//! # Register
//! 
//! This mod contains the definition of the Register structs
//! for use within the Machine module.

use crate::simulator::machine::{NUM_FP_REGS, NUM_INT_REGS};
use std::ops::{Add,  Sub};

/// Forcing the Register struct's generic type into having the following Traits
/// 
///  - Add
///  - Sub
///  - PartialEq
///  - Copy
/// 
/// Generally speaking, only numbers have the combinaison of these traits.
pub trait RegisterNum: Add<Output=Self> + Sub<Output=Self> + PartialEq + Copy {}

impl RegisterNum for i64 {}

impl RegisterNum for f32 {}

/// Machine register array
#[derive(PartialEq)]
pub struct Register<U: RegisterNum> {
	/// 32 available registers of type U
	register: [U; 32]
}

impl<U: RegisterNum> Register<U> {
	/// Returns the current value held in register *position*
	pub fn get_reg(&self, position: u8) -> U {
		self.register[position as usize]
	}

	/// Set value of register *position* to *value*
    /// 
    /// Checking against trying to set a new value to the 0th register
    /// as its value is NOT supposed to change
	pub fn set_reg(&mut self, position: u8, value: U) {
		if position != 0 { self.register[position as usize] = value; }
	}
}

impl Register<i64> {
	/// i64 register constructor
	pub fn init() -> Register<i64> {
		Register { 
			register: [0i64; NUM_INT_REGS]
		}
	}
}

impl Register<f32> {
	/// f32 register constructor
	pub fn init() -> Register<f32> {
		Register { 
			register: [0f32; NUM_FP_REGS]
		}
	}
}