Curtail

Project Overview

Curtail is a URL shortener built in Haskell using the Servant framework. It leverages Haskell’s type system to define API contracts at the type level, with SQLite persistence via the persistent library. Short URLs support click tracking and statistics.

API

Method	Route	Description
POST	/api/shorten	Create a short URL
GET	/:code	Redirect to original URL
GET	/api/stats/:code	View click statistics

Key Features

Type-Safe API Design

• Servant defines the entire API as a Haskell type
• Compile-time guarantees that handlers match the API spec
• Automatic request parsing and validation

Persistent Storage

• SQLite database via the persistent library
• Type-safe database queries
• Automatic schema migration

Click Tracking

• Track redirect counts per short URL
• Statistics endpoint for monitoring usage

Technical Implementation

Technologies Used

• Haskell: Pure functional programming language
• Servant: Type-level web framework
• SQLite: Lightweight embedded database
• Persistent: Type-safe ORM for Haskell
• Stack: Haskell build tool

Learning Outcomes

Functional Programming

• Type-level programming for API definitions
• Monad transformers for effect composition
• Haskell’s type system for correctness guarantees
• Working with persistent for database access

Web Development in Haskell

• Servant’s approach to API design vs traditional frameworks
• How type safety eliminates entire categories of bugs
• Trade-offs of functional web development