import logging
import os
import mimetypes
import asyncio
import json
from datetime import datetime
import time
from contextlib import asynccontextmanager

import magic
from pyrogram import errors
from starlette.background import BackgroundTask  # imported for background file deletion
from fastapi import FastAPI, HTTPException, Response
from fastapi.responses import HTMLResponse, FileResponse
from telegram_client import TelegramClient
from config import get_settings
from rss_generator import generate_channel_rss
from post_parser import PostParser
from url_signer import verify_media_digest

logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)

if not logger.handlers:
    handler = logging.StreamHandler()
    handler.setFormatter(logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s'))
    logger.addHandler(handler)

client = TelegramClient()
Config = get_settings()

@asynccontextmanager
async def lifespan(_: FastAPI):
    await client.start()
    
    # Start background task
    background_task = asyncio.create_task(cache_media_files())
    
    yield
    
    # Cleanup
    background_task.cancel()
    try:
        await background_task
    except asyncio.CancelledError:
        pass
    
    await client.stop()

app = FastAPI( title="Pyrogram Bridge", lifespan=lifespan)

if __name__ == "__main__":
    import uvicorn
    uvicorn.run("api_server:app", host=Config["api_host"], port=Config["api_port"], reload=True)


async def find_file_id_in_message(message, file_unique_id: str):
    """Find file_id by checking all possible media types in message"""
    if message.media == "MessageMediaType.POLL":
        logger.debug(f"Message {message.id} is a poll, skipping media search")
        return None
        
    if message.photo and message.photo.file_unique_id == file_unique_id:
        return message.photo.file_id
    elif message.video and message.video.file_unique_id == file_unique_id:
        return message.video.file_id
    elif message.animation and message.animation.file_unique_id == file_unique_id:
        return message.animation.file_id
    elif message.video_note and message.video_note.file_unique_id == file_unique_id:
        return message.video_note.file_id
    elif message.audio and message.audio.file_unique_id == file_unique_id:
        return message.audio.file_id
    elif message.voice and message.voice.file_unique_id == file_unique_id:
        return message.voice.file_id
    elif message.sticker and message.sticker.file_unique_id == file_unique_id:
        return message.sticker.file_id
    elif message.web_page and message.web_page.photo and message.web_page.photo.file_unique_id == file_unique_id:
        return message.web_page.photo.file_id
    elif message.document and message.document.file_unique_id == file_unique_id:
        return message.document.file_id
    return None


def delayed_delete_file(file_path: str, delay: int = 300):
    """
    Delete temporary file after a delay to ensure complete file delivery.
    Delay is set to 5 minutes by default.
    """
    time.sleep(delay)
    try:
        os.remove(file_path)
        logger.info(f"Deleted temporary file {file_path} after delay of {delay} seconds")
    except Exception as e:
        logger.error(f"Failed to delete temporary file {file_path}: {str(e)}")


async def prepare_file_response(file_path: str, delete_after: bool = False):
    """Prepare file response with proper headers"""
    if not os.path.exists(file_path):
        raise HTTPException(status_code=404, detail="File not found")
    
    # Try to determine MIME type using python-magic first
    try:
        mime = magic.Magic(mime=True)
        media_type = mime.from_file(file_path)
    except Exception as e:
        logger.warning(f"Failed to determine MIME type using python-magic: {str(e)}")
        media_type = None
    
    if not media_type: media_type, _ = mimetypes.guess_type(file_path) # Fallback to mimetypes if python-magic failed
    if not media_type: media_type = "application/octet-stream" # Final fallback to octet-stream
    
    logger.debug(f"Determined media type for {os.path.basename(file_path)}: {media_type}")
    headers = {"Content-Disposition": f"inline; filename={os.path.basename(file_path)}"}
    if delete_after:
        return FileResponse(path=file_path, media_type=media_type, headers=headers, background=BackgroundTask(delayed_delete_file, file_path))
    else:
        return FileResponse(path=file_path, media_type=media_type, headers=headers)

async def download_media_file(channel: str, post_id: int, file_unique_id: str) -> str:
    """
    Download media file from Telegram and save to cache
    Returns path to downloaded file
    """
    cache_dir = os.path.abspath("./data/cache")
    os.makedirs(cache_dir, exist_ok=True)
    
    message = await client.client.get_messages(channel, post_id)
    if message.media == "MessageMediaType.POLL":
        return None, False
    
