import asyncio
import re
import subprocess
import threading
import time
import shutil
from pathlib import Path
from collections import deque

from bilibili_api import HEADERS, get_client, video  # pip install bilibili-api-python


BASE_DIR = Path(__file__).resolve().parent
OUTPUT_DIR = BASE_DIR / "downloads"
DOWNLOADED_BVID_FILE = BASE_DIR / "downloaded_bvids.txt"  # 已下载 bvid 记录文件
SKIPPED_BVID_FILE = BASE_DIR / "skipped_bvids.txt"  # 跳过的 bvid 记录文件
FFMPEG_PATH = None  # Will be set by find_ffmpeg()
POLL_SECONDS = 2
FETCH_RELATED_LIMIT = 20


def find_ffmpeg():
    """查找 ffmpeg 可执行文件的路径"""
    # 首先尝试在系统 PATH 中查找
    ffmpeg_path = shutil.which("ffmpeg")
    if ffmpeg_path:
        return ffmpeg_path
    
    # Windows 常见的 ffmpeg 安装位置
    common_paths = [
        r"C:\ffmpeg\bin\ffmpeg.exe",
        r"C:\Program Files\ffmpeg\bin\ffmpeg.exe",
        r"C:\Program Files (x86)\ffmpeg\bin\ffmpeg.exe",
        Path.home() / "ffmpeg" / "bin" / "ffmpeg.exe",
        Path.home() / "Downloads" / "ffmpeg" / "bin" / "ffmpeg.exe",
        BASE_DIR / "ffmpeg" / "bin" / "ffmpeg.exe",
        BASE_DIR / "ffmpeg.exe",
    ]
    
    for path in common_paths:
        if Path(path).exists():
            return str(path)
    
    return None

# 使用线程安全的队列替代数据库
video_queue = deque()  # 待下载的视频队列
downloaded_set = set()  # 已下载的视频集合，防止重复
queue_lock = threading.Lock()


def load_downloaded_bvids():
    """从文件加载已下载的 bvid 列表"""
    global downloaded_set
    if DOWNLOADED_BVID_FILE.exists():
        try:
            with open(DOWNLOADED_BVID_FILE, "r", encoding="utf-8") as f:
                downloaded_set = set(line.strip() for line in f if line.strip())
            print(f"loaded {len(downloaded_set)} downloaded bvids from file")
        except Exception as e:
            print(f"failed to load downloaded bvids: {e}")
            downloaded_set = set()
    else:
        print("no downloaded bvids file found, starting fresh")
        downloaded_set = set()


def save_downloaded_bvid(bvid: str):
    """将 bvid 追加保存到文件"""
    try:
        with open(DOWNLOADED_BVID_FILE, "a", encoding="utf-8") as f:
            f.write(bvid + "\n")
    except Exception as e:
        print(f"failed to save bvid {bvid}: {e}")


def save_skipped_bvid(bvid: str, view_count: int, title: str):
    """将跳过的 bvid 及其信息追加保存到文件"""
    try:
        with open(SKIPPED_BVID_FILE, "a", encoding="utf-8") as f:
            f.write(f"{bvid}\t{view_count}\t{title}\n")
    except Exception as e:
        print(f"failed to save skipped bvid {bvid}: {e}")


def get_bvid_from_url(url: str) -> str:
    match = re.search(r"BV[0-9A-Za-z]{10}", url)
    if not match:
        raise ValueError(f"link does not contain bvid: {url}")
    return match.group(0)


def sanitize_title(title: str, max_length: int = 80) -> str:
    # 只保留字母、数字和中文，其他全部移除
    cleaned = re.sub(r'[^\w\u4e00-\u9fff]', '', title)
    # 移除连续下划线
    cleaned = re.sub(r'_+', '_', cleaned)
    cleaned = cleaned.strip('_')
    if not cleaned:
        cleaned = "video"
    return cleaned[:max_length].rstrip('_')


def build_output_file_name(bvid: str, title: str) -> str:
    return f"{bvid}_{sanitize_title(title)}.mp4"


