metro-line-inspector.ps1

# Metro Bundle Line Inspector
# Usage: .\metro-line-inspector.ps1 <line_or_offset> [port] [context]
# Example: .\metro-line-inspector.ps1 2141134
# Example: .\metro-line-inspector.ps1 2141134 8081 15

param(
    [Parameter(Mandatory=$true, Position=0)]
    [int]$Position,

    [Parameter(Position=1)]
    [int]$Port = 8081,

    [Parameter(Position=2)]
    [int]$Context = 10
)

$bundleFile = "$env:TEMP\metro-bundle-$Port.js"

# Ask user: download fresh or use cached?
if (Test-Path $bundleFile) {
    $cachedSize = [math]::Round((Get-Item $bundleFile).Length / 1MB, 1)
    $choice = Read-Host "Cached bundle found (${cachedSize}MB). Download fresh or use cached? [D]ownload / [C]ached (default: C)"
    if ($choice -match '^[Dd]') {
        $download = $true
    } else {
        $download = $false
        Write-Host "Using cached bundle." -ForegroundColor DarkGray
    }
} else {
    $download = $true
}

if ($download) {
    $url = "http://localhost:$Port/col-mobile-expo/index.bundle?platform=android&dev=true&minify=false"
    Write-Host "Fetching bundle from $url ..." -ForegroundColor Cyan
    Write-Host "(this may take a while for large bundles)" -ForegroundColor DarkGray
    Invoke-WebRequest -Uri $url -OutFile $bundleFile -UseBasicParsing

    if (-not (Test-Path $bundleFile) -or (Get-Item $bundleFile).Length -lt 1000) {
        Write-Host "ERROR: Failed to download bundle. Is Metro running on port $Port?" -ForegroundColor Red
        exit 1
    }
    $size = [math]::Round((Get-Item $bundleFile).Length / 1MB, 1)
    Write-Host "Downloaded: ${size}MB" -ForegroundColor Green
}

# Get bundle stats
$totalLines = (Get-Content $bundleFile | Measure-Object -Line).Lines
$totalChars = (Get-Item $bundleFile).Length
Write-Host "Bundle: $totalLines lines, $totalChars chars ($([math]::Round($totalChars / 1MB, 1))MB)" -ForegroundColor Cyan
Write-Host ""

# === ATTEMPT 1: Try as line number ===
$lineWorked = $false
if ($Position -le $totalLines) {
    Write-Host "=== LINE MODE (line $Position) ===" -ForegroundColor Yellow
    $start = [Math]::Max(1, $Position - $Context)
    $count = $Context * 2 + 1

    Get-Content $bundleFile |
        Select-Object -Skip ($start - 1) -First $count |
        ForEach-Object -Begin { $i = $start } -Process {
            $prefix = if ($i -eq $Position) { ">>>" } else { "   " }
            $color = if ($i -eq $Position) { "Yellow" } else { "Gray" }
            Write-Host ("{0} {1,7}: {2}" -f $prefix, $i, ($_.Substring(0, [Math]::Min($_.Length, 200)))) -ForegroundColor $color
            if ($_.Length -gt 200) { Write-Host "         ... (line truncated, $($_.Length) chars total)" -ForegroundColor DarkGray }
            $i++
        }
    $lineWorked = $true
    Write-Host ""
} else {
    Write-Host "Line $Position exceeds bundle ($totalLines lines) - skipping line mode." -ForegroundColor DarkYellow
    Write-Host ""
}

# === ATTEMPT 2: Try as character offset ===
Write-Host "=== OFFSET MODE (char offset $Position) ===" -ForegroundColor Yellow

$content = [System.IO.File]::ReadAllText($bundleFile)

if ($Position -ge $content.Length) {
    Write-Host "Offset $Position also exceeds file length ($($content.Length) chars)." -ForegroundColor Red
    Write-Host ""
    Write-Host "The Hermes error position doesn't match the downloaded bundle." -ForegroundColor Red
    Write-Host "Possible causes:" -ForegroundColor Yellow
    Write-Host "  - Metro cache is stale (try: yarn expo start --clear)" -ForegroundColor Gray
    Write-Host "  - Device loaded an old pre-bundled JS from the APK" -ForegroundColor Gray
    Write-Host "  - Line endings differ (CRLF vs LF)" -ForegroundColor Gray
    exit 1
}

# Specific bytes: +/- 30 chars
$specStart = [Math]::Max(0, $Position - 30)
$specLen = [Math]::Min(61, $content.Length - $specStart)
$specific = $content.Substring($specStart, $specLen)

Write-Host ""
Write-Host "--- Specific bytes (+/- 30 chars around offset $Position) ---" -ForegroundColor Magenta
Write-Host $specific -ForegroundColor White
Write-Host ""

# Wide context: +/- 1000 chars
$wideStart = [Math]::Max(0, $Position - 1000)
$wideLen = [Math]::Min(2001, $content.Length - $wideStart)
$wide = $content.Substring($wideStart, $wideLen)

Write-Host "--- Wide context (+/- 1000 chars around offset $Position) ---" -ForegroundColor Magenta
Write-Host $wide -ForegroundColor Gray
Write-Host ""

# Try to find the module name from __d( wrapper
$searchStart = [Math]::Max(0, $Position - 5000)
$searchLen = [Math]::Min(5000, $Position - $searchStart)
$before = $content.Substring($searchStart, $searchLen)
$moduleMatch = [regex]::Match($before, '__d\(function.*?"([^"]+)"', 'RightToLeft')
if ($moduleMatch.Success) {
    Write-Host "Likely module: $($moduleMatch.Groups[1].Value)" -ForegroundColor Green
}

Write-Host ""
Write-Host "Bundle saved at: $bundleFile" -ForegroundColor DarkGray