#pragma once

#include "io_device.hpp"
#include <array>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <span>
#include <utility>

namespace vc5 {

enum class Op : uint16_t {
    Nop,
    Hlt,
    Jmp,
    Jnz,
    Mov,
    LoadWord,
    StoreWord,
    LoadByte,
    StoreByte,
    Cmp,
    Or,
    And,
    Xor,
    Shl,
    RShl,
    Shr,
    RShr,
    Add,
    Sub,
    RSub,

    // return from interrupt
    RetI,
    // load video character display
    LVCD,
    // load keyboard
    LKBD,
};

const char* op_str(Op op);

enum class Reg : uint16_t {
    R0 = 0,
    R1 = 1,
    R2 = 2,
    R3 = 3,
    R4 = 4,
    R5 = 5,
    Rbp = 6,
    Rsp = 7,
    Rfl = 8,
    Rip = 9,
};

enum class Flag : uint16_t {
    Zero = 0,
    Eq = 1,
    Be = 2,
    Lt = 3,
    Err = 4,
};

struct VcdDescript {
    uint16_t map_base_addr;
};

struct KbdDescript {
    uint16_t status_addr;
    uint16_t keycode_addr;
    uint16_t int_handler;
};

enum class KbdStatusFlag : uint16_t {
    /// 0 Press
    /// 1 Release
    Type = 0,
    Shift = 1,
    Ctrl = 2,
    Alt = 3,
    AltGr = 4,
};

class VM {
public:
    VM(IoDevice& device)
        : m_device(&device)
    {
    }

    void load(uint16_t offset, const uint8_t* data, size_t data_size);
    int run();

    auto reg(Reg reg) const -> uint16_t;
    auto word(uint16_t addr) const -> uint16_t;
    auto byte(uint16_t addr) const -> uint8_t;

    void set_reg(Reg reg, uint16_t value);
    void set_word(uint16_t addr, uint16_t value);
    void set_byte(uint16_t addr, uint8_t value);

    uint16_t eat_word();

private:
    int run_instruction();
    void poll_events();

    void vcd_maybe_send_byte(uint16_t addr, uint8_t value);

    void interrupt(uint16_t handler_addr);

    std::array<uint8_t, 65536> m_mem = {};
    std::array<uint16_t, 10> m_regs = {};

    uint16_t* m_rsp = &m_regs[std::to_underlying(Reg::Rsp)];
    uint16_t* m_rfl = &m_regs[std::to_underlying(Reg::Rfl)];
    uint16_t* m_rip = &m_regs[std::to_underlying(Reg::Rip)];

    IoDevice* m_device;

    bool m_on = true;
    bool m_halted = false;
    bool m_interrupts_enabled = true;
    bool m_vcd_loaded = false;
    bool m_kbd_loaded = false;

    VcdDescript m_vcd_descriptor {};
    KbdDescript m_kbd_descriptor {};
};

}