/**
 ******************************************************************************
 * Xenia : Xbox 360 Emulator Research Project                                 *
 ******************************************************************************
 * Copyright 2013 Ben Vanik. All rights reserved.                             *
 * Released under the BSD license - see LICENSE in the root for more details. *
 ******************************************************************************
 */

#include "xenia/emulator.h"

#include <gflags/gflags.h>

#include "xenia/apu/audio_system.h"
#include "xenia/base/assert.h"
#include "xenia/base/byte_stream.h"
#include "xenia/base/clock.h"
#include "xenia/base/debugging.h"
#include "xenia/base/exception_handler.h"
#include "xenia/base/logging.h"
#include "xenia/base/mapped_memory.h"
#include "xenia/base/profiling.h"
#include "xenia/base/string.h"
#include "xenia/cpu/backend/code_cache.h"
#include "xenia/gpu/graphics_system.h"
#include "xenia/hid/input_driver.h"
#include "xenia/hid/input_system.h"
#include "xenia/kernel/kernel_state.h"
#include "xenia/kernel/user_module.h"
#include "xenia/kernel/xam/xam_module.h"
#include "xenia/kernel/xboxkrnl/xboxkrnl_module.h"
#include "xenia/memory.h"
#include "xenia/ui/imgui_dialog.h"
#include "xenia/vfs/devices/disc_image_device.h"
#include "xenia/vfs/devices/host_path_device.h"
#include "xenia/vfs/devices/stfs_container_device.h"
#include "xenia/vfs/virtual_file_system.h"

DEFINE_double(time_scalar, 1.0,
              "Scalar used to speed or slow time (1x, 2x, 1/2x, etc).");

namespace xe {

Emulator::Emulator(const std::wstring& command_line)
    : command_line_(command_line) {}

Emulator::~Emulator() {
  // Note that we delete things in the reverse order they were initialized.

  if (debugger_) {
    // Kill the debugger first, so that we don't have it messing with things.
    debugger_->StopSession();
  }

  // Give the systems time to shutdown before we delete them.
  if (graphics_system_) {
    graphics_system_->Shutdown();
  }
  if (audio_system_) {
    audio_system_->Shutdown();
  }

  input_system_.reset();
  graphics_system_.reset();
  audio_system_.reset();

  kernel_state_.reset();
  file_system_.reset();

  processor_.reset();

  debugger_.reset();

  export_resolver_.reset();

  ExceptionHandler::Uninstall(Emulator::ExceptionCallbackThunk, this);
}

X_STATUS Emulator::Setup(
    ui::Window* display_window,
    std::function<std::unique_ptr<apu::AudioSystem>(cpu::Processor*)>
        audio_system_factory,
    std::function<std::unique_ptr<gpu::GraphicsSystem>()>
        graphics_system_factory,
    std::function<std::vector<std::unique_ptr<hid::InputDriver>>(ui::Window*)>
        input_driver_factory) {
  X_STATUS result = X_STATUS_UNSUCCESSFUL;

  display_window_ = display_window;

  // Initialize clock.
  // 360 uses a 50MHz clock.
  Clock::set_guest_tick_frequency(50000000);
  // We could reset this with save state data/constant value to help replays.
  Clock::set_guest_system_time_base(Clock::QueryHostSystemTime());
  // This can be adjusted dynamically, as well.
  Clock::set_guest_time_scalar(FLAGS_time_scalar);

  // Before we can set thread affinity we must enable the process to use all
  // logical processors.
  xe::threading::EnableAffinityConfiguration();

  // Create memory system first, as it is required for other systems.
  memory_ = std::make_unique<Memory>();
  if (!memory_->Initialize()) {
    return false;
  }

  // Shared export resolver used to attach and query for HLE exports.
  export_resolver_ = std::make_unique<xe::cpu::ExportResolver>();

  if (FLAGS_debug) {
    // Debugger first, as other parts hook into it.
    debugger_.reset(new debug::Debugger(this));

    // Create debugger first. Other types hook up to it.
    debugger_->StartSession();
  }

