app.py

import streamlit as st
import libtorrent as lt
import time
import threading
import os

# Session状态初始化
if 'download_progress' not in st.session_state:
    st.session_state.download_progress = 0
if 'downloading' not in st.session_state:
    st.session_state.downloading = False
if 'download_complete' not in st.session_state:
    st.session_state.download_complete = False
if 'download_filename' not in st.session_state:
    st.session_state.download_filename = None
if 'error_message' not in st.session_state:
    st.session_state.error_message = None

def download_torrent(magnet_link, save_path):
    try:
        ses = lt.session()
        ses.listen_on(6881, 6891)
        params = {
            'save_path': save_path,
            'storage_mode': lt.storage_mode_t(2)
        }
        
        handle = lt.add_magnet_uri(ses, magnet_link, params)
        ses.start_dht()
        ses.start_lsd()
        ses.start_upnp()
        ses.start_natpmp()

        # 等待元数据
        st.session_state.error_message = "正在获取元数据..."
        while not handle.has_metadata():
            time.sleep(1)
            if not st.session_state.downloading:
                return

        # 获取文件信息
        torinfo = handle.get_torrent_info()
        files = torinfo.files()
        if files.num_files() > 1:
            st.session_state.error_message = "暂不支持多文件种子"
            st.session_state.downloading = False
            return

        file_path = files.file_path(0)
        st.session_state.download_filename = os.path.join(save_path, file_path)

        st.session_state.error_message = None
        st.session_state.downloading = True

        # 更新下载进度
        while handle.status().state != lt.torrent_status.seeding:
            if not st.session_state.downloading:
                handle.pause()
                return
            s = handle.status()
            progress = s.progress * 100
            st.session_state.download_progress = progress
            time.sleep(0.5)

        st.session_state.download_progress = 100
        st.session_state.download_complete = True
        st.session_state.downloading = False

    except Exception as e:
        st.session_state.error_message = f"下载出错：{str(e)}"
        st.session_state.downloading = False
        st.session_state.download_complete = False

def start_download_thread(magnet_link):
    save_path = './downloads'
    if not os.path.exists(save_path):
        os.makedirs(save_path)
    
    thread = threading.Thread(target=download_torrent, args=(magnet_link, save_path))
    thread.start()

# 界面布局
st.title("磁力链接下载器 🧲")

with st.form("magnet_form"):
    magnet_link = st.text_input("输入磁力链接：", placeholder="magnet:?xt=urn:btih:...")
    submitted = st.form_submit_button("开始下载")

    if submitted and magnet_link:
        if st.session_state.downloading:
            st.warning("当前已有下载任务在进行中")
        else:
            # 重置状态
            st.session_state.download_progress = 0
            st.session_state.download_complete = False
            st.session_state.download_filename = None
            st.session_state.error_message = None
            st.session_state.downloading = True
            start_download_thread(magnet_link)

if st.session_state.downloading:
    st.info("下载状态")
    progress_col, control_col = st.columns([4, 1])
    
    with progress_col:
        progress_bar = st.progress(int(st.session_state.download_progress))
        st.write(f"当前进度：{st.session_state.download_progress:.1f}%")
    
    with control_col:
        if st.button("取消下载"):
            st.session_state.downloading = False
            st.session_state.download_complete = False
            st.session_state.error_message = "下载已取消"
            st.experimental_rerun()

if st.session_state.error_message:
    st.error(st.session_state.error_message)

if st.session_state.download_complete:
    st.success("下载完成！✅")
    if st.session_state.download_filename and os.path.exists(st.session_state.download_filename):
        file_size = os.path.getsize(st.session_state.download_filename)
        st.write(f"文件大小：{file_size/1024/1024:.2f} MB")
        
        with open(st.session_state.download_filename, "rb") as f:
            st.download_button(
                label="下载文件",
                data=f,
                file_name=os.path.basename(st.session_state.download_filename),
                mime="application/octet-stream"
            )
    else:
        st.error("文件不存在，可能下载失败")

# 注意事项提示
st.markdown("---")
st.info("""
**使用说明：**
1. 输入有效的磁力链接（必须以'magnet:?xt='开头）
2. 点击开始下载按钮
3. 下载完成后会出现文件下载按钮
4. 大文件下载可能需要较长时间，请保持页面开启

**注意：** 下载速度取决于种子可用性和网络环境
""")