#include "ecs.hpp"

#include <new>

TypeSafeInt_B(EntityHandle);
const uint64_t maxBucketItemCount = 256;

struct EntityBucket {
	Entity entities[maxBucketItemCount];
};
struct GrBindsBucket {
	CompGrBinds compGrBinds[maxBucketItemCount];
};
struct InstanceBucket {
	CompInstance instances[maxBucketItemCount];
};

DynArray<EntityHandle> EntitiesToBeRemoved{16}; // public

DynArray<EntityHandle> entitiesMarkedForRemoval{16};
BucketContainer<EntityBucket, EntityHandle_T> Entities_BucketContainer{};
BucketContainer<GrBindsBucket, GrBindsHandle_T> Comp_GrBinds_BucketContainer{};
BucketContainer<InstanceBucket, InstanceHandle_T> Comp_Instance_BucketContainer{};

void ECS_GetEntity_Inner(EntityHandle entHandle, Entity*& ent) {
	EntityHandle_T entHandle_t{static_cast<EntityHandle_T>(entHandle)};
	assert(entHandle_t != EntityHandle_T_MAX && "Unknown entity handle");
	auto b = Buckets_GetBucketIndex(static_cast<EntityHandle_T>(entHandle));
	auto e = Buckets_GetItemIndex(static_cast<EntityHandle_T>(entHandle));
	ent = &Entities_BucketContainer.buckets[b].entities[e];
}

void ECS_Init() {
	Buckets_Init(Entities_BucketContainer);
	Buckets_Init(Comp_GrBinds_BucketContainer);
	Buckets_Init(Comp_Instance_BucketContainer);
}

uint64_t ECS_GetEntities_BucketCount() {
	return Entities_BucketContainer.bucketCounter;
}
Entity *ECS_GetEntities(uint64_t bucketIndex, uint64_t &itemCount) {
	assert(bucketIndex <= Entities_BucketContainer.bucketCounter);
	itemCount = bucketIndex == Entities_BucketContainer.bucketCounter ? Entities_BucketContainer.itemCounter >> 32 : maxBucketItemCount;
	return Entities_BucketContainer.buckets[bucketIndex].entities;
}

EntityHandle ECS_CreateEntity_Inner(EntityHandle parentEntHandle) {
	EntityHandle_T entityHandle_T{Buckets_NewHandle<EntityBucket>(maxBucketItemCount, Entities_BucketContainer)};
	EntityHandle entityHandle{entityHandle_T};

	auto b = Buckets_GetBucketIndex(static_cast<EntityHandle_T>(entityHandle));
	auto e = Buckets_GetItemIndex(static_cast<EntityHandle_T>(entityHandle));
	Entity *entity = &Entities_BucketContainer.buckets[b].entities[e];
	entity = new (entity) Entity{};
	entity->handle = entityHandle;
	entity->parentHandle = parentEntHandle;

	return entityHandle;
}

EntityHandle ECS_CreateEntity(EntityHandle parentEntHandle) {
	return ECS_CreateEntity_Inner(parentEntHandle);
}

void ECS_MarkForRemoval(EntityHandle entityHandle) {
	auto b = Buckets_GetBucketIndex(static_cast<EntityHandle_T>(entityHandle));
	auto e = Buckets_GetItemIndex(static_cast<EntityHandle_T>(entityHandle));
	const Entity *ent = &Entities_BucketContainer.buckets[b].entities[e];
	assert(ent->isMarkedForRemoval == false && "Entity already marked for removal");
	entitiesMarkedForRemoval.Push(entityHandle);
}

