import os
import uuid
import logging
from pathlib import Path
from typing import Optional, Literal, Union # Import Union

# --- FastAPI Imports ---
from fastapi import FastAPI, Request, HTTPException, BackgroundTasks, Body
from fastapi.responses import JSONResponse, FileResponse
from fastapi.staticfiles import StaticFiles
from pydantic import BaseModel, HttpUrl, Field, field_validator # Import field_validator

# --- yt-dlp Import ---
from yt_dlp import YoutubeDL

# --- Logging Configuration ---
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# --- Constants ---
DOWNLOAD_DIR = Path('downloads') # Use pathlib for paths
COOKIE_FILE = 'www.youtube.com_cookies.txt' # Define cookie file path

# --- Create Download Directory ---
DOWNLOAD_DIR.mkdir(parents=True, exist_ok=True)

# --- FastAPI App Initialization ---
app = FastAPI(
    title="YouTube Downloader API",
    description="API to fetch info and download audio/video from YouTube using yt-dlp.",
    version="1.4.0", # Incremented version
)

# --- Mount Static Files Directory ---
app.mount("/downloads", StaticFiles(directory=DOWNLOAD_DIR), name="downloads")

# --- Pydantic Models for Request/Response Validation ---

class UrlRequest(BaseModel):
    """Request model for endpoints needing just a URL."""
    url: HttpUrl

# Define allowed quality string literals (including numerical ones)
AllowedQualityStr = Literal['best', '240', '480', '720', '1080', '1440', '2160']

class MaxDownloadRequest(BaseModel):
    """Request model for the /max endpoint."""
    url: HttpUrl
    # Accept 'best' or specific numerical resolutions as strings
    quality: Optional[AllowedQualityStr] = 'best'

class InfoResponse(BaseModel):
    """Response model for the /get-info endpoint."""
    title: Optional[str] = None
    thumbnail: Optional[str] = None
    duration: Optional[float] = None
    channel: Optional[str] = None

class DownloadResponse(BaseModel):
    """Response model for download endpoints."""
    url: str
    filename: str
    message: Optional[str] = None

class ErrorResponse(BaseModel):
    """Standard error response model."""
    detail: str

# --- Helper Function for Download ---
def perform_download(ydl_opts: dict, url: str, file_path: Path):
    """Synchronously downloads using yt-dlp."""
    try:
        logger.info(f"Starting download for URL: {url} with options: {ydl_opts}")
        ydl_opts['outtmpl'] = str(file_path.with_suffix('.%(ext)s'))

        with YoutubeDL(ydl_opts) as ydl:
            ydl.extract_info(url, download=True)
        logger.info(f"Download finished successfully for URL: {url}")

        downloaded_files = list(DOWNLOAD_DIR.glob(f"{file_path.stem}.*"))
        if not downloaded_files:
             logger.error(f"Download completed but no file found for stem: {file_path.stem}")
             part_files = list(DOWNLOAD_DIR.glob(f"{file_path.stem}.*.part"))
             for part_file in part_files:
                 try:
                     os.remove(part_file)
                     logger.info(f"Removed leftover part file: {part_file}")
                 except OSError as rm_err:
                     logger.error(f"Error removing part file {part_file}: {rm_err}")
             raise RuntimeError(f"Could not find downloaded file for {url}")
        return downloaded_files[0]

    except Exception as e:
        logger.error(f"yt-dlp download failed for URL {url}: {e}", exc_info=True)
        possible_files = list(DOWNLOAD_DIR.glob(f"{file_path.stem}.*"))
        for f in possible_files:
             if f.is_file():
                 try:
                     os.remove(f)
                     logger.info(f"Removed potentially incomplete/failed file: {f}")
                 except OSError as rm_err:
                     logger.error(f"Error removing file {f}: {rm_err}")
        raise

# --- API Endpoints ---

@app.get("/")
async def root():
    """Root endpoint providing basic API info."""
    return {"message": "YouTube Downloader API. Use /docs for documentation."}

