import { FloatType, RGBAFormat } from '../../constants.js';
import { DataTexture2DArray } from '../../textures/DataTexture2DArray.js';
import { Vector3 } from '../../math/Vector3.js';
import { Vector2 } from '../../math/Vector2.js';

function numericalSort(a, b) {
	return a[0] - b[0];
}

function absNumericalSort(a, b) {
	return Math.abs(b[1]) - Math.abs(a[1]);
}

function denormalize(morph, attribute) {
	let denominator = 1;
	const array = attribute.isInterleavedBufferAttribute ? attribute.data.array : attribute.array;

	if (array instanceof Int8Array) denominator = 127;
	else if (array instanceof Int16Array) denominator = 32767;
	else if (array instanceof Int32Array) denominator = 2147483647;
	else console.error('THREE.WebGLMorphtargets: Unsupported morph attribute data type: ', array);

	morph.divideScalar(denominator);
}

function WebGLMorphtargets(gl, capabilities, textures) {
	const influencesList = {};
	const morphInfluences = new Float32Array(8);
	const morphTextures = new WeakMap();
	const morph = new Vector3();

	const workInfluences = [];

	for (let i = 0; i < 8; i++) {
		workInfluences[i] = [i, 0];
	}

	function update(object, geometry, material, program) {
		const objectInfluences = object.morphTargetInfluences;

		if (capabilities.isWebGL2 === true) {
			// instead of using attributes, the WebGL 2 code path encodes morph targets
			// into an array of data textures. Each layer represents a single morph target.

			const numberOfMorphTargets = geometry.morphAttributes.position.length;

			let entry = morphTextures.get(geometry);

			if (entry === undefined || entry.count !== numberOfMorphTargets) {
				if (entry !== undefined) entry.texture.dispose();

				const hasMorphNormals = geometry.morphAttributes.normal !== undefined;

				const morphTargets = geometry.morphAttributes.position;
				const morphNormals = geometry.morphAttributes.normal || [];

				const numberOfVertices = geometry.attributes.position.count;
				const numberOfVertexData = hasMorphNormals === true ? 2 : 1; // (v,n) vs. (v)

				let width = numberOfVertices * numberOfVertexData;
				let height = 1;

				if (width > capabilities.maxTextureSize) {
					height = Math.ceil(width / capabilities.maxTextureSize);
					width = capabilities.maxTextureSize;
				}

				const buffer = new Float32Array(width * height * 4 * numberOfMorphTargets);

				const texture = new DataTexture2DArray(buffer, width, height, numberOfMorphTargets);
				texture.format = RGBAFormat; // using RGBA since RGB might be emulated (and is thus slower)
				texture.type = FloatType;
				texture.needsUpdate = true;

				// fill buffer

				const vertexDataStride = numberOfVertexData * 4;

				for (let i = 0; i < numberOfMorphTargets; i++) {
					const morphTarget = morphTargets[i];
					const morphNormal = morphNormals[i];

					const offset = width * height * 4 * i;

					for (let j = 0; j < morphTarget.count; j++) {
						morph.fromBufferAttribute(morphTarget, j);

						if (morphTarget.normalized === true) denormalize(morph, morphTarget);

						const stride = j * vertexDataStride;

						buffer[offset + stride + 0] = morph.x;
						buffer[offset + stride + 1] = morph.y;
						buffer[offset + stride + 2] = morph.z;
						buffer[offset + stride + 3] = 0;

						if (hasMorphNormals === true) {
							morph.fromBufferAttribute(morphNormal, j);

							if (morphNormal.normalized === true) denormalize(morph, morphNormal);

							buffer[offset + stride + 4] = morph.x;
							buffer[offset + stride + 5] = morph.y;
							buffer[offset + stride + 6] = morph.z;
							buffer[offset + stride + 7] = 0;
						}
					}
				}

				entry = {
					count: numberOfMorphTargets,
					texture: texture,
					size: new Vector2(width, height),
				};

