no session is created, and no ACE
    state can be disturbed.

    Coverage: terrain, terrain blending, scenery, static world meshes, sky and
    fog, and the full retained UI (vitals, spell bar, toolbar, chat, radar).
    It does NOT cover EnvCell interiors, particles, or the paperdoll viewport —
    those still need the connected route, so slices touching them (V4e, V4g)
    must additionally be gated by the user.

    Determinism levers: ACDREAM_DAY_GROUP pins the sky day-group so weather and
    lighting do not drift between runs, and a fixed warm-up lets streaming settle
    before the frame is captured.

.PARAMETER Out
    Directory to write this capture into. Created if absent, emptied if present.

.PARAMETER Baseline
    Optional. A directory from a previous capture. When supplied, every PNG is
    compared against its namesake and the script fails on any mismatch.

.PARAMETER WarmupMs
    Milliseconds to let the world stream and settle before capturing. Default
    12000, which reliably reaches a fully populated view on the reference machine.

.PARAMETER DayGroup
    Sky day-group index to pin. Default 0.

.PARAMETER Tolerance
    Per-channel absolute difference allowed. Default 2, matching the project's
    pinned screenshot rule.

.PARAMETER MaxDifferentFraction
    Fraction of differing pixels allowed. Default 0.001, likewise pinned.

.PARAMETER MaskTopPixels
    Height in pixels of the sky band excluded from comparison. Default 280.

    This is not a fudge factor. Two captures at the SAME commit were measured to
    differ in 0.29% of pixels, and the differences were confined to the top ~180
    rows: the sky legitimately animates (clouds scroll, the sun moves) and the
    Dereth clock advances with wall time, so the sky cannot be identical between
    two launches. Everything below the horizon — terrain, blending, scenery,
    static meshes, water, and the whole retained UI — was bit-stable. Masking the
    animated band is what makes the rest a strict identity check rather than
    forcing a loose tolerance that would hide real regressions everywhere else.

    Consequence: this gate does NOT cover sky rendering. Slice V4f must be gated
    by the user instead.

.PARAMETER SkipBuild
    Skip the Release build (use when the caller already built).

.EXAMPLE
    # Capture a baseline at the parent commit, then gate the slice:
    git stash
    tools/run-offline-pixel-gate.ps1 -Out artifacts/gate-base
    git stash pop
    tools/run-offline-pixel-gate.ps1 -Out artifacts/gate-head -Baseline artifacts/gate-base
#>
[CmdletBinding()]
param(
    [Parameter(Mandatory = $true)][string]$Out,
    [string]$Baseline,
    [int]$WarmupMs = 12000,
    [int]$DayGroup = 0,
    [int]$Tolerance = 2,
    [double]$MaxDifferentFraction = 0.001,
    [int]$MaskTopPixels = 280,
    [switch]$SkipBuild
)

$ErrorActionPreference = 'Stop'
$repo = Split-Path -Parent $PSScriptRoot
$exe = Join-Path $repo 'src\AcDream.App\bin\Release\net10.0\AcDream.App.exe'
$cli = Join-Path $repo 'src\AcDream.Cli\bin\Release\net10.0\AcDream.Cli.dll'

function Write-Step($message) { Write-Host "[pixel-gate] $message" }

# --- 1. Build -----------------------------------------------------------------
if (-not $SkipBuild) {
    Write-Step 'building Release'
    & dotnet build (Join-Path $repo 'AcDream.slnx') -c Release --nologo -v q | Out-Null
    if ($LASTEXITCODE -ne 0) { throw "Release build failed with exit code $LASTEXITCODE." }
}
if (-not (Test-Path $exe)) { throw "Client not found at $exe. Build Release first." }

# --- 2. Prepare the capture directory and probe script ------------------------
if (Test-Path $Out) { Remove-Item -Recurse -Force $Out }
New-Item -ItemType Directory -Force -Path $Out | Out-Null

$probe = Join-Path $Out 'offline.probe.txt'
# The script runner reads one command per line. A single settled capture is the
# whole gate: a second stop would need camera movement, which offline has no
# deterministic way to drive.
Set-Content -Encoding utf8 -Path $probe -Value @"
sleep $WarmupMs
screenshot world-offline 30000
sleep 500
"@

$log = Join-Path $Out 'client.log'

# --- 3. Launch offline --------------------------------------------------------
$previousLive = $env:ACDREAM_LIVE
Remove-Item Env:\ACDREAM_LIVE -ErrorAction SilentlyContinue
$env:ACDREAM_DAT_DIR = Join-Path $env:USERPROFILE "Documents\Asheron's Call"
$env:ACDREAM_NO_AUDIO = '1'
$env:ACDREAM_RETAIL_UI = '1'
$env:ACDREAM_DAY_GROUP = "$DayGroup"
$env:ACDREAM_UI_PROBE_SCRIPT = $probe
$env:ACDREAM_AUTOMATION_ARTIFACT_DIR = $Out

