// SPDX-FileCopyrightText: 2019-2024 Connor McLaughlin <stenzek@gmail.com>
// SPDX-License-Identifier: CC-BY-NC-ND-4.0

#include "bus.h"
#include "bios.h"
#include "cdrom.h"
#include "cpu_code_cache.h"
#include "cpu_core.h"
#include "cpu_core_private.h"
#include "cpu_disasm.h"
#include "dma.h"
#include "gpu.h"
#include "host.h"
#include "interrupt_controller.h"
#include "mdec.h"
#include "pad.h"
#include "pio.h"
#include "psf_loader.h"
#include "settings.h"
#include "sio.h"
#include "spu.h"
#include "system.h"
#include "timers.h"
#include "timing_event.h"

#include "util/cd_image.h"
#include "util/elf_file.h"
#include "util/state_wrapper.h"

#include "common/align.h"
#include "common/assert.h"
#include "common/binary_reader_writer.h"
#include "common/error.h"
#include "common/file_system.h"
#include "common/intrin.h"
#include "common/log.h"
#include "common/memmap.h"
#include "common/path.h"
#include "common/string_util.h"

#include <cstdio>
#include <tuple>
#include <utility>

LOG_CHANNEL(Bus);

// Exports for external debugger access
#ifndef __ANDROID__
namespace Exports {

extern "C" {
#ifdef _WIN32
_declspec(dllexport) uintptr_t RAM;
_declspec(dllexport) u32 RAM_SIZE, RAM_MASK;
#else
__attribute__((visibility("default"), used)) uintptr_t RAM;
__attribute__((visibility("default"), used)) u32 RAM_SIZE, RAM_MASK;
#endif
}

} // namespace Exports
#endif

namespace Bus {

namespace {
union MEMDELAY
{
  u32 bits;

  BitField<u32, u8, 4, 4> access_time; // cycles
  BitField<u32, bool, 8, 1> use_com0_time;
  BitField<u32, bool, 9, 1> use_com1_time;
  BitField<u32, bool, 10, 1> use_com2_time;
  BitField<u32, bool, 11, 1> use_com3_time;
  BitField<u32, bool, 12, 1> data_bus_16bit;
  BitField<u32, u8, 16, 5> memory_window_size;

  static constexpr u32 WRITE_MASK = 0b10101111'00011111'11111111'11111111;
};

union COMDELAY
{
  u32 bits;

  BitField<u32, u8, 0, 4> com0;
  BitField<u32, u8, 4, 4> com1;
  BitField<u32, u8, 8, 4> com2;
  BitField<u32, u8, 12, 4> com3;
  BitField<u32, u8, 16, 2> comunk;

  static constexpr u32 WRITE_MASK = 0b00000000'00000011'11111111'11111111;
};

union MEMCTRL
{
  u32 regs[MEMCTRL_REG_COUNT];

  struct
  {
    u32 exp1_base;
    u32 exp2_base;
    MEMDELAY exp1_delay_size;
    MEMDELAY exp3_delay_size;
    MEMDELAY bios_delay_size;
    MEMDELAY spu_delay_size;
    MEMDELAY cdrom_delay_size;
    MEMDELAY exp2_delay_size;
    COMDELAY common_delay;
  };
};

union RAM_SIZE_REG
{
  u32 bits;

  // All other bits unknown/unhandled.
  BitField<u32, u8, 9, 3> memory_window;
};
} // namespace

static void* s_shmem_handle = nullptr;
static std::string s_shmem_name;

std::bitset<RAM_8MB_CODE_PAGE_COUNT> g_ram_code_bits{};
u8* g_ram = nullptr;
u8* g_unprotected_ram = nullptr;
u32 g_ram_size = 0;
u32 g_ram_mapped_size = 0;
u32 g_ram_mask = 0;
u8* g_bios = nullptr;
void** g_memory_handlers = nullptr;
void** g_memory_handlers_isc = nullptr;

std::array<TickCount, 3> g_exp1_access_time = {};
std::array<TickCount, 3> g_exp2_access_time = {};
std::array<TickCount, 3> g_bios_access_time = {};
std::array<TickCount, 3> g_cdrom_access_time = {};
std::array<TickCount, 3> g_spu_access_time = {};

static MEMCTRL s_MEMCTRL = {};
static RAM_SIZE_REG s_RAM_SIZE = {};

static std::string s_tty_line_buffer;

#ifdef ENABLE_MMAP_FASTMEM
static SharedMemoryMappingArea s_fastmem_arena;
static std::vector<std::pair<u8*, size_t>> s_fastmem_ram_views;
#endif

static u8** s_fastmem_lut = nullptr;

static bool s_kernel_initialize_hook_run = false;

static bool AllocateMemoryMap(bool export_shared_memory, Error* error);
static void ReleaseMemoryMap();
static void SetRAMSize(bool enable_8mb_ram);

static std::tuple<TickCount, TickCount, TickCount> CalculateMemoryTiming(MEMDELAY mem_delay, COMDELAY common_delay);
static void RecalculateMemoryTimings();

static void MapFastmemViews();
static void UnmapFastmemViews();
static u8* GetLUTFastmemPointer(u32 address, u8* ram_ptr);

static void SetRAMPageWritable(u32 page_index, bool writable);

static void KernelInitializedHook();
static bool SideloadEXE(const std::string& path, Error* error);
static bool InjectCPE(std::span<const u8> buffer, bool set_pc, Error* error);
static bool InjectELF(const ELFFile& elf, bool set_pc, Error* error);

static void SetHandlers();
static void UpdateMappedRAMSize();

} // namespace Bus

namespace MemoryMap {
static constexpr size_t RAM_OFFSET = 0;
static constexpr size_t RAM_SIZE = Bus::RAM_8MB_SIZE;
static constexpr size_t BIOS_OFFSET = RAM_OFFSET + RAM_SIZE;
static constexpr size_t BIOS_SIZE = Bus::BIOS_SIZE;
static constexpr size_t LUT_OFFSET = BIOS_OFFSET + BIOS_SIZE;
static constexpr size_t LUT_SIZE = (sizeof(void*) * Bus::MEMORY_LUT_SLOTS) * 2; // normal and isolated
static constexpr size_t TOTAL_SIZE = LUT_OFFSET + LUT_SIZE;
} // namespace MemoryMap

#define FIXUP_HALFWORD_OFFSET(size, offset) ((size >= MemoryAccessSize::HalfWord) ? (offset) : ((offset) & ~1u))
#define FIXUP_HALFWORD_READ_VALUE(size, offset, value)                                                                 \
  ((size >= MemoryAccessSize::HalfWord) ? (value) : ((value) >> (((offset) & u32(1)) * 8u)))
#define FIXUP_HALFWORD_WRITE_VALUE(size, offset, value)                                                                \
  ((size >= MemoryAccessSize::HalfWord) ? (value) : ((value) << (((offset) & u32(1)) * 8u)))

#define FIXUP_WORD_OFFSET(size, offset) ((size == MemoryAccessSize::Word) ? (offset) : ((offset) & ~3u))
#define FIXUP_WORD_READ_VALUE(size, offset, value)                                                                     \
  ((size == MemoryAccessSize::Word) ? (value) : ((value) >> (((offset) & 3u) * 8)))
#define FIXUP_WORD_WRITE_VALUE(size, offset, value)                                                                    \
  ((size == MemoryAccessSize::Word) ? (value) : ((value) << (((offset) & 3u) * 8)))

bool Bus::AllocateMemoryMap(bool export_shared_memory, Error* error)
{
  INFO_LOG("Allocating{} shared memory map.", export_shared_memory ? " EXPORTED" : "");
  if (export_shared_memory)
  {
    s_shmem_name = MemMap::GetFileMappingName("duckstation");
    INFO_LOG("Shared memory object name is \"{}\".", s_shmem_name);
  }
  s_shmem_handle = MemMap::CreateSharedMemory(s_shmem_name.c_str(), MemoryMap::TOTAL_SIZE, error);
  if (!s_shmem_handle)
  {
#ifndef __linux__
    Error::AddSuffix(error, "\nYou may need to close some programs to free up additional memory.");
#else
    Error::AddSuffix(
      error, "\nYou may need to close some programs to free up additional memory, or increase the size of /dev/shm.");
#endif
    return false;
  }

  g_ram = static_cast<u8*>(MemMap::MapSharedMemory(s_shmem_handle, MemoryMap::RAM_OFFSET, nullptr, MemoryMap::RAM_SIZE,
                                                   PageProtect::ReadWrite));
  g_unprotected_ram = static_cast<u8*>(MemMap::MapSharedMemory(s_shmem_handle, MemoryMap::RAM_OFFSET, nullptr,
                                                               MemoryMap::RAM_SIZE, PageProtect::ReadWrite));
  if (!g_ram || !g_unprotected_ram)
  {
    Error::SetStringView(error, "Failed to map memory for RAM");
    ReleaseMemoryMap();
    return false;
  }

  VERBOSE_LOG("RAM is mapped at {}.", static_cast<void*>(g_ram));

  g_bios = static_cast<u8*>(MemMap::MapSharedMemory(s_shmem_handle, MemoryMap::BIOS_OFFSET, nullptr,
                                                    MemoryMap::BIOS_SIZE, PageProtect::ReadWrite));
  if (!g_bios)
  {
    Error::SetStringView(error, "Failed to map memory for BIOS");
    ReleaseMemoryMap();
    return false;
  }

  VERBOSE_LOG("BIOS is mapped at {}.", static_cast<void*>(g_bios));

  g_memory_handlers = static_cast<void**>(MemMap::MapSharedMemory(s_shmem_handle, MemoryMap::LUT_OFFSET, nullptr,
                                                                  MemoryMap::LUT_SIZE, PageProtect::ReadWrite));
  if (!g_memory_handlers)
  {
    Error::SetStringView(error, "Failed to map memory for LUTs");
    ReleaseMemoryMap();
    return false;
  }

  VERBOSE_LOG("LUTs are mapped at {}.", static_cast<void*>(g_memory_handlers));
  g_memory_handlers_isc = g_memory_handlers + MEMORY_LUT_SLOTS;
  g_ram_mapped_size = RAM_8MB_SIZE;
  SetHandlers();

