#include "terrain.h"
#include "core/config/engine.h"
#include "terrain/terrain_chunk.h"
#include "terrain/terrain_modifier.h"

void Terrain::_bind_methods() {
	BIND_HPROPERTY(Variant::OBJECT, mesh_material, PROPERTY_HINT_RESOURCE_TYPE, "Material");
	BIND_PROPERTY(Variant::INT, side_length);
	BIND_PROPERTY(Variant::INT, chunk_size);
	BIND_PROPERTY(Variant::INT, thread_count);
	BIND_HPROPERTY(Variant::ARRAY, terrain_meshes, PROPERTY_HINT_ARRAY_TYPE, vformat("%s/%s:TerrainMeshChunk", Variant::OBJECT, PROPERTY_HINT_NODE_TYPE), PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_READ_ONLY);
}

void Terrain::stop_threads() {
	this->workload_lock.lock();
	this->threads_stop = true;
	this->workload_lock.unlock();
	for (Thread &thread : this->threads) {
		if (thread.is_started()) {
			thread.wait_to_finish();
		}
	}
}

void Terrain::start_threads() {
	this->workload_lock.lock();
	print_line(vformat("Starting threads; workload: %d", this->workload.size()));
	this->threads_stop = false;
	for (Thread &thread : this->threads) {
		if (!thread.is_started()) {
			thread.start(Terrain::generate_meshes_thread, this);
		}
	}
	this->workload_lock.unlock(); // don't let the threads proceed until all are started
}

void Terrain::child_order_changed() {
	this->modifiers.clear();
	for (Variant var : get_children()) {
		if (TerrainModifier * mod{ cast_to<TerrainModifier>(var) }) {
			mod->set_terrain(this);
			this->modifiers.push_back(mod);
		}
	}
}

void Terrain::update_meshes() {
	size_t num{ max_mesh_assignments_per_frame };
	this->dirty_meshes_lock.lock();
	num = num > this->dirty_meshes.size() ? this->dirty_meshes.size() : num;
	this->dirty_meshes_lock.unlock();
	for (size_t i{ 0 }; i < num; i++) {
		this->dirty_meshes_lock.lock();
		TerrainChunkMesh *mesh{ this->dirty_meshes[0] };
		this->dirty_meshes.remove_at(0);
		this->dirty_meshes_lock.unlock();
		mesh->apply_new_mesh();
	}
}

void Terrain::update_threads() {
	if (this->workload.is_empty()) {
		stop_threads();
	} else {
		start_threads();
	}
}

void Terrain::update_process() {
	// check if there is any tasks going on that would require processing each frame
	// any running threads?
	for (Thread &thread : this->threads) {
		if (thread.is_started()) {
			return;
		}
	}
	// dirty meshes?
	this->dirty_meshes_lock.lock();
	bool workload_empty{ this->dirty_meshes.is_empty() };
	this->dirty_meshes_lock.unlock();
	if (!workload_empty) {
		return;
	}
	// queued mesh generation tasks?
	this->workload_lock.lock();
	workload_empty = this->workload.is_empty();
	this->workload_lock.unlock();
	if (!workload_empty) {
		return;
	}
	// stop processing each frame
	print_line("Terrain processing stopped");
	set_process(false);
}

void Terrain::synchronous_generate_terrain() {
	print_line("Blocking regenerate terrain");
	this->workload_lock.lock();
	this->threads_stop = false;
	// queue all meshes
	this->workload.clear();
	this->workload.append_array(this->meshes);
	start_threads();
	// wait for workload to empty out
	do {
		this->workload_lock.unlock();
		Thread::yield();
		this->workload_lock.lock();
	} while (!this->workload.is_empty());
	this->threads_stop = true;
	this->workload_lock.unlock();
	stop_threads();
	for (TerrainChunkMesh *mesh : this->dirty_meshes) {
		mesh->apply_new_mesh();
	}
	this->dirty_meshes.clear();
}

void Terrain::_notification(int what) {
	if (!Engine::get_singleton()->is_editor_hint()) {
		return;
	}
	switch (what) {
		default:
			return;
		case NOTIFICATION_CHILD_ORDER_CHANGED:
			if (is_ready()) {
				this->child_order_changed();
			}
			return;
		case NOTIFICATION_READY: {
			this->meshes.clear();
			this->modifiers.clear();
			for (Variant var : get_children()) {
				if (TerrainChunkMesh * mesh{ cast_to<TerrainChunkMesh>(var) }) {
					this->meshes.push_back(mesh);
					mesh->set_terrain(this);
				}
				if (TerrainModifier * mod{ cast_to<TerrainModifier>(var) }) {
					this->modifiers.push_back(mod);
					mod->set_terrain(this);
				}
			}
			size_t expected_size{ this->side_length / this->chunk_size };
			if (this->meshes.size() != expected_size * expected_size) {
				construct_chunk_grid();
				synchronous_generate_terrain();
			}
			return;
		}
		case NOTIFICATION_PROCESS:
			update_meshes();
			update_threads();
			update_process();
			return;
		case NOTIFICATION_EXIT_TREE:
			this->workload_lock.lock();
			this->threads_stop = true;
			this->workload_lock.unlock();
			for (Thread &thread : this->threads) {
				if (thread.is_started()) {
					thread.wait_to_finish();
				}
			}
			return;
	}
}

