/**************************************************************************/
/*  jolt_job_system.cpp                                                   */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "jolt_job_system.h"

#include "core/debugger/engine_debugger.h"
#include "core/object/worker_thread_pool.h"
#include "core/os/os.h"
#include "core/os/time.h"

#include <Jolt/Physics/PhysicsSettings.h>

void JoltJobSystem::Job::_execute(void *p_user_data) {
	Job *job = static_cast<Job *>(p_user_data);

#ifdef DEBUG_ENABLED
	const uint64_t time_start = Time::get_singleton()->get_ticks_usec();
#endif

	job->Execute();

#ifdef DEBUG_ENABLED
	const uint64_t time_end = Time::get_singleton()->get_ticks_usec();
	const uint64_t time_elapsed = time_end - time_start;

	timings_lock.lock();
	timings_by_job[job->name] += time_elapsed;
	timings_lock.unlock();
#endif

	job->Release();
}

JoltJobSystem::Job::Job(const char *p_name, JPH::ColorArg p_color, JPH::JobSystem *p_job_system, const JPH::JobSystem::JobFunction &p_job_function, JPH::uint32 p_dependency_count) :
		JPH::JobSystem::Job(p_name, p_color, p_job_system, p_job_function, p_dependency_count)
#ifdef DEBUG_ENABLED
		,
		name(p_name)
#endif
{
}

JoltJobSystem::Job::~Job() {
	if (task_id != -1) {
		WorkerThreadPool::get_singleton()->wait_for_task_completion(task_id);
	}
}

void JoltJobSystem::Job::push_completed(Job *p_job) {
	Job *prev_head = nullptr;

	do {
		prev_head = completed_head.load(std::memory_order_relaxed);
		p_job->completed_next = prev_head;
	} while (!completed_head.compare_exchange_weak(prev_head, p_job, std::memory_order_release, std::memory_order_relaxed));
}

JoltJobSystem::Job *JoltJobSystem::Job::pop_completed() {
	Job *prev_head = nullptr;

	do {
		prev_head = completed_head.load(std::memory_order_relaxed);
		if (prev_head == nullptr) {
			return nullptr;
		}
	} while (!completed_head.compare_exchange_weak(prev_head, prev_head->completed_next, std::memory_order_acquire, std::memory_order_relaxed));

	return prev_head;
}

void JoltJobSystem::Job::queue() {
	AddRef();

	// Ideally we would use Jolt's actual job name here, but I'd rather not incur the overhead of a memory allocation or
	// thread-safe lookup every time we create/queue a task. So instead we use the same cached description for all of them.
	static const String task_name("Jolt Physics");

	task_id = WorkerThreadPool::get_singleton()->add_native_task(&_execute, this, true, task_name);
}

int JoltJobSystem::GetMaxConcurrency() const {
	return thread_count;
}

JPH::JobHandle JoltJobSystem::CreateJob(const char *p_name, JPH::ColorArg p_color, const JPH::JobSystem::JobFunction &p_job_function, JPH::uint32 p_dependency_count) {
	Job *job = nullptr;

	while (true) {
		JPH::uint32 job_index = jobs.ConstructObject(p_name, p_color, this, p_job_function, p_dependency_count);

		if (job_index != JPH::FixedSizeFreeList<Job>::cInvalidObjectIndex) {
			job = &jobs.Get(job_index);
			break;
		}

		WARN_PRINT_ONCE("Jolt Physics job system exceeded the maximum number of jobs. This should not happen. Please report this. Waiting for jobs to become available...");

		OS::get_singleton()->delay_usec(100);

		_reclaim_jobs();
	}

	// This will increment the job's reference count, so must happen before we queue the job
	JPH::JobHandle job_handle(job);

	if (p_dependency_count == 0) {
		QueueJob(job);
	}

	return job_handle;
}

void JoltJobSystem::QueueJob(JPH::JobSystem::Job *p_job) {
	static_cast<Job *>(p_job)->queue();
}

void JoltJobSystem::QueueJobs(JPH::JobSystem::Job **p_jobs, JPH::uint p_job_count) {
	for (JPH::uint i = 0; i < p_job_count; ++i) {
		QueueJob(p_jobs[i]);
	}
}

void JoltJobSystem::FreeJob(JPH::JobSystem::Job *p_job) {
	Job::push_completed(static_cast<Job *>(p_job));
}

void JoltJobSystem::_reclaim_jobs() {
	while (Job *job = Job::pop_completed()) {
		jobs.DestructObject(job);
	}
}

JoltJobSystem::JoltJobSystem() :
		JPH::JobSystemWithBarrier(JPH::cMaxPhysicsBarriers),
		thread_count(MAX(1, WorkerThreadPool::get_singleton()->get_thread_count())) {
	jobs.Init(JPH::cMaxPhysicsJobs, JPH::cMaxPhysicsJobs);
}

void JoltJobSystem::pre_step() {
	// Nothing to do.
}

void JoltJobSystem::post_step() {
	_reclaim_jobs();
}

#ifdef DEBUG_ENABLED

void JoltJobSystem::flush_timings() {
	const StringName profiler_name = SNAME("servers");

	EngineDebugger *engine_debugger = EngineDebugger::get_singleton();

	if (engine_debugger->is_profiling(profiler_name)) {
		Array timings;

		for (const KeyValue<const void *, uint64_t> &E : timings_by_job) {
			timings.push_back(static_cast<const char *>(E.key));
			timings.push_back(USEC_TO_SEC(E.value));
		}

		timings.push_front("physics_3d");

		engine_debugger->profiler_add_frame_data(profiler_name, timings);
	}

	for (KeyValue<const void *, uint64_t> &E : timings_by_job) {
		E.value = 0;
	}
}

#endif