    # Check if it is a video and if its size exceeds 100 MB
    is_large_video = False
    if message.video:
        try:
            if message.video.file_size > 100 * 1024 * 1024:
                is_large_video = True
        except Exception as e:
            logger.error(f"Failed to get video file size for message {post_id}: {str(e)}")
    
    if is_large_video:
        # For large video, download without permanent caching; use a temporary file.
        temp_file_path = os.path.join(cache_dir, f"temp_{channel}-{post_id}-{file_unique_id}")
        if os.path.exists(temp_file_path):
            logger.info(f"Temporary file {temp_file_path} already exists, serving cached large video")
            return temp_file_path, False
        file_id = await find_file_id_in_message(message, file_unique_id)
        if not file_id:
            logger.error(f"Media with file_unique_id {file_unique_id} not found in message {post_id}")
            raise HTTPException(status_code=404, detail="File not found in message")
        logger.info(f"Downloading large video file {file_unique_id} to temporary path {temp_file_path}")
        file_path = await client.client.download_media(file_id, file_name=temp_file_path)
        logger.info(f"Downloaded large video file {file_unique_id} to temporary path {temp_file_path}")
        return file_path, False

    # Normal caching flow
    cache_path = os.path.join(cache_dir, f"{channel}-{post_id}-{file_unique_id}")
    if os.path.exists(cache_path):
        logger.info(f"Found cached media file: {cache_path}")
        file_id = f"{channel}-{post_id}-{file_unique_id}"
        file_ids_path = os.path.join(os.path.abspath("./data"), 'media_file_ids.json')
        try:
            if os.path.exists(file_ids_path):
                with open(file_ids_path, 'r', encoding='utf-8') as f:
                    media_files = json.load(f)
                for file_data in media_files:
                    if file_data['file_id'] == file_id:
                        file_data['added'] = datetime.now().timestamp()
                        break
                with open(file_ids_path, 'w', encoding='utf-8') as f:
                    json.dump(media_files, f, ensure_ascii=False, indent=2)
        except Exception as e:
            logger.error(f"Failed to update timestamp for {file_id}: {str(e)}")
        return cache_path, False

    file_id = await find_file_id_in_message(message, file_unique_id)
    if not file_id:
        logger.error(f"Media with file_unique_id {file_unique_id} not found in message {post_id}")
        raise HTTPException(status_code=404, detail="File not found in message")
    file_path = await client.client.download_media(file_id, file_name=cache_path)
    logger.info(f"Downloaded media file {file_unique_id} to {cache_path}")
    return file_path, False


async def remove_old_cached_files(media_files: list, cache_dir: str) -> tuple[list, int]:
    """
    Remove files that haven't been accessed for more than 20 days
    Returns tuple of (updated media files list, number of removed files)
    """
    current_time = datetime.now().timestamp()
    updated_media_files = []
    files_removed = 0

    for file_data in media_files:
        try:
            file_id = file_data.get('file_id')
            if not file_id:
                continue

            last_access_time = file_data.get('added', 0)
            days_since_access = (current_time - last_access_time) / (24 * 3600)

            if days_since_access > 20:
                channel, post_id_str, file_unique_id = file_id.split('-', 2)
                cache_path = os.path.join(cache_dir, f"{channel}-{post_id_str}-{file_unique_id}")
                
                if os.path.exists(cache_path):
                    try:
                        os.remove(cache_path)
                        files_removed += 1
                        logger.info(f"Removed old cached file: {cache_path}, last access {days_since_access:.1f} days ago")
                    except Exception as e:
                        logger.error(f"Failed to remove cached file {cache_path}: {str(e)}")
                        updated_media_files.append(file_data)
                continue

            updated_media_files.append(file_data)

        except Exception as e:
            logger.error(f"Error processing cache entry {file_data}: {str(e)}")
            continue

