rust-rule-engine 0.1.1

# 🦀 Rust Rule Engine - GRL Edition

A powerful, high-performance rule engine for Rust supporting **GRL (Grule Rule Language)** syntax with advanced features like method calls, custom functions, object interactions, and both file-based and inline rule management.

[![Crates.io](https://img.shields.io/crates/v/rust-rule-engine.svg)](https://crates.io/crates/rust-rule-engine)
[![Documentation](https://docs.rs/rust-rule-engine/badge.svg)](https://docs.rs/rust-rule-engine)
[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)

## 🌟 Key Features

- **🔥 GRL-Only Support**: Pure Grule Rule Language syntax (no JSON)
- **📄 Rule Files**: External `.grl` files for organized rule management  
- **📝 Inline Rules**: Define rules as strings directly in your code
- **📞 Custom Functions**: Register and call user-defined functions from rules
- **🎯 Method Calls**: Support for `Object.method(args)` and property access
- **🧠 Knowledge Base**: Centralized rule management with salience-based execution
- **💾 Working Memory**: Facts system for complex object interactions  
- **⚡ High Performance**: Optimized execution engine with cycle detection
- **🛡️ Type Safety**: Rust's type system ensures runtime safety
- **🏗️ Builder Pattern**: Clean API with `RuleEngineBuilder`
- **📈 Execution Statistics**: Detailed performance metrics and debugging

## 🚀 Quick Start

Add to your `Cargo.toml`:

```toml
[dependencies]
rust-rule-engine = "0.1.0"
```

### 📄 File-Based Rules

Create a rule file `rules/example.grl`:

```grl
rule "AgeCheck" salience 10 {
    when
        User.Age >= 18 && User.Country == "US"
    then
        User.setIsAdult(true);
        User.setCategory("Adult");
        log("User qualified as adult");
}

rule "VIPUpgrade" salience 20 {
    when
        User.IsAdult == true && User.SpendingTotal > 1000.0
    then
        User.setIsVIP(true);
        log("User upgraded to VIP status");
}
```

```rust
use rust_rule_engine::{RuleEngineBuilder, Value, Facts};
use std::collections::HashMap;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create engine with rule file
    let mut engine = RuleEngineBuilder::new()
        .with_rule_file("rules/example.grl")?
        .build();

    // Register custom functions
    engine.register_function("User.setIsAdult", |args, _| {
        println!("Setting adult status: {}", args[0]);
        Ok(Value::Boolean(true))
    });

    engine.register_function("User.setCategory", |args, _| {
        println!("Setting category: {}", args[0]);
        Ok(Value::String(args[0].to_string()))
    });

    // Create facts
    let facts = Facts::new();
    let mut user = HashMap::new();
    user.insert("Age".to_string(), Value::Integer(25));
    user.insert("Country".to_string(), Value::String("US".to_string()));
    user.insert("SpendingTotal".to_string(), Value::Number(1500.0));

    facts.add_value("User", Value::Object(user))?;

    // Execute rules
    let result = engine.execute(&facts)?;
    println!("Rules fired: {}", result.rules_fired);

    Ok(())
}
```

### 📝 Inline String Rules

Define rules directly in your code:

```rust
use rust_rule_engine::{RuleEngineBuilder, Value, Facts};
use std::collections::HashMap;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let grl_rules = r#"
        rule "HighValueCustomer" salience 20 {
            when
                Customer.TotalSpent > 1000.0
            then
                sendWelcomeEmail(Customer.Email, "GOLD");
                log("Customer upgraded to GOLD tier");
        }

        rule "LoyaltyBonus" salience 15 {
            when
                Customer.OrderCount >= 10
            then
                applyLoyaltyBonus(Customer.Id, 50.0);
                log("Loyalty bonus applied");
        }
    "#;

    // Create engine with inline rules
    let mut engine = RuleEngineBuilder::new()
        .with_inline_grl(grl_rules)?
        .build();

    // Register custom functions
    engine.register_function("sendWelcomeEmail", |args, _| {
        println!("📧 Welcome email sent to {} for {} tier", args[0], args[1]);
        Ok(Value::Boolean(true))
    });

    engine.register_function("applyLoyaltyBonus", |args, _| {
        println!("💰 Loyalty bonus of {} applied to customer {}", args[1], args[0]);
        Ok(Value::Number(args[1].as_number().unwrap_or(0.0)))
    });

    // Create facts
    let facts = Facts::new();
    let mut customer = HashMap::new();
    customer.insert("TotalSpent".to_string(), Value::Number(1250.0));
    customer.insert("OrderCount".to_string(), Value::Integer(12));
    customer.insert("Email".to_string(), Value::String("john@example.com".to_string()));
    customer.insert("Id".to_string(), Value::String("CUST001".to_string()));

    facts.add_value("Customer", Value::Object(customer))?;

    // Execute rules
    let result = engine.execute(&facts)?;
    println!("Rules fired: {}", result.rules_fired);

    Ok(())
}
```

## 🎯 GRL Rule Language Features

### Supported Syntax

```grl
rule "RuleName" salience 10 {
    when
        Object.Property > 100 &&
        Object.Status == "ACTIVE"
    then
        Object.setCategory("HIGH_VALUE");
        processTransaction(Object.Id, Object.Amount);
        log("Rule executed successfully");
}
```

### Operators

- **Comparison**: `>`, `>=`, `<`, `<=`, `==`, `!=`
- **Logical**: `&&`, `||` 
- **Value Types**: Numbers, Strings (quoted), Booleans (`true`/`false`)