  // Initialize the CPU.
  processor_ = std::make_unique<xe::cpu::Processor>(
      this, memory_.get(), export_resolver_.get(), debugger_.get());
  if (!processor_->Setup()) {
    return X_STATUS_UNSUCCESSFUL;
  }

  // Initialize the APU.
  if (audio_system_factory) {
    audio_system_ = audio_system_factory(processor_.get());
    if (!audio_system_) {
      return X_STATUS_NOT_IMPLEMENTED;
    }
  }

  // Initialize the GPU.
  graphics_system_ = graphics_system_factory();
  if (!graphics_system_) {
    return X_STATUS_NOT_IMPLEMENTED;
  }

  // Initialize the HID.
  input_system_ = std::make_unique<xe::hid::InputSystem>(display_window_);
  if (!input_system_) {
    return X_STATUS_NOT_IMPLEMENTED;
  }
  if (input_driver_factory) {
    auto input_drivers = input_driver_factory(display_window_);
    for (size_t i = 0; i < input_drivers.size(); ++i) {
      input_system_->AddDriver(std::move(input_drivers[i]));
    }
  }

  result = input_system_->Setup();
  if (result) {
    return result;
  }

  // Bring up the virtual filesystem used by the kernel.
  file_system_ = std::make_unique<xe::vfs::VirtualFileSystem>();

  // Shared kernel state.
  kernel_state_ = std::make_unique<xe::kernel::KernelState>(this);

  // Setup the core components.
  result = graphics_system_->Setup(processor_.get(), kernel_state_.get(),
                                   display_window_);
  if (result) {
    return result;
  }

  if (audio_system_) {
    result = audio_system_->Setup(kernel_state_.get());
    if (result) {
      return result;
    }
  }

  // HLE kernel modules.
  kernel_state_->LoadKernelModule<kernel::xboxkrnl::XboxkrnlModule>();
  kernel_state_->LoadKernelModule<kernel::xam::XamModule>();

  // Initialize emulator fallback exception handling last.
  ExceptionHandler::Install(Emulator::ExceptionCallbackThunk, this);

  // Finish initializing the display.
  display_window_->loop()->PostSynchronous([this]() {
    xe::ui::GraphicsContextLock context_lock(display_window_->context());
    Profiler::set_window(display_window_);
  });

  return result;
}

X_STATUS Emulator::LaunchPath(std::wstring path) {
  // Launch based on file type.
  // This is a silly guess based on file extension.
  auto last_slash = path.find_last_of(xe::kPathSeparator);
  auto last_dot = path.find_last_of('.');
  if (last_dot < last_slash) {
    last_dot = std::wstring::npos;
  }
  if (last_dot == std::wstring::npos) {
    // Likely an STFS container.
    return LaunchStfsContainer(path);
  } else if (path.substr(last_dot) == L".xex" ||
             path.substr(last_dot) == L".elf") {
    // Treat as a naked xex file.
    return LaunchXexFile(path);
  } else {
    // Assume a disc image.
    return LaunchDiscImage(path);
  }
}

X_STATUS Emulator::LaunchXexFile(std::wstring path) {
  // We create a virtual filesystem pointing to its directory and symlink
  // that to the game filesystem.
  // e.g., /my/files/foo.xex will get a local fs at:
  // \\Device\\Harddisk0\\Partition1
  // and then get that symlinked to game:\, so
  // -> game:\foo.xex

  auto mount_path = "\\Device\\Harddisk0\\Partition0";

  // Register the local directory in the virtual filesystem.
  auto parent_path = xe::find_base_path(path);
  auto device =
      std::make_unique<vfs::HostPathDevice>(mount_path, parent_path, true);
  if (!device->Initialize()) {
    XELOGE("Unable to scan host path");
    return X_STATUS_NO_SUCH_FILE;
  }
  if (!file_system_->RegisterDevice(std::move(device))) {
    XELOGE("Unable to register host path");
    return X_STATUS_NO_SUCH_FILE;
  }

  // Create symlinks to the device.
  file_system_->RegisterSymbolicLink("game:", mount_path);
  file_system_->RegisterSymbolicLink("d:", mount_path);

  // Get just the filename (foo.xex).
  auto file_name = xe::find_name_from_path(path);