void ECS_Tick(double delta) {
	static DynArray<Entity> entitiesYetToBeRemoved{0};
	entitiesYetToBeRemoved.Resize(EntitiesToBeRemoved.Count());
	EntitiesToBeRemoved.Resize(0);
	for (long b = 0; b <= Entities_BucketContainer.bucketCounter; ++b) {
		uint64_t entCount = b == Entities_BucketContainer.bucketCounter ? Entities_BucketContainer.itemCounter >> 32 : maxBucketItemCount;
		for (long e  = 0; e < entCount; ++e) {
			Entity *ent = &Entities_BucketContainer.buckets[b].entities[e];
			if (ent->handle == EntityHandle_MAX) continue;
			if (ent->isMarkedForRemoval) {
				ent->handle = EntityHandle_MAX;
				ent->parentHandle = EntityHandle_MAX;
				ent->isMarkedForRemoval = false;
				entitiesYetToBeRemoved[0] = *ent;
			} else {
				if (entitiesMarkedForRemoval.Has(ent->handle) || EntitiesToBeRemoved.Has(ent->parentHandle)) {
					ent->isMarkedForRemoval = true;
					EntitiesToBeRemoved.Push(ent->handle);
				}
			}
		}
	}	
	for (long e = 0; e < entitiesYetToBeRemoved.Count(); ++e) {
		Entity &clonedEnt = entitiesYetToBeRemoved[e];
		CompGrBinds *grBinds = nullptr;
		InstanceBucket *instBucket = nullptr;
		CompInstance *inst = nullptr;
		uint64_t instBucketIndex = 0;
		if (clonedEnt.grBindsHandle != GrBindsHandle_MAX) {
			GrBindsHandle_T bindsHandle_t{static_cast<GrBindsHandle_T>(clonedEnt.grBindsHandle)};
			auto b = Buckets_GetBucketIndex(bindsHandle_t);
			auto i = Buckets_GetItemIndex(bindsHandle_t);
			grBinds = &Comp_GrBinds_BucketContainer.buckets[b].compGrBinds[i];
		}
		if (grBinds != nullptr && clonedEnt.instanceHandle != InstanceHandle_MAX) {
			InstanceHandle_T instanceHandle_t{static_cast<InstanceHandle_T>(clonedEnt.instanceHandle)};
			auto b = Buckets_GetBucketIndex(instanceHandle_t);
			auto i = Buckets_GetItemIndex(instanceHandle_t);
			instBucket = &Comp_Instance_BucketContainer.buckets[b];
			inst = &instBucket->instances[i];
			instBucketIndex = b;
		}
		if (inst != nullptr) {
			grBinds->instances.Remove(inst->index);
			for (long bi = instBucketIndex; bi <= Comp_Instance_BucketContainer.bucketCounter; ++bi) {
				uint64_t instCounter = 0;
				if (bi == Comp_Instance_BucketContainer.bucketCounter) {
					instCounter = Comp_Instance_BucketContainer.itemCounter;
				} else {
					instCounter = maxBucketItemCount;
				}
				auto &bucket = Comp_Instance_BucketContainer.buckets[bi];
				for (long ii = 0; ii < instCounter; ++ii) {
					if (bucket.instances[ii].grBindsHandle != clonedEnt.grBindsHandle) {
						continue;
					}
					if (bucket.instances[ii].instanceHandle < clonedEnt.instanceHandle) {
						continue;
					}
					bucket.instances[ii].index -= 1;
				}
			}
			inst->entHandle = EntityHandle_MAX;
			inst->grBindsHandle = GrBindsHandle_MAX;
			inst->index = ECS_UNSET_VAL;
			inst->instanceHandle = InstanceHandle_MAX;
			inst->ptr = CAFE_BABE(InstPos);
		} else if (grBinds != nullptr) {
			/*
			 * 2023-09-05 JB note - the Vulkan assets (device memory, buffers,
			 *  pipeline layout, and descriptor set) are unloaded elsewhere, just,
			 *  as they were created elsewhere.
			 */
			DynArrayDestroy(&grBinds->instances);
		}
	}
	entitiesMarkedForRemoval.Resize(0);
}

CompGrBinds &ECS_CreateGrBinds(EntityHandle entHandle) {
	assert(entHandle != EntityHandle_MAX);

	Entity *ent = nullptr;
	ECS_GetEntity_Inner(entHandle, ent);

	assert(ent->grBindsHandle == GrBindsHandle_MAX);

	GrBindsHandle_T newHandle{Buckets_NewHandle(maxBucketItemCount, Comp_GrBinds_BucketContainer)};
	ent->grBindsHandle = GrBindsHandle{newHandle};
	auto b = Buckets_GetBucketIndex(newHandle);
	auto i = Buckets_GetItemIndex(newHandle);
	auto *comp = &Comp_GrBinds_BucketContainer.buckets[b].compGrBinds[i];
	comp = new (comp) CompGrBinds{};
	comp->entHandle = entHandle;
	comp->grBindsHandle = ent->grBindsHandle;
	return *comp;
}