@app.post(
    "/get-info",
    response_model=InfoResponse,
    responses={500: {"model": ErrorResponse}}
)
async def get_info(payload: UrlRequest = Body(...)):
    """
    Extracts video information (title, thumbnail, duration, channel) from a given URL.
    """
    logger.info(f"Received /get-info request for URL: {payload.url}")
    ydl_opts = {}
    if os.path.exists(COOKIE_FILE):
         ydl_opts['cookiefile'] = COOKIE_FILE
         logger.info("Using cookie file.")
    else:
         logger.warning(f"Cookie file '{COOKIE_FILE}' not found. Some videos might require login/cookies.")

    try:
        # Use str(payload.url) to pass the URL string to yt-dlp
        with YoutubeDL(ydl_opts) as ydl:
            info = ydl.extract_info(str(payload.url), download=False)
            return InfoResponse(
                title=info.get('title'),
                thumbnail=info.get('thumbnail'),
                duration=info.get('duration'),
                channel=info.get('channel')
            )
    except Exception as e:
        logger.error(f"Error fetching info for {payload.url}: {e}", exc_info=True)
        raise HTTPException(status_code=500, detail=f"Failed to extract video info: {str(e)}")

'''@app.post(
    "/download",
    response_model=DownloadResponse,
    responses={400: {"model": ErrorResponse}, 500: {"model": ErrorResponse}}
)
async def download_audio(request: Request, payload: UrlRequest = Body(...)):
    """
    Downloads the audio track of a video as an MP3 file (128kbps).
    """
    logger.info(f"Received /download (audio) request for URL: {payload.url}")
    unique_id = str(uuid.uuid4())
    file_path_stem = DOWNLOAD_DIR / unique_id

    ydl_opts = {
        'format': '140/m4a/bestaudio/best',
        'outtmpl': str(file_path_stem.with_suffix('.%(ext)s')),
        'postprocessors': [{
            'key': 'FFmpegExtractAudio',
            'preferredcodec': 'mp3',
            'preferredquality': '128',
        }],
        'noplaylist': True,
        'quiet': False,
        'progress_hooks': [lambda d: logger.debug(f"Download progress: {d['status']} - {d.get('_percent_str', '')}")],
    }
    if os.path.exists(COOKIE_FILE):
         ydl_opts['cookiefile'] = COOKIE_FILE
         logger.info("Using cookie file for audio download.")
    else:
         logger.warning(f"Cookie file '{COOKIE_FILE}' not found for audio download.")

    try:
        # Use str(payload.url) to pass the URL string to the helper
        final_file_path = perform_download(ydl_opts, str(payload.url), file_path_stem)
        final_filename = final_file_path.name
        download_url = f"{str(request.base_url).rstrip('/')}/downloads/{final_filename}"
        logger.info(f"Audio download complete for {payload.url}. URL: {download_url}")
        return DownloadResponse(url=download_url, filename=final_filename)

    except Exception as e:
        # Error logged in perform_download
        raise HTTPException(status_code=500, detail=f"Audio download failed: {str(e)}")
'''

@app.post(
    "/max",
    response_model=DownloadResponse,
    responses={400: {"model": ErrorResponse}, 500: {"model": ErrorResponse}}
)
async def download_video_max_quality(request: Request, payload: MaxDownloadRequest = Body(...)):
    """
    Downloads the video in the specified quality or 'best' available, handling
    both landscape and portrait videos correctly. Attempts H.264 codec for 1080
    and lower. Merges video and audio into MP4.

    Accepted qualities: 'best', '240', '480', '720', '1080', '1440', '2160'.
    Quality number (as string) refers to the maximum dimension (height or width).
    """
    logger.info(f"Received /max (video) request for URL: {payload.url} with quality: {payload.quality}")

    unique_id = str(uuid.uuid4())
    file_path_stem = DOWNLOAD_DIR / unique_id

    # --- Determine yt-dlp Format Selector based on Quality and Codec Preference ---
    quality_str = payload.quality # Quality is now guaranteed to be a string from AllowedQualityStr
    format_selector = None
    max_dim = 0 # Initialize max_dim