    # Additionally, remove temporary files with prefix "temp_" if they are older than a threshold (1 hour)
    temp_threshold = 3600  # 1 hour in seconds
    for file in os.listdir(cache_dir):
        file_path = os.path.join(cache_dir, file)
        if os.path.isfile(file_path) and file.startswith("temp_"):
            try:
                file_mod_time = os.path.getmtime(file_path)
                if time.time() - file_mod_time > temp_threshold:
                    os.remove(file_path)
                    files_removed += 1
                    logger.info(f"Removed temporary file: {file_path}")
            except Exception as e:
                logger.error(f"Failed to remove temporary file {file_path}: {str(e)}")

    return updated_media_files, files_removed


async def download_new_files(media_files: list, cache_dir: str):
    """
    Download files that are not in cache yet
    """
    if not media_files:
        logger.info("No media files found for download")
        return

    files_to_download = 0
    for file_data in media_files:
        try:
            file_id = file_data['file_id']
            if not file_id:
                continue

            channel, post_id_str, file_unique_id = file_id.split('-', 2)
            post_id = int(post_id_str)
            cache_path = os.path.join(cache_dir, f"{channel}-{post_id}-{file_unique_id}")
            
            if not os.path.exists(cache_path):
                files_to_download += 1
                logger.debug(f"Background download started for {file_id}")
                await download_media_file(channel, post_id, file_unique_id)
                await asyncio.sleep(1)  # Delay between downloads
        
        except Exception as e:
            logger.error(f"Background download failed for {file_id}: {str(e)}")
            continue

    if files_to_download == 0:
        logger.info("All media files are already in cache")


async def cache_media_files():
    """Background task for cache management: removes old files and downloads new ones"""
    delay = 60
    while True:
        try:
            file_path = os.path.join(os.path.abspath("./data"), 'media_file_ids.json')
            if not os.path.exists(file_path):
                await asyncio.sleep(delay)
                continue

            with open(file_path, 'r', encoding='utf-8') as f:
                media_files = json.load(f)

            cache_dir = os.path.abspath("./data/cache")
            updated_media_files, files_removed = await remove_old_cached_files(media_files, cache_dir)

            if files_removed > 0:
                try:
                    with open(file_path, 'w', encoding='utf-8') as f:
                        json.dump(updated_media_files, f, ensure_ascii=False, indent=2)
                    logger.info(f"Removed {files_removed} old files from cache")
                except Exception as e:
                    logger.error(f"Failed to update media_file_ids.json: {str(e)}")

            await download_new_files(updated_media_files, cache_dir)
            await asyncio.sleep(delay)  # Check every delay seconds
            
        except Exception as e:
            logger.error(f"Cache media files error: {str(e)}")
            await asyncio.sleep(delay)


def calculate_cache_stats():
    """
    Calculate cache statistics including file count, total size in MB, and time difference in days.
    Returns a dictionary with keys: 'cache_files_count', 'cache_total_size_mb', 'cache_time_diff_days'.
    """
    cache_dir = os.path.abspath("./data/cache")
    if os.path.isdir(cache_dir):
        files = [f for f in os.listdir(cache_dir) if os.path.isfile(os.path.join(cache_dir, f))]
        cache_files_count = len(files)
        cache_total_size_bytes = sum(os.path.getsize(os.path.join(cache_dir, f)) for f in files)
        cache_total_size_mb = round(cache_total_size_bytes / (1024 * 1024), 2)  # rounded size in MB
    else:
        cache_files_count = 0
        cache_total_size_mb = 0

    media_file_ids_path = os.path.join(os.path.abspath("./data"), "media_file_ids.json")
    cache_times = []
    if os.path.exists(media_file_ids_path):
        try:
            with open(media_file_ids_path, "r", encoding="utf-8") as f:
                media_files = json.load(f)
            for entry in media_files:
                if "added" in entry:
                    cache_times.append(entry["added"])
        except Exception as e:
            logger.error(f"Error reading media_file_ids.json: {str(e)}")
    if cache_times:
        cache_time_diff_seconds = max(cache_times) - min(cache_times)
        cache_time_diff_days = round(cache_time_diff_seconds / 86400, 2)  # rounded to two decimals
    else:
        cache_time_diff_days = 0

    return {
        "cache_files_count": cache_files_count,
        "cache_total_size_mb": cache_total_size_mb,
        "cache_time_diff_days": cache_time_diff_days
    }


