From d3778d1171f9ebc14b3a9afd5a1048432fc7d1d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Katariina=20J=C3=A4rvenm=C3=A4ki?=
 <katariina.jarvenmaki@proton.me>
Date: Mon, 2 Mar 2026 09:35:34 +0200
Subject: [PATCH] Add URL shortening functionality with FastAPI

---
 .gitignore  |  3 ++-
 README.md   |  6 ++---
 app/main.py | 74 +++++++++++++++++++++++++++++++++++++----------------
 3 files changed, 57 insertions(+), 26 deletions(-)

diff --git a/.gitignore b/.gitignore
index 8750bee..9aaeae7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 app/__pycache__
-venv/
\ No newline at end of file
+venv/
+test.txt
\ No newline at end of file
diff --git a/README.md b/README.md
index 2bde86f..dfe6b60 100644
--- a/README.md
+++ b/README.md
@@ -12,11 +12,11 @@ source venv/bin/activate
 ```bash
 uvicorn app.main:app --reload
 ```
-Then check: 
-http://127.0.0.1:8000 
+Then check:<br> 
+http://127.0.0.1:8000<br>
 http://127.0.0.1:8000/docs
 
-Test Short URL Endpoint
+Test Short URL Endpoint:<br>
 http://127.0.0.1:8000/shorten
 
 ## Running a test
diff --git a/app/main.py b/app/main.py
index 079aec0..f7a96db 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,13 +1,18 @@
 from fastapi import FastAPI, HTTPException
 from fastapi.responses import RedirectResponse
 from contextlib import asynccontextmanager
-from pydantic import BaseModel
 from app.utils import generate_short_code
-from dotenv import load_dotenv
-import os
+from pydantic import BaseModel, HttpUrl
+from pydantic_settings import BaseSettings
 import sqlite3
 import logging
 
+class AppSettings(BaseSettings):
+    base_url: str = "http://localhost:8000"
+    database_url: str = "urls.db"
+
+settings = AppSettings()  # Load environment variables
+
 # Set up logging configuration
 logging.basicConfig(level=logging.INFO,
                     format="%(asctime)s - %(levelname)s - %(message)s")
@@ -17,8 +22,18 @@ logger = logging.getLogger(__name__)
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     conn = sqlite3.connect('urls.db')
-    conn.execute('''CREATE TABLE IF NOT EXISTS urls
-                    (id INTEGER PRIMARY KEY, short_code TEXT, original_url TEXT, clicks INTEGER)''')
+    conn = sqlite3.connect(settings.database_url)
+    conn.execute("""
+    CREATE TABLE IF NOT EXISTS urls (
+        id INTEGER PRIMARY KEY,
+        short_code TEXT UNIQUE,
+        original_url TEXT NOT NULL,
+        clicks INTEGER DEFAULT 0
+    );
+    """)
+    conn.execute("""
+    CREATE INDEX IF NOT EXISTS idx_short_code ON urls(short_code);
+    """)
     conn.commit()
     logger.info("Database initialized or already exists.")
     yield
@@ -28,11 +43,10 @@ async def lifespan(app: FastAPI):
 app = FastAPI(lifespan=lifespan)
 
 def get_db_connection():
-    conn = sqlite3.connect('urls.db')
-    return conn
+    return sqlite3.connect(settings.database_url, check_same_thread=False)
 
 class URLRequest(BaseModel):
-    url: str
+    url: HttpUrl
 
 @app.get("/")
 def home():
@@ -41,36 +55,52 @@ def home():
 
 @app.post("/shorten")
 def shorten_url(request: URLRequest):
-    logger.info(f"Request received to shorten URL: {request.url}")
-    short_code = generate_short_code()
     conn = get_db_connection()
 
-    while conn.execute("SELECT 1 FROM urls WHERE short_code = ?", (short_code,)).fetchone():
+    existing = conn.execute(
+        "SELECT short_code FROM urls WHERE original_url = ?",
+        (str(request.url),)
+    ).fetchone()
+
+    if existing:
+        conn.close()
+        return {"short_url": f"{settings.base_url}/{existing[0]}"}
+
+    short_code = generate_short_code()
+    while conn.execute(
+        "SELECT 1 FROM urls WHERE short_code = ?",
+        (short_code,)
+    ).fetchone():
         short_code = generate_short_code()
 
-    conn.execute("INSERT INTO urls (short_code, original_url, clicks) VALUES (?, ?, ?)",
-                 (short_code, request.url, 0))
+    conn.execute(
+        "INSERT INTO urls (short_code, original_url, clicks) VALUES (?, ?, 0)",
+        (short_code, str(request.url))
+    )
     conn.commit()
     conn.close()
 
-    short_url = f"{os.getenv('BASE_URL', 'http://localhost:8000')}/{short_code}"
-    logger.info(f"Shortened URL created: {short_url}")
-    return {"short_url": short_url}
+    return {"short_url": f"{settings.base_url}/{short_code}"}
 
 @app.get("/{short_code}")
 def redirect_to_url(short_code: str):
-    logger.info(f"Redirect request received for short_code: {short_code}")
     conn = get_db_connection()
-    url_data = conn.execute("SELECT original_url, clicks FROM urls WHERE short_code = ?", (short_code,)).fetchone()
+    url_data = conn.execute(
+        "SELECT original_url FROM urls WHERE short_code = ?",
+        (short_code,)
+    ).fetchone()
 
     if url_data is None:
-        logger.warning(f"Shortened URL for {short_code} not found.")
+        conn.close()
         raise HTTPException(status_code=404, detail="Shortened URL not found")
 
-    original_url, clicks = url_data
-    conn.execute("UPDATE urls SET clicks = ? WHERE short_code = ?", (clicks + 1, short_code))
+    original_url = url_data[0]
+
+    conn.execute(
+        "UPDATE urls SET clicks = clicks + 1 WHERE short_code = ?",
+        (short_code,)
+    )
     conn.commit()
     conn.close()
 
-    logger.info(f"Redirecting to {original_url}. Total clicks: {clicks + 1}")
     return RedirectResponse(url=original_url)
\ No newline at end of file