<#
  play-mr.ps1 - replay a MechWarrior4 / FireStorm mission-review (.mr) file IN-ENGINE,
  using the game's built-in -mrtest developer hook.

  How the game's replay works (reverse-engineered from MW4Application.cpp / mreplay2.cpp):
    * MW4.exe parses "-mrtest" -> g_bMRTest = true.
    * With -mrtest set, when you START A SINGLE-PLAYER (Instant Action) game from the menu,
      the app does NOT start a live match -- it calls CMRPFull::LoadDefaultMR() then DoReplay(),
      which spins up a local loopback "server", feeds the recorded packets back through the
      net-message handlers, and reconstructs the whole match in full 3D.
    * LoadDefaultMR() opens a HARD-CODED path (drive "c:" is baked in):
          C:\mw4files\00000000-0000-0000-0000-000000000000.mr     (the GUID_NULL name)
      So to replay any .mr we just stage it there, then launch with -mrtest.

  This launcher: validates the .mr, stages it to that path (backing up any existing one),
  applies the Win11 DirectDraw compat shim to the exe, and launches MW4.exe -mrtest.

  REQUIREMENTS / CAVEATS
    * Use a game build whose MW4.exe supports -mrtest (our rebuilt rel.bin\MW4.exe does;
      the string "-mrtest" + g_bMRTest are present in MW4.map). Retail Mektek builds may not.
    * CONTENT MUST MATCH THE RECORDING. DoReplay rebuilds the match from create-messages that
      reference content by resource id + content version (63). Replay a FireStorm .mr only on
      the same FireStorm build/content it was recorded on, or it will desync / STOP.
    * The .mr default path is on C: regardless of where the game is installed (drive is hard-coded).

  USAGE
    powershell -ExecutionPolicy Bypass -File play-mr.ps1 -MrFile "match.mr"
    powershell -ExecutionPolicy Bypass -File play-mr.ps1 -MrFile "match.mr" -GameDir "D:\Games\FireStorm"
  Then in the game: Main Menu -> Instant Action -> configure -> Launch.  The replay starts
  instead of a live match. (No auto-start switch exists, so that one click is required.)
  -window -dragon -nomovie
#>
[CmdletBinding()]
param(
    [Parameter(Mandatory=$true)] [string]$MrFile,
    [string]$GameDir = "C:\VWE\firestorm\MW4",          # point this at your game install on another system
    [string]$Exe     = "MW4.exe",
    [string]$ExtraArgs = "-window -dragon -nomovie",                    # e.g. "-window -nomovie"
    [switch]$NoShim,                           # skip the DirectDraw AppCompat shim
    [switch]$KeepStaged                        # don't restore the previous default .mr afterwards
)
$ErrorActionPreference = "Stop"

# --- validate inputs ---------------------------------------------------------
if (-not (Test-Path -LiteralPath $MrFile)) { throw "Mission-review file not found: $MrFile" }
$MrFile = (Resolve-Path -LiteralPath $MrFile).Path
$exePath = Join-Path $GameDir $Exe
if (-not (Test-Path -LiteralPath $exePath)) { throw "Game exe not found: $exePath  (pass -GameDir <install folder>)" }

# magic check: mreplay2 .mr starts with DWORD 0xAB9A655F (LE: 5F 65 9A AB); also accept old variants
$sig = [System.IO.File]::ReadAllBytes($MrFile)[0..3]
$magic = '{0:X2}{1:X2}{2:X2}{3:X2}' -f $sig[3],$sig[2],$sig[1],$sig[0]
if ($magic -notin @('AB9A655F','AB9A654F','AB9A655E')) {
    Write-Host "WARNING: '$MrFile' doesn't start with the mreplay2 magic (got 0x$magic)." -ForegroundColor Yellow
    Write-Host "         It may be a top-down 'lastgame.mr' MissionReview log, not a DoReplay file." -ForegroundColor Yellow
}

# --- stage to the hard-coded default path ------------------------------------
$mrDir   = "C:\mw4files"
$target  = Join-Path $mrDir "00000000-0000-0000-0000-000000000000.mr"
if (-not (Test-Path $mrDir)) { New-Item -ItemType Directory -Path $mrDir -Force | Out-Null }

$backup = $null
if ((Test-Path -LiteralPath $target) -and -not $KeepStaged) {
    $backup = "$target.prev"
    Move-Item -LiteralPath $target -Destination $backup -Force
    Write-Host "  (backed up existing default .mr -> $backup)"
}
Copy-Item -LiteralPath $MrFile -Destination $target -Force
Write-Host "Staged replay:" -ForegroundColor Cyan
Write-Host "  source : $MrFile"
Write-Host "  -> $target"

# --- Win11 DirectDraw 16-bit compat shim on the exe path ---------------------
if (-not $NoShim) {
    $layers = "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers"
    if (-not (Test-Path $layers)) { New-Item -Path $layers -Force | Out-Null }
    Set-ItemProperty -Path $layers -Name $exePath -Value "DWM8And16BitMitigation HIGHDPIAWARE" -Type String
    Write-Host "  (applied DirectDraw compat shim to $exePath)"
}

# --- launch ------------------------------------------------------------------
$argList = "-mrtest"
if ($ExtraArgs.Trim()) { $argList = "$argList $($ExtraArgs.Trim())" }
Write-Host "`nLaunching: $Exe $argList   (cwd: $GameDir)" -ForegroundColor Green
Write-Host "==> In the game: Main Menu -> INSTANT ACTION -> Launch.  The replay starts instead of a live match." -ForegroundColor Green
Write-Host "    (ESC / quit the match to end the replay.)`n"

$proc = Start-Process -FilePath $exePath -ArgumentList $argList -WorkingDirectory $GameDir -PassThru
Write-Host "MW4.exe started (PID $($proc.Id))."

if ($backup -and -not $KeepStaged) {
    Write-Host "`nWhen you're done, restore the previous default .mr with:"
    Write-Host "    Move-Item -Force '$backup' '$target'"
}