param(
  [switch]$Yes
)

$ErrorActionPreference = 'Stop'

$codexDir = if ($env:CODEX_HOME) { $env:CODEX_HOME } else { Join-Path $HOME '.codex' }
$configFile = Join-Path $codexDir 'config.toml'
$model = if ($env:CODEX_MODEL) { $env:CODEX_MODEL } else { 'gpt-5.6-sol' }

if ($model -notmatch '^[A-Za-z0-9._-]+$') {
  throw 'CODEX_MODEL contains unsupported characters.'
}

Write-Host 'Codex GPT-5.6 200K auto-compaction setup'
Write-Host ''
Write-Host "Config file: $configFile"
Write-Host "  model = `"$model`""
Write-Host '  model_context_window = 272000'
Write-Host '  model_auto_compact_token_limit = 200000'
Write-Host '  model_auto_compact_token_limit_scope = "total"'
Write-Host ''
Write-Host 'Existing providers, API key references, and custom settings will be preserved.'
Write-Host 'Do not continue if your job intentionally needs more than 272K active context tokens.'

if (-not $Yes -and $env:CODEX_GPT56_200K_YES -ne '1') {
  $answer = Read-Host 'Apply these settings? [Y/n]'
  if ($answer -and $answer -notmatch '^(y|yes)$') {
    Write-Host 'Cancelled.'
    exit 0
  }
}

New-Item -ItemType Directory -Force -Path $codexDir | Out-Null
if (-not (Test-Path $configFile)) {
  New-Item -ItemType File -Path $configFile | Out-Null
}

$timestamp = Get-Date -Format 'yyyyMMddHHmmss'
$backupBase = "$configFile.bak.$timestamp"
$backupFile = $backupBase
$backupIndex = 1
while (Test-Path $backupFile) {
  $backupFile = "$backupBase.$backupIndex"
  $backupIndex++
}
Copy-Item -Force $configFile "$configFile.bak"
Copy-Item -Force $configFile $backupFile

$settings = [ordered]@{
  model = "`"$model`""
  model_context_window = '272000'
  model_auto_compact_token_limit = '200000'
  model_auto_compact_token_limit_scope = '"total"'
}

$lines = [System.IO.File]::ReadAllLines($configFile)
$output = [System.Collections.Generic.List[string]]::new()
$seen = @{}
$inRoot = $true

function Add-MissingSettings {
  $added = $false
  foreach ($key in $settings.Keys) {
    if (-not $seen.ContainsKey($key)) {
      $output.Add("$key = $($settings[$key])")
      $seen[$key] = $true
      $added = $true
    }
  }
  if ($added) {
    $output.Add('')
  }
}

foreach ($line in $lines) {
  if ($inRoot -and $line -match '^\s*\[') {
    Add-MissingSettings
    $inRoot = $false
  }

  $matched = $false
  if ($inRoot) {
    foreach ($key in $settings.Keys) {
      if ($line -match ('^\s*' + [regex]::Escape($key) + '\s*=')) {
        if (-not $seen.ContainsKey($key)) {
          $output.Add("$key = $($settings[$key])")
        }
        $seen[$key] = $true
        $matched = $true
        break
      }
    }
  }

  if (-not $matched) {
    $output.Add($line)
  }
}

if ($inRoot) {
  Add-MissingSettings
}

$tempFile = Join-Path $codexDir ".config.toml.gpt56-200k.$PID"
$utf8NoBom = [System.Text.UTF8Encoding]::new($false)

try {
  [System.IO.File]::WriteAllLines($tempFile, $output, $utf8NoBom)
  Move-Item -Force $tempFile $configFile
} catch {
  if (Test-Path $tempFile) {
    Remove-Item -Force $tempFile
  }
  Copy-Item -Force $backupFile $configFile
  throw
}

Write-Host ''
Write-Host "Updated: $configFile"
Write-Host "Backup: $backupFile"
Write-Host 'Fully quit and restart Codex to load the new settings.'