implement url unshortening for t.co links

server/requirements.txt

@@ -1,2 +1,3 @@
 fastapi
-uvicorn[standard]
+uvicorn[standard]
+requests

server/src/main.py

@@ -1,3 +1,5 @@
+import re
+import requests
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from typing import Optional
@@ -18,6 +20,21 @@ app.add_middleware(
 )
 
 
+def unshorten_url(url: str):
+    pattern = re.compile(r"<title>(.*?)<\/title>")
+
+    response = requests.get(
+        url=url,
+        headers={"User-Agent": "Mozilla/5.0 (X11; Linux x86_64; rv:124.0) Gecko/20100101 Firefox/124.0"}
+    )
+
+    match = pattern.search(response.text)
+    if match:
+        return match.group(1)
+    else:
+        return None
+
+
 @app.get('/')
 async def receive_url(url: Optional[str] = None):
     if url is None:
@@ -25,7 +42,9 @@ async def receive_url(url: Optional[str] = None):
 
     domain = urlparse(url).netloc
 
-    if domain in SHORTEN_DOMAINS:
-        return {"result": "shortened url"}
-    else:
+    if domain not in SHORTEN_DOMAINS:
         return {"error": f"cannot shorten {url}"}
+
+    unshortened = unshorten_url(url)
+
+    return {"result": unshortened}