def get_output_path(file_name: str) -> Path:
    return OUTPUT_DIR / file_name


def add_to_queue(bvid: str, source_url: str = ""):
    """添加视频到下载队列"""
    with queue_lock:
        if bvid not in downloaded_set and bvid not in [item["bvid"] for item in video_queue]:
            video_queue.append({
                "bvid": bvid,
                "source_url": source_url or f"https://www.bilibili.com/video/{bvid}",
                "added_at": time.time()
            })
            print(f"added to queue: {bvid}, queue size: {len(video_queue)}")
            return True
        else:
            print(f"skipped duplicate: {bvid}")
            return False


def get_from_queue():
    """从队列获取一个待下载的视频"""
    with queue_lock:
        if video_queue:
            return video_queue.popleft()
        return None


async def fetch_video_info_and_related(bvid: str):
    v = video.Video(bvid=bvid)
    info = await v.get_info()
    related_items = await v.get_related()
    return info, related_items


def save_related_bvids(parent_bvid: str, related_items):
    """将相关视频添加到队列"""
    inserted = 0
    skipped = 0
    for item in related_items[:FETCH_RELATED_LIMIT]:
        related_bvid = item.get("bvid")
        if not related_bvid:
            continue
        
        if add_to_queue(related_bvid, f"https://www.bilibili.com/video/{related_bvid}"):
            inserted += 1
        else:
            skipped += 1
    
    return inserted, skipped


async def download_stream(url: str, output_path: Path, intro: str):
    download_id = await get_client().download_create(url, HEADERS)
    written = 0
    total = get_client().download_content_length(download_id)
    with open(output_path, "wb") as file_obj:
        while True:
            chunk = await get_client().download_chunk(download_id)
            written += file_obj.write(chunk)
            print(f"{intro} - {output_path.name} [{written} / {total}]", end="\r")
            if written >= total:
                break
    print()


def merge_media(video_path: Path, audio_path: Path, output_path: Path):
    if not FFMPEG_PATH:
        raise RuntimeError("ffmpeg not found. Please install ffmpeg and add it to PATH.")
    subprocess.run(
        [
            FFMPEG_PATH,
            "-y",
            "-i",
            str(video_path),
            "-i",
            str(audio_path),
            "-vcodec",
            "copy",
            "-acodec",
            "copy",
            str(output_path),
        ],
        check=True,
    )


def convert_flv_to_mp4(source_path: Path, output_path: Path):
    if not FFMPEG_PATH:
        raise RuntimeError("ffmpeg not found. Please install ffmpeg and add it to PATH.")
    subprocess.run(
        [FFMPEG_PATH, "-y", "-i", str(source_path), str(output_path)],
        check=True,
    )


async def download_video_file(bvid: str, output_file_name: str):
    OUTPUT_DIR.mkdir(parents=True, exist_ok=True)

    final_path = get_output_path(output_file_name)
    temp_video_path = OUTPUT_DIR / f"{final_path.stem}_video_temp.m4s"
    temp_audio_path = OUTPUT_DIR / f"{final_path.stem}_audio_temp.m4s"
    temp_flv_path = OUTPUT_DIR / f"{final_path.stem}_temp.flv"

    v = video.Video(bvid=bvid)
    download_url_data = await v.get_download_url(0)
    detector = video.VideoDownloadURLDataDetecter(data=download_url_data)
    streams = detector.detect_best_streams()

    if detector.check_flv_mp4_stream():
        await download_stream(streams[0].url, temp_flv_path, "download flv")
        convert_flv_to_mp4(temp_flv_path, final_path)
        temp_flv_path.unlink(missing_ok=True)
    else:
        await download_stream(streams[0].url, temp_video_path, "download video")
        await download_stream(streams[1].url, temp_audio_path, "download audio")
        merge_media(temp_video_path, temp_audio_path, final_path)
        temp_video_path.unlink(missing_ok=True)
        temp_audio_path.unlink(missing_ok=True)

    return final_path


def download_with_youget(bvid: str, title: str, output_dir: Path) -> bool:
    """使用 you-get 下载视频"""
    url = f"https://www.bilibili.com/video/{bvid}"
    # 生成自定义文件名：bvid_清理后的标题
    custom_filename = f"{bvid}_{sanitize_title(title)}"
    try:
        # 使用 you-get 下载视频，指定文件名，禁用字幕
        result = subprocess.run(
            ["you-get", "-o", str(output_dir), "-O", custom_filename, "--no-caption", url],
            capture_output=True,
            text=True,
            check=True
        )
        print(f"you-get output: {result.stdout}")
        return True
    except subprocess.CalledProcessError as e:
        print(f"you-get download failed: {e.stderr}")
        return False
    except FileNotFoundError:
        print("you-get not found, please install it: pip install you-get")
        return False


def process_download(bvid: str):
    """处理单个视频的下载"""
    try:
        # 获取视频信息
        info, related_items = asyncio.run(fetch_video_info_and_related(bvid))
        title = info.get("title", bvid)
        