#ifndef __ANDROID__
  Exports::RAM = reinterpret_cast<uintptr_t>(g_unprotected_ram);
#endif

  return true;
}

void Bus::ReleaseMemoryMap()
{
#ifndef __ANDROID__
  Exports::RAM = 0;
  Exports::RAM_SIZE = 0;
  Exports::RAM_MASK = 0;
#endif

  g_memory_handlers_isc = nullptr;
  if (g_memory_handlers)
  {
    MemMap::UnmapSharedMemory(g_memory_handlers, MemoryMap::LUT_SIZE);
    g_memory_handlers = nullptr;
  }

  if (g_bios)
  {
    MemMap::UnmapSharedMemory(g_bios, MemoryMap::BIOS_SIZE);
    g_bios = nullptr;
  }

  if (g_unprotected_ram)
  {
    MemMap::UnmapSharedMemory(g_unprotected_ram, MemoryMap::RAM_SIZE);
    g_unprotected_ram = nullptr;
  }

  if (g_ram)
  {
    MemMap::UnmapSharedMemory(g_ram, MemoryMap::RAM_SIZE);
    g_ram = nullptr;
  }

  if (s_shmem_handle)
  {
    MemMap::DestroySharedMemory(s_shmem_handle);
    s_shmem_handle = nullptr;

    if (!s_shmem_name.empty())
    {
      MemMap::DeleteSharedMemory(s_shmem_name.c_str());
      s_shmem_name = {};
    }
  }
}

bool Bus::AllocateMemory(bool export_shared_memory, Error* error)
{
  if (!AllocateMemoryMap(export_shared_memory, error))
    return false;

#ifdef ENABLE_MMAP_FASTMEM
  if (!s_fastmem_arena.Create(FASTMEM_ARENA_SIZE))
  {
    Error::SetStringView(error, "Failed to create fastmem arena");
    ReleaseMemory();
    return false;
  }

  INFO_LOG("Fastmem base: {}", static_cast<void*>(s_fastmem_arena.BasePointer()));
#endif

  return true;
}

void Bus::ReleaseMemory()
{
#ifdef ENABLE_MMAP_FASTMEM
  DebugAssert(s_fastmem_ram_views.empty());
  s_fastmem_arena.Destroy();
#endif

  std::free(s_fastmem_lut);
  s_fastmem_lut = nullptr;

  ReleaseMemoryMap();
}

bool Bus::ReallocateMemoryMap(bool export_shared_memory, Error* error)
{
  // Need to back up RAM+BIOS.
  DynamicHeapArray<u8> ram_backup;
  DynamicHeapArray<u8> bios_backup;

  if (System::IsValid())
  {
    CPU::CodeCache::InvalidateAllRAMBlocks();
    UnmapFastmemViews();

    ram_backup.resize(RAM_8MB_SIZE);
    std::memcpy(ram_backup.data(), g_unprotected_ram, RAM_8MB_SIZE);
    bios_backup.resize(BIOS_SIZE);
    std::memcpy(bios_backup.data(), g_bios, BIOS_SIZE);
  }

  ReleaseMemoryMap();
  if (!AllocateMemoryMap(export_shared_memory, error)) [[unlikely]]
    return false;

  if (System::IsValid())
  {
    UpdateMappedRAMSize();
    std::memcpy(g_unprotected_ram, ram_backup.data(), RAM_8MB_SIZE);
    std::memcpy(g_bios, bios_backup.data(), BIOS_SIZE);
    MapFastmemViews();
  }

  return true;
}

void Bus::CleanupMemoryMap()
{
#if !defined(_WIN32) && !defined(__ANDROID__)
  // This is only needed on Linux.
  if (!s_shmem_name.empty())
    MemMap::DeleteSharedMemory(s_shmem_name.c_str());
#endif
}

void Bus::Initialize()
{
  SetRAMSize(g_settings.enable_8mb_ram);
  MapFastmemViews();
}

void Bus::SetRAMSize(bool enable_8mb_ram)
{
  g_ram_size = enable_8mb_ram ? RAM_8MB_SIZE : RAM_2MB_SIZE;
  g_ram_mask = enable_8mb_ram ? RAM_8MB_MASK : RAM_2MB_MASK;

#ifndef __ANDROID__
  Exports::RAM_SIZE = g_ram_size;
  Exports::RAM_MASK = g_ram_mask;
#endif
}

void Bus::Shutdown()
{
  UnmapFastmemViews();
  CPU::g_state.fastmem_base = nullptr;

  g_ram_mask = 0;
  g_ram_size = 0;
}

void Bus::Reset()
{
  std::memset(g_ram, 0, g_ram_size);
  s_MEMCTRL.exp1_base = 0x1F000000;
  s_MEMCTRL.exp2_base = 0x1F802000;
  s_MEMCTRL.exp1_delay_size.bits = 0x0013243F;
  s_MEMCTRL.exp3_delay_size.bits = 0x00003022;
  s_MEMCTRL.bios_delay_size.bits = 0x0013243F;
  s_MEMCTRL.spu_delay_size.bits = 0x200931E1;
  s_MEMCTRL.cdrom_delay_size.bits = 0x00020843;
  s_MEMCTRL.exp2_delay_size.bits = 0x00070777;
  s_MEMCTRL.common_delay.bits = 0x00031125;
  g_ram_code_bits = {};
  s_kernel_initialize_hook_run = false;
  RecalculateMemoryTimings();

  // Avoid remapping if unchanged.
  if (s_RAM_SIZE.bits != 0x00000B88)
  {
    s_RAM_SIZE.bits = 0x00000B88;
    UpdateMappedRAMSize();
  }
}

bool Bus::DoState(StateWrapper& sw)
{
  u32 ram_size = g_ram_size;
  sw.DoEx(&ram_size, 52, static_cast<u32>(RAM_2MB_SIZE));
  if (ram_size != g_ram_size)
  {
    const bool using_8mb_ram = (ram_size == RAM_8MB_SIZE);
    SetRAMSize(using_8mb_ram);
    RemapFastmemViews();
  }

  sw.Do(&g_exp1_access_time);
  sw.Do(&g_exp2_access_time);
  sw.Do(&g_bios_access_time);
  sw.Do(&g_cdrom_access_time);
  sw.Do(&g_spu_access_time);
  sw.DoBytes(g_ram, g_ram_size);

  if (sw.GetVersion() < 58) [[unlikely]]
  {
    WARNING_LOG("Overwriting loaded BIOS with old save state.");
    sw.DoBytes(g_bios, BIOS_SIZE);
  }

  sw.DoArray(s_MEMCTRL.regs, countof(s_MEMCTRL.regs));

  const RAM_SIZE_REG old_ram_size_reg = s_RAM_SIZE;
  sw.Do(&s_RAM_SIZE.bits);
  if (s_RAM_SIZE.memory_window != old_ram_size_reg.memory_window)
    UpdateMappedRAMSize();

  sw.Do(&s_tty_line_buffer);

  sw.DoEx(&s_kernel_initialize_hook_run, 68, true);

  return !sw.HasError();
}

std::tuple<TickCount, TickCount, TickCount> Bus::CalculateMemoryTiming(MEMDELAY mem_delay, COMDELAY common_delay)
{
  // from nocash spec
  s32 first = 0, seq = 0, min = 0;
  if (mem_delay.use_com0_time)
  {
    first += s32(common_delay.com0) - 1;
    seq += s32(common_delay.com0) - 1;
  }
  if (mem_delay.use_com2_time)
  {
    first += s32(common_delay.com2);
    seq += s32(common_delay.com2);
  }
  if (mem_delay.use_com3_time)
  {
    min = s32(common_delay.com3);
  }
  if (first < 6)
    first++;

  first = first + s32(mem_delay.access_time) + 2;
  seq = seq + s32(mem_delay.access_time) + 2;

  if (first < (min + 6))
    first = min + 6;
  if (seq < (min + 2))
    seq = min + 2;

  const TickCount byte_access_time = first;
  const TickCount halfword_access_time = mem_delay.data_bus_16bit ? first : (first + seq);
  const TickCount word_access_time = mem_delay.data_bus_16bit ? (first + seq) : (first + seq + seq + seq);
  return std::tie(std::max(byte_access_time - 1, 0), std::max(halfword_access_time - 1, 0),
                  std::max(word_access_time - 1, 0));
}

void Bus::RecalculateMemoryTimings()
{
  std::tie(g_bios_access_time[0], g_bios_access_time[1], g_bios_access_time[2]) =
    CalculateMemoryTiming(s_MEMCTRL.bios_delay_size, s_MEMCTRL.common_delay);
  std::tie(g_cdrom_access_time[0], g_cdrom_access_time[1], g_cdrom_access_time[2]) =
    CalculateMemoryTiming(s_MEMCTRL.cdrom_delay_size, s_MEMCTRL.common_delay);
  std::tie(g_spu_access_time[0], g_spu_access_time[1], g_spu_access_time[2]) =
    CalculateMemoryTiming(s_MEMCTRL.spu_delay_size, s_MEMCTRL.common_delay);
  std::tie(g_exp1_access_time[0], g_exp1_access_time[1], g_exp1_access_time[2]) =
    CalculateMemoryTiming(s_MEMCTRL.exp1_delay_size, s_MEMCTRL.common_delay);

  TRACE_LOG("BIOS Memory Timing: {} bit bus, byte={}, halfword={}, word={}",
            s_MEMCTRL.bios_delay_size.data_bus_16bit ? 16 : 8, g_bios_access_time[0] + 1, g_bios_access_time[1] + 1,
            g_bios_access_time[2] + 1);
  TRACE_LOG("CDROM Memory Timing: {} bit bus, byte={}, halfword={}, word={}",
            s_MEMCTRL.cdrom_delay_size.data_bus_16bit ? 16 : 8, g_cdrom_access_time[0] + 1, g_cdrom_access_time[1] + 1,
            g_cdrom_access_time[2] + 1);
  TRACE_LOG("SPU Memory Timing: {} bit bus, byte={}, halfword={}, word={}",
            s_MEMCTRL.spu_delay_size.data_bus_16bit ? 16 : 8, g_spu_access_time[0] + 1, g_spu_access_time[1] + 1,
            g_spu_access_time[2] + 1);
  TRACE_LOG("EXP1 Memory Timing: {} bit bus, byte={}, halfword={}, word={}",
            s_MEMCTRL.spu_delay_size.data_bus_16bit ? 16 : 8, g_spu_access_time[0] + 1, g_spu_access_time[1] + 1,
            g_spu_access_time[2] + 1);
}

void* Bus::GetFastmemBase(bool isc)
{
#ifdef ENABLE_MMAP_FASTMEM
  if (g_settings.cpu_fastmem_mode == CPUFastmemMode::MMap)
    return isc ? nullptr : s_fastmem_arena.BasePointer();
#endif
  if (g_settings.cpu_fastmem_mode == CPUFastmemMode::LUT)
    return reinterpret_cast<u8*>(s_fastmem_lut + (isc ? (FASTMEM_LUT_SIZE * sizeof(void*)) : 0));

  return nullptr;
}

u8* Bus::GetLUTFastmemPointer(u32 address, u8* ram_ptr)
{
  return ram_ptr - address;
}

void Bus::MapFastmemViews()
{
#ifdef ENABLE_MMAP_FASTMEM
  Assert(s_fastmem_ram_views.empty());
#endif

  const CPUFastmemMode mode = g_settings.cpu_fastmem_mode;
  if (mode == CPUFastmemMode::MMap)
  {
#ifdef ENABLE_MMAP_FASTMEM
    auto MapRAM = [](u32 base_address) {
      u8* map_address = s_fastmem_arena.BasePointer() + base_address;
      if (!s_fastmem_arena.Map(s_shmem_handle, 0, map_address, g_ram_size, PageProtect::ReadWrite)) [[unlikely]]
      {
        ERROR_LOG("Failed to map RAM at fastmem area {} (offset 0x{:08X})", static_cast<void*>(map_address),
                  g_ram_size);
        return;
      }

