import {
	CubeReflectionMapping,
	CubeRefractionMapping,
	CubeUVReflectionMapping,
	LinearEncoding,
	LinearFilter,
	NoToneMapping,
	NoBlending,
	RGBAFormat,
	HalfFloatType,
} from '../constants.js';

import { BufferAttribute } from '../core/BufferAttribute.js';
import { BufferGeometry } from '../core/BufferGeometry.js';
import { Mesh } from '../objects/Mesh.js';
import { OrthographicCamera } from '../cameras/OrthographicCamera.js';
import { PerspectiveCamera } from '../cameras/PerspectiveCamera.js';
import { RawShaderMaterial } from '../materials/RawShaderMaterial.js';
import { Vector2 } from '../math/Vector2.js';
import { Vector3 } from '../math/Vector3.js';
import { Color } from '../math/Color.js';
import { WebGLRenderTarget } from '../renderers/WebGLRenderTarget.js';
import { MeshBasicMaterial } from '../materials/MeshBasicMaterial.js';
import { BoxGeometry } from '../geometries/BoxGeometry.js';
import { BackSide } from '../constants.js';

const LOD_MIN = 4;
const LOD_MAX = 8;
const SIZE_MAX = Math.pow(2, LOD_MAX);

// The standard deviations (radians) associated with the extra mips. These are
// chosen to approximate a Trowbridge-Reitz distribution function times the
// geometric shadowing function. These sigma values squared must match the
// variance #defines in cube_uv_reflection_fragment.glsl.js.
const EXTRA_LOD_SIGMA = [0.125, 0.215, 0.35, 0.446, 0.526, 0.582];

const TOTAL_LODS = LOD_MAX - LOD_MIN + 1 + EXTRA_LOD_SIGMA.length;

// The maximum length of the blur for loop. Smaller sigmas will use fewer
// samples and exit early, but not recompile the shader.
const MAX_SAMPLES = 20;

const _flatCamera = /*@__PURE__*/ new OrthographicCamera();
const { _lodPlanes, _sizeLods, _sigmas } = /*@__PURE__*/ _createPlanes();
const _clearColor = /*@__PURE__*/ new Color();
let _oldTarget = null;

// Golden Ratio
const PHI = (1 + Math.sqrt(5)) / 2;
const INV_PHI = 1 / PHI;

// Vertices of a dodecahedron (except the opposites, which represent the
// same axis), used as axis directions evenly spread on a sphere.
const _axisDirections = [
	/*@__PURE__*/ new Vector3(1, 1, 1),
	/*@__PURE__*/ new Vector3(-1, 1, 1),
	/*@__PURE__*/ new Vector3(1, 1, -1),
	/*@__PURE__*/ new Vector3(-1, 1, -1),
	/*@__PURE__*/ new Vector3(0, PHI, INV_PHI),
	/*@__PURE__*/ new Vector3(0, PHI, -INV_PHI),
	/*@__PURE__*/ new Vector3(INV_PHI, 0, PHI),
	/*@__PURE__*/ new Vector3(-INV_PHI, 0, PHI),
	/*@__PURE__*/ new Vector3(PHI, INV_PHI, 0),
	/*@__PURE__*/ new Vector3(-PHI, INV_PHI, 0),
];

/**
 * This class generates a Prefiltered, Mipmapped Radiance Environment Map
 * (PMREM) from a cubeMap environment texture. This allows different levels of
 * blur to be quickly accessed based on material roughness. It is packed into a
 * special CubeUV format that allows us to perform custom interpolation so that
 * we can support nonlinear formats such as RGBE. Unlike a traditional mipmap
 * chain, it only goes down to the LOD_MIN level (above), and then creates extra
 * even more filtered 'mips' at the same LOD_MIN resolution, associated with
 * higher roughness levels. In this way we maintain resolution to smoothly
 * interpolate diffuse lighting while limiting sampling computation.
 *
 * Paper: Fast, Accurate Image-Based Lighting
 * https://drive.google.com/file/d/15y8r_UpKlU9SvV4ILb0C3qCPecS8pvLz/view
 */