@app.get("/html/{channel}/{post_id}", response_class=HTMLResponse)
@app.get("/post/html/{channel}/{post_id}", response_class=HTMLResponse)
async def get_post_html(channel: str, post_id: int):
    try:
        parser = PostParser(client.client)
        html_content = await parser.get_post(channel, post_id, 'html')
        if not html_content:
            raise HTTPException(status_code=404, detail="Post not found")
        return html_content
    except Exception as e:
        error_message = f"Failed to get HTML post for channel {channel}, post_id {post_id}: {str(e)}"
        logger.error(error_message)
        raise HTTPException(status_code=500, detail=error_message) from e


@app.get("/json/{channel}/{post_id}")
@app.get("/post/json/{channel}/{post_id}")
async def get_post(channel: str, post_id: int):
    try:
        parser = PostParser(client.client)
        json_content = await parser.get_post(channel, post_id, 'json')
        if not json_content:
            raise HTTPException(status_code=404, detail="Post not found")
        return json_content
    except Exception as e:
        error_message = f"Failed to get JSON post for channel {channel}, post_id {post_id}: {str(e)}"
        logger.error(error_message)
        raise HTTPException(status_code=500, detail=error_message) from e


@app.get("/health")
async def health_check():
    try:
        me = await client.client.get_me()

        cache_stats = calculate_cache_stats()

        return {
            "status": "ok",
            "tg_connected": client.client.is_connected,
            "tg_name": me.username,
            "tg_id": me.id,
            "tg_phone": me.phone_number,
            "tg_first_name": me.first_name,
            "tg_last_name": me.last_name,
            **cache_stats
        }
    except Exception as e:
        error_message = f"Failed to get health check: {str(e)}"
        logger.error(error_message)
        raise HTTPException(status_code=500, detail=error_message) from e

@app.get("/media/{channel}/{post_id}/{file_unique_id}/{digest}")
@app.get("/media/{channel}/{post_id}/{file_unique_id}")
async def get_media(channel: str, post_id: int, file_unique_id: str, digest: str | None = None):
    try:
        url = f"{channel}/{post_id}/{file_unique_id}"
        if not verify_media_digest(url, digest):
            logger.error(f"Invalid digest for media: url={url}")
            #raise HTTPException(status_code=403, detail="Invalid URL signature")
        else:
            logger.info(f"Valid digest for media: url={url}")   
            
        file_path, delete_after = await download_media_file(channel, post_id, file_unique_id)
        return await prepare_file_response(file_path, delete_after=delete_after)
    except HTTPException:
        raise
    except errors.RPCError as e:
        logger.error(f"Media request RPC error for file_unique_id {file_unique_id} in message {post_id}: {type(e).__name__} - {str(e)}")
        raise HTTPException(status_code=404, detail="File not found in Telegram") from e
    except Exception as e:
        error_message = f"Failed to get media for file_unique_id {file_unique_id} in message {post_id}: {str(e)}"
        logger.error(error_message)
        raise HTTPException(status_code=500, detail=error_message) from e

@app.get("/rss/{channel}", response_class=Response)
@app.get("/rss/{channel}/{token}", response_class=Response)
async def get_rss_feed(channel: str, token: str | None = None, limit: int = 20):
    if Config["token"]:
        if token != Config["token"]:
            logger.error(f"Invalid token for RSS feed: {token}")
            raise HTTPException(status_code=403, detail="Invalid token")
        else:
            logger.info(f"Valid token for RSS feed: {token}")
    
    while True:
        try:
            rss_content = await generate_channel_rss(channel, client=client.client, limit=limit)
            return Response(content=rss_content, media_type="application/xml")
        except ValueError as e:
            error_message = f"Invalid parameters for RSS feed generation: {str(e)}"
            logger.error(error_message)
            raise HTTPException(status_code=400, detail=error_message) from e
        except errors.FloodWait as e:
            wait_time = e.value
            logger.warning(f"FloodWait detected for channel {channel}, waiting {wait_time} seconds")
            await asyncio.sleep(wait_time)
            logger.info(f"FloodWait finished for channel {channel}, retrying RSS feed generation")
            continue
        except Exception as e:
            error_message = f"Failed to generate RSS feed for channel {channel}: {str(e)}"
            logger.error(error_message)
            raise HTTPException(status_code=500, detail=error_message) from e