void Terrain::generate_meshes_thread(void *terrain) {
	Terrain *self{ static_cast<Terrain *>(terrain) };
	print_line("thread", Thread::get_caller_id(), "start");
	for (;;) {
		self->workload_lock.lock();
		if (self->threads_stop) {
			self->workload_lock.unlock();
			print_line(Thread::get_caller_id(), "exiting");
			break;
		}
		if (self->workload.is_empty()) {
			self->workload_lock.unlock();
			Thread::yield();
			continue;
		}
		TerrainChunkMesh *mesh{ self->workload[0] };
		self->workload.remove_at(0);
		self->workload_lock.unlock();
		if (!mesh->is_inside_tree()) {
			print_line(Thread::get_caller_id(), "mesh is outside tree, exiting");
			break;
		}
		mesh->update_mesh();
		Thread::yield();
	}
	print_line(Thread::get_caller_id(), "done");
	return;
}

void Terrain::construct_chunk_grid() {
	print_line("Constructing chunk grid");
	this->workload_lock.lock();
	this->threads_stop = true;
	this->workload_lock.unlock();
	for (Thread &thread : this->threads) {
		if (thread.is_started()) {
			thread.wait_to_finish();
		}
	}
	this->workload_lock.lock();
	for (TerrainChunkMesh *mesh : this->meshes) {
		remove_child(mesh);
		mesh->queue_free();
	}
	this->meshes.clear();
	this->workload.clear();
	size_t const chunks_per_side{ this->side_length / this->chunk_size };
	Vector3 const origin{ (float)this->chunk_size / 2.f, 0.f, (float)this->chunk_size / 2.f };
	for (size_t y{ 0 }; y < chunks_per_side; ++y) {
		for (size_t x{ 0 }; x < chunks_per_side; ++x) {
			TerrainChunkMesh *chunk{ memnew(TerrainChunkMesh) };
			chunk->set_size(this->chunk_size);
			chunk->set_detail(this->detail);
			chunk->set_terrain(this);
			chunk->set_material_override(this->mesh_material);
			chunk->set_position(origin + Vector3{ (float)this->chunk_size * (float)x, 0.f, (float)this->chunk_size * (float)y });
			chunk->set_name(vformat("Chunk%dx%d", x, y));
			add_child(chunk);
			chunk->set_owner(get_owner());
			this->meshes.push_back(chunk);
			this->workload.push_back(chunk);
		}
	}
	this->threads_stop = false;
	this->dirty_meshes.clear();
	this->workload_lock.unlock();
	set_process(true);
}

float Terrain::height_at(Vector2 world_coordinate) {
	float height{ 0 };
	for (TerrainModifier *mod : this->modifiers) {
		if (!mod->is_inside_tree()) {
			return height;
		}
		height = mod->evaluate_at(world_coordinate, height);
	}
	return height;
}

void Terrain::push_changed(Rect2 area) {
	for (TerrainChunkMesh *mesh : this->meshes) {
		this->workload_lock.lock();
		if (area.intersects(mesh->get_bounds()) && !this->workload.has(mesh)) {
			workload.push_back(mesh);
		}
		this->workload_lock.unlock();
	}
	set_process(true);
}

void Terrain::mesh_dirty(TerrainChunkMesh *mesh) {
	this->dirty_meshes_lock.lock();
	this->dirty_meshes.push_back(mesh);
	callable_mp(cast_to<Node>(this), &self_type::set_process).call_deferred(true);
	this->dirty_meshes_lock.unlock();
}

void Terrain::set_mesh_material(Ref<Material> material) {
	this->mesh_material = material;
	for (TerrainChunkMesh *mesh : this->meshes) {
		mesh->set_material_override(material);
	}
}

Ref<Material> Terrain::get_mesh_material() const {
	return this->mesh_material;
}

void Terrain::set_side_length(size_t length) {
	this->side_length = length;
	if (is_inside_tree()) {
		construct_chunk_grid();
	}
}

size_t Terrain::get_side_length() const {
	return this->side_length;
}

void Terrain::set_chunk_size(size_t size) {
	this->chunk_size = size;
	if (is_inside_tree()) {
		construct_chunk_grid();
	}
}

size_t Terrain::get_chunk_size() const {
	return this->chunk_size;
}

void Terrain::set_detail(size_t detail) {
	this->detail = detail;
	if (is_inside_tree()) {
		construct_chunk_grid();
	}
}

size_t Terrain::get_detail() const {
	return this->detail;
}

void Terrain::set_thread_count(size_t num) {
	this->workload_lock.lock();
	this->threads_stop = true;
	this->workload_lock.unlock();
	for (Thread &thread : this->threads) {
		thread.wait_to_finish();
	}
	this->threads_stop = false;
	this->threads.resize_initialized(num);
}

size_t Terrain::get_thread_count() const {
	return this->threads.size();
}

void Terrain::set_terrain_meshes(Array array) {
	return;
	this->meshes.clear();
	for (Variant var : array) {
		if (TerrainChunkMesh * mesh{ cast_to<TerrainChunkMesh>(var) }) {
			mesh->set_terrain(this);
			this->meshes.push_back(mesh);
		}
	}
}

Array Terrain::get_terrain_meshes() const {
	Array a{};
	for (TerrainChunkMesh *mesh : this->meshes) {
		a.push_back(mesh);
	}
	return a;
}