class PMREMGenerator {
	constructor(renderer) {
		this._renderer = renderer;
		this._pingPongRenderTarget = null;

		this._blurMaterial = _getBlurShader(MAX_SAMPLES);
		this._equirectShader = null;
		this._cubemapShader = null;

		this._compileMaterial(this._blurMaterial);
	}

	/**
	 * Generates a PMREM from a supplied Scene, which can be faster than using an
	 * image if networking bandwidth is low. Optional sigma specifies a blur radius
	 * in radians to be applied to the scene before PMREM generation. Optional near
	 * and far planes ensure the scene is rendered in its entirety (the cubeCamera
	 * is placed at the origin).
	 */
	fromScene(scene, sigma = 0, near = 0.1, far = 100) {
		_oldTarget = this._renderer.getRenderTarget();
		const cubeUVRenderTarget = this._allocateTargets();

		this._sceneToCubeUV(scene, near, far, cubeUVRenderTarget);
		if (sigma > 0) {
			this._blur(cubeUVRenderTarget, 0, 0, sigma);
		}

		this._applyPMREM(cubeUVRenderTarget);
		this._cleanup(cubeUVRenderTarget);

		return cubeUVRenderTarget;
	}

	/**
	 * Generates a PMREM from an equirectangular texture, which can be either LDR
	 * or HDR. The ideal input image size is 1k (1024 x 512),
	 * as this matches best with the 256 x 256 cubemap output.
	 */
	fromEquirectangular(equirectangular, renderTarget = null) {
		return this._fromTexture(equirectangular, renderTarget);
	}

	/**
	 * Generates a PMREM from an cubemap texture, which can be either LDR
	 * or HDR. The ideal input cube size is 256 x 256,
	 * as this matches best with the 256 x 256 cubemap output.
	 */
	fromCubemap(cubemap, renderTarget = null) {
		return this._fromTexture(cubemap, renderTarget);
	}

	/**
	 * Pre-compiles the cubemap shader. You can get faster start-up by invoking this method during
	 * your texture's network fetch for increased concurrency.
	 */
	compileCubemapShader() {
		if (this._cubemapShader === null) {
			this._cubemapShader = _getCubemapShader();
			this._compileMaterial(this._cubemapShader);
		}
	}

	/**
	 * Pre-compiles the equirectangular shader. You can get faster start-up by invoking this method during
	 * your texture's network fetch for increased concurrency.
	 */
	compileEquirectangularShader() {
		if (this._equirectShader === null) {
			this._equirectShader = _getEquirectShader();
			this._compileMaterial(this._equirectShader);
		}
	}

	/**
	 * Disposes of the PMREMGenerator's internal memory. Note that PMREMGenerator is a static class,
	 * so you should not need more than one PMREMGenerator object. If you do, calling dispose() on
	 * one of them will cause any others to also become unusable.
	 */
	dispose() {
		this._blurMaterial.dispose();

		if (this._pingPongRenderTarget !== null) this._pingPongRenderTarget.dispose();

		if (this._cubemapShader !== null) this._cubemapShader.dispose();
		if (this._equirectShader !== null) this._equirectShader.dispose();

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

	// private interface

	_cleanup(outputTarget) {
		this._renderer.setRenderTarget(_oldTarget);
		outputTarget.scissorTest = false;
		_setViewport(outputTarget, 0, 0, outputTarget.width, outputTarget.height);
	}

