// Copyright 2025 Xenon Emulator Project. All rights reserved.

#include "Thread.h" 
#include "Error.h"
#include "Logging/Log.h"

#ifdef __APPLE__
#include <mach/mach.h>
#include <mach/mach_time.h>
#include <pthread.h>
#elif defined(_WIN32)
#include <Windows.h>
#include "StringUtil.h"
#else

#if defined(__Bitrig__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__OpenBSD__)
#include <pthread_np.h>
#else
#include <pthread.h>
#endif
#include <sched.h>
#endif
#ifndef _WIN32
#include <unistd.h>
#endif
#include <thread>
#include <algorithm>

#ifdef __FreeBSD__
#define cpu_set_t cpuset_t
#endif

namespace Base {

#ifdef __APPLE__

void SetCurrentThreadRealtime(const std::chrono::nanoseconds period_ns) {
  // CPU time to grant.
  const std::chrono::nanoseconds computation_ns = period_ns / 2;

  // Determine the timebase for converting time to ticks.
  struct mach_timebase_info timebase {};
  mach_timebase_info(&timebase);
  const auto ticks_per_ns =
    static_cast<f64>(timebase.denom) / static_cast<f64>(timebase.numer);

  const auto period_ticks =
    static_cast<u32>(static_cast<f64>(period_ns.count()) * ticks_per_ns);
  const auto computation_ticks =
    static_cast<u32>(static_cast<f64>(computation_ns.count()) * ticks_per_ns);

  thread_time_constraint_policy policy = {
    .period = period_ticks,
    .computation = computation_ticks,
    // Should not matter since preemptible is false, but needs to be >= computation regardless.
    .constraint = computation_ticks,
    .preemptible = false,
  };

  int ret = thread_policy_set(
    pthread_mach_thread_np(pthread_self()), THREAD_TIME_CONSTRAINT_POLICY,
    reinterpret_cast<thread_policy_t>(&policy), THREAD_TIME_CONSTRAINT_POLICY_COUNT);
  if (ret != KERN_SUCCESS) {
    LOG_ERROR(Base, "Could not set thread to real-time with period {} ns: {}",
          period_ns.count(), ret);
  }
}

#else

void SetCurrentThreadRealtime(const std::chrono::nanoseconds period_ns) {
  // Not implemented
}

#endif

#ifdef _WIN32

void SetCurrentThreadPriority(ThreadPriority new_priority) {
  const auto handle = GetCurrentThread();
  int windows_priority = 0;
  switch (new_priority) {
  case ThreadPriority::Low:
    windows_priority = THREAD_PRIORITY_BELOW_NORMAL;
    break;
  case ThreadPriority::Normal:
    windows_priority = THREAD_PRIORITY_NORMAL;
    break;
  case ThreadPriority::High:
    windows_priority = THREAD_PRIORITY_ABOVE_NORMAL;
    break;
  case ThreadPriority::VeryHigh:
    windows_priority = THREAD_PRIORITY_HIGHEST;
    break;
  case ThreadPriority::Critical:
    windows_priority = THREAD_PRIORITY_TIME_CRITICAL;
    break;
  default:
    windows_priority = THREAD_PRIORITY_NORMAL;
    break;
  }
  SetThreadPriority(handle, windows_priority);
}

static void AccurateSleep(std::chrono::nanoseconds duration) {
  LARGE_INTEGER interval{
    .QuadPart = -1 * (duration.count() / 100u),
  };
  const HANDLE timer = ::CreateWaitableTimer(nullptr, TRUE, nullptr);
  SetWaitableTimer(timer, &interval, 0, nullptr, nullptr, 0);
  WaitForSingleObject(timer, INFINITE);
  ::CloseHandle(timer);
}

#else

void SetCurrentThreadPriority(ThreadPriority new_priority) {
  pthread_t this_thread = pthread_self();

  constexpr auto scheduling_type = SCHED_OTHER;
  const s32 max_prio = sched_get_priority_max(scheduling_type);
  const s32 min_prio = sched_get_priority_min(scheduling_type);
  const u32 level = std::max(static_cast<u32>(new_priority) + 1, 4U);

  struct sched_param params;
  if (max_prio > min_prio) {
    params.sched_priority = min_prio + ((max_prio - min_prio) * level) / 4;
  } else {
    params.sched_priority = min_prio - ((min_prio - max_prio) * level) / 4;
  }

  pthread_setschedparam(this_thread, scheduling_type, &params);
}

static void AccurateSleep(std::chrono::nanoseconds duration) {
  std::this_thread::sleep_for(duration);
}

#endif

#if defined(_MSC_VER) || defined(__MINGW32__)

// Sets the debugger-visible name of the current thread.
void SetCurrentThreadName(const std::string_view &name) {
  SetThreadDescription(GetCurrentThread(), UTF8ToUTF16W(name).data());
}

void SetThreadName(void *thread, const std::string_view &name) {
  const char* nchar = name.data();
  std::string truncated(nchar, std::min(name.size(), static_cast<size_t>(15)));
  SetThreadDescription(thread, UTF8ToUTF16W(name).data());
}

#else // !MSVC_VER, so must be POSIX threads

// MinGW with the POSIX threading model does not support pthread_setname_np
#if !defined(_WIN32) || defined(_MSC_VER)
void SetCurrentThreadName(const std::string_view &name) {
  const char* nchar = name.data();
#ifdef __APPLE__
  pthread_setname_np(nchar);
#elif defined(__Bitrig__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__OpenBSD__)
  pthread_set_name_np(pthread_self(), nchar);
#elif defined(__NetBSD__)
  pthread_setname_np(pthread_self(), "%s", (void*)nchar);
#elif defined(__linux__)
  // Linux limits thread names to 15 characters and will outright reject any
  // attempt to set a longer name with ERANGE.
  std::string truncated(nchar, std::min(name.size(), static_cast<size_t>(15)));
  if (int e = pthread_setname_np(pthread_self(), truncated.c_str())) {
    errno = e;
  }
#else
  pthread_setname_np(pthread_self(), nchar);
#endif
}

void SetThreadName(void *thread, const std::string_view &name) {
  // TODO
}
#endif

#if defined(_WIN32)
void SetCurrentThreadName(const std::string_view &name) {
  // Do Nothing on MinGW
}

void SetThreadName(void *thread, const std::string_view &name) {
  // Do Nothing on MinGW
}
#endif

#endif

AccurateTimer::AccurateTimer(std::chrono::nanoseconds target_interval) :
  target_interval(target_interval)
{}

void AccurateTimer::Start() {
  const auto begin_sleep = std::chrono::high_resolution_clock::now();
  if (total_wait.count() > 0) {
    AccurateSleep(total_wait);
  }
  start_time = std::chrono::high_resolution_clock::now();
  total_wait -= std::chrono::duration_cast<std::chrono::nanoseconds>(start_time - begin_sleep);
}

void AccurateTimer::End() {
  const auto now = std::chrono::high_resolution_clock::now();
  total_wait +=
    target_interval - std::chrono::duration_cast<std::chrono::nanoseconds>(now - start_time);
}

} // namespace Base