### Actions

- **Method Calls**: `Object.method(args)`
- **Function Calls**: `functionName(args)`
- **Logging**: `log("message")`

## 📚 Examples

### 🛒 E-commerce Rules

```grl
rule "VIPCustomer" salience 20 {
    when
        Customer.TotalSpent > 5000.0 && Customer.YearsActive >= 2
    then
        Customer.setTier("VIP");
        sendWelcomePackage(Customer.Email, "VIP");
        applyDiscount(Customer.Id, 15.0);
        log("Customer upgraded to VIP");
}

rule "LoyaltyReward" salience 15 {
    when
        Customer.OrderCount >= 50
    then
        addLoyaltyPoints(Customer.Id, 500);
        log("Loyalty reward applied");
}
```

### 🚗 Vehicle Monitoring

```grl
rule "SpeedLimit" salience 25 {
    when
        Vehicle.Speed > Vehicle.SpeedLimit
    then
        triggerAlert(Vehicle.Id, "SPEED_VIOLATION");
        logViolation(Vehicle.Driver, Vehicle.Speed);
        Vehicle.setStatus("FLAGGED");
}

rule "MaintenanceDue" salience 10 {
    when
        Vehicle.Mileage > Vehicle.NextMaintenance
    then
        scheduleService(Vehicle.Id, Vehicle.Mileage);
        notifyDriver(Vehicle.Driver, "Maintenance due");
}
```

## ⚡ Performance & Architecture

### Benchmarks

```text
Rule Execution Performance:
• Simple conditions: ~10-50 microseconds
• Complex multi-condition rules: ~100-500 microseconds  
• Custom function calls: ~50-200 microseconds
• File-based rule loading: ~1-5 milliseconds

Memory Usage:
• Rule storage: ~1KB per rule
• Facts storage: ~100-500 bytes per fact
• Engine overhead: ~10KB base memory
```

### Key Design Decisions

- **GRL-Only**: Removed JSON support for cleaner, focused API
- **Dual Sources**: Support both file-based and inline rule definitions
- **Custom Functions**: Extensible function registry for business logic
- **Builder Pattern**: Fluent API for easy engine configuration
- **Type Safety**: Leverages Rust's type system for runtime safety
- **Zero-Copy**: Efficient string and memory management

## 🏗️ Development

### Building from Source

```bash
git clone https://github.com/your-repo/rust-rule-engine.git
cd rust-rule-engine
cargo build --release
```

### Running Examples

```bash
# File-based rules with custom functions
cargo run --example rule_file_functions_demo

# Inline rules demonstration  
cargo run --example inline_rules_demo

# Complete GRL feature showcase
cargo run --example grule_demo

# Custom function registry
cargo run --example custom_functions_demo

# Builder pattern usage
cargo run --example builder_test
```

### Testing

```bash
# Run all tests
cargo test

# Run with output
cargo test -- --nocapture

# Run specific test
cargo test integration_tests
```

### Publishing

```bash
# Check package
cargo check

# Run all tests
cargo test

# Build documentation
cargo doc --no-deps

# Publish dry run
cargo publish --dry-run

# Publish to crates.io
cargo publish
```

## 📋 API Reference

### Core Types

```rust
// Main engine builder
RuleEngineBuilder::new()
    .with_rule_file("path/to/rules.grl")?
    .with_inline_grl("rule content")?
    .with_config(config)
    .build()

// Value types
Value::Integer(42)
Value::Number(3.14)
Value::String("text".to_string())
Value::Boolean(true)
Value::Object(HashMap<String, Value>)

// Facts management
let facts = Facts::new();
facts.add_value("Object", value)?;
facts.get("Object")?;

// Execution results
result.rules_fired       // Number of rules that executed
result.cycle_count       // Number of execution cycles
result.execution_time    // Duration of execution
```

### Function Registration

```rust
engine.register_function("functionName", |args, facts| {
    // args: Vec<Value> - function arguments
    // facts: &Facts - current facts state
    // Return: Result<Value, RuleEngineError>
    
    let param1 = &args[0];
    let param2 = args[1].as_number().unwrap_or(0.0);
    
    // Your custom business logic here
    println!("Function called with: {:?}", args);
    
    Ok(Value::String("Success".to_string()))
});
```

## 🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

### Development Setup

1. Fork the repository
2. Create your feature branch: `git checkout -b feature/amazing-feature`
3. Make your changes and add tests
4. Ensure all tests pass: `cargo test`
5. Commit your changes: `git commit -m 'Add amazing feature'`
6. Push to the branch: `git push origin feature/amazing-feature`
7. Open a Pull Request

### Guidelines

- Follow Rust naming conventions
- Add tests for new features
- Update documentation for API changes
- Ensure examples work with changes

## 📄 License

This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.

## 🎯 Roadmap

- [ ] **Enhanced GRL Support**: More operators and complex conditions
- [ ] **Rule Templates**: Reusable rule patterns
- [ ] **Performance Optimizations**: Rule compilation and caching
- [ ] **Debugging Tools**: Rule execution tracing and profiling
- [ ] **Integration Examples**: Database, HTTP APIs, message queues
- [ ] **Rule Validation**: Static analysis and rule conflict detection

## 📞 Support

- 📚 **Documentation**: [docs.rs/rust-rule-engine](https://docs.rs/rust-rule-engine)
- 🐛 **Issues**: [GitHub Issues](https://github.com/your-repo/rust-rule-engine/issues)
- 💬 **Discussions**: [GitHub Discussions](https://github.com/your-repo/rust-rule-engine/discussions)

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**Built with ❤️ in Rust** 🦀