CompGrBinds *ECS_GetGrBinds(EntityHandle entHandle) {
	Entity *ent = nullptr;
	ECS_GetEntity_Inner(entHandle, ent);
	if (ent->grBindsHandle == GrBindsHandle_MAX) return nullptr;
	GrBindsHandle_T grBindsHandle_t{static_cast<GrBindsHandle_T>(ent->grBindsHandle)};
	auto b = Buckets_GetBucketIndex(grBindsHandle_t);
	auto i = Buckets_GetItemIndex(grBindsHandle_t);
	return &Comp_GrBinds_BucketContainer.buckets[b].compGrBinds[i];
}

uint64_t ECS_GetGrBinds_BucketCount() {
	return Comp_GrBinds_BucketContainer.bucketCounter;
}

CompGrBinds *ECS_GetGrBinds(uint64_t bucketIndex, uint64_t &itemCount) {
	if (bucketIndex == Comp_GrBinds_BucketContainer.bucketCounter) {
		itemCount = Comp_GrBinds_BucketContainer.itemCounter >> 32;
	} else {
		itemCount = maxBucketItemCount;
	}
	return Comp_GrBinds_BucketContainer.buckets[bucketIndex].compGrBinds;
}

CompInstance &ECS_CreateInstance(EntityHandle entHandle, EntityHandle entityTypeEntityHandle) {
	assert(entHandle != EntityHandle_MAX);
	assert(entityTypeEntityHandle != EntityHandle_MAX);

	Entity *ent = nullptr;
	Entity *entTypeEnt = nullptr;
	ECS_GetEntity_Inner(entHandle, ent);
	ECS_GetEntity_Inner(entityTypeEntityHandle, entTypeEnt);

	assert(ent->grBindsHandle == GrBindsHandle_MAX);
	assert(entTypeEnt->grBindsHandle != GrBindsHandle_MAX);

	InstanceHandle_T newHandle{Buckets_NewHandle(maxBucketItemCount, Comp_Instance_BucketContainer)};
	ent->instanceHandle = InstanceHandle{newHandle};
	GrBindsHandle_T grBindsHandle_t{static_cast<GrBindsHandle_T>(entTypeEnt->grBindsHandle)};

	auto b2 = Buckets_GetBucketIndex(grBindsHandle_t);
	auto i2 = Buckets_GetItemIndex(grBindsHandle_t);
	auto &grBinds = Comp_GrBinds_BucketContainer.buckets[b2].compGrBinds[i2];
	auto b = Buckets_GetBucketIndex(newHandle);
	auto i = Buckets_GetItemIndex(newHandle);
	auto *comp = &Comp_Instance_BucketContainer.buckets[b].instances[i];
	comp = new (comp) CompInstance{};
	comp->entHandle = entHandle;
	comp->grBindsHandle = ent->grBindsHandle;
	comp->instanceHandle = ent->instanceHandle;
	comp->index = grBinds.instances.Count();
	grBinds.instances.Push({
		.pos = glm::vec3(0),
		.rot = glm::vec3(1),
		.scale = glm::vec3(1),
	});
	comp->ptr = &grBinds.instances[comp->index];
	return *comp;
}

CompInstance *ECS_GetInstance(EntityHandle entHandle) {
	Entity *ent = nullptr;
	ECS_GetEntity_Inner(entHandle, ent);
	if (ent->grBindsHandle == GrBindsHandle_MAX) return nullptr;
	if (ent->instanceHandle == InstanceHandle_MAX) return nullptr;
	GrBindsHandle_T grBindsHandle_t{static_cast<GrBindsHandle_T>(ent->grBindsHandle)};
	InstanceHandle_T instanceHandle_t{static_cast<InstanceHandle_T>(ent->instanceHandle)};

	auto b2 = Buckets_GetBucketIndex(grBindsHandle_t);
	auto i2 = Buckets_GetItemIndex(grBindsHandle_t);
	auto &grBinds = Comp_GrBinds_BucketContainer.buckets[b2].compGrBinds[i2];
	auto b = Buckets_GetBucketIndex(instanceHandle_t);
	auto i = Buckets_GetItemIndex(instanceHandle_t);
	auto &comp = Comp_Instance_BucketContainer.buckets[b].instances[i];

	if (comp.index == ECS_UNSET_VAL)
		return nullptr;
	comp.ptr = &grBinds.instances[comp.index];
	return &comp;
}