import re
from flask import Flask, request, Response
import requests
from urllib.parse import urlparse

app = Flask(__name__)

# --- Whitelist filtering rules (Unchanged) ---
ALLOWED_PATTERNS = [
    re.compile(r'^https://github\.com/[^/]+/[^/]+/(?:releases|archive)/.*$', re.IGNORECASE),
    re.compile(r'^https://github\.com/[^/]+/[^/]+/(?:blob|raw)/.*$', re.IGNORECASE),
    re.compile(r'^https://github\.com/[^/]+/[^/]+/(?:info|git-).*/.*$', re.IGNORECASE), # This is key for git clone
    re.compile(r'^https://raw\.(?:githubusercontent|github)\.com/[^/]+/[^/]+/.*/.*$', re.IGNORECASE),
    re.compile(r'^https://gist\.(?:githubusercontent|github)\.com/[^/]+/[^/]+/.*/.*$', re.IGNORECASE),
    re.compile(r'^https://github\.com/[^/]+/[^/]+/tags.*$', re.IGNORECASE),
    re.compile(r'^https://avatars\.githubusercontent\.com/.*$', re.IGNORECASE),
    re.compile(r'^https://github\.githubassets\.com/.*$', re.IGNORECASE),
    re.compile(r'^https://github\.com/[^/]+/?$', re.IGNORECASE),
    re.compile(r'^https://github\.com/[^/]+/[^/]+/?$', re.IGNORECASE),
]

def is_url_allowed(url):
    """Checks if the given URL matches any pattern in the whitelist."""
    for pattern in ALLOWED_PATTERNS:
        if pattern.match(url):
            return True
    return False

# --- Core Proxy Logic ---

# A single, consolidated route to capture all requests and methods
@app.route('/', defaults={'path': ''}, methods=['GET', 'POST', 'PUT', 'DELETE'])
@app.route('/<path:path>', methods=['GET', 'POST', 'PUT', 'DELETE'])
def proxy(path):
    """
    A universal reverse proxy that takes the target URL as part of the path.
    """
    
    # --- 1. Construct target URL from the request path ---
    # request.full_path includes the query string, which is essential for git
    target_path = request.full_path
    
    # Remove the leading slash
    if target_path.startswith('/'):
        target_path = target_path[1:]

    # If the path is empty (root request), return a simple landing page
    if not target_path:
        return ("<p>This is a GitHub reverse proxy. Usage:</p>"
                "<p><code>&lt;proxy_url&gt;/&lt;target_github_url&gt;</code></p>"
                "<p>Example: <code>/github.com/python/cpython.git</code></p>"), 200

    # Prepend https:// if no scheme is present
    if not target_path.startswith(('http://', 'https://')):
        target_url = 'https://' + target_path
    else:
        target_url = target_path
        
    # --- 2. Perform security filter check ---
    if not is_url_allowed(target_url):
        error_message = (
            "<h1>403 Forbidden</h1>"
            "<p>This request is blocked by the proxy's security policy.</p>"
            f"<p>Blocked URL: {target_url}</p>"
        )
        return error_message, 403

    # --- 3. Forward the request ---
    try:
        target_host = urlparse(target_url).hostname
        if not target_host:
            raise ValueError("Could not parse hostname from target URL")
    except Exception as e:
        return f"Invalid target URL in path: {e}", 400

    headers = {key: value for (key, value) in request.headers if key.lower() != 'host'}
    headers['Host'] = target_host

    try:
        resp = requests.request(
            method=request.method,
            url=target_url,
            headers=headers,
            data=request.get_data(),
            cookies=request.cookies,
            allow_redirects=False,
            stream=True,
            timeout=30  # Added a timeout for robustness
        )

        excluded_headers = ['content-encoding', 'content-length', 'transfer-encoding', 'connection']
        response_headers = [(name, value) for (name, value) in resp.raw.headers.items() if name.lower() not in excluded_headers]

        return Response(resp.iter_content(chunk_size=8192), status=resp.status_code, headers=response_headers)

    except requests.exceptions.RequestException as e:
        return f"An error occurred while proxying: {e}", 502


if __name__ == '__main__':
    # For production, use a proper WSGI server like Gunicorn
    app.run(host='0.0.0.0', port=7860)