Fix relative links

Closes https://github.com/wasi-master/13ft/issues/10

app/index.py

@@ -1,12 +1,35 @@
 import flask
 import requests
 from flask import request
+from bs4 import BeautifulSoup
+from urllib.parse import urlparse, urljoin
 
 app = flask.Flask(__name__)
 googlebot_headers = {
     "User-Agent": "Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/W.X.Y.Z Mobile Safari/537.36 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
 }
 
+def add_base_tag(html_content, original_url):
+    soup = BeautifulSoup(html_content, 'html.parser')
+    parsed_url = urlparse(original_url)
+    base_url = f"{parsed_url.scheme}://{parsed_url.netloc}/"
+    
+    # Handle paths that are not root, e.g., "https://x.com/some/path/w.html"
+    if parsed_url.path and not parsed_url.path.endswith('/'):
+        base_url = urljoin(base_url, parsed_url.path.rsplit('/', 1)[0] + '/')
+    base_tag = soup.find('base')
+    
+    print(base_url)
+    if not base_tag:
+        new_base_tag = soup.new_tag('base', href=base_url)
+        if soup.head:
+            soup.head.insert(0, new_base_tag)
+        else:
+            head_tag = soup.new_tag('head')
+            head_tag.insert(0, new_base_tag)
+            soup.insert(0, head_tag)
+    
+    return str(soup)
 
 def bypass_paywall(url):
     """
@@ -15,7 +38,7 @@ def bypass_paywall(url):
     if url.startswith("http"):
         response = requests.get(url, headers=googlebot_headers)
         response.encoding = response.apparent_encoding
-        return response.text
+        return add_base_tag(response.text, response.url)
 
     try:
         return bypass_paywall("https://" + url)

app/requirements.txt

@@ -1,2 +1,3 @@
 flask
 requests
+bs4