📞 PhoneCheck - Expert-Level Phone Validation REST API

A high-performance, production-ready REST API for phone number validation built with Zig and wrapping Google's libphonenumber C++ library.

🚀 Free alternative to Twilio Lookup - Validate 10M numbers/month for $40 instead of $50,000

⚡ 2,500+ req/s throughput - Battle-tested with simulated annealing load analysis

🔒 Memory-safe - Zig's compile-time guarantees + arena allocators

Documentation

• Quick Start - Get started in 5 minutes
• Architecture - Technical design and implementation
• Testing - Comprehensive testing guide
• Production Readiness - Deployment checklist
• Advanced Testing - Simulated annealing breaking point analysis

🚀 Features

• Industry-Standard Validation: Powered by Google's libphonenumber (used by Google, Android, iOS)
• Zero-Copy FFI: Direct C/C++ interop with no marshalling overhead
• Ultra-Fast: Zig's performance + libphonenumber's battle-tested algorithms
• Comprehensive Analysis:
  • ✅ Validity checking (correct for region)
  • ✅ Possibility checking (correct length/structure)
  • ✅ Phone type detection (mobile, fixed-line, toll-free, etc.)
  • ✅ Region/country code extraction
  • ✅ Multiple format outputs (E.164, international, national)
  • ✅ Number comparison and matching
• 190+ Countries: Full international support
• REST API: Simple HTTP JSON interface
• Production-Ready: CORS support, error handling, health checks

📋 Prerequisites

System Dependencies

You need to install Google's libphonenumber C++ library:

Ubuntu/Debian:

sudo apt-get update
sudo apt-get install -y \
    libphonenumber-dev \
    libprotobuf-dev \
    libicu-dev \
    cmake \
    build-essential

macOS (Homebrew):

brew install libphonenumber protobuf icu4c

Arch Linux:

sudo pacman -S libphonenumber protobuf icu

Build from source (if packages not available):

# Clone and build libphonenumber
git clone https://github.com/google/libphonenumber.git
cd libphonenumber/cpp
mkdir build && cd build
cmake ..
make -j$(nproc)
sudo make install
sudo ldconfig

Zig

Install Zig 0.15.2 or later:

# Download from https://ziglang.org/download/
# Or use your package manager

🔧 Installation

1. Clone the repository:

git clone <your-repo>
cd phonecheck

1. Build the C++ wrapper:

./build_wrapper.sh

1. Build the Zig application:

zig build

1. Run the server:

zig build run

The API will start on http://0.0.0.0:8080

📚 API Documentation

Health Check

Endpoint: GET /health

Response:

{
  "status": "healthy",
  "service": "phonecheck",
  "version": "1.0.0"
}

Validate Phone Number

Endpoint: POST /validate

Request Body:

{
  "phone_number": "+14155552671",
  "region": "US"  // Optional: ISO 3166-1 alpha-2 country code
}

Response:

{
  "valid": true,
  "possible": true,
  "type": "FIXED_LINE_OR_MOBILE",
  "country_code": 1,
  "national_number": 4155552671,
  "region": "US",
  "e164_format": "+14155552671",
  "international_format": "+1 415-555-2671",
  "national_format": "(415) 555-2671",
  "possibility_reason": "IS_POSSIBLE"
}

Phone Types:

• FIXED_LINE - Traditional landline
• MOBILE - Mobile phone
• FIXED_LINE_OR_MOBILE - Could be either
• TOLL_FREE - Toll-free number
• PREMIUM_RATE - Premium rate number
• SHARED_COST - Shared cost service
• VOIP - VoIP number
• PERSONAL_NUMBER - Personal number
• PAGER - Pager
• UAN - Universal Access Number
• VOICEMAIL - Voicemail access
• UNKNOWN - Unknown type

Possibility Reasons:

