app.py

import streamlit as st
import requests
import re

def download_youtube_video(url: str, output_path: str = "./videos") -> str:
    """
    Download a YouTube video using requests library and save it to the local file system.

    :param url: The URL of the YouTube video to download.
    :param output_path: The path where the downloaded video will be saved.
    :return: The absolute path of the downloaded video file.
    """
    # Get the video ID from the URL
    video_id = url.split("v=")[1]

    # Get the video info
    video_info_url = f"https://www.youtube.com/get_video_info?video_id={video_id}"
    video_info_response = requests.get(video_info_url)
    video_info = video_info_response.text

    # Extract the video title and streams
    title_search = re.search(r"title=([^&]+)", video_info)
    title = title_search.group(1) if title_search else "video"
    stream_map_search = re.search(r"url_encoded_fmt_stream_map=([^&]+)", video_info)
    stream_map = stream_map_search.group(1) if stream_map_search else None

    if not stream_map:
        raise Exception("Could not extract video streams")

    # Decode the stream map and extract the video URLs
    stream_map = requests.utils.unquote(stream_map)
    streams = stream_map.split(",")
    urls = [re.search(r"url=([^&]+)", stream).group(1) for stream in streams]

    # Choose the best quality URL
    url = urls[0]

    # Download the video and save it to the specified output path
    response = requests.get(url, stream=True)
    filename = f"{output_path}/{title}.mp4"
    with open(filename, "wb") as f:
        for chunk in response.iter_content(chunk_size=1024):
            if chunk:
                f.write(chunk)

    # Return the absolute path of the downloaded video file
    return filename

st.title("YouTube Video Downloader")

url = st.text_input("Enter a YouTube URL:")

if url:
    st.write(f"Downloading video from {url}...")
    try:
        video_path = download_youtube_video(url)
        st.success(f"Downloaded video to: {video_path}")
        st.video(video_path)
    except Exception as e:
        st.error(f"Failed to download video: {e}")