#include "thread-pool.hpp"

#include "bucketed-array.hpp"

#include <functional>
#include <future>

struct ThreadPool {
	bool isRunning;
	bool isPaused;
	uint8_t maxJobQueueCount;
	std::mutex mutex;
	std::atomic<uint64_t> completedCount;
	std::condition_variable condition;
	DynArray<std::packaged_task<void()> *> *jobQueue;
	DynArray<std::thread> *threads;
	struct pk_membucket *bkt = nullptr;
};

const pk_handle_item_index_T MAX_THREADS_PER_BUCKET = 8;

BucketContainer<ThreadPool, ThreadPoolHandle> ThreadPool_BucketContainer{};

void ThreadRun(ThreadPool *tp) {
	std::packaged_task<void()> *j = nullptr;
	while (tp->isRunning && !tp->isPaused) {
		{
			std::unique_lock<std::mutex> lck(tp->mutex);
			tp->condition.wait(lck, [tp] {
				if (!tp->isRunning) return true;
				if (tp->isPaused) return true;
				if (tp->jobQueue == nullptr) return true;
				if (tp->jobQueue == CAFE_BABE(DynArray<std::packaged_task<void()> *>)) return true;
				return tp->jobQueue->Count() != 0;
			});
			if (!tp->isRunning || tp->isPaused || tp->jobQueue == nullptr || tp->jobQueue == CAFE_BABE(DynArray<std::packaged_task<void()> *>)) {
				return;
			}
			if (tp->jobQueue->Count() == 0) {
				continue;
			}
			j = (*tp->jobQueue)[0];
			tp->jobQueue->Remove(0, 1);
		}
		assert(j != nullptr);
		(*j)();
		pk_delete<std::packaged_task<void()>>(j, tp->bkt);
		tp->completedCount = tp->completedCount + 1;
	}
}

void inline PkeThreads_JoinAll_Inner(ThreadPool &tp) {
	tp.condition.notify_all();
	long count = tp.threads->Count();
	for (long l = 0; l < count; ++l) {
		auto &t = (*tp.threads)[l];
		if (t.joinable()) {
			t.join();
		}
	}
}

void inline PkeThreads_DetatchAll_Inner(ThreadPool &tp) {
	long count = tp.threads->Count();
	for (long i = 0; i < count; ++i) {
		auto &t = (*tp.threads)[i];
		t.detach();
	}
	tp.condition.notify_all();
}

void inline PkeThreads_Reset_Inner(ThreadPool &tp) {
	tp.mutex.lock();
	tp.maxJobQueueCount = 0;
	tp.completedCount = 0;
	tp.jobQueue->Resize(0);
	tp.threads->Resize(0);
	tp.mutex.unlock();
}

bool inline PkeThreads_Enqueue_Inner(ThreadPool &tp, std::packaged_task<void()> *job) {
	tp.mutex.lock();
	if (tp.isRunning == true) {
		if (tp.jobQueue->Count() < tp.maxJobQueueCount) {
			tp.jobQueue->Push(job);
			tp.condition.notify_one();
			tp.mutex.unlock();
			return true;
		}
	}
	tp.mutex.unlock();
	return false;
}

void inline PkeThreads_Pause_Inner(ThreadPool &tp) {
	tp.mutex.lock();
	if (tp.isPaused == true) {
		return; // called more than once
	}
	tp.isPaused = true;
	tp.mutex.unlock();
	PkeThreads_JoinAll_Inner(tp);
}

void inline PkeThreads_Resume_Inner(ThreadPool &tp) {
	tp.mutex.lock();
	tp.isPaused = false;
	long count = tp.threads->Count();
	for (size_t i = 0; i < count; i++) {
		(*tp.threads)[i] = std::thread(std::bind(ThreadRun, &tp));
	}
	tp.mutex.unlock();
}

void inline PkeThreads_Shutdown_Inner(ThreadPool &tp) {
	tp.mutex.lock();
	if (tp.isRunning == false) {
		return;
	}
	tp.isRunning = false;
	tp.isPaused = false;
	tp.jobQueue->Resize(0);
	tp.mutex.unlock();
}

void PkeThreads_Init() {
	Buckets_Init(ThreadPool_BucketContainer, MAX_THREADS_PER_BUCKET);
}