• IS_POSSIBLE - Number is valid
• INVALID_COUNTRY_CODE - Invalid country code
• TOO_SHORT - Too few digits
• TOO_LONG - Too many digits
• IS_POSSIBLE_LOCAL_ONLY - Valid locally only
• INVALID_LENGTH - Invalid length for region

🧪 Testing

Run the test suite:

zig build test

📖 Usage Examples

cURL

# Validate a US number
curl -X POST http://localhost:8080/validate \
  -H "Content-Type: application/json" \
  -d '{"phone_number": "+14155552671"}'

# Validate with explicit region
curl -X POST http://localhost:8080/validate \
  -H "Content-Type: application/json" \
  -d '{"phone_number": "4155552671", "region": "US"}'

# International number
curl -X POST http://localhost:8080/validate \
  -H "Content-Type: application/json" \
  -d '{"phone_number": "+442071838750", "region": "GB"}'

Python

import requests

def validate_phone(number: str, region: str = None):
    response = requests.post(
        "http://localhost:8080/validate",
        json={"phone_number": number, "region": region}
    )
    return response.json()

# Example usage
result = validate_phone("+14155552671")
print(f"Valid: {result['valid']}")
print(f"Type: {result['type']}")
print(f"International: {result['international_format']}")

JavaScript/TypeScript

async function validatePhone(
  phoneNumber: string,
  region?: string
): Promise<ValidationResult> {
  const response = await fetch('http://localhost:8080/validate', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ phone_number: phoneNumber, region })
  });
  return response.json();
}

// Example usage
const result = await validatePhone('+14155552671');
console.log(`Valid: ${result.valid}`);
console.log(`Type: ${result.type}`);

🏗️ Architecture

┌─────────────┐
│   Client    │
│ (HTTP/JSON) │
└──────┬──────┘
       │
       ▼
┌─────────────────────┐
│   Zig HTTP Server   │
│  - Routing          │
│  - JSON parsing     │
│  - Error handling   │
└──────┬──────────────┘
       │ Zero-copy FFI
       ▼
┌─────────────────────┐
│  C++ Wrapper        │
│  - Type conversion  │
│  - Memory safety    │
└──────┬──────────────┘
       │
       ▼
┌─────────────────────┐
│  libphonenumber     │
│  - Parsing          │
│  - Validation       │
│  - Formatting       │
└─────────────────────┘

🎯 Performance

• Sub-millisecond validation latency
• Zero allocation in hot paths (using arena allocators)
• Concurrent request handling via Zig threads
• Direct C FFI with no serialization overhead

🔒 Safety

Following Tiger Style principles:

• ✅ Explicit bounds on all buffers
• ✅ No recursion
• ✅ Arena allocators for request scoping
• ✅ Fail-fast error handling
• ✅ Comprehensive input validation

🚢 Deployment

Docker

FROM ubuntu:22.04

RUN apt-get update && apt-get install -y \
    libphonenumber-dev libprotobuf-dev libicu-dev

COPY zig-out/bin/phonecheck /usr/local/bin/
EXPOSE 8080
CMD ["phonecheck"]

Systemd Service

[Unit]
Description=PhoneCheck REST API
After=network.target

[Service]
Type=simple
User=phonecheck
ExecStart=/usr/local/bin/phonecheck
Restart=always

[Install]
WantedBy=multi-user.target

📊 Monitoring

The API exposes structured logs via stdout. Key metrics:

• Request method and path
• Response status codes
• Error messages
• Connection handling

Integrate with your logging infrastructure (ELK, Loki, CloudWatch, etc.)

🤝 Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Run tests: zig build test
5. Submit a pull request

📄 License

MIT License - See LICENSE file

🙏 Acknowledgments

• Google's libphonenumber: The gold standard for phone number handling
• Zig: Modern systems programming with safety and performance
• TigerBeetle: Inspiration for robust, zero-technical-debt coding practices

📞 Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions

Built with ❤️ using Zig and libphonenumber