  // Launch the game.
  std::string fs_path = "game:\\" + xe::to_string(file_name);
  return CompleteLaunch(path, fs_path);
}

X_STATUS Emulator::LaunchDiscImage(std::wstring path) {
  auto mount_path = "\\Device\\Cdrom0";

  // Register the disc image in the virtual filesystem.
  auto device = std::make_unique<vfs::DiscImageDevice>(mount_path, path);
  if (!device->Initialize()) {
    xe::FatalError("Unable to mount disc image; file not found or corrupt.");
    return X_STATUS_NO_SUCH_FILE;
  }
  if (!file_system_->RegisterDevice(std::move(device))) {
    xe::FatalError("Unable to register disc image.");
    return X_STATUS_NO_SUCH_FILE;
  }

  // Create symlinks to the device.
  file_system_->RegisterSymbolicLink("game:", mount_path);
  file_system_->RegisterSymbolicLink("d:", mount_path);

  // Launch the game.
  return CompleteLaunch(path, "game:\\default.xex");
}

X_STATUS Emulator::LaunchStfsContainer(std::wstring path) {
  auto mount_path = "\\Device\\Cdrom0";

  // Register the container in the virtual filesystem.
  auto device = std::make_unique<vfs::StfsContainerDevice>(mount_path, path);
  if (!device->Initialize()) {
    xe::FatalError(
        "Unable to mount STFS container; file not found or corrupt.");
    return X_STATUS_NO_SUCH_FILE;
  }
  if (!file_system_->RegisterDevice(std::move(device))) {
    xe::FatalError("Unable to register STFS container.");
    return X_STATUS_NO_SUCH_FILE;
  }

  file_system_->RegisterSymbolicLink("game:", mount_path);
  file_system_->RegisterSymbolicLink("d:", mount_path);

  // Launch the game.
  return CompleteLaunch(path, "game:\\default.xex");
}

void Emulator::Pause() {
  auto lock = global_critical_region::AcquireDirect();
  if (paused_) {
    return;
  }
  paused_ = true;

  auto threads =
      kernel_state()->object_table()->GetObjectsByType<kernel::XThread>(
          kernel::XObject::kTypeThread);
  for (auto thread : threads) {
    if (!thread->can_debugger_suspend()) {
      // Don't pause host threads.
      continue;
    }

    thread->thread()->Suspend(nullptr);
  }

  XELOGD("! EMULATOR PAUSED !");
}

void Emulator::Resume() {
  if (!paused_) {
    return;
  }
  paused_ = false;
  XELOGD("! EMULATOR RESUMED !");

  auto threads =
      kernel_state()->object_table()->GetObjectsByType<kernel::XThread>(
          kernel::XObject::kTypeThread);
  for (auto thread : threads) {
    if (!thread->can_debugger_suspend()) {
      // Don't pause host threads.
      continue;
    }

    thread->thread()->Resume(nullptr);
  }
}

bool Emulator::SaveToFile(const std::wstring& path) {
  Pause();

  filesystem::CreateFile(path);
  auto map = MappedMemory::Open(path, MappedMemory::Mode::kReadWrite, 0,
                                1024ull * 1024ull * 1024ull * 4ull);
  if (!map) {
    return false;
  }

  // Save the emulator state to a file
  ByteStream stream(map->data(), map->size());
  stream.Write('XSAV');

  // It's important we don't hold the global lock here! XThreads need to step
  // forward (possibly through guarded regions) without worry!
  kernel_state_->Save(&stream);
  memory_->Save(&stream);
  map->Close(stream.offset());

  Resume();
  return true;
}

bool Emulator::RestoreFromFile(const std::wstring& path) {
  // Restore the emulator state from a file
  auto map = MappedMemory::Open(path, MappedMemory::Mode::kReadWrite);
  if (!map) {
    return false;
  }

  restoring_ = true;

  // Terminate any loaded titles.
  Pause();
  kernel_state_->TerminateTitle();

  auto lock = global_critical_region::AcquireDirect();
  ByteStream stream(map->data(), map->size());
  if (stream.Read<uint32_t>() != 'XSAV') {
    return false;
  }

  if (!kernel_state_->Restore(&stream)) {
    return false;
  }
  if (!memory_->Restore(&stream)) {
    return false;
  }

