path: root/src/lib.rs

use sdl2::keyboard::Keycode;
use rand::prelude::*; 
use std::fs::File;
use std::io::Read;
use sdl2::rect::Rect;
use sdl2::pixels::Color;

pub const WIDTH : u32 = 64;
pub const HEIGHT : u32 = 32;
pub const SCALE : u32 = 20;

//length for the array of display "pixels" where pixels are the rectangles being rendered
const DISPLAY_LENGTH : usize = (WIDTH * HEIGHT) as usize;


//Basic struct to represent the Chip-8 interpreter structure
pub struct Chip {
    mem : [u8; 4096], //4kb of memory
    registers: [u8; 16], //16 8-bit registers
    index: u16, //16-bit index pointer
    pc: u16, //Program counter
    stack: [u16; 16], //16 level stack
    sp: usize, //stack pointer
    delay_timer: u8, //delay timer 
    sound_timer: u8, //sound timer
    keys : [Keycode; 16], //mapping keys to chip-8 input keys
    keys_pressed : i8, //mapping keys to chip-8 input keys
    fonts : [u8; 80], //all the 16 chars that can be rendered 16 * 5
    display:  [u16; DISPLAY_LENGTH as usize], //the display array 
    instr: u16,                                //current exec instr
    v: u8, 
    x: usize,
    y: usize,
    n: u8,
    nn: u8, 
    nnn: u16,
}

impl Chip {
    //return a new Chip, with memory 0-initialized
    pub fn new() -> Self {
        Chip {
            mem : [0; 4096],
            registers: [0; 16],
            index: 0,
            pc: 0x200,
            stack: [0; 16],
            sp: 0,
            delay_timer: 0,
            sound_timer: 0,
            keys: [Keycode::Num1, Keycode::Num2, Keycode::Num3, Keycode::Num4, Keycode::Q, Keycode::W, Keycode::E, Keycode::R, Keycode::A, Keycode::S, Keycode::D, Keycode::F, Keycode::Z, Keycode::X, Keycode::C, Keycode::V],
            keys_pressed : -1,
            fonts: [
                0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
                0x20, 0x60, 0x20, 0x20, 0x70, // 1
                0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
                0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
                0x90, 0x90, 0xF0, 0x10, 0x10, // 4
                0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
                0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
                0xF0, 0x10, 0x20, 0x40, 0x40, // 7
                0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
                0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
                0xF0, 0x90, 0xF0, 0x90, 0x90, // A
                0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
                0xF0, 0x80, 0x80, 0x80, 0xF0, // C
                0xE0, 0x90, 0x90, 0x90, 0xE0, // D
                0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
                0xF0, 0x80, 0xF0, 0x80, 0x80  // F
            ],
            display: [0; DISPLAY_LENGTH],
            instr: 0x0000,
            v: 0,
            x: 0,
            y: 0,
            n: 0,
            nn: 0, 
            nnn: 0,
        }
    }
    //initialize memory with all the starting values
    pub fn init(&mut self) {
        for i in 0..80 {
            self.mem[0x50 + i] = self.fonts[i];
        }
        println!("Init Chip: Loaded fonts!");
    }

    pub fn read_rom(&mut self, rom : &str) {
        let mut buf = Vec::new();
        let mut rom = File::open(rom).unwrap_or_else(|_err| panic!("Valid ROM needed"));

        rom.read_to_end(&mut buf).unwrap_or_else(|_err| panic!("Error reading ROM"));

        let mut start = 0x200;
        for i in buf {
            self.mem[start] = i;
            start += 1;
        }
        println!("Loading ROM in memory!");
    }

    pub fn clear_input(&mut self) {
        self.keys_pressed = -1;
    }
    pub fn feed_input(&mut self, key : Keycode) {
        let idx = self.keys.into_iter().position(|r| r == key);
        let m_idx = match idx {
            Some(v) => v as i8,
            None =>  -1 as i8,
        };
        self.keys_pressed = m_idx;
    }

    pub fn fetch(&mut self) {
        self.instr = ((self.mem[self.pc as usize] as u16) << 8) | self.mem[(self.pc + 1) as usize] as u16;
        self.pc += 2;
        println!("Fetching next instruction: {:#06X}", self.instr);
    }
    
    pub fn execute(&mut self) {
        self.v = ((self.instr & 0xF000) >> 12) as u8;
        self.x = ((self.instr & 0x0F00) >> 8) as usize;
        self.y = ((self.instr & 0x00F0) >> 4) as usize;
        self.n = (self.instr & 0x000F) as u8;
        self.nn = (self.instr & 0x00FF) as u8;
        self.nnn = self.instr & 0x0FFF;

        match self.instr {

            0x00e0 => { self.cls_00e0() },
            0x00ee => { self.ret_00ee() },
            0x1000..=0x1fff => { self.jmp_1nnn() },
            0x2000..=0x2fff => { self.call_2nnn() },
            0x3000..=0x3fff => { self.se_3xkk() }
            0x4000..=0x4fff => { self.sne_4xkk() }
            0x5000..=0x5ff0 => { self.se_5xy0() }
            0x6000..=0x6fff => { self.ld_6xkk() },
            0x7000..=0x7fff => { self.add_7xkk() },
            0x8000..=0x8ffe => { self.match_8xxk() }
            0x9000..=0x9ff0 => { self.sne_9xy0() }
            0xa000..=0xafff => { self.ld_annn() },
            0xb000..=0xbfff => { self.jp_bnnn() }
            0xc000..=0xcfff => { self.rnd_cxnn() }
            0xd000..=0xdfff => { self.drw_dxyn() },
            0xe000..=0xefa1 => { self.match_exxk() }
            0xf000..=0xff65 => { self.match_fxxk() }
            _ => { println!("Doing nothing!"); }
        }

    }
//            0x8000..=0x8ff0 => { self.ld_8xy0() }
//            0x8001..=0x8ff1 => { self.or_8xy1() }
//            0x8002..=0x8ff2 => { self.and_8xy2() }
//            0x8003..=0x8ff3 => { self.xor_8xy3() }
//            0x8004..=0x8ff4 => { self.add_8xy4() }
//            0x8005..=0x8ff5 => { self.sub_8xy5() }
//            0x8006..=0x8ff6 => { self.shr_8xy6() }
//            0x8007..=0x8ff7 => { self.sub_8xy7() }
//            0x800e..=0x8ffe => { self.shl_8xye() }

    fn match_fxxk