src/streamlit_app.py

import streamlit as st
import yt_dlp
import tempfile
import os
import threading
import time
from pathlib import Path

# 頁面配置
st.set_page_config(
    page_title="🎬 YouTube 下載器",
    page_icon="🎬",
    layout="centered"
)

# 初始化狀態
if 'download_status' not in st.session_state:
    st.session_state.download_status = ""
if 'is_downloading' not in st.session_state:
    st.session_state.is_downloading = False
if 'download_progress' not in st.session_state:
    st.session_state.download_progress = 0
if 'video_info' not in st.session_state:
    st.session_state.video_info = None
if 'download_path' not in st.session_state:
    st.session_state.download_path = None

def progress_hook(d):
    """下載進度回調"""
    if d['status'] == 'downloading':
        if 'total_bytes' in d or '_total_bytes_str' in d:
            try:
                downloaded = d.get('downloaded_bytes', 0)
                total = d.get('total_bytes') or d.get('_total_bytes_estimate', 1)
                if total and total > 0:
                    percent = min((downloaded / total) * 100, 100)
                    st.session_state.download_progress = percent
                    st.session_state.download_status = f"📥 下載中... {percent:.1f}%"
                else:
                    st.session_state.download_status = "📥 下載中..."
            except:
                st.session_state.download_status = "📥 下載中..."
        else:
            st.session_state.download_status = "📥 下載中..."
    elif d['status'] == 'finished':
        st.session_state.download_progress = 100
        st.session_state.download_status = "✅ 下載完成！"
        filename = os.path.basename(d['filename'])
        st.session_state.download_path = d['filename']

def get_video_info(url):
    """獲取影片資訊"""
    try:
        ydl_opts = {
            'quiet': True,
            'no_warnings': True,
        }
        
        with yt_dlp.YoutubeDL(ydl_opts) as ydl:
            info = ydl.extract_info(url, download=False)
            return {
                'title': info.get('title', '未知標題'),
                'uploader': info.get('uploader', '未知上傳者'),
                'duration': info.get('duration', 0),
                'thumbnail': info.get('thumbnail', ''),
                'view_count': info.get('view_count', 0)
            }
    except Exception as e:
        st.error(f"❌ 無法獲取影片資訊: {str(e)}")
        return None

def download_video(url, quality, audio_only):
    """下載影片"""
    try:
        # 創建臨時目錄
        temp_dir = tempfile.mkdtemp()
        
        # 設定下載選項
        if audio_only:
            format_selector = 'bestaudio/best'
            filename = '%(title)s.%(ext)s'
            postprocessors = [{
                'key': 'FFmpegExtractAudio',
                'preferredcodec': 'mp3',
                'preferredquality': '192',
            }]
        else:
            height = quality.replace('p', '')
            format_selector = f'best[height<={height}]/best'
            filename = '%(title)s.%(ext)s'
            postprocessors = []
        
        ydl_opts = {
            'format': format_selector,
            'outtmpl': os.path.join(temp_dir, filename),
            'progress_hooks': [progress_hook],
            'quiet': True,
            'no_warnings': True,
            'postprocessors': postprocessors,
        }
        
        st.session_state.download_status = "🚀 開始下載..."
        
        with yt_dlp.YoutubeDL(ydl_opts) as ydl:
            ydl.download([url])
        
        st.session_state.is_downloading = False
        
    except Exception as e:
        st.session_state.download_status = f"❌ 下載失敗: {str(e)}"
        st.session_state.is_downloading = False

# 主介面
st.title("🎬 YouTube 下載器")
st.markdown("簡單快速的YouTube影片下載工具")

# URL 輸入
url = st.text_input("🔗 請輸入 YouTube 影片連結", placeholder="https://www.youtube.com/watch?v=...")

# 下載設定
col1, col2 = st.columns(2)

with col1:
    download_type = st.selectbox("📱 下載類型", ["影片", "音訊 (MP3)"])

with col2:
    if download_type == "影片":
        quality = st.selectbox("🎯 影片品質", ["1080p", "720p", "480p", "360p"], index=1)
    else:
        quality = None
        st.info("音訊品質: 192kbps MP3")

# 按鈕區域
btn_col1, btn_col2 = st.columns(2)

with btn_col1:
    if st.button("🔍 預覽影片資訊", use_container_width=True):
        if url:
            with st.spinner("正在獲取影片資訊..."):
                info = get_video_info(url)
                if info:
                    st.session_state.video_info = info
        else:
            st.error("請先輸入影片連結！")

with btn_col2:
    if st.button("⬇️ 開始下載", use_container_width=True, disabled=st.session_state.is_downloading):
        if not url:
            st.error("請輸入影片連結！")
        else:
            st.session_state.is_downloading = True
            st.session_state.download_progress = 0
            st.session_state.download_status = "準備下載..."
            st.session_state.download_path = None
            
            audio_only = download_type == "音訊 (MP3)"
            thread = threading.Thread(
                target=download_video,
                args=(url, quality, audio_only),
                daemon=True
            )
            thread.start()

# 顯示影片資訊
if st.session_state.video_info:
    st.markdown("---")
    st.subheader("📹 影片資訊")
    
    info = st.session_state.video_info
    
    # 創建兩欄布局
    info_col1, info_col2 = st.columns([2, 1])
    
    with info_col1:
        st.write(f"**📝 標題:** {info['title']}")
        st.write(f"**👤 上傳者:** {info['uploader']}")
        
        if info['duration']:
            minutes = info['duration'] // 60
            seconds = info['duration'] % 60
            st.write(f"**⏱️ 長度:** {minutes}:{seconds:02d}")
        
        if info['view_count']:
            st.write(f"**👁️ 觀看次數:** {info['view_count']:,}")
    
    with info_col2:
        if info['thumbnail']:
            st.image(info['thumbnail'], caption="影片縮圖", width=200)

# 顯示下載進度
if st.session_state.is_downloading or st.session_state.download_progress > 0:
    st.markdown("---")
    st.subheader("📊 下載進度")
    
    if st.session_state.download_progress > 0:
        progress_bar = st.progress(st.session_state.download_progress / 100)
    
    if st.session_state.download_status:
        st.write(st.session_state.download_status)

# 下載完成後提供下載連結
if st.session_state.download_path and os.path.exists(st.session_state.download_path):
    st.markdown("---")
    st.success("🎉 下載完成！")
    
    try:
        with open(st.session_state.download_path, 'rb') as file:
            file_data = file.read()
            filename = os.path.basename(st.session_state.download_path)
            
            st.download_button(
                label="📁 下載檔案",
                data=file_data,
                file_name=filename,
                mime="application/octet-stream",
                use_container_width=True
            )
    except Exception as e:
        st.error(f"檔案讀取失敗: {e}")

# 自動刷新進度
if st.session_state.is_downloading:
    time.sleep(0.5)
    st.rerun()

# 頁腳資訊
st.markdown("---")
st.markdown("""
<div style="text-align: center; color: #666;">
    <small>⚠️ 請確保您有權下載所選內容，並遵守相關版權法規</small>
</div>
""", unsafe_allow_html=True)