$ErrorActionPreference = 'Stop'

$ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
$Root = Split-Path -Parent $ScriptDir
$SingBox = Join-Path $Root 'works/sing-box'
$PatchDir = Join-Path $Root 'works/patch'
$Core = Join-Path $Root 'works/core'

if (-not (Test-Path (Join-Path $SingBox '.git'))) {
    Write-Error 'works/sing-box not found. Run update first.'
    exit 1
}

if (-not (Test-Path $Core)) {
    Write-Error 'works/core not found. Run generate first.'
    exit 1
}

$IgnoreFile = Join-Path $Root 'works/ignore'
$IgnorePatterns = @()
if (Test-Path $IgnoreFile) {
    $IgnorePatterns = Get-Content $IgnoreFile | Where-Object { $_ -ne '' -and $_ -notmatch '^\s*#' }
}

function Test-Ignored {
    param([string]$RelPath)
    foreach ($pattern in $IgnorePatterns) {
        if ($pattern -match '/') {
            if ($RelPath -like $pattern) { return $true }
        } else {
            if ((Split-Path -Leaf $RelPath) -like $pattern) { return $true }
        }
    }
    return $false
}

Write-Host 'Clearing existing patches...'
if (Test-Path $PatchDir) { Remove-Item -Recurse -Force $PatchDir }
New-Item -ItemType Directory -Path $PatchDir -Force | Out-Null

Write-Host 'Generating patches for modified/new files...'
Get-ChildItem -Path $Core -Recurse -File | Where-Object {
    $_.FullName -notmatch [regex]::Escape((Join-Path $Core '.git'))
} | Sort-Object FullName | ForEach-Object {
    $rel = $_.FullName.Substring($Core.Length + 1) -replace '\\', '/'
    if (Test-Ignored $rel) { return }
    $srcFile = Join-Path $SingBox $rel
    $patchFile = Join-Path $PatchDir "$rel.patch"
    $patchFileDir = Split-Path -Parent $patchFile
    if (-not (Test-Path $patchFileDir)) { New-Item -ItemType Directory -Path $patchFileDir -Force | Out-Null }

    if (Test-Path $srcFile) {
        $srcHash = (Get-FileHash $srcFile -Algorithm MD5).Hash
        $dstHash = (Get-FileHash $_.FullName -Algorithm MD5).Hash
        if ($srcHash -ne $dstHash) {
            diff -u $srcFile $_.FullName | Out-File -FilePath $patchFile -Encoding utf8
            Write-Host "  Modified: $rel"
        }
    } else {
        diff -u /dev/null $_.FullName | Out-File -FilePath $patchFile -Encoding utf8
        Write-Host "  New: $rel"
    }
}

Write-Host 'Generating patches for deleted files...'
Get-ChildItem -Path $SingBox -Recurse -File | Where-Object {
    $_.FullName -notmatch [regex]::Escape((Join-Path $SingBox '.git'))
} | Sort-Object FullName | ForEach-Object {
    $rel = $_.FullName.Substring($SingBox.Length + 1) -replace '\\', '/'
    if (Test-Ignored $rel) { return }
    $dstFile = Join-Path $Core $rel
    $patchFile = Join-Path $PatchDir "$rel.patch"

    if (-not (Test-Path $dstFile)) {
        $patchFileDir = Split-Path -Parent $patchFile
        if (-not (Test-Path $patchFileDir)) { New-Item -ItemType Directory -Path $patchFileDir -Force | Out-Null }
        diff -u $_.FullName /dev/null | Out-File -FilePath $patchFile -Encoding utf8
        Write-Host "  Deleted: $rel"
    }
}

Write-Host 'Done.'