ThreadPoolHandle PkeThreads_Init(uint8_t threadCount, uint8_t maxQueueCount, struct pk_membucket *bkt) {
	assert(threadCount > 0);
	ThreadPoolHandle newHandle{Buckets_NewHandle(ThreadPool_BucketContainer)};

	auto *tp = &ThreadPool_BucketContainer.buckets[newHandle.bucketIndex][newHandle.itemIndex];

	tp->bkt = bkt;
	tp->isRunning = true;
	tp->isPaused = false;
	tp->maxJobQueueCount = maxQueueCount;
	tp->completedCount = 0;
	tp->jobQueue = pk_new<DynArray<std::packaged_task<void()> *>>(bkt);
	tp->threads = pk_new<DynArray<std::thread>>(bkt);

	tp->threads->Resize(threadCount);
	for (long l = 0; l < threadCount; ++l) {
		(*tp->threads)[l] = std::thread(std::bind(ThreadRun, tp));
	}

	return newHandle;
}

void PkeThreads_Reset(ThreadPoolHandle handle) {
	assert(handle != ThreadPoolHandle_MAX);
	auto *tp = &ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];
	PkeThreads_Reset_Inner(*tp);
}

bool PkeThreads_Enqueue(ThreadPoolHandle handle, std::packaged_task<void()> *job) {
	assert(handle != ThreadPoolHandle_MAX);
	auto *tp = &ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];
	if (tp->bkt != nullptr) {
		/* 2023-12-22 JCB
		 * Note that if this becomes an issue we can change it.
		 * Technically speaking, if we call the right pk_delete
		 * we don't even need to worry about passing the struct pk_membucket
		 */
		assert(pk_memory_is_in_bucket(job, tp->bkt) == true && "cannot enqueue packaged task from a non-matching struct pk_membucket");
	}

	return PkeThreads_Enqueue_Inner(*tp, job);
}

int64_t PkeThreads_GetQueueCount (ThreadPoolHandle handle) {
	auto &threadPool = ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];
	return threadPool.jobQueue->Count();
}

void PkeThreads_Pause(ThreadPoolHandle handle) {
	assert(handle != ThreadPoolHandle_MAX);
	auto *tp = &ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];

	PkeThreads_Pause_Inner(*tp);
}

void PkeThreads_Resume(ThreadPoolHandle handle) {
	assert(handle != ThreadPoolHandle_MAX);
	auto *tp = &ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];

	PkeThreads_Resume_Inner(*tp);
}

void PkeThreads_Shutdown(ThreadPoolHandle handle) {
	assert(handle != ThreadPoolHandle_MAX);
	auto *tp = &ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];

	PkeThreads_Shutdown_Inner(*tp);
	PkeThreads_JoinAll_Inner(*tp);
}

void PkeThreads_Teardown(ThreadPoolHandle handle) {
	assert(handle != ThreadPoolHandle_MAX);
	auto *tp = &ThreadPool_BucketContainer.buckets[handle.bucketIndex][handle.itemIndex];

	PkeThreads_Shutdown_Inner(*tp);
	PkeThreads_JoinAll_Inner(*tp);
	PkeThreads_Reset_Inner(*tp);
	pk_delete<DynArray<std::packaged_task<void()> *>>(tp->jobQueue, tp->bkt);
	pk_delete<DynArray<std::thread>>(tp->threads, tp->bkt);
	tp->jobQueue = CAFE_BABE(DynArray<std::packaged_task<void()> *>);
	tp->threads = CAFE_BABE(DynArray<std::thread>);
	tp->bkt = CAFE_BABE(struct pk_membucket);
}

void PkeThreads_Teardown() {
	Buckets_Destroy(ThreadPool_BucketContainer);
}