import { Color } from '../../math/Color.js';
import { Matrix4 } from '../../math/Matrix4.js';
import { Vector2 } from '../../math/Vector2.js';
import { Vector3 } from '../../math/Vector3.js';
import { UniformsLib } from '../shaders/UniformsLib.js';

function UniformsCache() {
	const lights = {};

	return {
		get: function (light) {
			if (lights[light.id] !== undefined) {
				return lights[light.id];
			}

			let uniforms;

			switch (light.type) {
				case 'DirectionalLight':
					uniforms = {
						direction: new Vector3(),
						color: new Color(),
					};
					break;

				case 'SpotLight':
					uniforms = {
						position: new Vector3(),
						direction: new Vector3(),
						color: new Color(),
						distance: 0,
						coneCos: 0,
						penumbraCos: 0,
						decay: 0,
					};
					break;

				case 'PointLight':
					uniforms = {
						position: new Vector3(),
						color: new Color(),
						distance: 0,
						decay: 0,
					};
					break;

				case 'HemisphereLight':
					uniforms = {
						direction: new Vector3(),
						skyColor: new Color(),
						groundColor: new Color(),
					};
					break;

				case 'RectAreaLight':
					uniforms = {
						color: new Color(),
						position: new Vector3(),
						halfWidth: new Vector3(),
						halfHeight: new Vector3(),
					};
					break;
			}

			lights[light.id] = uniforms;

			return uniforms;
		},
	};
}

function ShadowUniformsCache() {
	const lights = {};

	return {
		get: function (light) {
			if (lights[light.id] !== undefined) {
				return lights[light.id];
			}

			let uniforms;

			switch (light.type) {
				case 'DirectionalLight':
					uniforms = {
						shadowBias: 0,
						shadowNormalBias: 0,
						shadowRadius: 1,
						shadowMapSize: new Vector2(),
					};
					break;

				case 'SpotLight':
					uniforms = {
						shadowBias: 0,
						shadowNormalBias: 0,
						shadowRadius: 1,
						shadowMapSize: new Vector2(),
					};
					break;

				case 'PointLight':
					uniforms = {
						shadowBias: 0,
						shadowNormalBias: 0,
						shadowRadius: 1,
						shadowMapSize: new Vector2(),
						shadowCameraNear: 1,
						shadowCameraFar: 1000,
					};
					break;

				// TODO (abelnation): set RectAreaLight shadow uniforms
			}

			lights[light.id] = uniforms;

			return uniforms;
		},
	};
}

let nextVersion = 0;

function shadowCastingLightsFirst(lightA, lightB) {
	return (lightB.castShadow ? 1 : 0) - (lightA.castShadow ? 1 : 0);
}

function WebGLLights(extensions, capabilities) {
	const cache = new UniformsCache();

	const shadowCache = ShadowUniformsCache();

	const state = {
		version: 0,

		hash: {
			directionalLength: -1,
			pointLength: -1,
			spotLength: -1,
			rectAreaLength: -1,
			hemiLength: -1,

			numDirectionalShadows: -1,
			numPointShadows: -1,
			numSpotShadows: -1,
		},

		ambient: [0, 0, 0],
		probe: [],
		directional: [],
		directionalShadow: [],
		directionalShadowMap: [],
		directionalShadowMatrix: [],
		spot: [],
		spotShadow: [],
		spotShadowMap: [],
		spotShadowMatrix: [],
		rectArea: [],
		rectAreaLTC1: null,
		rectAreaLTC2: null,
		point: [],
		pointShadow: [],
		pointShadowMap: [],
		pointShadowMatrix: [],
		hemi: [],
	};

	for (let i = 0; i < 9; i++) state.probe.push(new Vector3());

	const vector3 = new Vector3();
	const matrix4 = new Matrix4();
	const matrix42 = new Matrix4();

	function setup(lights, physicallyCorrectLights) {
		let r = 0,
			g = 0,
			b = 0;

		for (let i = 0; i < 9; i++) state.probe[i].set(0, 0, 0);

		let directionalLength = 0;
		let pointLength = 0;
		let spotLength = 0;
		let rectAreaLength = 0;
		let hemiLength = 0;

		let numDirectionalShadows = 0;
		let numPointShadows = 0;
		let numSpotShadows = 0;

		lights.sort(shadowCastingLightsFirst);