        # 获取观看量
        view_count = info.get("stat", {}).get("view", 0)
        
        print(f"fetching info done: {bvid}, title: {title}, views: {view_count}")
        
        # 判断观看量是否超过 50w (500000)
        if view_count < 500000:
            print(f"skipped: {bvid}, view count {view_count} < 500000")
            # 记录跳过的视频信息
            save_skipped_bvid(bvid, view_count, title)
            # 仍然添加相关视频到队列
            inserted, skipped = save_related_bvids(bvid, related_items)
            print(f"related videos: inserted={inserted}, skipped={skipped}")
            return
        
        print(f"view count {view_count} >= 500000, downloading...")
        
        file_name = build_output_file_name(bvid, title)
        
        # 检查文件是否已存在
        final_path = get_output_path(file_name)
        if final_path.exists():
            print(f"file already exists, skipped: {bvid} -> {final_path}")
            with queue_lock:
                downloaded_set.add(bvid)
            return
        
        # 使用 you-get 下载视频
        success = download_with_youget(bvid, title, OUTPUT_DIR)
        
        if success:
            print(f"download done: {bvid}")
            
            # 标记为已下载并保存到文件
            with queue_lock:
                downloaded_set.add(bvid)
            save_downloaded_bvid(bvid)
        else:
            print(f"download failed: {bvid}")
        
        # 添加相关视频到队列
        inserted, skipped = save_related_bvids(bvid, related_items)
        print(f"related videos: inserted={inserted}, skipped={skipped}")
        
    except Exception as exc:
        print(f"download failed: {bvid}, error={exc}")


def download_worker():
    """下载工作线程：从队列中取出视频并下载"""
    print("download worker started")
    while True:
        item = get_from_queue()
        if not item:
            time.sleep(POLL_SECONDS)
            continue
        
        bvid = item["bvid"]
        print(f"processing: {bvid}")
        process_download(bvid)


def input_worker():
    """输入工作线程：接收用户输入的链接"""
    print("input worker started, waiting for URLs...")
    print("Enter a bilibili URL (or 'quit' to exit):")
    
    while True:
        try:
            url = input("> ").strip()
            if url.lower() == 'quit':
                print("stopping...")
                break
            
            if not url:
                continue
            
            try:
                bvid = get_bvid_from_url(url)
                add_to_queue(bvid, url)
            except ValueError as e:
                print(f"invalid url: {e}")
                print("please enter a valid bilibili video URL")
                
        except EOFError:
            break
        except KeyboardInterrupt:
            break


def main():
    global FFMPEG_PATH
    
    # 查找 ffmpeg
    FFMPEG_PATH = find_ffmpeg()
    if not FFMPEG_PATH:
        print("=" * 50)
        print("ERROR: ffmpeg not found!")
        print("=" * 50)
        print("Please install ffmpeg and add it to your system PATH.")
        print("Download from: https://ffmpeg.org/download.html")
        print("Or place ffmpeg.exe in one of these locations:")
        print("  - C:\\ffmpeg\\bin\\")
        print("  - Current directory")
        print("=" * 50)
        return
    
    print(f"ffmpeg found at: {FFMPEG_PATH}")
    
    # 加载已下载的 bvid 列表
    load_downloaded_bvids()
    
    # 启动下载工作线程
    download_thread = threading.Thread(target=download_worker, daemon=True, name="download-worker")
    download_thread.start()
    
    print("=" * 50)
    print("Bilibili Video Downloader")
    print("=" * 50)
    print("Download worker started in background")
    print("Enter bilibili video URLs to download")
    print("Related videos will be automatically discovered and queued")
    print("Type 'quit' to exit")
    print("=" * 50)
    
    # 主线程处理用户输入
    input_worker()


if __name__ == "__main__":
    main()