param(
    [switch]$DryRun
)

$ErrorActionPreference = "Continue"

$script:RepoRoot = [System.IO.Path]::GetFullPath((Join-Path $PSScriptRoot ".."))
$script:LogPath = Join-Path $script:RepoRoot ".git/graphify-hook.log"

function Write-HookLog {
    param([string]$Message)

    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    $line = "[$timestamp] $Message"
    Write-Host $line
    try {
        Add-Content -Path $script:LogPath -Value $line -Encoding UTF8
    }
    catch {
        Write-Host "[graphify hook] Unable to write log: $($_.Exception.Message)"
    }
}

function Test-GraphifyPython {
    param([string]$PythonPath)

    if ([string]::IsNullOrWhiteSpace($PythonPath)) {
        return $false
    }

    try {
        & $PythonPath -c "import graphify" *> $null
        return ($LASTEXITCODE -eq 0)
    }
    catch {
        return $false
    }
}

function Get-GraphifyPython {
    $candidates = @()

    foreach ($relative in @("Unity/graphify-out/.graphify_python", "graphify-out/.graphify_python")) {
        $path = Join-Path $script:RepoRoot $relative
        if (Test-Path $path) {
            $value = (Get-Content -Raw -Path $path -Encoding UTF8).Trim()
            if ($value) {
                $candidates += $value
            }
        }
    }

    foreach ($command in @("python", "py")) {
        $cmd = Get-Command $command -ErrorAction SilentlyContinue
        if ($cmd) {
            $candidates += $cmd.Source
        }
    }

    foreach ($candidate in $candidates | Select-Object -Unique) {
        if (Test-GraphifyPython $candidate) {
            return $candidate
        }
    }

    return $null
}

function Get-ChangedFiles {
    $fromEnv = $env:GRAPHIFY_CHANGED
    if (-not [string]::IsNullOrWhiteSpace($fromEnv)) {
        return $fromEnv -split "`r?`n" | Where-Object { -not [string]::IsNullOrWhiteSpace($_) }
    }

    $git = Get-Command git -ErrorAction SilentlyContinue
    if (-not $git) {
        return @()
    }

    Push-Location $script:RepoRoot
    try {
        $files = & git diff --name-only HEAD~1 HEAD 2>$null
        if (-not $files) {
            $files = & git diff --name-only HEAD 2>$null
        }
        return @($files | Where-Object { -not [string]::IsNullOrWhiteSpace($_) })
    }
    finally {
        Pop-Location
    }
}

function Invoke-GraphifyRebuild {
    param(
        [string]$Label,
        [string]$RelativePath,
        [string]$PythonPath
    )

    $target = Join-Path $script:RepoRoot $RelativePath
    $graphPath = Join-Path $target "graphify-out/graph.json"

    if (-not (Test-Path $graphPath)) {
        Write-HookLog "Skipping ${Label}: no graphify-out/graph.json found."
        return
    }

    if ($DryRun) {
        Write-HookLog "Dry run: would rebuild $Label graph at $target."
        return
    }

    Write-HookLog "Rebuilding $Label graph at $target."
    Push-Location $target
    try {
        & $PythonPath -c "from pathlib import Path; from graphify.watch import _rebuild_code; _rebuild_code(Path('.'))" *> $null
        if ($LASTEXITCODE -eq 0) {
            Write-HookLog "Rebuilt $Label graph."
        }
        else {
            Write-HookLog "Rebuild failed for $Label with exit code $LASTEXITCODE."
        }
    }
    catch {
        Write-HookLog "Rebuild failed for ${Label}: $($_.Exception.Message)"
    }
    finally {
        Pop-Location
    }
}

Set-Location $script:RepoRoot

$changedFiles = @(Get-ChangedFiles)
if ($changedFiles.Count -eq 0) {
    Write-HookLog "No changed files detected; nothing to rebuild."
    exit 0
}

$codeExtensions = @(
    ".cs", ".asmdef", ".shader", ".hlsl", ".cginc",
    ".py", ".js", ".ts", ".json", ".toml", ".yaml", ".yml"
)

$changedCode = @(
    $changedFiles | Where-Object {
        $ext = [System.IO.Path]::GetExtension($_).ToLowerInvariant()
        $codeExtensions -contains $ext
    }
)

if ($changedCode.Count -eq 0) {
    Write-HookLog "$($changedFiles.Count) changed file(s), but no code/config files for AST graph rebuild."
    exit 0
}

$python = Get-GraphifyPython
if (-not $python) {
    Write-HookLog "No Python interpreter with graphify installed was found."
    exit 0
}

Write-HookLog "$($changedCode.Count) code/config file(s) changed; using Python: $python"

$touchesUnity = @($changedCode | Where-Object { $_ -like "Unity/*" -or $_ -like "Unity\*" }).Count -gt 0

Invoke-GraphifyRebuild -Label "root" -RelativePath "." -PythonPath $python

if ($touchesUnity) {
    Invoke-GraphifyRebuild -Label "Unity" -RelativePath "Unity" -PythonPath $python
}
else {
    Write-HookLog "Skipping Unity graph: no Unity path changed."
}