Refactor application to use SQLite for link storage, implement rate limiting, and enhance error handling; update README and add CI workflow

Author: SagarBiswas-MultiHAT

.github/workflows/ci.yml

@@ -0,0 +1,23 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt
+          pip install -r requirements-dev.txt
+      - name: Run tests
+        run: pytest -q

.gitignore

@@ -0,0 +1,12 @@
+.venv/
+__pycache__/
+*.pyc
+.pytest_cache/
+.env
+.env.*
+.vscode/
+*.sqlite
+*.db
+data/*.db
+data/*.sqlite
+data/*.json

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Sagar Biswas
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -8,9 +8,9 @@ This project lets you turn a long link into a short link.
 
 Example:
 
-- Long               : https://youtu.be/oUp4SWSrYYk?si=Z7r-93Y6WbqYXrns
-- Short   (yours)    : https://sharplink.onrender.com/MultiHAT
-- mirror  (TinyURL)  : https://tinyurl.com/2d89to88 
+- Long : https://youtu.be/oUp4SWSrYYk?si=Z7r-93Y6WbqYXrns
+- Short (yours) : https://sharplink.onrender.com/MultiHAT
+- mirror (TinyURL) : https://tinyurl.com/2d89to88
 
 When someone opens the short link, the website sends them to the long link.
 
@@ -67,8 +67,6 @@ python -m venv .venv
 
 ### Step 2: Install the project packages
 
-Remove gunicorn==22.0.0 from requirements.txt since it was used to host the web app on Render. Gunicorn==22.0.0 is not needed for local use.
-
 Run:
 
 ```powershell
@@ -102,9 +100,19 @@ http://localhost:5000
 
 ## Where the links are saved
 
-Your short links are saved in a small file on your computer:
+Your short links are saved in a small SQLite database file on your computer:
+
+- `data/url_store.db`
+
+If a legacy `data/url_store.json` exists, the app will migrate it on first run.
+
+You can override the database location with:
+
+```powershell
+$env:SHARPLINK_DB_PATH="C:\path\to\url_store.db"
+```
 
-- `data/url_store.json`
+You can also use a `.env` file. See [.env.example](.env.example).
 
 This file remembers:
 
@@ -128,7 +136,6 @@ To make links work for everyone on the internet, you must deploy this app on a p
 You can also call the backend directly:
 
 - `POST /api/shorten`
-
   - JSON body example:
     ```json
     {
@@ -147,10 +154,38 @@ You can also call the backend directly:
 
 - Health check: http://localhost:5000/health
 
-## Credits
+## Testing
 
-Developed by Sagar Biswas: https://github.com/SagarBiswas-MultiHAT
+Install dev dependencies:
 
+```powershell
+pip install -r requirements-dev.txt
+```
 
+Run tests:
 
+```powershell
+pytest
+```
+
+## Security notes
+
+- Only `http://` and `https://` URLs are accepted.
+- Aliases are length-limited and restricted to letters, numbers, `-`, and `_`.
+- API requests are rate-limited by IP.
+- If you deploy publicly, add abuse controls and monitoring.
+
+## Rate limiting (production)
+
+The default limiter uses in-memory storage, which is fine for local testing but not for production.
+Use Redis in production by setting:
+
+```powershell
+$env:RATELIMIT_STORAGE_URI="redis://localhost:6379/0"
+```
+
+Or add the same to your `.env` file. See [.env.example](.env.example).
 
+## Credits
+
+Developed by Sagar Biswas: https://github.com/SagarBiswas-MultiHAT