  // Update the main thread.
  auto threads = kernel_state_->object_table()->GetObjectsByType<kernel::XThread>();
  for (auto thread : threads) {
    if (thread->main_thread()) {
      main_thread_ = thread->thread();
      break;
    }
  }

  Resume();

  restore_fence_.Signal();
  restoring_ = false;

  return true;
}

bool Emulator::ExceptionCallbackThunk(Exception* ex, void* data) {
  return reinterpret_cast<Emulator*>(data)->ExceptionCallback(ex);
}

bool Emulator::ExceptionCallback(Exception* ex) {
  // Check to see if the exception occurred in guest code.
  auto code_cache = processor()->backend()->code_cache();
  auto code_base = code_cache->base_address();
  auto code_end = code_base + code_cache->total_size();

  if (!debugger() ||
      (!debugger()->is_attached() && debugging::IsDebuggerAttached())) {
    // If Xenia's debugger isn't attached but another one is, pass it to that
    // debugger.
    return false;
  } else if (debugger() && debugger()->is_attached()) {
    // Let the debugger handle this exception. It may decide to continue past it
    // (if it was a stepping breakpoint, etc).
    return debugger()->OnUnhandledException(ex);
  }

  if (!(ex->pc() >= code_base && ex->pc() < code_end)) {
    // Didn't occur in guest code. Let it pass.
    return false;
  }

  auto global_lock = global_critical_region::AcquireDirect();

  // Within range. Pause the emulator and eat the exception.
  auto threads =
      kernel_state()->object_table()->GetObjectsByType<kernel::XThread>(
          kernel::XObject::kTypeThread);
  auto current_thread = kernel::XThread::GetCurrentThread();
  for (auto thread : threads) {
    if (!thread->can_debugger_suspend()) {
      // Don't pause host threads.
      continue;
    }
    if (current_thread == thread.get()) {
      continue;
    }
    thread->Suspend(nullptr);
  }

  // Display a dialog telling the user the guest has crashed.
  display_window()->loop()->PostSynchronous([&]() {
    xe::ui::ImGuiDialog::ShowMessageBox(display_window(), "Uh-oh!",
                                        "The guest has crashed.\n\n"
                                        "Xenia has now paused itself.");
  });

  // Now suspend ourself (we should be a guest thread).
  assert_true(current_thread->can_debugger_suspend());
  current_thread->Suspend(nullptr);

  // We should not arrive here!
  assert_always();
  return false;
}

void Emulator::WaitUntilExit() {
  while (true) {
    xe::threading::Wait(main_thread_, false);

    if (restoring_) {
      restore_fence_.Wait();
    } else {
      // Not restoring and the thread exited. We're finished.
      break;
    }
  }
}

X_STATUS Emulator::CompleteLaunch(const std::wstring& path,
                                  const std::string& module_path) {
  // Allow xam to request module loads.
  auto xam = kernel_state()->GetKernelModule<kernel::xam::XamModule>("xam.xex");

  int result = 0;
  auto next_module = module_path;
  while (next_module != "") {
    XELOGI("Launching module %s", next_module.c_str());
    auto module = kernel_state_->LoadUserModule(next_module.c_str());
    if (!module) {
      XELOGE("Failed to load user module %s", path);
      return X_STATUS_NOT_FOUND;
    }

    kernel_state_->SetExecutableModule(module);
    auto main_xthread = module->Launch();
    if (!main_xthread) {
      return X_STATUS_UNSUCCESSFUL;
    }

    main_thread_ = main_xthread->thread();
    WaitUntilExit();

    // Check xam and see if they want us to load another module.
    auto& loader_data = xam->loader_data();
    next_module = loader_data.launch_path;

    // And blank out the launch path to avoid an infinite loop.
    loader_data.launch_path = "";
  }

  if (result == 0) {
    return X_STATUS_SUCCESS;
  } else {
    return X_STATUS_UNSUCCESSFUL;
  }
}

}  // namespace xe