      // mark all pages with code as non-writable
      const u32 page_count = g_ram_size >> HOST_PAGE_SHIFT;
      for (u32 i = 0; i < page_count; i++)
      {
        if (g_ram_code_bits[i])
        {
          u8* page_address = map_address + (i << HOST_PAGE_SHIFT);
          if (!MemMap::MemProtect(page_address, HOST_PAGE_SIZE, PageProtect::ReadOnly)) [[unlikely]]
          {
            ERROR_LOG("Failed to write-protect code page at {}", static_cast<void*>(page_address));
            s_fastmem_arena.Unmap(map_address, g_ram_size);
            return;
          }
        }
      }

      s_fastmem_ram_views.emplace_back(map_address, g_ram_size);
    };

    // KUSEG - cached
    MapRAM(0x00000000);

    // KSEG0 - cached
    MapRAM(0x80000000);

    // KSEG1 - uncached
    MapRAM(0xA0000000);

    // Mirrors of 2MB
    if (g_ram_size == RAM_2MB_SIZE)
    {
      // Instead of mapping all the RAM mirrors, we only map the KSEG0 uppermost mirror.
      // This is where some games place their stack, so we avoid the backpatching overhead/slowdown,
      // but don't pay the cost of 4x the mprotect() calls when a page's protection changes, which
      // can have a non-trivial impact on slow ARM devices.
      MapRAM(0x80600000);
    }
#else
    Panic("MMap fastmem should not be selected on this platform.");
#endif
  }
  else if (mode == CPUFastmemMode::LUT)
  {
    if (!s_fastmem_lut)
    {
      s_fastmem_lut = static_cast<u8**>(std::malloc(sizeof(u8*) * FASTMEM_LUT_SLOTS));
      Assert(s_fastmem_lut);

      INFO_LOG("Fastmem base (software): {}", static_cast<void*>(s_fastmem_lut));
    }

    // This assumes the top 4KB of address space is not mapped. It shouldn't be on any sane OSes.
    for (u32 i = 0; i < FASTMEM_LUT_SLOTS; i++)
      s_fastmem_lut[i] = GetLUTFastmemPointer(i << FASTMEM_LUT_PAGE_SHIFT, nullptr);

    auto MapRAM = [](u32 base_address) {
      // Don't map RAM that isn't accessible.
      if (CPU::VirtualAddressToPhysical(base_address) >= g_ram_mapped_size)
        return;

      u8* ram_ptr = g_ram + (base_address & g_ram_mask);
      for (u32 address = 0; address < g_ram_size; address += FASTMEM_LUT_PAGE_SIZE)
      {
        const u32 lut_index = (base_address + address) >> FASTMEM_LUT_PAGE_SHIFT;
        s_fastmem_lut[lut_index] = GetLUTFastmemPointer(base_address + address, ram_ptr);
        ram_ptr += FASTMEM_LUT_PAGE_SIZE;
      }
    };

    // KUSEG - cached
    MapRAM(0x00000000);
    MapRAM(0x00200000);
    MapRAM(0x00400000);
    MapRAM(0x00600000);

    // KSEG0 - cached
    MapRAM(0x80000000);
    MapRAM(0x80200000);
    MapRAM(0x80400000);
    MapRAM(0x80600000);

    // KSEG1 - uncached
    MapRAM(0xA0000000);
    MapRAM(0xA0200000);
    MapRAM(0xA0400000);
    MapRAM(0xA0600000);
  }

  CPU::UpdateMemoryPointers();
}

void Bus::UnmapFastmemViews()
{
#ifdef ENABLE_MMAP_FASTMEM
  for (const auto& it : s_fastmem_ram_views)
    s_fastmem_arena.Unmap(it.first, it.second);
  s_fastmem_ram_views.clear();
#endif
}

void Bus::RemapFastmemViews()
{
  UnmapFastmemViews();
  MapFastmemViews();
}

bool Bus::CanUseFastmemForAddress(VirtualMemoryAddress address)
{
  const PhysicalMemoryAddress paddr = CPU::VirtualAddressToPhysical(address);

  switch (g_settings.cpu_fastmem_mode)
  {
#ifdef ENABLE_MMAP_FASTMEM
    case CPUFastmemMode::MMap:
    {
      // Currently since we don't map the mirrors, don't use fastmem for them.
      // This is because the swapping of page code bits for SMC is too expensive.
      // Except for the uppermost mirror in KSEG0, see above.
      return (paddr < g_ram_size) || (address >= 0x80600000 && address < 0x80800000);
    }
#endif

    case CPUFastmemMode::LUT:
      return (paddr < RAM_MIRROR_END);

    case CPUFastmemMode::Disabled:
    default:
      return false;
  }
}

void Bus::SetRAMCodePage(u32 index)
{
  if (g_ram_code_bits[index])
    return;

  // protect fastmem pages
  g_ram_code_bits[index] = true;
  SetRAMPageWritable(index, false);
}

void Bus::ClearRAMCodePage(u32 index)
{
  if (!g_ram_code_bits[index])
    return;

  // unprotect fastmem pages
  g_ram_code_bits[index] = false;
  SetRAMPageWritable(index, true);
}

void Bus::SetRAMPageWritable(u32 page_index, bool writable)
{
  if (!MemMap::MemProtect(&g_ram[page_index << HOST_PAGE_SHIFT], HOST_PAGE_SIZE,
                          writable ? PageProtect::ReadWrite : PageProtect::ReadOnly)) [[unlikely]]
  {
    ERROR_LOG("Failed to set RAM host page {} ({}) to {}", page_index,
              reinterpret_cast<const void*>(&g_ram[page_index * HOST_PAGE_SIZE]),
              writable ? "read-write" : "read-only");
  }

#ifdef ENABLE_MMAP_FASTMEM
  if (g_settings.cpu_fastmem_mode == CPUFastmemMode::MMap)
  {
    const PageProtect protect = writable ? PageProtect::ReadWrite : PageProtect::ReadOnly;

    // unprotect fastmem pages
    for (const auto& it : s_fastmem_ram_views)
    {
      u8* page_address = it.first + (page_index << HOST_PAGE_SHIFT);
      if (!MemMap::MemProtect(page_address, HOST_PAGE_SIZE, protect)) [[unlikely]]
      {
        ERROR_LOG("Failed to {} code page {} (0x{:08X}) @ {}", writable ? "unprotect" : "protect", page_index,
                  page_index << HOST_PAGE_SHIFT, static_cast<void*>(page_address));
      }
    }

    return;
  }
#endif
}

void Bus::ClearRAMCodePageFlags()
{
  g_ram_code_bits.reset();

  if (!MemMap::MemProtect(g_ram, RAM_8MB_SIZE, PageProtect::ReadWrite))
    ERROR_LOG("Failed to restore RAM protection to read-write.");

#ifdef ENABLE_MMAP_FASTMEM
  if (g_settings.cpu_fastmem_mode == CPUFastmemMode::MMap)
  {
    // unprotect fastmem pages
    for (const auto& it : s_fastmem_ram_views)
    {
      if (!MemMap::MemProtect(it.first, it.second, PageProtect::ReadWrite))
        ERROR_LOG("Failed to unprotect code pages for fastmem view @ {}", static_cast<void*>(it.first));
    }
  }
#endif
}

bool Bus::IsCodePageAddress(PhysicalMemoryAddress address)
{
  return IsRAMAddress(address) ? g_ram_code_bits[(address & g_ram_mask) >> HOST_PAGE_SHIFT] : false;
}

bool Bus::HasCodePagesInRange(PhysicalMemoryAddress start_address, u32 size)
{
  if (!IsRAMAddress(start_address))
    return false;

  start_address = (start_address & g_ram_mask);

  const u32 end_address = start_address + size;
  while (start_address < end_address)
  {
    const u32 code_page_index = start_address >> HOST_PAGE_SHIFT;
    if (g_ram_code_bits[code_page_index])
      return true;

    start_address += HOST_PAGE_SIZE;
  }

  return false;
}

const TickCount* Bus::GetMemoryAccessTimePtr(PhysicalMemoryAddress address, MemoryAccessSize size)
{
  // Currently only BIOS, but could be EXP1 as well.
  if (address >= BIOS_BASE && address < (BIOS_BASE + BIOS_MIRROR_SIZE))
    return &g_bios_access_time[static_cast<size_t>(size)];
  else if (address >= EXP1_BASE && address < (EXP1_BASE + EXP1_SIZE))
    return &g_exp1_access_time[static_cast<size_t>(size)];

  return nullptr;
}

std::optional<Bus::MemoryRegion> Bus::GetMemoryRegionForAddress(PhysicalMemoryAddress address)
{
  if (address < RAM_2MB_SIZE)
    return MemoryRegion::RAM;
  else if (address < RAM_MIRROR_END)
    return static_cast<MemoryRegion>(static_cast<u32>(MemoryRegion::RAM) + (address / RAM_2MB_SIZE));
  else if (address >= EXP1_BASE && address < (EXP1_BASE + EXP1_SIZE))
    return MemoryRegion::EXP1;
  else if (address >= CPU::SCRATCHPAD_ADDR && address < (CPU::SCRATCHPAD_ADDR + CPU::SCRATCHPAD_SIZE))
    return MemoryRegion::Scratchpad;
  else if (address >= BIOS_BASE && address < (BIOS_BASE + BIOS_SIZE))
    return MemoryRegion::BIOS;

  return std::nullopt;
}

static constexpr std::array<std::tuple<PhysicalMemoryAddress, PhysicalMemoryAddress, bool>,
                            static_cast<u32>(Bus::MemoryRegion::Count)>
  s_code_region_ranges = {{
    {0, Bus::RAM_2MB_SIZE, true},
    {Bus::RAM_2MB_SIZE, Bus::RAM_2MB_SIZE * 2, true},
    {Bus::RAM_2MB_SIZE * 2, Bus::RAM_2MB_SIZE * 3, true},
    {Bus::RAM_2MB_SIZE * 3, Bus::RAM_MIRROR_END, true},
    {Bus::EXP1_BASE, Bus::EXP1_BASE + Bus::EXP1_SIZE, false},
    {CPU::SCRATCHPAD_ADDR, CPU::SCRATCHPAD_ADDR + CPU::SCRATCHPAD_SIZE, true},
    {Bus::BIOS_BASE, Bus::BIOS_BASE + Bus::BIOS_SIZE, false},
  }};

PhysicalMemoryAddress Bus::GetMemoryRegionStart(MemoryRegion region)
{
  return std::get<0>(s_code_region_ranges[static_cast<u32>(region)]);
}

