#!/usr/bin/env python3
"""
YouTube Video Downloader
Requires: yt-dlp  →  pip install yt-dlp
"""

import subprocess
import sys
import os
import shutil


def check_ytdlp():
    try:
        import yt_dlp  # noqa: F401
    except ImportError:
        print("Installing yt-dlp...")
        subprocess.check_call([sys.executable, "-m", "pip", "install", "yt-dlp"])


def has_ffmpeg() -> bool:
    """Return True if ffmpeg is available on PATH."""
    return shutil.which("ffmpeg") is not None


def list_formats(url: str):
    """Print available formats for a video."""
    import yt_dlp
    with yt_dlp.YoutubeDL({"quiet": True}) as ydl:
        info = ydl.extract_info(url, download=False)
        print(f"\nTitle: {info.get('title')}")
        print(f"Duration: {info.get('duration_string', 'N/A')}\n")
        print(f"{'ID':<12} {'EXT':<6} {'RESOLUTION':<12} {'FPS':<6} NOTE")
        print("-" * 60)
        for f in info.get("formats", []):
            fid = f.get("format_id", "")
            ext = f.get("ext", "")
            res = f.get("resolution") or f.get("format_note", "")
            fps = str(f.get("fps") or "")
            note = f.get("format_note", "")
            print(f"{fid:<12} {ext:<6} {res:<12} {fps:<6} {note}")


def build_format_string(quality: str, ffmpeg: bool) -> str:
    """
    Return a yt-dlp format string appropriate for whether ffmpeg is available.

    With ffmpeg   → prefer separate video+audio streams (best quality, then merge).
    Without ffmpeg → request a single pre-muxed file so no merging is needed.
    """
    if ffmpeg:
        return {
            "best":  "bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]/best",
            "1080p": "bestvideo[height<=1080][ext=mp4]+bestaudio[ext=m4a]/best[height<=1080][ext=mp4]/best[height<=1080]",
            "720p":  "bestvideo[height<=720][ext=mp4]+bestaudio[ext=m4a]/best[height<=720][ext=mp4]/best[height<=720]",
            "480p":  "bestvideo[height<=480][ext=mp4]+bestaudio[ext=m4a]/best[height<=480][ext=mp4]/best[height<=480]",
            "360p":  "bestvideo[height<=360][ext=mp4]+bestaudio[ext=m4a]/best[height<=360][ext=mp4]/best[height<=360]",
        }.get(quality, "bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]/best")
    else:
        # Single-file (pre-muxed) formats — no merging required
        return {
            "best":  "best[ext=mp4]/best",
            "1080p": "best[height<=1080][ext=mp4]/best[height<=1080]",
            "720p":  "best[height<=720][ext=mp4]/best[height<=720]",
            "480p":  "best[height<=480][ext=mp4]/best[height<=480]",
            "360p":  "best[height<=360][ext=mp4]/best[height<=360]",
        }.get(quality, "best[ext=mp4]/best")


def download(url: str, quality: str, output_dir: str, audio_only: bool):
    """Download a video or audio from YouTube."""
    import yt_dlp

    ffmpeg = has_ffmpeg()
    os.makedirs(output_dir, exist_ok=True)
    outtmpl = os.path.join(output_dir, "%(title)s.%(ext)s")

    if audio_only:
        if ffmpeg:
            ydl_opts = {
                "format": "bestaudio/best",
                "outtmpl": outtmpl,
                "postprocessors": [{
                    "key": "FFmpegExtractAudio",
                    "preferredcodec": "mp3",
                    "preferredquality": "192",
                }],
            }
        else:
            # Without ffmpeg, download best audio as-is (usually .m4a)
            print("  ⚠️  ffmpeg not found — audio will be saved as .m4a instead of .mp3")
            ydl_opts = {
                "format": "bestaudio[ext=m4a]/bestaudio",
                "outtmpl": outtmpl,
            }
    else:
        fmt = build_format_string(quality, ffmpeg)
        ydl_opts = {
            "format": fmt,
            "outtmpl": outtmpl,
        }
        if ffmpeg:
            ydl_opts["merge_output_format"] = "mp4"

    with yt_dlp.YoutubeDL(ydl_opts) as ydl:
        ydl.download([url])


def prompt_quality() -> str:
    options = ["best", "1080p", "720p", "480p", "360p"]
    print("\nSelect quality:")
    for i, opt in enumerate(options, 1):
        print(f"  {i}. {opt}")
    while True:
        choice = input("Enter number (default 1 = best): ").strip() or "1"
        if choice.isdigit() and 1 <= int(choice) <= len(options):
            return options[int(choice) - 1]
        print("Invalid choice, try again.")


def main():
    check_ytdlp()

    print("=" * 50)
    print("       YouTube Downloader (powered by yt-dlp)")
    print("=" * 50)

    # Show ffmpeg status upfront
    if has_ffmpeg():
        print("  ✅ ffmpeg detected — full quality available")
    else:
        print("  ⚠️  ffmpeg NOT found — quality may be limited (max ~720p)")
        print("     Run install_dependencies.py to fix this\n")

    url = input("\nEnter YouTube URL: ").strip()
    if not url:
        print("No URL provided. Exiting.")
        sys.exit(1)

    print("\nWhat would you like to do?")
    print("  1. Download video")
    print("  2. Download audio only (MP3)")
    print("  3. List available formats")

    mode = input("Enter choice (1/2/3): ").strip()

    if mode == "3":
        list_formats(url)
        sys.exit(0)

    audio_only = mode == "2"
    quality = "best"

    if not audio_only:
        quality = prompt_quality()

    output_dir = input("\nSave to folder (default: ./downloads): ").strip() or "./downloads"

    print(f"\nDownloading {'audio' if audio_only else f'{quality} video'}...")
    print(f"Saving to: {os.path.abspath(output_dir)}\n")

    try:
        download(url, quality, output_dir, audio_only)
        print("\n✅ Download complete!")
    except Exception as e:
        print(f"\n❌ Error: {e}")
        sys.exit(1)


if __name__ == "__main__":
    main()