    if quality_str == 'best':
        format_selector = 'bestvideo+bestaudio/best' # Best video and audio, merged if possible
        logger.info("Using format selector for 'best' quality.")
    else:
        # Quality is a numerical string ('240', '480', etc.)
        try:
            # Convert the validated string quality to an integer for logic
            max_dim = int(quality_str)
        except ValueError:
            # This should not happen if Pydantic validation works, but good practice
            logger.error(f"Internal error: Could not convert validated quality string '{quality_str}' to int. Falling back to 'best'.")
            format_selector = 'bestvideo+bestaudio/best'
            # Set max_dim to a high value to skip specific logic below if format_selector is set
            max_dim = 99999

        # Only proceed if format_selector wasn't set in the except block
        long_edge = int(max_dim * 1.8)
        if not format_selector:
            # --- Codec Preference Logic ---
            if max_dim <= 1080:
                # Prefer H.264 (avc1) for 1080 or lower max dimension
                logger.info(f"Attempting H.264 codec for requested quality (max dimension): {max_dim}")
                format_selector = f'bestvideo[vcodec^=avc][height<={long_edge}][width<={long_edge}]+bestaudio/best'
                    #f'bestvideo[height<={long_edge}]/bestvideo[width<={long_edge}]+bestaudio/'
                    #f'best[height<={long_edge}]/best[width<={long_edge}]'
            else:
                # For > 1080 max dimension, prioritize best available codec
                logger.info(f"Attempting best available codec for requested quality (max dimension): {max_dim}")
                format_selector = f'bestvideo[height<={long_edge}][width<={long_edge}]+bestaudio/best'

    logger.info(f"Using format selector: '{format_selector}'")

    # --- yt-dlp Options for Video Download ---
    ydl_opts = {
        'format': format_selector,
        'outtmpl': str(file_path_stem.with_suffix('.%(ext)s')),
        'merge_output_format': 'mp4', # Merge into MP4 container
        'noplaylist': False,
        'quiet': True,
        #'verbose': True,
        'noprogress': True
    }
    if os.path.exists(COOKIE_FILE):
         ydl_opts['cookiefile'] = COOKIE_FILE
         logger.info("Using cookie file for video download.")
    else:
         logger.warning(f"Cookie file '{COOKIE_FILE}' not found for video download.")

    try:
        # Use str(payload.url) to pass the URL string to the helper
        final_file_path = perform_download(ydl_opts, str(payload.url), file_path_stem)
        final_filename = final_file_path.name
        download_url = f"{str(request.base_url).rstrip('/')}/downloads/{final_filename}"

        logger.info(f"Video download complete for {payload.url}. URL: {download_url}")
        # Changed 'download_url=' to 'url='
        return DownloadResponse(url=download_url, filename=final_filename)

    except Exception as e:
        # Error logged in perform_download
        raise HTTPException(status_code=500, detail=f"Video download failed: {str(e)}")

# --- Optional: Cleanup Task ---
async def cleanup_old_files(directory: Path, max_age_seconds: int):
    """Removes files older than max_age_seconds in the background."""
    import time
    now = time.time()
    count = 0
    try:
        for item in directory.iterdir():
            if item.is_file():
                try:
                    if now - item.stat().st_mtime > max_age_seconds:
                        os.remove(item)
                        logger.info(f"Cleaned up old file: {item.name}")
                        count += 1
                except OSError as e:
                    logger.error(f"Error removing file {item}: {e}")
        if count > 0:
             logger.info(f"Background cleanup finished. Removed {count} old files.")
        else:
             logger.info("Background cleanup finished. No old files found.")
    except Exception as e:
        logger.error(f"Error during background file cleanup: {e}", exc_info=True)

@app.post("/trigger-cleanup")
async def trigger_cleanup(background_tasks: BackgroundTasks):
    """Manually trigger a cleanup of files older than 1 day."""
    logger.info("Triggering background cleanup of old download files.")
    background_tasks.add_task(cleanup_old_files, DOWNLOAD_DIR, 86400) # 1 day
    return {"message": "Background cleanup task scheduled."}