Pasto

A Crystal-based pastebin application with live syntax highlighting preview and extensive theme support.

Features

🚀 Fast & Lightweight: Built with Crystal for excellent performance
🎨 Live Preview: Real-time syntax highlighting as you type
🌈 Extensive Theming: 321+ syntax highlighting themes from Tartrazine
🎭 Smart Language Detection: Filters unsupported languages (no more X10 errors!)
📱 Responsive Design: Works beautifully on desktop and mobile
🔒 Built-in Security: Rate limiting and size validation
🎯 Clean UI: Modern interface with Pico CSS

Live Preview

Pasto provides an innovative split-pane interface where you can:

Type code in the left pane
See instant syntax highlighting in the right pane
Switch languages and watch the preview update immediately
Change themes and see the highlighting update in real-time
Resize panels for your preferred viewing ratio

Theme Support

15 Pico CSS color schemes for UI styling
321 Tartrazine syntax themes for code highlighting
Light/Dark modes with system preference detection
Instant switching with localStorage persistence

Smart Language Filtering

Pasto intelligently handles language detection:

Hansa Integration: Uses advanced language classification
Tartrazine Filtering: Only shows languages that actually work with syntax highlighting
Graceful Fallback: Automatically selects the best supported language
No More Errors: Eliminates unsupported language errors like "X10"

Installation

Prerequisites

Crystal 1.0 or higher
Shards (Crystal package manager)

Build from Source

# Clone the repository
git clone https://github.com/ralsina/pasto.git
cd pasto

# Install dependencies
shards install

# Build the application
shards build

# Run the server
./bin/pasto --port 3000

Usage

Running the Server

# Start on default port 3000
./bin/pasto

# Start on custom port
./bin/pasto --port 8080

# Set maximum paste size (default: 100KB)
./bin/pasto --max-paste-size 5242880  # 5MB

# Specify default theme
./bin/pasto --theme dracula

Configuration

Pasto can be configured via:

Command line arguments
Environment variables
Configuration file (pasto.yml)

Environment Variables

export PASTO_PORT=3000
export PASTO_MAX_PASTE_SIZE=102400
export PASTO_THEME=monokai
export PASTO_RATE_LIMIT=10
export PASTO_RATE_WINDOW=60

Configuration File

Create pasto.yml:

port: 3000
max_paste_size: 102400  # 100KB
theme: monokai
rate_limit:
  requests: 10
  window: 60

API Endpoints

Create Paste

curl -X POST http://localhost:3000 \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "content=print('Hello, World!')&language=python&theme=dracula"

Get Paste

curl http://localhost:3000/{paste-id}

Live Syntax Highlighting API

curl -X POST http://localhost:3000/highlight \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "content=def hello(): pass&language=python&theme=monokai"

Security Features

Rate Limiting: 10 requests per minute per IP (configurable)
Size Validation: Configurable maximum paste size limits
Input Sanitization: Proper HTML escaping for all content
Error Handling: Graceful fallbacks for unsupported languages

Supported Languages

Pasto supports 32+ programming languages including:

Popular: Python, JavaScript, TypeScript, Java, C, C++, C#, Go, Rust
Web: HTML, CSS, SCSS, JSON, XML, Markdown
Systems: Bash, Shell, PowerShell
Data: SQL, MySQL, PostgreSQL
Many more: PHP, Ruby, Perl, Kotlin, Scala, and more

Note: Only languages with working Tartrazine lexers are shown in the dropdown.

Development

Project Structure

pasto/
├── src/
│   ├── pasto.cr          # Main application logic
│   ├── server.cr         # Web server and routes
│   └── paste.cr          # Paste model and highlighting
├── shards.yml            # Crystal dependencies
├── pasto.yml             # Configuration file
└── README.md

Development Commands

# Install dependencies
shards install

# Run tests
crystal spec

# Check formatting
crystal tool format src/

# Linting
ameba src/

# Build in development mode
shards build

# Build with release optimizations
shards build --release