<#
.SYNOPSIS
  Download YouTube video(s) at highest quality as merged MP4.
.DESCRIPTION
  Wraps yt-dlp with the settings needed for modern YouTube:
   - JS runtime (bun preferred; deno auto-downloaded to .\bin if missing)
   - yt-dlp (auto-downloaded to .\bin if missing)
   - ffmpeg (must be on PATH, or set -FfmpegDir)
   - cookies.txt next to this script is used automatically if present
.EXAMPLE
  .\yt-download.ps1 "https://www.youtube.com/watch?v=xxxx"
.EXAMPLE
  .\yt-download.ps1 URL1 URL2 URL3 -OutDir "D:\Videos"
#>
[CmdletBinding()]
param(
    [Parameter(Mandatory = $true, Position = 0, ValueFromRemainingArguments = $true)]
    [string[]] $Urls,

    [string] $OutDir = (Join-Path $env:USERPROFILE 'Downloads'),

    # Override format selection if you want (e.g. H.264 only, or <=1080p)
    [string] $Format = 'bestvideo+bestaudio/best',

    # Path to ffmpeg's bin dir. Auto-detected from PATH if omitted.
    [string] $FfmpegDir = '',

    # Path to a Netscape cookies.txt. Defaults to cookies.txt beside this script.
    [string] $Cookies = ''
)

$ErrorActionPreference = 'Stop'
$ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
$BinDir = Join-Path $ScriptDir 'bin'
New-Item -ItemType Directory -Force $BinDir | Out-Null

function Get-Tool($name, $url, $outFile) {
    $local = Join-Path $BinDir $outFile
    if (Test-Path $local) { return $local }
    $onPath = (Get-Command $name -ErrorAction SilentlyContinue)
    if ($onPath) { return $onPath.Source }
    Write-Host "[setup] downloading $name ..." -ForegroundColor Cyan
    Invoke-WebRequest -Uri $url -OutFile $local
    return $local
}

# --- yt-dlp ---
$ytdlp = Get-Tool 'yt-dlp' 'https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp.exe' 'yt-dlp.exe'

# --- JS runtime (bun preferred; deno fallback; required by YouTube) ---
$jsRuntime = ''
$bun = Get-Command 'bun' -ErrorAction SilentlyContinue
if ($bun) {
    $jsRuntime = "bun:$($bun.Source)"
} else {
    $deno = Join-Path $BinDir 'deno.exe'
    if (-not (Test-Path $deno)) {
        $onPath = Get-Command 'deno' -ErrorAction SilentlyContinue
        if ($onPath) {
            $deno = $onPath.Source
        } else {
            Write-Host "[setup] downloading deno ..." -ForegroundColor Cyan
            $zip = Join-Path $BinDir 'deno.zip'
            Invoke-WebRequest -Uri 'https://github.com/denoland/deno/releases/latest/download/deno-x86_64-pc-windows-msvc.zip' -OutFile $zip
            Expand-Archive $zip -DestinationPath $BinDir -Force
            Remove-Item $zip -Force
        }
    }
    $jsRuntime = "deno:$deno"
}

# --- ffmpeg ---
if (-not $FfmpegDir) {
    $ff = Get-Command 'ffmpeg' -ErrorAction SilentlyContinue
    if ($ff) {
        $FfmpegDir = Split-Path -Parent $ff.Source
    } else {
        Write-Warning "ffmpeg not found on PATH. Install it (winget install Gyan.FFmpeg) or pass -FfmpegDir. Merging video+audio will fail without it."
    }
}

# --- cookies ---
if (-not $Cookies) {
    $defaultCookies = Join-Path $ScriptDir 'cookies.txt'
    if (Test-Path $defaultCookies) { $Cookies = $defaultCookies }
}

New-Item -ItemType Directory -Force $OutDir | Out-Null

$common = @(
    '--no-js-runtimes',
    '--js-runtimes', $jsRuntime,
    '-f', $Format,
    '--merge-output-format', 'mp4',
    '-o', (Join-Path $OutDir '%(title)s [%(height)sp].%(ext)s'),
    '--no-playlist'
)
if ($FfmpegDir) { $common += @('--ffmpeg-location', $FfmpegDir) }
if ($Cookies)   { $common += @('--cookies', $Cookies); Write-Host "[info] using cookies: $Cookies" -ForegroundColor DarkGray }
else            { Write-Host "[info] no cookies.txt -- public videos only. See SKILL.md if you hit 'Sign in to confirm you're not a bot'." -ForegroundColor DarkGray }

$fail = 0
foreach ($u in $Urls) {
    Write-Host "`n==== downloading: $u ====" -ForegroundColor Green
    & $ytdlp @common $u
    if ($LASTEXITCODE -ne 0) { $fail++; Write-Warning "failed: $u" }
}
if ($fail) { Write-Warning "$fail download(s) failed."; exit 1 }
Write-Host "`nAll done. Saved to: $OutDir" -ForegroundColor Green