"""
后台下载模块：支持 HTTP URL 下载和磁力链接下载（需要安装 aria2c）
"""
import os
import uuid
import mimetypes
import threading
import subprocess
import requests
from urllib.parse import urlparse, unquote
from flask import current_app
from app.extensions import db
from app.utils.file_handler import guess_resource_type


def _get_filename_from_url(url):
    """从 URL 猜测文件名"""
    path = urlparse(url).path
    name = unquote(os.path.basename(path))
    return name if name else 'download'


def _update_resource(app, resource_id, **kwargs):
    """在 app context 内更新 Resource 记录"""
    with app.app_context():
        from app.models.resource import Resource
        res = db.session.get(Resource, resource_id)
        if res:
            for k, v in kwargs.items():
                setattr(res, k, v)
            db.session.commit()


def download_url(app, resource_id, url, resource_type, user_id):
    """后台线程：HTTP 下载"""
    try:
        _update_resource(app, resource_id,
                         download_status='downloading', download_progress=0)

        headers = {'User-Agent': 'Mozilla/5.0 (compatible; ResourceLibrary/1.0)'}
        response = requests.get(url, stream=True, timeout=60, headers=headers)
        response.raise_for_status()

        # 确定文件名和类型
        orig_name = _get_filename_from_url(url)
        content_type = response.headers.get('content-type', '').split(';')[0].strip()
        ext = mimetypes.guess_extension(content_type) or \
              ('.' + orig_name.rsplit('.', 1)[-1] if '.' in orig_name else '')
        ext = ext.lstrip('.')

        if not resource_type:
            resource_type = guess_resource_type(orig_name, content_type) or 'text'

        unique_name = f"{uuid.uuid4().hex}.{ext}" if ext else uuid.uuid4().hex
        save_dir = os.path.join(app.config['UPLOAD_FOLDER'], resource_type)
        os.makedirs(save_dir, exist_ok=True)
        save_path = os.path.join(save_dir, unique_name)

        total = int(response.headers.get('content-length', 0))
        downloaded = 0
        chunk_size = 65536  # 64KB

        with open(save_path, 'wb') as f:
            for chunk in response.iter_content(chunk_size=chunk_size):
                if chunk:
                    f.write(chunk)
                    downloaded += len(chunk)
                    if total > 0:
                        progress = int(downloaded * 100 / total)
                        _update_resource(app, resource_id,
                                         download_progress=progress)

        file_size = os.path.getsize(save_path)
        rel_path = f"uploads/{resource_type}/{unique_name}"

        _update_resource(app, resource_id,
                         download_status='done',
                         download_progress=100,
                         filename=unique_name,
                         original_name=orig_name,
                         file_path=rel_path,
                         file_size=file_size,
                         mime_type=content_type,
                         resource_type=resource_type)

    except Exception as e:
        _update_resource(app, resource_id,
                         download_status='failed',
                         download_error=str(e)[:500])


def start_url_download(app, resource_id, url, resource_type, user_id):
    """启动 URL 下载线程"""
    t = threading.Thread(
        target=download_url,
        args=(app, resource_id, url, resource_type, user_id),
        daemon=True
    )
    t.start()


def start_magnet_download(app, resource_id, magnet_uri, resource_type):
    """启动磁力下载线程（需要 aria2c）"""
    t = threading.Thread(
        target=_magnet_download_worker,
        args=(app, resource_id, magnet_uri, resource_type),
        daemon=True
    )
    t.start()


def _magnet_download_worker(app, resource_id, magnet_uri, resource_type):
    """使用 aria2c 下载磁力链接"""
    if not resource_type:
        resource_type = 'video'  # 磁力下载默认视频

    save_dir = os.path.join(app.config['UPLOAD_FOLDER'], resource_type)
    os.makedirs(save_dir, exist_ok=True)

    try:
        _update_resource(app, resource_id,
                         download_status='downloading', download_progress=0)

        # 检查 aria2c 是否可用
        result = subprocess.run(
            ['aria2c', '--version'],
            capture_output=True, text=True, timeout=5
        )
        if result.returncode != 0:
            raise RuntimeError('aria2c 未安装或不可用，请先安装 aria2c')

        cmd = [
            'aria2c',
            '--dir', save_dir,
            '--seed-time=0',
            '--max-connection-per-server=4',
            '--console-log-level=warn',
            magnet_uri
        ]

        proc = subprocess.Popen(
            cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
            text=True, encoding='utf-8', errors='replace'
        )

        # 实时读取输出更新进度（简单估算）
        progress = 10
        for line in proc.stdout:
            line = line.strip()
            if '[' in line and '%' in line:
                try:
                    pct_str = line.split('%')[0].split()[-1]
                    progress = int(float(pct_str))
                    _update_resource(app, resource_id,
                                     download_progress=min(progress, 99))
                except (ValueError, IndexError):
                    pass

        proc.wait()

        if proc.returncode == 0:
            # 查找下载的文件
            files = []
            for root, dirs, fnames in os.walk(save_dir):
                for fname in fnames:
                    fpath = os.path.join(root, fname)
                    files.append((fpath, os.path.getmtime(fpath)))
            if files:
                latest = max(files, key=lambda x: x[1])[0]
                orig_name = os.path.basename(latest)
                rel_path = os.path.relpath(
                    latest,
                    os.path.join(app.root_path, 'static')
                ).replace('\\', '/')
                _update_resource(app, resource_id,
                                 download_status='done',
                                 download_progress=100,
                                 filename=orig_name,
                                 original_name=orig_name,
                                 file_path=rel_path,
                                 file_size=os.path.getsize(latest))
            else:
                raise RuntimeError('下载完成但未找到文件')
        else:
            raise RuntimeError(f'aria2c 退出码: {proc.returncode}')

    except FileNotFoundError:
        _update_resource(app, resource_id,
                         download_status='failed',
                         download_error='aria2c 未安装，请安装后重试')
    except Exception as e:
        _update_resource(app, resource_id,
                         download_status='failed',
                         download_error=str(e)[:500])