PhysicalMemoryAddress Bus::GetMemoryRegionEnd(MemoryRegion region)
{
  return std::get<1>(s_code_region_ranges[static_cast<u32>(region)]);
}

bool Bus::IsMemoryRegionWritable(MemoryRegion region)
{
  return std::get<2>(s_code_region_ranges[static_cast<u32>(region)]);
}

u8* Bus::GetMemoryRegionPointer(MemoryRegion region)
{
  switch (region)
  {
    case MemoryRegion::RAM:
      return g_unprotected_ram;

    case MemoryRegion::RAMMirror1:
      return (g_unprotected_ram + (RAM_2MB_SIZE & g_ram_mask));

    case MemoryRegion::RAMMirror2:
      return (g_unprotected_ram + ((RAM_2MB_SIZE * 2) & g_ram_mask));

    case MemoryRegion::RAMMirror3:
      return (g_unprotected_ram + ((RAM_8MB_SIZE * 3) & g_ram_mask));

    case MemoryRegion::EXP1:
      return nullptr;

    case MemoryRegion::Scratchpad:
      return CPU::g_state.scratchpad.data();

    case MemoryRegion::BIOS:
      return g_bios;

    default:
      return nullptr;
  }
}

static ALWAYS_INLINE_RELEASE bool MaskedMemoryCompare(const u8* pattern, const u8* mask, u32 pattern_length,
                                                      const u8* mem)
{
  if (!mask)
    return std::memcmp(mem, pattern, pattern_length) == 0;

  for (u32 i = 0; i < pattern_length; i++)
  {
    if ((mem[i] & mask[i]) != (pattern[i] & mask[i]))
      return false;
  }

  return true;
}

std::optional<PhysicalMemoryAddress> Bus::SearchMemory(PhysicalMemoryAddress start_address, const u8* pattern,
                                                       const u8* mask, u32 pattern_length)
{
  std::optional<MemoryRegion> region = GetMemoryRegionForAddress(start_address);
  if (!region.has_value())
    return std::nullopt;

  PhysicalMemoryAddress current_address = start_address;
  MemoryRegion current_region = region.value();
  while (current_region != MemoryRegion::Count)
  {
    const u8* mem = GetMemoryRegionPointer(current_region);
    const PhysicalMemoryAddress region_start = GetMemoryRegionStart(current_region);
    const PhysicalMemoryAddress region_end = GetMemoryRegionEnd(current_region);

    if (mem)
    {
      PhysicalMemoryAddress region_offset = current_address - region_start;
      PhysicalMemoryAddress bytes_remaining = region_end - current_address;
      while (bytes_remaining >= pattern_length)
      {
        if (MaskedMemoryCompare(pattern, mask, pattern_length, mem + region_offset))
          return region_start + region_offset;

        region_offset++;
        bytes_remaining--;
      }
    }

    // skip RAM mirrors
    if (current_region == MemoryRegion::RAM)
      current_region = MemoryRegion::EXP1;
    else
      current_region = static_cast<MemoryRegion>(static_cast<int>(current_region) + 1);

    if (current_region != MemoryRegion::Count)
      current_address = GetMemoryRegionStart(current_region);
  }

  return std::nullopt;
}

void Bus::AddTTYCharacter(char ch)
{
  if (ch == '\r')
  {
  }
  else if (ch == '\n')
  {
    if (!s_tty_line_buffer.empty())
    {
      Log::FastWrite(Log::Channel::TTY, Log::Level::Info, Log::Color::StrongBlue, s_tty_line_buffer);
#if defined(_DEBUG) || defined(_DEVEL)
      if (CPU::IsTraceEnabled())
        CPU::WriteToExecutionLog("TTY: %s\n", s_tty_line_buffer.c_str());
#endif
    }
    s_tty_line_buffer.clear();
  }
  else if (ch != '\0')
  {
    s_tty_line_buffer += ch;
  }
}

void Bus::AddTTYString(std::string_view str)
{
  for (char ch : str)
    AddTTYCharacter(ch);
}

bool Bus::InjectExecutable(std::span<const u8> buffer, bool set_pc, Error* error)
{
  BIOS::PSEXEHeader header;
  if (buffer.size() < sizeof(header))
  {
    Error::SetStringView(error, "Executable does not contain a header.");
    return false;
  }

  std::memcpy(&header, buffer.data(), sizeof(header));
  if (!BIOS::IsValidPSExeHeader(header, buffer.size()))
  {
    Error::SetStringView(error, "Executable does not contain a valid header.");
    return false;
  }

  if (header.memfill_size > 0 &&
      !CPU::SafeZeroMemoryBytes(header.memfill_start & ~UINT32_C(3), Common::AlignDownPow2(header.memfill_size, 4)))
  {
    Error::SetStringFmt(error, "Failed to zero {} bytes of memory at address 0x{:08X}.", header.memfill_start,
                        header.memfill_size);
    return false;
  }

  const u32 data_load_size =
    std::min(static_cast<u32>(static_cast<u32>(buffer.size() - sizeof(BIOS::PSEXEHeader))), header.file_size);
  if (data_load_size > 0)
  {
    if (!CPU::SafeWriteMemoryBytes(header.load_address, &buffer[sizeof(header)], data_load_size))
    {
      Error::SetStringFmt(error, "Failed to upload {} bytes to memory at address 0x{:08X}.", data_load_size,
                          header.load_address);
    }
  }

  // patch the BIOS to jump to the executable directly
  if (set_pc)
  {
    const u32 r_pc = header.initial_pc;
    const u32 r_gp = header.initial_gp;
    const u32 r_sp = header.initial_sp_base + header.initial_sp_offset;
    CPU::g_state.regs.gp = r_gp;
    if (r_sp != 0)
    {
      CPU::g_state.regs.sp = r_sp;
      CPU::g_state.regs.fp = r_sp;
    }
    CPU::SetPC(r_pc);
  }

  return true;
}

bool Bus::InjectCPE(std::span<const u8> buffer, bool set_pc, Error* error)
{
  // https://psx-spx.consoledev.net/cdromfileformats/#cdrom-file-psyq-cpe-files-debug-executables
  BinarySpanReader reader(buffer);
  if (reader.ReadU32() != BIOS::CPE_MAGIC)
  {
    Error::SetStringView(error, "Invalid CPE signature.");
    return false;
  }

  static constexpr auto set_register = [](u32 reg, u32 value) {
    if (reg == 0x90)
    {
      CPU::SetPC(value);
    }
    else
    {
      WARNING_LOG("Ignoring set register 0x{:X} to 0x{:X}", reg, value);
    }
  };

  for (;;)
  {
    if (!reader.CheckRemaining(1))
    {
      Error::SetStringView(error, "End of file reached before EOF chunk.");
      return false;
    }

    // Little error checking on chunk sizes, because if any of them run out of buffer,
    // it'll loop around and hit the EOF if above.
    const u8 chunk = reader.ReadU8();
    switch (chunk)
    {
      case 0x00:
      {
        // End of file
        return true;
      }

      case 0x01:
      {
        // Load data
        const u32 addr = reader.ReadU32();
        const u32 size = reader.ReadU32();
        if (size > 0)
        {
          if (!reader.CheckRemaining(size))
          {
            Error::SetStringFmt(error, "EOF reached in the middle of load to 0x{:08X}", addr);
            return false;
          }

          if (const auto data = reader.GetRemainingSpan(size); !CPU::SafeWriteMemoryBytes(addr, data))
          {
            Error::SetStringFmt(error, "Failed to write {} bytes to address 0x{:08X}", size, addr);
            return false;
          }

          reader.IncrementPosition(size);
        }
      }
      break;

      case 0x02:
      {
        // Run address, ignored
        DEV_LOG("Ignoring run address 0x{:X}", reader.ReadU32());
      }
      break;

      case 0x03:
      {
        // Set register 32-bit
        const u16 reg = reader.ReadU16();
        const u32 value = reader.ReadU32();
        set_register(reg, value);
      }
      break;

      case 0x04:
      {
        // Set register 16-bit
        const u16 reg = reader.ReadU16();
        const u16 value = reader.ReadU16();
        set_register(reg, value);
      }
      break;

      case 0x05:
      {
        // Set register 8-bit
        const u16 reg = reader.ReadU16();
        const u8 value = reader.ReadU8();
        set_register(reg, value);
      }
      break;

      case 0x06:
      {
        // Set register 24-bit
        const u16 reg = reader.ReadU16();
        const u16 low = reader.ReadU16();
        const u8 high = reader.ReadU8();
        set_register(reg, ZeroExtend32(low) | (ZeroExtend32(high) << 16));
      }
      break;

      case 0x07:
      {
        // Select workspace
        DEV_LOG("Ignoring set workspace 0x{:X}", reader.ReadU32());
      }
      break;

      case 0x08:
      {
        // Select unit
        DEV_LOG("Ignoring select unit 0x{:X}", reader.ReadU8());
      }
      break;

      default:
      {
        WARNING_LOG("Unknown chunk 0x{:02X} in CPE file, parsing will probably fail now.", chunk);
      }
      break;
    }
  }

  return true;
}

bool Bus::InjectELF(const ELFFile& elf, bool set_pc, Error* error)
{
  const bool okay = elf.LoadExecutableSections(
    [](std::span<const u8> data, u32 dest_addr, u32 dest_size, Error* error) {
      if (!data.empty() && !CPU::SafeWriteMemoryBytes(dest_addr, data))
      {
        Error::SetStringFmt(error, "Failed to load {} bytes to 0x{:08X}", data.size(), dest_addr);
        return false;
      }

      const u32 zero_addr = dest_addr + static_cast<u32>(data.size());
      const u32 zero_bytes = dest_size - static_cast<u32>(data.size());
      if (zero_bytes > 0 && !CPU::SafeZeroMemoryBytes(zero_addr, zero_bytes))
      {
        Error::SetStringFmt(error, "Failed to zero {} bytes at 0x{:08X}", zero_bytes, zero_addr);
        return false;
      }

      return true;
    },
    error);

  if (okay && set_pc)
    CPU::SetPC(elf.GetEntryPoint());

  return okay;
}

void Bus::KernelInitializedHook()
{
  if (s_kernel_initialize_hook_run)
    return;

  INFO_LOG("Kernel initialized.");
  s_kernel_initialize_hook_run = true;

  const System::BootMode boot_mode = System::GetBootMode();
  if (boot_mode == System::BootMode::BootEXE || boot_mode == System::BootMode::BootPSF)
  {
    Error error;
    if (((boot_mode == System::BootMode::BootEXE) ? SideloadEXE(System::GetExeOverride(), &error) :
                                                    PSFLoader::Load(System::GetExeOverride(), &error)))
    {
      // Clear all state, since we're blatently overwriting memory.
      CPU::CodeCache::Reset();
      CPU::ClearICache();