		// artist-friendly light intensity scaling factor
		const scaleFactor = physicallyCorrectLights !== true ? Math.PI : 1;

		for (let i = 0, l = lights.length; i < l; i++) {
			const light = lights[i];

			const color = light.color;
			const intensity = light.intensity;
			const distance = light.distance;

			const shadowMap = light.shadow && light.shadow.map ? light.shadow.map.texture : null;

			if (light.isAmbientLight) {
				r += color.r * intensity * scaleFactor;
				g += color.g * intensity * scaleFactor;
				b += color.b * intensity * scaleFactor;
			} else if (light.isLightProbe) {
				for (let j = 0; j < 9; j++) {
					state.probe[j].addScaledVector(light.sh.coefficients[j], intensity);
				}
			} else if (light.isDirectionalLight) {
				const uniforms = cache.get(light);

				uniforms.color.copy(light.color).multiplyScalar(light.intensity * scaleFactor);

				if (light.castShadow) {
					const shadow = light.shadow;

					const shadowUniforms = shadowCache.get(light);

					shadowUniforms.shadowBias = shadow.bias;
					shadowUniforms.shadowNormalBias = shadow.normalBias;
					shadowUniforms.shadowRadius = shadow.radius;
					shadowUniforms.shadowMapSize = shadow.mapSize;

					state.directionalShadow[directionalLength] = shadowUniforms;
					state.directionalShadowMap[directionalLength] = shadowMap;
					state.directionalShadowMatrix[directionalLength] = light.shadow.matrix;

					numDirectionalShadows++;
				}

				state.directional[directionalLength] = uniforms;

				directionalLength++;
			} else if (light.isSpotLight) {
				const uniforms = cache.get(light);

				uniforms.position.setFromMatrixPosition(light.matrixWorld);

				uniforms.color.copy(color).multiplyScalar(intensity * scaleFactor);
				uniforms.distance = distance;

				uniforms.coneCos = Math.cos(light.angle);
				uniforms.penumbraCos = Math.cos(light.angle * (1 - light.penumbra));
				uniforms.decay = light.decay;

				if (light.castShadow) {
					const shadow = light.shadow;

					const shadowUniforms = shadowCache.get(light);

					shadowUniforms.shadowBias = shadow.bias;
					shadowUniforms.shadowNormalBias = shadow.normalBias;
					shadowUniforms.shadowRadius = shadow.radius;
					shadowUniforms.shadowMapSize = shadow.mapSize;

					state.spotShadow[spotLength] = shadowUniforms;
					state.spotShadowMap[spotLength] = shadowMap;
					state.spotShadowMatrix[spotLength] = light.shadow.matrix;

					numSpotShadows++;
				}

				state.spot[spotLength] = uniforms;

				spotLength++;
			} else if (light.isRectAreaLight) {
				const uniforms = cache.get(light);

				// (a) intensity is the total visible light emitted
				//uniforms.color.copy( color ).multiplyScalar( intensity / ( light.width * light.height * Math.PI ) );

				// (b) intensity is the brightness of the light
				uniforms.color.copy(color).multiplyScalar(intensity);

				uniforms.halfWidth.set(light.width * 0.5, 0.0, 0.0);
				uniforms.halfHeight.set(0.0, light.height * 0.5, 0.0);

				state.rectArea[rectAreaLength] = uniforms;

				rectAreaLength++;
			} else if (light.isPointLight) {
				const uniforms = cache.get(light);

				uniforms.color.copy(light.color).multiplyScalar(light.intensity * scaleFactor);
				uniforms.distance = light.distance;
				uniforms.decay = light.decay;

				if (light.castShadow) {
					const shadow = light.shadow;

					const shadowUniforms = shadowCache.get(light);

					shadowUniforms.shadowBias = shadow.bias;
					shadowUniforms.shadowNormalBias = shadow.normalBias;
					shadowUniforms.shadowRadius = shadow.radius;
					shadowUniforms.shadowMapSize = shadow.mapSize;
					shadowUniforms.shadowCameraNear = shadow.camera.near;
					shadowUniforms.shadowCameraFar = shadow.camera.far;

					state.pointShadow[pointLength] = shadowUniforms;
					state.pointShadowMap[pointLength] = shadowMap;
					state.pointShadowMatrix[pointLength] = light.shadow.matrix;

					numPointShadows++;
				}

				state.point[pointLength] = uniforms;

				pointLength++;
			} else if (light.isHemisphereLight) {
				const uniforms = cache.get(light);

				uniforms.skyColor.copy(light.color).multiplyScalar(intensity * scaleFactor);
				uniforms.groundColor.copy(light.groundColor).multiplyScalar(intensity * scaleFactor);

				state.hemi[hemiLength] = uniforms;

				hemiLength++;
			}
		}

		if (rectAreaLength > 0) {
			if (capabilities.isWebGL2) {
				// WebGL 2

				state.rectAreaLTC1 = UniformsLib.LTC_FLOAT_1;
				state.rectAreaLTC2 = UniformsLib.LTC_FLOAT_2;
			} else {
				// WebGL 1

