param(
  [Parameter(Mandatory = $true)][string]$BinaryPath,
  [Parameter(Mandatory = $true)][string]$ExpectedSha256,
  [Parameter(Mandatory = $true)][string]$ExpectedVersion,
  [Parameter(Mandatory = $true)][string]$CurrentExecutable,
  [Parameter(Mandatory = $true)][string]$Portable,
  [Parameter(Mandatory = $true)][int]$ParentPid,
  [Parameter(Mandatory = $true)][string]$LogPath,
  [Parameter(Mandatory = $true)][string]$StatusPath,
  [Parameter(Mandatory = $true)][string]$UpdateId,
  [switch]$HandshakeOnly,
  [switch]$VerifyOnly
)

$ErrorActionPreference = "Stop"
$isPortable = $Portable -eq "True"

function Write-UpdateState {
  param([string]$State, [string]$Message = "", [bool]$RestartLaunched = $false)
  $payload = [ordered]@{
    schemaVersion = 1
    updateId = $UpdateId
    state = $State
    expectedVersion = $ExpectedVersion
    installedVersion = if ($State -eq "success") { $ExpectedVersion } else { $null }
    message = $Message
    restartLaunched = $RestartLaunched
    logPath = $LogPath
    updatedAt = [DateTime]::UtcNow.ToString("o")
  }
  if ($State -in @("success", "failed", "rolled-back")) { $payload.completedAt = [DateTime]::UtcNow.ToString("o") }
  $directory = Split-Path -Parent $StatusPath
  if ($directory) { New-Item -ItemType Directory -Force -Path $directory | Out-Null }
  $temporary = "$StatusPath.$PID.tmp"
  $backup = "$StatusPath.$PID.bak"
  $json = $payload | ConvertTo-Json -Depth 4
  $utf8NoBom = New-Object System.Text.UTF8Encoding($false)
  [IO.File]::WriteAllText($temporary, $json, $utf8NoBom)
  try {
    if ([IO.File]::Exists($StatusPath)) {
      [IO.File]::Replace($temporary, $StatusPath, $backup)
      [IO.File]::Delete($backup)
    } else {
      [IO.File]::Move($temporary, $StatusPath)
    }
  } catch {
    [IO.File]::Copy($temporary, $StatusPath, $true)
    [IO.File]::Delete($temporary)
    if ([IO.File]::Exists($backup)) { [IO.File]::Delete($backup) }
  }
}
function Write-Log([string]$Message) {
  "{0} {1}" -f [DateTime]::UtcNow.ToString("o"), $Message | Add-Content -LiteralPath $LogPath -Encoding UTF8
}
function Get-Sha256([string]$Path) {
  $stream = [IO.File]::OpenRead($Path)
  $algorithm = [Security.Cryptography.SHA256]::Create()
  try {
    return ([BitConverter]::ToString($algorithm.ComputeHash($stream))).Replace("-", "").ToLowerInvariant()
  } finally {
    $algorithm.Dispose()
    $stream.Dispose()
  }
}

function Start-ForgeFlowAndVerify([string]$Executable) {
  $process = Start-Process -FilePath $Executable -WorkingDirectory (Split-Path -Parent $Executable) -PassThru
  Start-Sleep -Milliseconds 1500
  if (-not $process -or $process.HasExited) { throw "ForgeFlow restart process exited before the application could stay running." }
  return $process
}

try {
  Write-Log "Validating ForgeFlow $ExpectedVersion binary update."
  if ($HandshakeOnly) {
    Write-UpdateState -State "started" -Message "Binary updater owns the update request."
    Write-Log "Handshake-only verification completed successfully."
    exit 0
  }
  $actualSha256 = Get-Sha256 -Path $BinaryPath
  if ($actualSha256 -ne $ExpectedSha256.ToLowerInvariant()) { throw "Binary update SHA-256 verification failed." }
  if (-not (Test-Path -LiteralPath $CurrentExecutable -PathType Leaf)) { throw "Current ForgeFlow executable was not found." }
  Write-UpdateState -State "started" -Message "Binary preflight passed; updater owns the update request."
  if ($VerifyOnly) {
    Write-Log "Verification-only SHA-256 check completed successfully."
    exit 0
  }

  Write-UpdateState -State "waiting-for-exit" -Message "Waiting for ForgeFlow to close."
  try { Wait-Process -Id $ParentPid -Timeout 60 -ErrorAction Stop } catch {
    if (Get-Process -Id $ParentPid -ErrorAction SilentlyContinue) { throw "ForgeFlow did not close within 60 seconds." }
  }

  if ($isPortable) {
    Write-UpdateState -State "applying" -Message "Replacing the portable executable."
    $backupPath = "$CurrentExecutable.previous"
    Copy-Item -LiteralPath $CurrentExecutable -Destination $backupPath -Force
    try {
      Copy-Item -LiteralPath $BinaryPath -Destination $CurrentExecutable -Force
    } catch {
      $copyFailure = $_.Exception.Message
      try {
        Copy-Item -LiteralPath $backupPath -Destination $CurrentExecutable -Force
        $rollbackRestart = Start-ForgeFlowAndVerify -Executable $CurrentExecutable
        Write-Log "Portable replacement failed; previous ForgeFlow restored and restarted as PID $($rollbackRestart.Id)."
        Write-UpdateState -State "rolled-back" -Message $copyFailure -RestartLaunched $true
      } catch {
        Write-UpdateState -State "failed" -Message "$copyFailure Rollback also failed: $($_.Exception.Message)" -RestartLaunched $false
      }
      throw $copyFailure
    }
  } else {
    Write-UpdateState -State "applying" -Message "Running the verified ForgeFlow installer."
    $installer = Start-Process -FilePath $BinaryPath -ArgumentList "/S" -PassThru -Wait -WindowStyle Hidden
    if ($installer.ExitCode -ne 0) { throw "ForgeFlow installer exited with code $($installer.ExitCode)." }
  }

  try {
    $restart = Start-ForgeFlowAndVerify -Executable $CurrentExecutable
    Write-Log "ForgeFlow $ExpectedVersion installed; verified restart PID $($restart.Id)."
    Write-UpdateState -State "success" -Message "ForgeFlow $ExpectedVersion installed successfully." -RestartLaunched $true
  } catch {
    $restartFailure = $_.Exception.Message
    if ($isPortable -and $backupPath -and (Test-Path -LiteralPath $backupPath -PathType Leaf)) {
      Write-Log "Updated portable executable failed its restart probe; restoring the previous executable."
      try {
        Copy-Item -LiteralPath $backupPath -Destination $CurrentExecutable -Force
        $rollbackRestart = Start-ForgeFlowAndVerify -Executable $CurrentExecutable
        Write-Log "Previous ForgeFlow restored and restarted as PID $($rollbackRestart.Id)."
        Write-UpdateState -State "rolled-back" -Message $restartFailure -RestartLaunched $true
      } catch {
        Write-UpdateState -State "failed" -Message "$restartFailure Rollback also failed: $($_.Exception.Message)" -RestartLaunched $false
      }
      exit 1
    }
    Write-Log "ForgeFlow $ExpectedVersion installed, but automatic restart failed: $restartFailure"
    Write-UpdateState -State "success" -Message "ForgeFlow $ExpectedVersion installed successfully, but must be started manually." -RestartLaunched $false
  }
} catch {
  Write-Log $_.Exception.Message
  $current = $null
  try { $current = Get-Content -LiteralPath $StatusPath -Raw | ConvertFrom-Json } catch {}
  if ($current.state -notin @("rolled-back", "failed")) { Write-UpdateState -State "failed" -Message $_.Exception.Message }
  exit 1
}