CHIP8.h

//
// Created by chunibyo on 2022/2/16.
//

#ifndef INC_19_CHIP8_CHIP8_H
#define INC_19_CHIP8_CHIP8_H

#include <iostream>
#include <fstream>

typedef unsigned char Byte;
typedef unsigned short Word;

struct Memory {
    // PC 的起始位置
    static constexpr Word pcStartMemory = 0x200;

    // 内存的最大值
    static constexpr Word endMemory = 0xFFF;

    Byte &operator[](Word address);

    // 4KB 大小内存
    // https://en.wikipedia.org/wiki/CHIP-8#Memory
    Byte memory[endMemory + 1]{};

    bool loadROM(std::string &file);

    void clear();
};

struct CPU {
    Memory memory;

    static constexpr int registerNum = 16;

    // 16个8Bit(1Byte)个大小的寄存器
    // https://en.wikipedia.org/wiki/CHIP-8#Registers
    Byte VRegister[registerNum]{};

    // 程序计数器: 16 Bit
    // http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.2
    Word PC{};

    // stack pointer: 8 Bit
    // http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.2
    Byte SP{};

    Word IRegister{};

    Byte delayTimer;

    Byte soundTimer;

    // The stack is an array of 16 16-bit values
    Word stack[16];
};

struct Display {
    static constexpr int squareSize = 20;

    static constexpr int width = 64;

    static constexpr int height = 32;

    static int getScreenWidth() { return squareSize * width; }

    static int getScreenHeight() { return squareSize * height; }

    bool data[height][width] = {false};

    static constexpr Byte chip8_fontset[80] =
            {
                    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
            };
};

struct CHIP8 {
    CPU cpu;

    std::shared_ptr<Display> _display;

    CHIP8() {
        _display = std::make_shared<Display>();
    };

    void init();

    void reset();

    std::shared_ptr<Display> getDisplay() const;

    bool loadROM(std::string &file);

    [[noreturn]] void run();

    Word readOperationCode();

    bool processOperationCode(Word &opcode);
};

#endif //INC_19_CHIP8_CHIP8_H