				if (extensions.has('OES_texture_float_linear') === true) {
					state.rectAreaLTC1 = UniformsLib.LTC_FLOAT_1;
					state.rectAreaLTC2 = UniformsLib.LTC_FLOAT_2;
				} else if (extensions.has('OES_texture_half_float_linear') === true) {
					state.rectAreaLTC1 = UniformsLib.LTC_HALF_1;
					state.rectAreaLTC2 = UniformsLib.LTC_HALF_2;
				} else {
					console.error('THREE.WebGLRenderer: Unable to use RectAreaLight. Missing WebGL extensions.');
				}
			}
		}

		state.ambient[0] = r;
		state.ambient[1] = g;
		state.ambient[2] = b;

		const hash = state.hash;

		if (
			hash.directionalLength !== directionalLength ||
			hash.pointLength !== pointLength ||
			hash.spotLength !== spotLength ||
			hash.rectAreaLength !== rectAreaLength ||
			hash.hemiLength !== hemiLength ||
			hash.numDirectionalShadows !== numDirectionalShadows ||
			hash.numPointShadows !== numPointShadows ||
			hash.numSpotShadows !== numSpotShadows
		) {
			state.directional.length = directionalLength;
			state.spot.length = spotLength;
			state.rectArea.length = rectAreaLength;
			state.point.length = pointLength;
			state.hemi.length = hemiLength;

			state.directionalShadow.length = numDirectionalShadows;
			state.directionalShadowMap.length = numDirectionalShadows;
			state.pointShadow.length = numPointShadows;
			state.pointShadowMap.length = numPointShadows;
			state.spotShadow.length = numSpotShadows;
			state.spotShadowMap.length = numSpotShadows;
			state.directionalShadowMatrix.length = numDirectionalShadows;
			state.pointShadowMatrix.length = numPointShadows;
			state.spotShadowMatrix.length = numSpotShadows;

			hash.directionalLength = directionalLength;
			hash.pointLength = pointLength;
			hash.spotLength = spotLength;
			hash.rectAreaLength = rectAreaLength;
			hash.hemiLength = hemiLength;

			hash.numDirectionalShadows = numDirectionalShadows;
			hash.numPointShadows = numPointShadows;
			hash.numSpotShadows = numSpotShadows;

			state.version = nextVersion++;
		}
	}

	function setupView(lights, camera) {
		let directionalLength = 0;
		let pointLength = 0;
		let spotLength = 0;
		let rectAreaLength = 0;
		let hemiLength = 0;

		const viewMatrix = camera.matrixWorldInverse;

		for (let i = 0, l = lights.length; i < l; i++) {
			const light = lights[i];

			if (light.isDirectionalLight) {
				const uniforms = state.directional[directionalLength];

				uniforms.direction.setFromMatrixPosition(light.matrixWorld);
				vector3.setFromMatrixPosition(light.target.matrixWorld);
				uniforms.direction.sub(vector3);
				uniforms.direction.transformDirection(viewMatrix);

				directionalLength++;
			} else if (light.isSpotLight) {
				const uniforms = state.spot[spotLength];

				uniforms.position.setFromMatrixPosition(light.matrixWorld);
				uniforms.position.applyMatrix4(viewMatrix);

				uniforms.direction.setFromMatrixPosition(light.matrixWorld);
				vector3.setFromMatrixPosition(light.target.matrixWorld);
				uniforms.direction.sub(vector3);
				uniforms.direction.transformDirection(viewMatrix);

				spotLength++;
			} else if (light.isRectAreaLight) {
				const uniforms = state.rectArea[rectAreaLength];

				uniforms.position.setFromMatrixPosition(light.matrixWorld);
				uniforms.position.applyMatrix4(viewMatrix);

				// extract local rotation of light to derive width/height half vectors
				matrix42.identity();
				matrix4.copy(light.matrixWorld);
				matrix4.premultiply(viewMatrix);
				matrix42.extractRotation(matrix4);

				uniforms.halfWidth.set(light.width * 0.5, 0.0, 0.0);
				uniforms.halfHeight.set(0.0, light.height * 0.5, 0.0);

				uniforms.halfWidth.applyMatrix4(matrix42);
				uniforms.halfHeight.applyMatrix4(matrix42);

				rectAreaLength++;
			} else if (light.isPointLight) {
				const uniforms = state.point[pointLength];

				uniforms.position.setFromMatrixPosition(light.matrixWorld);
				uniforms.position.applyMatrix4(viewMatrix);

				pointLength++;
			} else if (light.isHemisphereLight) {
				const uniforms = state.hemi[hemiLength];

				uniforms.direction.setFromMatrixPosition(light.matrixWorld);
				uniforms.direction.transformDirection(viewMatrix);
				uniforms.direction.normalize();

				hemiLength++;
			}
		}
	}

	return {
		setup: setup,
		setupView: setupView,
		state: state,
	};
}

export { WebGLLights };