	_fromTexture(texture, renderTarget) {
		_oldTarget = this._renderer.getRenderTarget();
		const cubeUVRenderTarget = renderTarget || this._allocateTargets(texture);
		this._textureToCubeUV(texture, cubeUVRenderTarget);
		this._applyPMREM(cubeUVRenderTarget);
		this._cleanup(cubeUVRenderTarget);

		return cubeUVRenderTarget;
	}

	_allocateTargets(texture) {
		// warning: null texture is valid

		const params = {
			magFilter: LinearFilter,
			minFilter: LinearFilter,
			generateMipmaps: false,
			type: HalfFloatType,
			format: RGBAFormat,
			encoding: LinearEncoding,
			depthBuffer: false,
		};

		const cubeUVRenderTarget = _createRenderTarget(params);
		cubeUVRenderTarget.depthBuffer = texture ? false : true;

		if (this._pingPongRenderTarget === null) {
			this._pingPongRenderTarget = _createRenderTarget(params);
		}

		return cubeUVRenderTarget;
	}

	_compileMaterial(material) {
		const tmpMesh = new Mesh(_lodPlanes[0], material);
		this._renderer.compile(tmpMesh, _flatCamera);
	}

	_sceneToCubeUV(scene, near, far, cubeUVRenderTarget) {
		const fov = 90;
		const aspect = 1;
		const cubeCamera = new PerspectiveCamera(fov, aspect, near, far);
		const upSign = [1, -1, 1, 1, 1, 1];
		const forwardSign = [1, 1, 1, -1, -1, -1];
		const renderer = this._renderer;

		const originalAutoClear = renderer.autoClear;
		const toneMapping = renderer.toneMapping;
		renderer.getClearColor(_clearColor);

		renderer.toneMapping = NoToneMapping;
		renderer.autoClear = false;

		const backgroundMaterial = new MeshBasicMaterial({
			name: 'PMREM.Background',
			side: BackSide,
			depthWrite: false,
			depthTest: false,
		});

		const backgroundBox = new Mesh(new BoxGeometry(), backgroundMaterial);

		let useSolidColor = false;
		const background = scene.background;

		if (background) {
			if (background.isColor) {
				backgroundMaterial.color.copy(background);
				scene.background = null;
				useSolidColor = true;
			}
		} else {
			backgroundMaterial.color.copy(_clearColor);
			useSolidColor = true;
		}

		for (let i = 0; i < 6; i++) {
			const col = i % 3;
			if (col === 0) {
				cubeCamera.up.set(0, upSign[i], 0);
				cubeCamera.lookAt(forwardSign[i], 0, 0);
			} else if (col === 1) {
				cubeCamera.up.set(0, 0, upSign[i]);
				cubeCamera.lookAt(0, forwardSign[i], 0);
			} else {
				cubeCamera.up.set(0, upSign[i], 0);
				cubeCamera.lookAt(0, 0, forwardSign[i]);
			}

			_setViewport(cubeUVRenderTarget, col * SIZE_MAX, i > 2 ? SIZE_MAX : 0, SIZE_MAX, SIZE_MAX);
			renderer.setRenderTarget(cubeUVRenderTarget);

			if (useSolidColor) {
				renderer.render(backgroundBox, cubeCamera);
			}

			renderer.render(scene, cubeCamera);
		}

		backgroundBox.geometry.dispose();
		backgroundBox.material.dispose();

		renderer.toneMapping = toneMapping;
		renderer.autoClear = originalAutoClear;
		scene.background = background;
	}

	_textureToCubeUV(texture, cubeUVRenderTarget) {
		const renderer = this._renderer;

		const isCubeTexture = texture.mapping === CubeReflectionMapping || texture.mapping === CubeRefractionMapping;

		if (isCubeTexture) {
			if (this._cubemapShader === null) {
				this._cubemapShader = _getCubemapShader();
			}

			this._cubemapShader.uniforms.flipEnvMap.value = texture.isRenderTargetTexture === false ? -1 : 1;
		} else {
			if (this._equirectShader === null) {
				this._equirectShader = _getEquirectShader();
			}
		}

		const material = isCubeTexture ? this._cubemapShader : this._equirectShader;
		const mesh = new Mesh(_lodPlanes[0], material);

		const uniforms = material.uniforms;

		uniforms['envMap'].value = texture;

		if (!isCubeTexture) {
			uniforms['texelSize'].value.set(1.0 / texture.image.width, 1.0 / texture.image.height);
		}

