use std::io::prelude::*;
use std::fs::File;

#[allow(dead_code)]
struct CPU {
    pub opcode: u16,
    pub memory: [u8; 4096],
    pub i: u16,
    pub v: [u8; 16],
    pub sound_timer: u8,
    pub delay_timer: u8,
    pub pc: u16,
    pub sp: u8,
    pub stack: [u16; 16],
}

type Instruction = fn(&mut CPU);

fn ldi(cpu: &mut CPU) {
    let code = cpu.opcode;
    let register = ((code & 0x0F00) >> 8) as usize;
    let value = (code & 0xFF) as u8;
    cpu.v[register] = value;
    cpu.pc += 2;
}

fn ldii(cpu: &mut CPU) {
    cpu.i = cpu.opcode & 0x0FFF;
    cpu.pc += 2;
}

fn call(cpu: &mut CPU) {
    let addr = cpu.opcode & 0x0FFF;
    cpu.stack[cpu.sp as usize] = cpu.pc;
    cpu.sp += 1;
    cpu.pc = addr;
}

fn load_program_in_vect(path: &str) -> Vec<u8> {
    let mut vect: Vec<u8> = Vec::new();
    let mut file = File::open(path)
        .expect("Fichier pas trouvé");
    file.read_to_end(&mut vect).expect("Impossible de lire le fichier");
    return vect;
}

fn load_vect_in_memory(cpu: &mut CPU, vect: Vec<u8>) {
    for i in 0..vect.len() {
        cpu.memory[i + (cpu.i as usize)] = vect[i];
    }
}

fn initialize_instructions(inst: &mut Vec<(u16, Instruction)>) {
    inst.push((0x6000, ldi));
    inst.push((0x2000, call));
    inst.push((0xa000, ldii));
}

fn main() {
    //let _display = [[0u8; 32]; 64];
    let mut cpu = CPU {
        opcode: 0,
        v: [0; 16],
        i: 0x200,
        sound_timer: 0,
        delay_timer: 0,
        pc: 0x200,
        sp: 0,
        memory: [0; 4096],
        stack: [0; 16],
    };
    let vect = load_program_in_vect("test.ch8");
    load_vect_in_memory(&mut cpu, vect);
    let mut instr: Vec<(u16, Instruction)> = Vec::new();
    initialize_instructions(&mut instr);
    //while true {

    cpu.opcode = ((cpu.memory[cpu.pc as usize] as u16) << 8) | (cpu.memory[(cpu.pc + 1) as usize] as u16);
    let test = ((cpu.memory[842] as u16) << 8) | (cpu.memory[843] as u16);
    println!("test {:04x}", test);
    println!("opcode {:04x}", cpu.opcode);
    while true {
        for inst in &instr {
            let (code, function) = *inst;
            if cpu.opcode & code == code {
                function(&mut cpu);
                break;
            }
        }
    }
}