      // Stop executing the current block and shell init, and jump straight to the new code.
      DebugAssert(!TimingEvents::IsRunningEvents());
      CPU::ExitExecution();
    }
    else
    {
      // Shut down system on load failure.
      Host::ReportErrorAsync("EXE/PSF Load Failed", error.GetDescription());
      System::ShutdownSystem(false);
    }
  }
}

bool Bus::SideloadEXE(const std::string& path, Error* error)
{
  std::optional<DynamicHeapArray<u8>> exe_data = FileSystem::ReadBinaryFile(path.c_str(), error);
  if (!exe_data.has_value())
  {
    Error::AddPrefixFmt(error, "Failed to read {}: ", Path::GetFileName(path));
    return false;
  }

  // Stupid Android...
  std::string filename = FileSystem::GetDisplayNameFromPath(path);

  bool okay = true;
  if (StringUtil::EndsWithNoCase(filename, ".cpe"))
  {
    okay = InjectCPE(exe_data->cspan(), true, error);
  }
  else if (StringUtil::EndsWithNoCase(filename, ".elf"))
  {
    ELFFile elf;
    if (!elf.Open(std::move(exe_data.value()), error))
      return false;

    okay = InjectELF(elf, true, error);
  }
  else
  {
    // look for a libps.exe next to the exe, if it exists, load it
    if (const std::string libps_path = Path::BuildRelativePath(path, "libps.exe");
        FileSystem::FileExists(libps_path.c_str()))
    {
      const std::optional<DynamicHeapArray<u8>> libps_data = FileSystem::ReadBinaryFile(libps_path.c_str(), error);
      if (!libps_data.has_value() || !InjectExecutable(libps_data->cspan(), false, error))
      {
        Error::AddPrefix(error, "Failed to load libps.exe: ");
        return false;
      }
    }

    okay = InjectExecutable(exe_data->cspan(), true, error);
  }

  if (!okay)
  {
    Error::AddPrefixFmt(error, "Failed to load {}: ", Path::GetFileName(path));
    return false;
  }

  return okay;
}

#define BUS_CYCLES(n) CPU::g_state.pending_ticks += n

// TODO: Move handlers to own files for better inlining.
namespace Bus {
static void ClearHandlers(void** handlers);
static void SetHandlerForRegion(void** handlers, VirtualMemoryAddress address, u32 size,
                                MemoryReadHandler read_byte_handler, MemoryReadHandler read_halfword_handler,
                                MemoryReadHandler read_word_handler, MemoryWriteHandler write_byte_handler,
                                MemoryWriteHandler write_halfword_handler, MemoryWriteHandler write_word_handler);

// clang-format off
template<MemoryAccessSize size> static u32 UnknownReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void UnknownWriteHandler(VirtualMemoryAddress address, u32 value);
template<MemoryAccessSize size> static void IgnoreWriteHandler(VirtualMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 UnmappedReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void UnmappedWriteHandler(VirtualMemoryAddress address, u32 value);

template<MemoryAccessSize size> static u32 RAMReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void RAMWriteHandler(VirtualMemoryAddress address, u32 value);

template<MemoryAccessSize size> static u32 BIOSReadHandler(VirtualMemoryAddress address);

template<MemoryAccessSize size> static u32 ScratchpadReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void ScratchpadWriteHandler(VirtualMemoryAddress address, u32 value);

template<MemoryAccessSize size> static u32 CacheControlReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void CacheControlWriteHandler(VirtualMemoryAddress address, u32 value);

template<MemoryAccessSize size> static u32 ICacheReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void ICacheWriteHandler(VirtualMemoryAddress address, u32 value);

template<MemoryAccessSize size> static u32 EXP1ReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void EXP1WriteHandler(VirtualMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 EXP2ReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void EXP2WriteHandler(VirtualMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 EXP3ReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void EXP3WriteHandler(VirtualMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 SIO2ReadHandler(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void SIO2WriteHandler(PhysicalMemoryAddress address, u32 value);

template<MemoryAccessSize size> static u32 HardwareReadHandler(VirtualMemoryAddress address);
template<MemoryAccessSize size> static void HardwareWriteHandler(VirtualMemoryAddress address, u32 value);

// clang-format on
} // namespace Bus

template<MemoryAccessSize size>
u32 Bus::UnknownReadHandler(VirtualMemoryAddress address)
{
  static constexpr const char* sizes[3] = {"byte", "halfword", "word"};
  ERROR_LOG("Invalid {} read at address 0x{:08X}, pc 0x{:08X}", sizes[static_cast<u32>(size)], address,
            CPU::g_state.pc);
  return 0xFFFFFFFFu;
}

template<MemoryAccessSize size>
void Bus::UnknownWriteHandler(VirtualMemoryAddress address, u32 value)
{
  static constexpr const char* sizes[3] = {"byte", "halfword", "word"};
  ERROR_LOG("Invalid {} write at address 0x{:08X}, value 0x{:08X}, pc 0x{:08X}", sizes[static_cast<u32>(size)], address,
            value, CPU::g_state.pc);
  CPU::g_state.bus_error = true;
}

template<MemoryAccessSize size>
void Bus::IgnoreWriteHandler(VirtualMemoryAddress address, u32 value)
{
  // noop
}

template<MemoryAccessSize size>
u32 Bus::UnmappedReadHandler(VirtualMemoryAddress address)
{
  CPU::g_state.bus_error = true;
  return UnknownReadHandler<size>(address);
}

template<MemoryAccessSize size>
void Bus::UnmappedWriteHandler(VirtualMemoryAddress address, u32 value)
{
  CPU::g_state.bus_error = true;
  UnknownWriteHandler<size>(address, value);
}

template<MemoryAccessSize size>
u32 Bus::RAMReadHandler(VirtualMemoryAddress address)
{
  BUS_CYCLES(RAM_READ_TICKS);

  const u32 offset = address & g_ram_mask;
  if constexpr (size == MemoryAccessSize::Byte)
  {
    return ZeroExtend32(g_ram[offset]);
  }
  else if constexpr (size == MemoryAccessSize::HalfWord)
  {
    u16 temp;
    std::memcpy(&temp, &g_ram[offset], sizeof(u16));
    return ZeroExtend32(temp);
  }
  else if constexpr (size == MemoryAccessSize::Word)
  {
    u32 value;
    std::memcpy(&value, &g_ram[offset], sizeof(u32));
    return value;
  }
}

template<MemoryAccessSize size>
void Bus::RAMWriteHandler(VirtualMemoryAddress address, u32 value)
{
  const u32 offset = address & g_ram_mask;

  if constexpr (size == MemoryAccessSize::Byte)
  {
    g_ram[offset] = Truncate8(value);
  }
  else if constexpr (size == MemoryAccessSize::HalfWord)
  {
    const u16 temp = Truncate16(value);
    std::memcpy(&g_ram[offset], &temp, sizeof(u16));
  }
  else if constexpr (size == MemoryAccessSize::Word)
  {
    std::memcpy(&g_ram[offset], &value, sizeof(u32));
  }
}

template<MemoryAccessSize size>
u32 Bus::BIOSReadHandler(VirtualMemoryAddress address)
{
  BUS_CYCLES(g_bios_access_time[static_cast<u32>(size)]);

  // TODO: Configurable mirroring.
  const u32 offset = address & UINT32_C(0x7FFFF);
  if constexpr (size == MemoryAccessSize::Byte)
  {
    return ZeroExtend32(g_bios[offset]);
  }
  else if constexpr (size == MemoryAccessSize::HalfWord)
  {
    u16 temp;
    std::memcpy(&temp, &g_bios[offset], sizeof(u16));
    return ZeroExtend32(temp);
  }
  else
  {
    u32 value;
    std::memcpy(&value, &g_bios[offset], sizeof(u32));
    return value;
  }
}

template<MemoryAccessSize size>
u32 Bus::ScratchpadReadHandler(VirtualMemoryAddress address)
{
  const PhysicalMemoryAddress cache_offset = address & MEMORY_LUT_PAGE_MASK;
  if (cache_offset >= CPU::SCRATCHPAD_SIZE) [[unlikely]]
    return UnknownReadHandler<size>(address);

  if constexpr (size == MemoryAccessSize::Byte)
  {
    return ZeroExtend32(CPU::g_state.scratchpad[cache_offset]);
  }
  else if constexpr (size == MemoryAccessSize::HalfWord)
  {
    u16 temp;
    std::memcpy(&temp, &CPU::g_state.scratchpad[cache_offset], sizeof(temp));
    return ZeroExtend32(temp);
  }
  else
  {
    u32 value;
    std::memcpy(&value, &CPU::g_state.scratchpad[cache_offset], sizeof(value));
    return value;
  }
}

template<MemoryAccessSize size>
void Bus::ScratchpadWriteHandler(VirtualMemoryAddress address, u32 value)
{
  const PhysicalMemoryAddress cache_offset = address & MEMORY_LUT_PAGE_MASK;
  if (cache_offset >= CPU::SCRATCHPAD_SIZE) [[unlikely]]
  {
    UnknownWriteHandler<size>(address, value);
    return;
  }

  if constexpr (size == MemoryAccessSize::Byte)
    CPU::g_state.scratchpad[cache_offset] = Truncate8(value);
  else if constexpr (size == MemoryAccessSize::HalfWord)
    std::memcpy(&CPU::g_state.scratchpad[cache_offset], &value, sizeof(u16));
  else if constexpr (size == MemoryAccessSize::Word)
    std::memcpy(&CPU::g_state.scratchpad[cache_offset], &value, sizeof(u32));
}

template<MemoryAccessSize size>
u32 Bus::CacheControlReadHandler(VirtualMemoryAddress address)
{
  if (address != 0xFFFE0130)
    return UnknownReadHandler<size>(address);

  return CPU::g_state.cache_control.bits;
}

template<MemoryAccessSize size>
void Bus::CacheControlWriteHandler(VirtualMemoryAddress address, u32 value)
{
  if (address != 0xFFFE0130)
    return UnknownWriteHandler<size>(address, value);

  DEV_LOG("Cache control <- 0x{:08X}", value);
  CPU::g_state.cache_control.bits = value;
}

template<MemoryAccessSize size>
u32 Bus::ICacheReadHandler(VirtualMemoryAddress address)
{
  const u32 line = CPU::GetICacheLine(address);
  const u32* line_data = &CPU::g_state.icache_data[line * CPU::ICACHE_WORDS_PER_LINE];
  const u32 offset = CPU::GetICacheLineOffset(address);
  u32 result;
  std::memcpy(&result, reinterpret_cast<const u8*>(line_data) + offset, sizeof(result));
  return result;
}

template<MemoryAccessSize size>
void Bus::ICacheWriteHandler(VirtualMemoryAddress address, u32 value)
{
  const u32 line = CPU::GetICacheLine(address);
  u32* line_data = &CPU::g_state.icache_data[line * CPU::ICACHE_WORDS_PER_LINE];
  const u32 offset = CPU::GetICacheLineOffset(address);
  CPU::g_state.icache_tags[line] = CPU::GetICacheTagForAddress(address) | CPU::ICACHE_INVALID_BITS;
  if constexpr (size == MemoryAccessSize::Byte)
    std::memcpy(reinterpret_cast<u8*>(line_data) + offset, &value, sizeof(u8));
  else if constexpr (size == MemoryAccessSize::HalfWord)
    std::memcpy(reinterpret_cast<u8*>(line_data) + offset, &value, sizeof(u16));
  else
    std::memcpy(reinterpret_cast<u8*>(line_data) + offset, &value, sizeof(u32));
}

template<MemoryAccessSize size>
u32 Bus::EXP1ReadHandler(VirtualMemoryAddress address)
{
  BUS_CYCLES(g_exp1_access_time[static_cast<u32>(size)]);