				morphTextures.set(geometry, entry);

				function disposeTexture() {
					texture.dispose();

					morphTextures.delete(geometry);

					geometry.removeEventListener('dispose', disposeTexture);
				}

				geometry.addEventListener('dispose', disposeTexture);
			}

			//

			let morphInfluencesSum = 0;

			for (let i = 0; i < objectInfluences.length; i++) {
				morphInfluencesSum += objectInfluences[i];
			}

			const morphBaseInfluence = geometry.morphTargetsRelative ? 1 : 1 - morphInfluencesSum;

			program.getUniforms().setValue(gl, 'morphTargetBaseInfluence', morphBaseInfluence);
			program.getUniforms().setValue(gl, 'morphTargetInfluences', objectInfluences);

			program.getUniforms().setValue(gl, 'morphTargetsTexture', entry.texture, textures);
			program.getUniforms().setValue(gl, 'morphTargetsTextureSize', entry.size);
		} else {
			// When object doesn't have morph target influences defined, we treat it as a 0-length array
			// This is important to make sure we set up morphTargetBaseInfluence / morphTargetInfluences

			const length = objectInfluences === undefined ? 0 : objectInfluences.length;

			let influences = influencesList[geometry.id];

			if (influences === undefined || influences.length !== length) {
				// initialise list

				influences = [];

				for (let i = 0; i < length; i++) {
					influences[i] = [i, 0];
				}

				influencesList[geometry.id] = influences;
			}

			// Collect influences

			for (let i = 0; i < length; i++) {
				const influence = influences[i];

				influence[0] = i;
				influence[1] = objectInfluences[i];
			}

			influences.sort(absNumericalSort);

			for (let i = 0; i < 8; i++) {
				if (i < length && influences[i][1]) {
					workInfluences[i][0] = influences[i][0];
					workInfluences[i][1] = influences[i][1];
				} else {
					workInfluences[i][0] = Number.MAX_SAFE_INTEGER;
					workInfluences[i][1] = 0;
				}
			}

			workInfluences.sort(numericalSort);

			const morphTargets = geometry.morphAttributes.position;
			const morphNormals = geometry.morphAttributes.normal;

			let morphInfluencesSum = 0;

			for (let i = 0; i < 8; i++) {
				const influence = workInfluences[i];
				const index = influence[0];
				const value = influence[1];

				if (index !== Number.MAX_SAFE_INTEGER && value) {
					if (morphTargets && geometry.getAttribute('morphTarget' + i) !== morphTargets[index]) {
						geometry.setAttribute('morphTarget' + i, morphTargets[index]);
					}

					if (morphNormals && geometry.getAttribute('morphNormal' + i) !== morphNormals[index]) {
						geometry.setAttribute('morphNormal' + i, morphNormals[index]);
					}

					morphInfluences[i] = value;
					morphInfluencesSum += value;
				} else {
					if (morphTargets && geometry.hasAttribute('morphTarget' + i) === true) {
						geometry.deleteAttribute('morphTarget' + i);
					}

					if (morphNormals && geometry.hasAttribute('morphNormal' + i) === true) {
						geometry.deleteAttribute('morphNormal' + i);
					}

					morphInfluences[i] = 0;
				}
			}

			// GLSL shader uses formula baseinfluence * base + sum(target * influence)
			// This allows us to switch between absolute morphs and relative morphs without changing shader code
			// When baseinfluence = 1 - sum(influence), the above is equivalent to sum((target - base) * influence)
			const morphBaseInfluence = geometry.morphTargetsRelative ? 1 : 1 - morphInfluencesSum;

			program.getUniforms().setValue(gl, 'morphTargetBaseInfluence', morphBaseInfluence);
			program.getUniforms().setValue(gl, 'morphTargetInfluences', morphInfluences);
		}
	}

	return {
		update: update,
	};
}

export { WebGLMorphtargets };