Previous

Is a binary protocol and BFF framework.

Previous is made of a Schema definition, a compiler, client and server utils to help you create complete solutions with one tool.

Compiler Status

Phase	Status	Docs
1. AST Construction	✅ Complete	README.md
2. Type Resolution + IR	✅ Complete	PHASE2_COMPLETE.md
3. Binary Encoding	✅ Complete	PHASE3_COMPLETE.md
4. Code Generation	✅ Complete	PHASE4_COMPLETE.md
5. CLI & File I/O	✅ Complete	PHASE5_COMPLETE.md

🎉 PROJECT COMPLETE! All 5 phases implemented. The Previous compiler is production-ready!

Quick Start

# Compile a schema file
cargo run -- examples/user.pr --out ./generated

# Run demo
cargo run -- demo

# Show help
cargo run -- --help

Design

Previous is built around Resource's.

Resources are a way to describe the data your server and client can interchange.

Anatomy of a Resource schema

You can create your Resources by defining its shape with field types and names.

resource User {
    string   name
    string   email
    optional number age
    bool     active
}

resource Names {
    list string name
}

resource Users {
    list User
}

resource Settings {
    nullable bool notifications
}

resource Notification {
    number default(10) interval
}

This will be compiled to TypeScript client and server code using the Previous compiler:

# Compile the schema
previouscc schema.pr --out ./generated

Generated TypeScript Client:

import { User } from './generated/client';

const response = await fetch('/api/user/1');
const buffer = await response.arrayBuffer();
const user = new User(new Uint8Array(buffer));

console.log(user.getName());    // Lazy parsed
console.log(user.getEmail());   // Lazy parsed
console.log(user.toJSON());     // Full JSON conversion

Generated TypeScript Server:

import { User } from './generated/server';

// Build user with builder pattern
const user = new User()
    .name("John")
    .email("john@email.com")
    .age(30)
    .active(false);

// Encode to binary
const binary_data = user.encode();

// Send to client
return new Response(binary_data);

The Previous compiler handles all the serialization/deserialization automatically. The binary protocol is more efficient than JSON while maintaining type safety on both client and server.