  // TODO: auto-increment should be handled elsewhere...

  const u32 offset = address & EXP1_MASK;
  u32 ret;

  if constexpr (size >= MemoryAccessSize::HalfWord)
  {
    ret = g_pio_device->ReadHandler(offset);
    ret |= ZeroExtend32(g_pio_device->ReadHandler(offset + 1)) << 8;
    if constexpr (size == MemoryAccessSize::Word)
    {
      ret |= ZeroExtend32(g_pio_device->ReadHandler(offset + 2)) << 16;
      ret |= ZeroExtend32(g_pio_device->ReadHandler(offset + 3)) << 24;
    }
  }
  else
  {
    ret = ZeroExtend32(g_pio_device->ReadHandler(offset));
  }

  return ret;
}

template<MemoryAccessSize size>
void Bus::EXP1WriteHandler(VirtualMemoryAddress address, u32 value)
{
  // TODO: auto-increment should be handled elsewhere...

  const u32 offset = address & EXP1_MASK;
  if constexpr (size >= MemoryAccessSize::HalfWord)
  {
    g_pio_device->WriteHandler(offset, Truncate8(value));
    g_pio_device->WriteHandler(offset + 1, Truncate8(value >> 8));
    if constexpr (size == MemoryAccessSize::Word)
    {
      g_pio_device->WriteHandler(offset + 2, Truncate8(value >> 16));
      g_pio_device->WriteHandler(offset + 3, Truncate8(value >> 24));
    }
  }
  else
  {
    g_pio_device->WriteHandler(offset, Truncate8(value));
  }
}

template<MemoryAccessSize size>
u32 Bus::EXP2ReadHandler(VirtualMemoryAddress address)
{
  BUS_CYCLES(g_exp2_access_time[static_cast<u32>(size)]);

  const u32 offset = address & EXP2_MASK;
  u32 value;

  // rx/tx buffer empty
  if (offset == 0x21)
  {
    value = 0x04 | 0x08;
  }
  else if (offset >= 0x60 && offset <= 0x67)
  {
    // nocash expansion area
    value = UINT32_C(0xFFFFFFFF);
  }
  else if (offset == 0x80)
  {
    // pcsx_present()
    value = UINT32_C(0xFFFFFFFF);
  }
  else
  {
    WARNING_LOG("EXP2 read: 0x{:08X}", address);
    value = UINT32_C(0xFFFFFFFF);
  }

  return value;
}

template<MemoryAccessSize size>
void Bus::EXP2WriteHandler(VirtualMemoryAddress address, u32 value)
{
  const u32 offset = address & EXP2_MASK;
  if (offset == 0x23 || offset == 0x80)
  {
    AddTTYCharacter(static_cast<char>(value));
  }
  else if (offset == 0x41 || offset == 0x42)
  {
    const u32 post_code = value & UINT32_C(0x0F);
    DEV_LOG("BIOS POST status: {:02X}", post_code);
    if (post_code == 0x07)
      KernelInitializedHook();
  }
  else if (offset == 0x70)
  {
    DEV_LOG("BIOS POST2 status: {:02X}", value & UINT32_C(0x0F));
  }
#if 0
  // TODO: Put behind configuration variable
  else if (offset == 0x81)
  {
    Log_WarningPrint("pcsx_debugbreak()");
    Host::ReportErrorAsync("Error", "pcsx_debugbreak()");
    System::PauseSystem(true);
    CPU::ExitExecution();
  }
  else if (offset == 0x82)
  {
    Log_WarningFmt("pcsx_exit() with status 0x{:02X}", value & UINT32_C(0xFF));
    Host::ReportErrorAsync("Error", fmt::format("pcsx_exit() with status 0x{:02X}", value & UINT32_C(0xFF)));
    System::ShutdownSystem(false);
    CPU::ExitExecution();
  }
#endif
  else
  {
    WARNING_LOG("EXP2 write: 0x{:08X} <- 0x{:08X}", address, value);
  }
}

template<MemoryAccessSize size>
u32 Bus::EXP3ReadHandler(VirtualMemoryAddress address)
{
  WARNING_LOG("EXP3 read: 0x{:08X}", address);
  return UINT32_C(0xFFFFFFFF);
}

template<MemoryAccessSize size>
void Bus::EXP3WriteHandler(VirtualMemoryAddress address, u32 value)
{
  const u32 offset = address & EXP3_MASK;
  if (offset == 0)
  {
    const u32 post_code = value & UINT32_C(0x0F);
    WARNING_LOG("BIOS POST3 status: {:02X}", post_code);
    if (post_code == 0x07)
      KernelInitializedHook();
  }
}

template<MemoryAccessSize size>
u32 Bus::SIO2ReadHandler(PhysicalMemoryAddress address)
{
  // Stub for using PS2 BIOS.
  if (System::IsUsingKnownPS1BIOS()) [[unlikely]]
  {
    // Throw exception when not using PS2 BIOS.
    return UnmappedReadHandler<size>(address);
  }

  WARNING_LOG("SIO2 read: 0x{:08X}", address);
  return 0;
}

template<MemoryAccessSize size>
void Bus::SIO2WriteHandler(PhysicalMemoryAddress address, u32 value)
{
  // Stub for using PS2 BIOS.
  if (System::IsUsingKnownPS1BIOS()) [[unlikely]]
  {
    // Throw exception when not using PS2 BIOS.
    UnmappedWriteHandler<size>(address, value);
    return;
  }

  WARNING_LOG("SIO2 write: 0x{:08X} <- 0x{:08X}", address, value);
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// HARDWARE HANDLERS
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

namespace Bus::HWHandlers {
// clang-format off
template<MemoryAccessSize size> static u32 MemCtrlRead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void MemCtrlWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 PADRead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void PADWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 SIORead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void SIOWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 MemCtrl2Read(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void MemCtrl2Write(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 INTCRead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void INTCWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 DMARead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void DMAWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 TimersRead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void TimersWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 CDROMRead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void CDROMWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 GPURead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void GPUWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 MDECRead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void MDECWrite(PhysicalMemoryAddress address, u32 value);
template<MemoryAccessSize size> static u32 SPURead(PhysicalMemoryAddress address);
template<MemoryAccessSize size> static void SPUWrite(PhysicalMemoryAddress address, u32 value);
// clang-format on
} // namespace Bus::HWHandlers

template<MemoryAccessSize size>
u32 Bus::HWHandlers::MemCtrlRead(PhysicalMemoryAddress address)
{
  const u32 offset = address & MEMCTRL_MASK;
  const u32 index = FIXUP_WORD_OFFSET(size, offset) / 4;
  if (index >= std::size(s_MEMCTRL.regs)) [[unlikely]]
    return 0;

  u32 value = s_MEMCTRL.regs[index];
  value = FIXUP_WORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::MemCtrlWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & MEMCTRL_MASK;
  const u32 index = FIXUP_WORD_OFFSET(size, offset) / 4;
  if (index >= std::size(s_MEMCTRL.regs)) [[unlikely]]
    return;

  value = FIXUP_WORD_WRITE_VALUE(size, offset, value);

  const u32 write_mask = (index == 8) ? COMDELAY::WRITE_MASK : MEMDELAY::WRITE_MASK;
  const u32 new_value = (s_MEMCTRL.regs[index] & ~write_mask) | (value & write_mask);
  if (s_MEMCTRL.regs[index] != new_value)
  {
    s_MEMCTRL.regs[index] = new_value;
    RecalculateMemoryTimings();
  }
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::MemCtrl2Read(PhysicalMemoryAddress address)
{
  const u32 offset = address & MEMCTRL2_MASK;

  u32 value;
  if (offset == 0x00)
  {
    value = s_RAM_SIZE.bits;
  }
  else
  {
    return UnknownReadHandler<size>(address);
  }

  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::MemCtrl2Write(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & MEMCTRL2_MASK;

  if (offset == 0x00)
  {
    if (s_RAM_SIZE.bits != value)
    {
      DEV_LOG("RAM size register set to 0x{:08X}", value);

      const RAM_SIZE_REG old_ram_size_reg = s_RAM_SIZE;
      s_RAM_SIZE.bits = value;

      if (s_RAM_SIZE.memory_window != old_ram_size_reg.memory_window)
        UpdateMappedRAMSize();
    }
  }
  else
  {
    return UnknownWriteHandler<size>(address, value);
  }
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::PADRead(PhysicalMemoryAddress address)
{
  const u32 offset = address & PAD_MASK;

  u32 value = Pad::ReadRegister(FIXUP_HALFWORD_OFFSET(size, offset));
  value = FIXUP_HALFWORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::PADWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & PAD_MASK;
  Pad::WriteRegister(FIXUP_HALFWORD_OFFSET(size, offset), FIXUP_HALFWORD_WRITE_VALUE(size, offset, value));
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::SIORead(PhysicalMemoryAddress address)
{
  const u32 offset = address & SIO_MASK;
  u32 value = SIO::ReadRegister(FIXUP_HALFWORD_OFFSET(size, offset));
  value = FIXUP_HALFWORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::SIOWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & SIO_MASK;
  SIO::WriteRegister(FIXUP_HALFWORD_OFFSET(size, offset), FIXUP_HALFWORD_WRITE_VALUE(size, offset, value));
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::CDROMRead(PhysicalMemoryAddress address)
{
  const u32 offset = address & CDROM_MASK;

  u32 value;
  switch (size)
  {
    case MemoryAccessSize::Word:
    {
      const u32 b0 = ZeroExtend32(CDROM::ReadRegister(offset));
      const u32 b1 = ZeroExtend32(CDROM::ReadRegister(offset + 1u));
      const u32 b2 = ZeroExtend32(CDROM::ReadRegister(offset + 2u));
      const u32 b3 = ZeroExtend32(CDROM::ReadRegister(offset + 3u));
      value = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
    }
    break;

    case MemoryAccessSize::HalfWord:
    {
      const u32 lsb = ZeroExtend32(CDROM::ReadRegister(offset));
      const u32 msb = ZeroExtend32(CDROM::ReadRegister(offset + 1u));
      value = lsb | (msb << 8);
    }
    break;

    case MemoryAccessSize::Byte:
    default:
      value = ZeroExtend32(CDROM::ReadRegister(offset));
      break;
  }

