#include "terrain_modifier.h"
#include "core/config/engine.h"
#include "core/variant/variant.h"
#include "macros.h"
#include "terrain/terrain.h"
#include <algorithm>

void TerrainModifier::_bind_methods() {
	BIND_PROPERTY(Variant::FLOAT, blend_distance);
}

void TerrainModifier::_notification(int what) {
	switch (what) {
		default:
			return;
		case NOTIFICATION_ENTER_TREE:
			if (Engine::get_singleton()->is_editor_hint()) {
				set_notify_transform(true);
			}
			this->thread_safe_global_position = get_global_position();
		case NOTIFICATION_TRANSFORM_CHANGED:
			this->thread_safe_global_position = get_global_position();
			return;
	}
}

float TerrainModifier::blend(float under, float over) {
	float const difference{ under - over };
	float const distance{ Math::abs(difference) };
	// .25 because we need half of each half of the blend range to be used
	float const center_distance{ this->blend_distance == 0.f ? 0.f : this->blend_distance * 0.25f - distance / this->blend_distance };
	if (center_distance <= 0.f) {
		return over;
	}
	float const smooth_center_distance{ center_distance * center_distance };
	return over + smooth_center_distance;
}

void TerrainModifier::push_changed(Rect2 area) {
	if (this->terrain) {
		this->terrain->push_changed(area);
	}
}

float TerrainModifier::evaluate_at(Vector2 world_coordinate, float before) {
	Vector3 const global_position{ get_thread_safe_global_position() };
	world_coordinate -= { global_position.x, global_position.z };
	return blend(before, 0.0);
}

Vector3 TerrainModifier::get_thread_safe_global_position() const {
	return this->thread_safe_global_position;
}

void TerrainModifier::set_blend_distance(float value) {
	this->blend_distance = value;
}

float TerrainModifier::get_blend_distance() const {
	return this->blend_distance;
}

void SharedMutex::lock_shared() {
	this->lock.lock();
	this->shared_count++;
	this->lock.unlock();
}

void SharedMutex::unlock_shared() {
	this->lock.lock();
	this->shared_count--;
	this->lock.unlock();
}

void SharedMutex::lock_exclusive() {
	while (true) {
		this->lock.lock();
		if (this->shared_count == 0) {
			return;
		}
		this->lock.unlock();
	}
}

void SharedMutex::unlock_exclusive() {
	this->lock.unlock();
}

void TerrainModifierDistance::_bind_methods() {
	BIND_HPROPERTY(Variant::OBJECT, distance_weight_curve, PROPERTY_HINT_RESOURCE_TYPE, "Curve");
}

void TerrainModifierDistance::curves_changed() {
	this->lock.lock_exclusive();
	if (this->distance_weight_curve.is_valid()) {
		this->distance_weight_curve->bake();
	}
	this->lock.unlock_exclusive();
	if (!update_bounds()) {
		push_changed(get_bounds());
	}
}

bool TerrainModifierDistance::update_bounds() {
	Rect2 const before{ get_bounds() };
	Rect2 bounds{};
	Vector3 position{ get_thread_safe_global_position() };
	bounds.position = { position.x, position.z };
	bounds.size = { 0, 0 };
	this->lock.lock_shared();
	if (this->distance_weight_curve.is_valid()) {
		float const max_radius{ this->distance_weight_curve->get_max_domain() };
		float const max_diameter{ 2.f * max_radius };
		bounds.size = { max_diameter, max_diameter };
		bounds.position -= { max_radius, max_radius };
	}
	this->lock.unlock_shared();
	this->lock.lock_exclusive();
	bool const changed{ before != bounds };
	if (changed) {
		set_bounds(bounds);
		push_changed(before);
		push_changed(bounds);
	}
	this->lock.unlock_exclusive();
	return changed;
}

void TerrainModifierDistance::_notification(int what) {
	switch (what) {
		default:
			return;
		case NOTIFICATION_READY:
			update_bounds();
			set_notify_transform(true);
			return;
		case NOTIFICATION_TRANSFORM_CHANGED:
			if (is_inside_tree()) {
				if (!update_bounds()) {
					push_changed(get_bounds());
				}
			}
			return;
	}
}

float TerrainModifierDistance::distance_at(Vector2 const &world_coordinate) {
	Vector3 const global_position{ get_thread_safe_global_position() };
	return world_coordinate.distance_to({ global_position.x, global_position.z });
}

float TerrainModifierDistance::evaluate_at(Vector2 world_coordinate, float before) {
	this->lock.lock_shared();
	if (this->distance_weight_curve.is_null()) {
		this->lock.unlock_shared();
		return before;
	}
	float const distance{ distance_at(world_coordinate) };
	if (distance >= this->distance_weight_curve->get_max_domain()) {
		this->lock.unlock_shared();
		return before;
	}
	float const weight_offset{
		std::clamp(distance, this->distance_weight_curve->get_min_domain(), this->distance_weight_curve->get_max_domain())
	};
	float const weight{ this->distance_weight_curve->sample(weight_offset) };
	float out{ weight <= 0.f ? before : Math::lerp(before, blend(before, get_thread_safe_global_position().y), weight) };
	this->lock.unlock_shared();

	return out;
}

PackedStringArray TerrainModifierDistance::get_configuration_warnings() const {
	PackedStringArray warnings{ super_type::get_configuration_warnings() };
	if (this->distance_weight_curve.is_null()) {
		warnings.push_back("distance_weight_curve is invalid, add a valid distance_weight_curve");
	}
	return warnings;
}

void TerrainModifierDistance::set_distance_weight_curve(Ref<Curve> curve) {
	this->lock.lock_exclusive();
	if (Engine::get_singleton()->is_editor_hint()) {
		if (this->distance_weight_curve.is_valid()) {
			this->distance_weight_curve->disconnect_changed(callable_mp(this, &self_type::curves_changed));
		}
		if (curve.is_valid()) {
			curve->connect_changed(callable_mp(this, &self_type::curves_changed));
		}
	}
	this->distance_weight_curve = curve;
	this->lock.unlock_exclusive();
	curves_changed();
	update_configuration_warnings();
}

Ref<Curve> TerrainModifierDistance::get_distance_weight_curve() const {
	return this->distance_weight_curve;
}