Write-Step "launching offline client (warmup ${WarmupMs}ms, day group $DayGroup)"
$proc = Start-Process -FilePath $exe -RedirectStandardOutput $log `
    -RedirectStandardError "$log.err" -PassThru -WindowStyle Minimized

try {
    $shots = Join-Path $Out 'screenshots'
    $deadline = (Get-Date).AddMilliseconds($WarmupMs + 60000)
    $captured = $false
    while ((Get-Date) -lt $deadline) {
        if ((Test-Path $shots) -and (Get-ChildItem $shots -Filter *.png -ErrorAction SilentlyContinue)) {
            $captured = $true
            break
        }
        if ($proc.HasExited) { break }
        Start-Sleep -Milliseconds 1000
    }

    if (-not $captured) {
        Write-Host (Get-Content $log -Tail 30 -ErrorAction SilentlyContinue)
        throw 'No screenshot was captured before the deadline.'
    }
    # Let the probe script finish its trailing sleep so the PNG is fully flushed.
    Start-Sleep -Milliseconds 1500
}
finally {
    # Graceful close: WM_CLOSE runs the shutdown path, so the ownership ledger
    # converges the way the lifecycle tests expect. No ACE session exists here,
    # but keeping the habit means this script is safe to point at a live run too.
    $app = Get-Process -Name AcDream.App -ErrorAction SilentlyContinue
    if ($app) {
        $app.CloseMainWindow() | Out-Null
        if (-not $app.WaitForExit(10000)) {
            Write-Step 'WM_CLOSE timed out; forcing'
            $app | Stop-Process -Force
        }
    }
    if ($previousLive) { $env:ACDREAM_LIVE = $previousLive }
}

$captures = Get-ChildItem (Join-Path $Out 'screenshots') -Filter *.png
Write-Step "captured $($captures.Count) screenshot(s) into $Out"

# The offline window is minimised but still focusable, so a stray scroll or key
# press from whoever is at the keyboard can move the camera mid-capture. That
# produces two screenshots of the same scene from different camera positions —
# a huge, entirely spurious pixel difference. This actually happened during
# slice V4b. Detect it and fail loudly rather than let a comparison be
# interpreted as a rendering regression.
$cameraInput = Select-String -Path $log -Pattern 'ScrollUp|ScrollDown|ZoomIn|ZoomOut|CameraZoom' `
    -CaseSensitive -ErrorAction SilentlyContinue
if ($cameraInput) {
    Write-Host ''
    Write-Host '[pixel-gate] ABORTED: camera-affecting input reached the capture window.' -ForegroundColor Red
    Write-Host '            The capture is not comparable. Re-run without touching the machine.' -ForegroundColor Red
    $cameraInput | Select-Object -First 5 | ForEach-Object { Write-Host "  $($_.Line)" -ForegroundColor Red }
    exit 2
}

# --- 4. Compare against the baseline -----------------------------------------
if (-not $Baseline) {
    Write-Step 'no baseline supplied; capture only'
    exit 0
}

if (-not (Test-Path $cli)) { throw "AcDream.Cli not found at $cli." }

# Build the sky mask. The comparer skips any pixel whose mask alpha is non-zero,
# so the band we exclude is opaque and everything compared is transparent.
$maskPath = $null
if ($MaskTopPixels -gt 0) {
    Add-Type -AssemblyName System.Drawing
    $probeImage = [System.Drawing.Bitmap]::FromFile($captures[0].FullName)
    $width = $probeImage.Width
    $height = $probeImage.Height
    $probeImage.Dispose()

    $mask = New-Object System.Drawing.Bitmap($width, $height, [System.Drawing.Imaging.PixelFormat]::Format32bppArgb)
    $graphics = [System.Drawing.Graphics]::FromImage($mask)
    $graphics.Clear([System.Drawing.Color]::FromArgb(0, 0, 0, 0))
    $opaque = New-Object System.Drawing.SolidBrush ([System.Drawing.Color]::FromArgb(255, 255, 0, 255))
    $graphics.FillRectangle($opaque, 0, 0, $width, [Math]::Min($MaskTopPixels, $height))
    $graphics.Dispose()
    $opaque.Dispose()

    $maskPath = Join-Path $Out 'sky-mask.png'
    $mask.Save($maskPath, [System.Drawing.Imaging.ImageFormat]::Png)
    $mask.Dispose()
    Write-Step "masking the top $MaskTopPixels rows (animated sky)"
}

$failed = @()
foreach ($shot in $captures) {
    $expected = Join-Path $Baseline "screenshots\$($shot.Name)"
    if (-not (Test-Path $expected)) {
        $failed += "$($shot.Name): no baseline counterpart"
        continue
    }

    $report = Join-Path $Out "compare-$($shot.BaseName).json"
    if ($maskPath) {
        & dotnet $cli compare-screenshots $expected $shot.FullName $report $Tolerance $MaxDifferentFraction $maskPath | Out-Null
    }
    else {
        & dotnet $cli compare-screenshots $expected $shot.FullName $report $Tolerance $MaxDifferentFraction | Out-Null
    }
    $verdict = Get-Content $report -Raw | ConvertFrom-Json

    $fraction = $verdict.differentPixelFraction
    if ($null -eq $fraction) { $fraction = $verdict.DifferentPixelFraction }
    $passed = $verdict.passed
    if ($null -eq $passed) { $passed = $verdict.Passed }

    if ($passed) {
        Write-Step "PASS $($shot.Name) (differing fraction $fraction)"
    }
    else {
        $failed += "$($shot.Name): differing fraction $fraction exceeds $MaxDifferentFraction (report: $report)"
    }
}

if ($failed.Count -gt 0) {
    Write-Host ''
    Write-Host '[pixel-gate] FAILED:' -ForegroundColor Red
    $failed | ForEach-Object { Write-Host "  - $_" -ForegroundColor Red }
    exit 1
}

Write-Step 'all screenshots match the baseline'
exit 0