  BUS_CYCLES(Bus::g_cdrom_access_time[static_cast<u32>(size)]);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::CDROMWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & CDROM_MASK;
  switch (size)
  {
    case MemoryAccessSize::Word:
    {
      CDROM::WriteRegister(offset, Truncate8(value & 0xFFu));
      CDROM::WriteRegister(offset + 1u, Truncate8((value >> 8) & 0xFFu));
      CDROM::WriteRegister(offset + 2u, Truncate8((value >> 16) & 0xFFu));
      CDROM::WriteRegister(offset + 3u, Truncate8((value >> 24) & 0xFFu));
    }
    break;

    case MemoryAccessSize::HalfWord:
    {
      CDROM::WriteRegister(offset, Truncate8(value & 0xFFu));
      CDROM::WriteRegister(offset + 1u, Truncate8((value >> 8) & 0xFFu));
    }
    break;

    case MemoryAccessSize::Byte:
    default:
      CDROM::WriteRegister(offset, Truncate8(value));
      break;
  }
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::GPURead(PhysicalMemoryAddress address)
{
  const u32 offset = address & GPU_MASK;
  u32 value = g_gpu.ReadRegister(FIXUP_WORD_OFFSET(size, offset));
  value = FIXUP_WORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::GPUWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & GPU_MASK;
  g_gpu.WriteRegister(FIXUP_WORD_OFFSET(size, offset), FIXUP_WORD_WRITE_VALUE(size, offset, value));
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::MDECRead(PhysicalMemoryAddress address)
{
  const u32 offset = address & MDEC_MASK;
  u32 value = MDEC::ReadRegister(FIXUP_WORD_OFFSET(size, offset));
  value = FIXUP_WORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::MDECWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & MDEC_MASK;
  MDEC::WriteRegister(FIXUP_WORD_OFFSET(size, offset), FIXUP_WORD_WRITE_VALUE(size, offset, value));
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::INTCRead(PhysicalMemoryAddress address)
{
  const u32 offset = address & INTERRUPT_CONTROLLER_MASK;
  u32 value = InterruptController::ReadRegister(FIXUP_WORD_OFFSET(size, offset));
  value = FIXUP_WORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::INTCWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & INTERRUPT_CONTROLLER_MASK;
  InterruptController::WriteRegister(FIXUP_WORD_OFFSET(size, offset), FIXUP_WORD_WRITE_VALUE(size, offset, value));
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::TimersRead(PhysicalMemoryAddress address)
{
  const u32 offset = address & TIMERS_MASK;
  u32 value = Timers::ReadRegister(FIXUP_WORD_OFFSET(size, offset));
  value = FIXUP_WORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::TimersWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & TIMERS_MASK;
  Timers::WriteRegister(FIXUP_WORD_OFFSET(size, offset), FIXUP_WORD_WRITE_VALUE(size, offset, value));
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::SPURead(PhysicalMemoryAddress address)
{
  const u32 offset = address & SPU_MASK;
  u32 value;

  switch (size)
  {
    case MemoryAccessSize::Word:
    {
      // 32-bit reads are read as two 16-bit accesses.
      const u16 lsb = SPU::ReadRegister(offset);
      const u16 msb = SPU::ReadRegister(offset + 2);
      value = ZeroExtend32(lsb) | (ZeroExtend32(msb) << 16);
    }
    break;

    case MemoryAccessSize::HalfWord:
    {
      value = ZeroExtend32(SPU::ReadRegister(offset));
    }
    break;

    case MemoryAccessSize::Byte:
    default:
    {
      const u16 value16 = SPU::ReadRegister(FIXUP_HALFWORD_OFFSET(size, offset));
      value = FIXUP_HALFWORD_READ_VALUE(size, offset, value16);
    }
    break;
  }

  BUS_CYCLES(Bus::g_spu_access_time[static_cast<u32>(size)]);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::SPUWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & SPU_MASK;

  // 32-bit writes are written as two 16-bit writes.
  switch (size)
  {
    case MemoryAccessSize::Word:
    {
      DebugAssert(Common::IsAlignedPow2(offset, 2));
      SPU::WriteRegister(offset, Truncate16(value));
      SPU::WriteRegister(offset + 2, Truncate16(value >> 16));
      break;
    }

    case MemoryAccessSize::HalfWord:
    {
      DebugAssert(Common::IsAlignedPow2(offset, 2));
      SPU::WriteRegister(offset, Truncate16(value));
      break;
    }

    case MemoryAccessSize::Byte:
    {
      // Byte writes to unaligned addresses are apparently ignored.
      if (address & 1)
        return;

      SPU::WriteRegister(offset, Truncate16(FIXUP_HALFWORD_READ_VALUE(size, offset, value)));
      break;
    }
  }
}

template<MemoryAccessSize size>
u32 Bus::HWHandlers::DMARead(PhysicalMemoryAddress address)
{
  const u32 offset = address & DMA_MASK;
  u32 value = DMA::ReadRegister(FIXUP_WORD_OFFSET(size, offset));
  value = FIXUP_WORD_READ_VALUE(size, offset, value);
  BUS_CYCLES(2);
  return value;
}

template<MemoryAccessSize size>
void Bus::HWHandlers::DMAWrite(PhysicalMemoryAddress address, u32 value)
{
  const u32 offset = address & DMA_MASK;
  DMA::WriteRegister(FIXUP_WORD_OFFSET(size, offset), FIXUP_WORD_WRITE_VALUE(size, offset, value));
}

#undef BUS_CYCLES

namespace Bus::HWHandlers {
// We index hardware registers by bits 15..8.
template<MemoryAccessType type, MemoryAccessSize size,
         typename RT = std::conditional_t<type == MemoryAccessType::Read, MemoryReadHandler, MemoryWriteHandler>>
static constexpr std::array<RT, 256> GetHardwareRegisterHandlerTable()
{
  std::array<RT, 256> ret = {};
  for (size_t i = 0; i < ret.size(); i++)
  {
    if constexpr (type == MemoryAccessType::Read)
      ret[i] = UnmappedReadHandler<size>;
    else
      ret[i] = UnmappedWriteHandler<size>;
  }

#if 0
  // Verifies no region has >1 handler, but doesn't compile on older GCC.
#define SET(raddr, rsize, read_handler, write_handler)                                                                 \
  static_assert(raddr >= 0x1F801000 && (raddr + rsize) <= 0x1F802000);                                                 \
  for (u32 taddr = raddr; taddr < (raddr + rsize); taddr += 16)                                                        \
  {                                                                                                                    \
    const u32 i = (taddr >> 4) & 0xFFu;                                                                                \
    if constexpr (type == MemoryAccessType::Read)                                                                      \
      ret[i] = (ret[i] == UnmappedReadHandler<size>) ? read_handler<size> : (abort(), read_handler<size>);             \
    else                                                                                                               \
      ret[i] = (ret[i] == UnmappedWriteHandler<size>) ? write_handler<size> : (abort(), write_handler<size>);          \
  }
#else
#define SET(raddr, rsize, read_handler, write_handler)                                                                 \
  static_assert(raddr >= 0x1F801000 && (raddr + rsize) <= 0x1F802000);                                                 \
  for (u32 taddr = raddr; taddr < (raddr + rsize); taddr += 16)                                                        \
  {                                                                                                                    \
    const u32 i = (taddr >> 4) & 0xFFu;                                                                                \
    if constexpr (type == MemoryAccessType::Read)                                                                      \
      ret[i] = read_handler<size>;                                                                                     \
    else                                                                                                               \
      ret[i] = write_handler<size>;                                                                                    \
  }
#endif

  SET(MEMCTRL_BASE, MEMCTRL_SIZE, MemCtrlRead, MemCtrlWrite);
  SET(PAD_BASE, PAD_SIZE, PADRead, PADWrite);
  SET(SIO_BASE, SIO_SIZE, SIORead, SIOWrite);
  SET(MEMCTRL2_BASE, MEMCTRL2_SIZE, MemCtrl2Read, MemCtrl2Write);
  SET(INTC_BASE, INTC_SIZE, INTCRead, INTCWrite);
  SET(DMA_BASE, DMA_SIZE, DMARead, DMAWrite);
  SET(TIMERS_BASE, TIMERS_SIZE, TimersRead, TimersWrite);
  SET(CDROM_BASE, CDROM_SIZE, CDROMRead, CDROMWrite);
  SET(GPU_BASE, GPU_SIZE, GPURead, GPUWrite);
  SET(MDEC_BASE, MDEC_SIZE, MDECRead, MDECWrite);
  SET(SPU_BASE, SPU_SIZE, SPURead, SPUWrite);

#undef SET

  return ret;
}
} // namespace Bus::HWHandlers

template<MemoryAccessSize size>
u32 Bus::HardwareReadHandler(VirtualMemoryAddress address)
{
  static constexpr const auto table = HWHandlers::GetHardwareRegisterHandlerTable<MemoryAccessType::Read, size>();
  const u32 table_index = (address >> 4) & 0xFFu;
  return table[table_index](address);
}

template<MemoryAccessSize size>
void Bus::HardwareWriteHandler(VirtualMemoryAddress address, u32 value)
{
  static constexpr const auto table = HWHandlers::GetHardwareRegisterHandlerTable<MemoryAccessType::Write, size>();
  const u32 table_index = (address >> 4) & 0xFFu;
  return table[table_index](address, value);
}

//////////////////////////////////////////////////////////////////////////

static constexpr u32 KUSEG = 0;
static constexpr u32 KSEG0 = 0x80000000U;
static constexpr u32 KSEG1 = 0xA0000000U;
static constexpr u32 KSEG2 = 0xC0000000U;

void Bus::SetHandlers()
{
  ClearHandlers(g_memory_handlers);
  ClearHandlers(g_memory_handlers_isc);

#define SET(table, start, size, read_handler, write_handler)                                                           \
  SetHandlerForRegion(table, start, size, read_handler<MemoryAccessSize::Byte>,                                        \
                      read_handler<MemoryAccessSize::HalfWord>, read_handler<MemoryAccessSize::Word>,                  \
                      write_handler<MemoryAccessSize::Byte>, write_handler<MemoryAccessSize::HalfWord>,                \
                      write_handler<MemoryAccessSize::Word>)
#define SETUC(start, size, read_handler, write_handler)                                                                \
  SET(g_memory_handlers, start, size, read_handler, write_handler);                                                    \
  SET(g_memory_handlers_isc, start, size, read_handler, write_handler)

