/* SPDX-License-Identifier: Unlicense
 */

#include "bus.hpp"
#include "musashi-m68k/m68k.h"
#include "utils.hpp"

#include <cassert>
#include <cstdarg>
#include <cstdbool>
#include <cstdio>
#include <cstdint>
#include <cstdlib>

unsigned char g_rom[ROM_SIZE] = {};
unsigned char g_ram[RAM_SIZE] = {};
unsigned char g_io1[IO1_SIZE] = {};
unsigned char g_io2[IO2_SIZE] = {};

std::vector<Breakpoint> code_bkpts{}, read_bkpts{}, write_bkpts{}, access_bkpts{};

static void exit_error(const char* fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    vfprintf(stderr, fmt, args);
    va_end(args);
    fprintf(stderr, "\n");
    unsigned int pc = m68k_get_reg(NULL, M68K_REG_PPC);
    char buff[100];
    m68k_disassemble(buff, pc, M68K_CPU_TYPE_68000);
    fprintf(stderr, "%08x: %s\n", pc, buff);
    exit(EXIT_FAILURE);
}

static inline bool is_in_range(uint32_t value, uint32_t begin, uint32_t length)
{
    return value >= begin && value <= begin + length;
}

enum bitness {
    BITNESS_8,
    BITNESS_16,
    BITNESS_32,
};

struct read_result {
    unsigned int result;
    bool successful;
};

static inline unsigned int memory_read_concrete(
        enum bitness bitness,
        unsigned char const * base,
        unsigned int address)
{
    switch (bitness) {
    case BITNESS_8:
        return base[address];
    case BITNESS_16:
        return (base[address] << 8) | base[address + 1];
    case BITNESS_32:
        return (base[address] << 24) |
            (base[address + 1] << 16) |
            (base[address + 2] << 8) |
            base[address + 3];
    }
    UNREACHABLE;
}

static inline struct read_result memory_read(
        enum bitness bitness,
        unsigned int address)
{
    if (is_in_range(address, ROM_START, ROM_SIZE)) {
        return read_result{
            memory_read_concrete(bitness, g_rom, address - ROM_START),
            true,
        };
    } else if (is_in_range(address, RAM_START, RAM_SIZE)) {
        return read_result{
            memory_read_concrete(bitness, g_ram, address - RAM_START),
            true,
        };
    } else if (is_in_range(address, IO1_START, IO1_SIZE)) {
        return read_result{
            memory_read_concrete(bitness, g_io1, address - IO1_START),
            true,
        };
    } else if (is_in_range(address, IO2_START, IO2_SIZE)) {
        return read_result{
            memory_read_concrete(bitness, g_io2, address - IO2_START),
            true,
        };
    }
    return read_result{0, false};
}

static inline void memory_write_concrete(
        enum bitness bitness,
        unsigned char * base,
        unsigned int address,
        unsigned int value)
{
    switch (bitness) {
    case BITNESS_8:
        base[address] = value & 0xff;
        break;
    case BITNESS_16:
        base[address + 0] = (value >> 8) & 0xff;
        base[address + 1] = value & 0xff;
        break;
    case BITNESS_32:
        base[address + 0] = (value >> 24) & 0xff;
        base[address + 1] = (value >> 16) & 0xff;
        base[address + 2] = (value >> 8) & 0xff;
        base[address + 3] = value & 0xff;
        break;
    }
}

static inline bool memory_write(
        enum bitness bitness,
        unsigned int address,
        unsigned int value)
{
    if (is_in_range(address, ROM_START, ROM_SIZE)) {
        memory_write_concrete(bitness, g_rom, address - ROM_START, value);
        return true;
    } else if (is_in_range(address, RAM_START, RAM_SIZE)) {
        memory_write_concrete(bitness, g_ram, address - RAM_START, value);
        return true;
    } else if (is_in_range(address, IO1_START, IO1_SIZE)) {
        memory_write_concrete(bitness, g_io1, address - IO1_START, value);
        return true;
    } else if (is_in_range(address, IO2_START, IO2_SIZE)) {
        memory_write_concrete(bitness, g_io2, address - IO2_START, value);
        return true;
    }
    return false;
}

#define MASK_24(X) ((X) & (0xFF << 24))

extern void m68k_read_callback(const uint32_t address, const uint32_t size);
extern void m68k_write_callback(const uint32_t address, const uint32_t size);

unsigned int m68k_read_memory_8(unsigned int address)
{
    assert(MASK_24(address) == 0); // Just curious
    m68k_read_callback(address, 4);
    const struct read_result ret = memory_read(BITNESS_8, address);
    if (!ret.successful)
        exit_error("Read error u8 @%08x", address);
    return ret.result;
}

unsigned int m68k_read_memory_16(unsigned int address)
{
    m68k_read_callback(address, 2);
    assert(MASK_24(address) == 0); // Just curious
    const struct read_result ret = memory_read(BITNESS_16, address);
    if (!ret.successful)
        exit_error("Read error u16 @%08x", address);
    return ret.result;
}

unsigned int m68k_read_memory_32(unsigned int address)
{
    m68k_read_callback(address, 1);
    assert(MASK_24(address) == 0); // Just curious
    const struct read_result ret = memory_read(BITNESS_32, address);
    if (!ret.successful)
        exit_error("Read error u32 @%08x", address);
    return ret.result;
}

unsigned int m68k_read_disassembler_16(unsigned int address)
{
    assert(MASK_24(address) == 0); // Just curious
    const struct read_result ret = memory_read(BITNESS_16, address);
    if (!ret.successful)
        exit_error("Disasm read error u16 @0x%08x", address);
    return ret.result;
}

unsigned int m68k_read_disassembler_32(unsigned int address)
{
    assert(MASK_24(address) == 0); // Just curious
    const struct read_result ret = memory_read(BITNESS_32, address);
    if (!ret.successful)
        exit_error("Disasm read error u32 @0x%08x", address);
    return ret.result;
}

void m68k_write_memory_8(unsigned int address, unsigned int value)
{
    assert(MASK_24(address) == 0); // Just curious
    m68k_write_callback(address, 1);
    const bool successful = memory_write(BITNESS_8, address, value);
    if (!successful)
        exit_error("Attempted to write %02x (u8) to address %08x", value&0xff, address);
}

void m68k_write_memory_16(unsigned int address, unsigned int value)
{
    assert(MASK_24(address) == 0); // Just curious
    m68k_write_callback(address, 2);
    const bool successful = memory_write(BITNESS_16, address, value);
    if (!successful)
        exit_error("Attempted to write %04x (u16) to address %08x", value&0xffff, address);
}

void m68k_write_memory_32(unsigned int address, unsigned int value)
{
    assert(MASK_24(address) == 0); // Just curious
    m68k_write_callback(address, 4);
    const bool successful = memory_write(BITNESS_16, address, value);
    if (!successful)
        exit_error("Attempted to write %08x (u32) to address %08x", value, address);
}