RUST: Struct methods

//! Comprehensive Struct Method Examples in Rust

#[derive(Debug, Clone, PartialEq)]
pub struct Circle {
    radius: f64,
    color: String,
}

impl Circle {
    // Constructor method
    pub fn new(radius: f64) -> Self {
        Circle {
            radius,
            color: String::from("red"),
        }
    }

    // Getter method
    pub fn radius(&self) -> f64 {
        self.radius
    }

    // Setter method
    pub fn set_radius(&mut self, radius: f64) {
        self.radius = radius;
    }

    // Instance method with immutable reference
    pub fn area(&self) -> f64 {
        std::f64::consts::PI * self.radius * self.radius
    }

    // Method taking ownership
    pub fn consume(self) -> String {
        format!("Consumed circle with radius {}", self.radius)
    }

    // Associated function (no self parameter)
    pub fn default() -> Self {
        Circle::new(1.0)
    }
}

// Builder pattern implementation
pub struct CircleBuilder {
    radius: Option<f64>,
    color: Option<String>,
}

impl CircleBuilder {
    pub fn new() -> Self {
        CircleBuilder {
            radius: None,
            color: None,
        }
    }

    pub fn radius(mut self, radius: f64) -> Self {
        self.radius = Some(radius);
        self
    }

    pub fn color(mut self, color: &str) -> Self {
        self.color = Some(color.to_string());
        self
    }

    pub fn build(self) -> Circle {
        Circle {
            radius: self.radius.unwrap_or(1.0),
            color: self.color.unwrap_or_else(|| "blue".to_string()),
        }
    }
}

pub fn demonstrate_struct_methods() {
    println!("=== BASIC STRUCT USAGE ===");
    let mut circle = Circle::new(2.5);
    println!("Original circle: {:?}", circle);
    println!("Area: {:.2}", circle.area());
    
    circle.set_radius(3.0);
    println!("Modified radius: {}", circle.radius());

    println!("\n=== BUILDER PATTERN ===");
    let custom = CircleBuilder::new()
        .radius(5.0)
        .color("green")
        .build();
    println!("Built circle: {:?}", custom);

    println!("\n=== OWNERSHIP DEMO ===");
    let message = circle.consume();
    println!("{}", message);
    // circle is now moved and can't be used

    println!("\n=== DEFAULT IMPLEMENTATION ===");
    let default = Circle::default();
    println!("Default circle: {:?}", default);
}

// Remember to add to src/menu_items/mod.rs:
// pub mod struct_methods;