  // KUSEG - Cached
  // Cache isolated appears to affect KUSEG+KSEG0.
  SET(g_memory_handlers, KUSEG | RAM_BASE, RAM_MIRROR_SIZE, RAMReadHandler, RAMWriteHandler);
  SET(g_memory_handlers, KUSEG | CPU::SCRATCHPAD_ADDR, 0x1000, ScratchpadReadHandler, ScratchpadWriteHandler);
  SET(g_memory_handlers, KUSEG | BIOS_BASE, BIOS_MIRROR_SIZE, BIOSReadHandler, IgnoreWriteHandler);
  SET(g_memory_handlers, KUSEG | EXP1_BASE, EXP1_SIZE, EXP1ReadHandler, EXP1WriteHandler);
  SET(g_memory_handlers, KUSEG | HW_BASE, HW_SIZE, HardwareReadHandler, HardwareWriteHandler);
  SET(g_memory_handlers, KUSEG | EXP2_BASE, EXP2_SIZE, EXP2ReadHandler, EXP2WriteHandler);
  SET(g_memory_handlers, KUSEG | EXP3_BASE, EXP3_SIZE, EXP3ReadHandler, EXP3WriteHandler);
  SET(g_memory_handlers, KUSEG | SIO2_BASE, SIO2_SIZE, SIO2ReadHandler, SIO2WriteHandler);
  SET(g_memory_handlers_isc, KUSEG, 0x80000000, ICacheReadHandler, ICacheWriteHandler);

  // KSEG0 - Cached
  SET(g_memory_handlers, KSEG0 | RAM_BASE, RAM_MIRROR_SIZE, RAMReadHandler, RAMWriteHandler);
  SET(g_memory_handlers, KSEG0 | CPU::SCRATCHPAD_ADDR, 0x1000, ScratchpadReadHandler, ScratchpadWriteHandler);
  SET(g_memory_handlers, KSEG0 | BIOS_BASE, BIOS_MIRROR_SIZE, BIOSReadHandler, IgnoreWriteHandler);
  SET(g_memory_handlers, KSEG0 | EXP1_BASE, EXP1_SIZE, EXP1ReadHandler, EXP1WriteHandler);
  SET(g_memory_handlers, KSEG0 | HW_BASE, HW_SIZE, HardwareReadHandler, HardwareWriteHandler);
  SET(g_memory_handlers, KSEG0 | EXP2_BASE, EXP2_SIZE, EXP2ReadHandler, EXP2WriteHandler);
  SET(g_memory_handlers, KSEG0 | EXP3_BASE, EXP3_SIZE, EXP3ReadHandler, EXP3WriteHandler);
  SET(g_memory_handlers, KSEG0 | SIO2_BASE, SIO2_SIZE, SIO2ReadHandler, SIO2WriteHandler);
  SET(g_memory_handlers_isc, KSEG0, 0x20000000, ICacheReadHandler, ICacheWriteHandler);

  // KSEG1 - Uncached
  SETUC(KSEG1 | RAM_BASE, RAM_MIRROR_SIZE, RAMReadHandler, RAMWriteHandler);
  SETUC(KSEG1 | BIOS_BASE, BIOS_MIRROR_SIZE, BIOSReadHandler, IgnoreWriteHandler);
  SETUC(KSEG1 | EXP1_BASE, EXP1_SIZE, EXP1ReadHandler, EXP1WriteHandler);
  SETUC(KSEG1 | HW_BASE, HW_SIZE, HardwareReadHandler, HardwareWriteHandler);
  SETUC(KSEG1 | EXP2_BASE, EXP2_SIZE, EXP2ReadHandler, EXP2WriteHandler);
  SETUC(KSEG1 | EXP3_BASE, EXP3_SIZE, EXP3ReadHandler, EXP3WriteHandler);
  SETUC(KSEG1 | SIO2_BASE, SIO2_SIZE, SIO2ReadHandler, SIO2WriteHandler);

  // KSEG2 - Uncached - 0xFFFE0130
  SETUC(KSEG2 | 0xFFFE0000, 0x1000, CacheControlReadHandler, CacheControlWriteHandler);
}

void Bus::UpdateMappedRAMSize()
{
  const u32 prev_mapped_size = g_ram_mapped_size;

  switch (s_RAM_SIZE.memory_window)
  {
    case 4: // 2MB memory + 6MB unmapped
    {
      // Used by Rock-Climbing - Mitouhou e no Chousen - Alps Hen (Japan).
      // By default, all 8MB is mapped, so we only need to remap the high 6MB.
      constexpr u32 MAPPED_SIZE = RAM_2MB_SIZE;
      constexpr u32 UNMAPPED_START = RAM_BASE + MAPPED_SIZE;
      constexpr u32 UNMAPPED_SIZE = RAM_MIRROR_SIZE - MAPPED_SIZE;
      SET(g_memory_handlers, KUSEG | UNMAPPED_START, UNMAPPED_SIZE, UnmappedReadHandler, UnmappedWriteHandler);
      SET(g_memory_handlers, KSEG0 | UNMAPPED_START, UNMAPPED_SIZE, UnmappedReadHandler, UnmappedWriteHandler);
      SET(g_memory_handlers, KSEG1 | UNMAPPED_START, UNMAPPED_SIZE, UnmappedReadHandler, UnmappedWriteHandler);
      g_ram_mapped_size = MAPPED_SIZE;
    }
    break;

    case 0: // 1MB memory + 7MB unmapped
    case 1: // 4MB memory + 4MB unmapped
    case 2: // 1MB memory + 1MB HighZ + 6MB unmapped
    case 3: // 4MB memory + 4MB HighZ
    case 6: // 2MB memory + 2MB HighZ + 4MB unmapped
    case 7: // 8MB memory
    {
      // These aren't implemented because nothing is known to use them, so it can't be tested.
      // If you find something that does, please let us know.
      WARNING_LOG("Unhandled memory window 0x{} (register 0x{:08X}). Please report this game to developers.",
                  s_RAM_SIZE.memory_window.GetValue(), s_RAM_SIZE.bits);
    }
      [[fallthrough]];

    case 5: // 8MB memory
    {
      // We only unmap the upper 6MB above, so we only need to remap this as well.
      constexpr u32 REMAP_START = RAM_BASE + RAM_2MB_SIZE;
      constexpr u32 REMAP_SIZE = RAM_MIRROR_SIZE - RAM_2MB_SIZE;
      SET(g_memory_handlers, KUSEG | REMAP_START, REMAP_SIZE, RAMReadHandler, RAMWriteHandler);
      SET(g_memory_handlers, KSEG0 | REMAP_START, REMAP_SIZE, RAMReadHandler, RAMWriteHandler);
      SET(g_memory_handlers, KSEG1 | REMAP_START, REMAP_SIZE, RAMReadHandler, RAMWriteHandler);
      g_ram_mapped_size = RAM_8MB_SIZE;
    }
    break;
  }

  // Fastmem needs to be remapped.
  if (prev_mapped_size != g_ram_mapped_size)
    RemapFastmemViews();
}

#undef SET
#undef SETUC

void Bus::ClearHandlers(void** handlers)
{
  for (u32 size = 0; size < 3; size++)
  {
    MemoryReadHandler* read_handlers =
      OffsetHandlerArray<MemoryReadHandler>(handlers, static_cast<MemoryAccessSize>(size), MemoryAccessType::Read);
    const MemoryReadHandler read_handler =
      (size == 0) ?
        UnmappedReadHandler<MemoryAccessSize::Byte> :
        ((size == 1) ? UnmappedReadHandler<MemoryAccessSize::HalfWord> : UnmappedReadHandler<MemoryAccessSize::Word>);
    MemsetPtrs(read_handlers, read_handler, MEMORY_LUT_SIZE);

    MemoryWriteHandler* write_handlers =
      OffsetHandlerArray<MemoryWriteHandler>(handlers, static_cast<MemoryAccessSize>(size), MemoryAccessType::Write);
    const MemoryWriteHandler write_handler =
      (size == 0) ?
        UnmappedWriteHandler<MemoryAccessSize::Byte> :
        ((size == 1) ? UnmappedWriteHandler<MemoryAccessSize::HalfWord> : UnmappedWriteHandler<MemoryAccessSize::Word>);
    MemsetPtrs(write_handlers, write_handler, MEMORY_LUT_SIZE);
  }
}

void Bus::SetHandlerForRegion(void** handlers, VirtualMemoryAddress address, u32 size,
                              MemoryReadHandler read_byte_handler, MemoryReadHandler read_halfword_handler,
                              MemoryReadHandler read_word_handler, MemoryWriteHandler write_byte_handler,
                              MemoryWriteHandler write_halfword_handler, MemoryWriteHandler write_word_handler)
{
  // Should be 4K aligned.
  DebugAssert(Common::IsAlignedPow2(size, MEMORY_LUT_PAGE_SIZE));

  const u32 start_page = (address / MEMORY_LUT_PAGE_SIZE);
  const u32 num_pages = ((size + (MEMORY_LUT_PAGE_SIZE - 1)) / MEMORY_LUT_PAGE_SIZE);

  for (u32 acc_size = 0; acc_size < 3; acc_size++)
  {
    MemoryReadHandler* read_handlers =
      OffsetHandlerArray<MemoryReadHandler>(handlers, static_cast<MemoryAccessSize>(acc_size), MemoryAccessType::Read) +
      start_page;
    const MemoryReadHandler read_handler =
      (acc_size == 0) ? read_byte_handler : ((acc_size == 1) ? read_halfword_handler : read_word_handler);
#if 0
    for (u32 i = 0; i < num_pages; i++)
    {
      DebugAssert((acc_size == 0 && read_handlers[i] == UnmappedReadHandler<MemoryAccessSize::Byte>) ||
                  (acc_size == 1 && read_handlers[i] == UnmappedReadHandler<MemoryAccessSize::HalfWord>) ||
                  (acc_size == 2 && read_handlers[i] == UnmappedReadHandler<MemoryAccessSize::Word>));

      read_handlers[i] = read_handler;
    }
#else
    MemsetPtrs(read_handlers, read_handler, num_pages);
#endif

    MemoryWriteHandler* write_handlers = OffsetHandlerArray<MemoryWriteHandler>(
                                           handlers, static_cast<MemoryAccessSize>(acc_size), MemoryAccessType::Write) +
                                         start_page;
    const MemoryWriteHandler write_handler =
      (acc_size == 0) ? write_byte_handler : ((acc_size == 1) ? write_halfword_handler : write_word_handler);
#if 0
    for (u32 i = 0; i < num_pages; i++)
    {
      DebugAssert((acc_size == 0 && write_handlers[i] == UnmappedWriteHandler<MemoryAccessSize::Byte>) ||
                  (acc_size == 1 && write_handlers[i] == UnmappedWriteHandler<MemoryAccessSize::HalfWord>) ||
                  (acc_size == 2 && write_handlers[i] == UnmappedWriteHandler<MemoryAccessSize::Word>));

      write_handlers[i] = write_handler;
    }
#else
    MemsetPtrs(write_handlers, write_handler, num_pages);
#endif
  }
}

void** Bus::GetMemoryHandlers(bool isolate_cache, bool swap_caches)
{
  if (!isolate_cache)
    return g_memory_handlers;

#if defined(_DEBUG) || defined(_DEVEL)
  if (swap_caches)
    WARNING_LOG("Cache isolated and swapped, icache will be written instead of scratchpad?");
#endif

  return g_memory_handlers_isc;
}