		_setViewport(cubeUVRenderTarget, 0, 0, 3 * SIZE_MAX, 2 * SIZE_MAX);

		renderer.setRenderTarget(cubeUVRenderTarget);
		renderer.render(mesh, _flatCamera);
	}

	_applyPMREM(cubeUVRenderTarget) {
		const renderer = this._renderer;
		const autoClear = renderer.autoClear;
		renderer.autoClear = false;

		for (let i = 1; i < TOTAL_LODS; i++) {
			const sigma = Math.sqrt(_sigmas[i] * _sigmas[i] - _sigmas[i - 1] * _sigmas[i - 1]);

			const poleAxis = _axisDirections[(i - 1) % _axisDirections.length];

			this._blur(cubeUVRenderTarget, i - 1, i, sigma, poleAxis);
		}

		renderer.autoClear = autoClear;
	}

	/**
	 * This is a two-pass Gaussian blur for a cubemap. Normally this is done
	 * vertically and horizontally, but this breaks down on a cube. Here we apply
	 * the blur latitudinally (around the poles), and then longitudinally (towards
	 * the poles) to approximate the orthogonally-separable blur. It is least
	 * accurate at the poles, but still does a decent job.
	 */
	_blur(cubeUVRenderTarget, lodIn, lodOut, sigma, poleAxis) {
		const pingPongRenderTarget = this._pingPongRenderTarget;

		this._halfBlur(cubeUVRenderTarget, pingPongRenderTarget, lodIn, lodOut, sigma, 'latitudinal', poleAxis);

		this._halfBlur(pingPongRenderTarget, cubeUVRenderTarget, lodOut, lodOut, sigma, 'longitudinal', poleAxis);
	}

	_halfBlur(targetIn, targetOut, lodIn, lodOut, sigmaRadians, direction, poleAxis) {
		const renderer = this._renderer;
		const blurMaterial = this._blurMaterial;

		if (direction !== 'latitudinal' && direction !== 'longitudinal') {
			console.error('blur direction must be either latitudinal or longitudinal!');
		}

		// Number of standard deviations at which to cut off the discrete approximation.
		const STANDARD_DEVIATIONS = 3;

		const blurMesh = new Mesh(_lodPlanes[lodOut], blurMaterial);
		const blurUniforms = blurMaterial.uniforms;

		const pixels = _sizeLods[lodIn] - 1;
		const radiansPerPixel = isFinite(sigmaRadians) ? Math.PI / (2 * pixels) : (2 * Math.PI) / (2 * MAX_SAMPLES - 1);
		const sigmaPixels = sigmaRadians / radiansPerPixel;
		const samples = isFinite(sigmaRadians) ? 1 + Math.floor(STANDARD_DEVIATIONS * sigmaPixels) : MAX_SAMPLES;

		if (samples > MAX_SAMPLES) {
			console.warn(
				`sigmaRadians, ${sigmaRadians}, is too large and will clip, as it requested ${samples} samples when the maximum is set to ${MAX_SAMPLES}`
			);
		}

		const weights = [];
		let sum = 0;

		for (let i = 0; i < MAX_SAMPLES; ++i) {
			const x = i / sigmaPixels;
			const weight = Math.exp((-x * x) / 2);
			weights.push(weight);

			if (i === 0) {
				sum += weight;
			} else if (i < samples) {
				sum += 2 * weight;
			}
		}

		for (let i = 0; i < weights.length; i++) {
			weights[i] = weights[i] / sum;
		}

		blurUniforms['envMap'].value = targetIn.texture;
		blurUniforms['samples'].value = samples;
		blurUniforms['weights'].value = weights;
		blurUniforms['latitudinal'].value = direction === 'latitudinal';

		if (poleAxis) {
			blurUniforms['poleAxis'].value = poleAxis;
		}

		blurUniforms['dTheta'].value = radiansPerPixel;
		blurUniforms['mipInt'].value = LOD_MAX - lodIn;

		const outputSize = _sizeLods[lodOut];
		const x = 3 * Math.max(0, SIZE_MAX - 2 * outputSize);
		const y = (lodOut === 0 ? 0 : 2 * SIZE_MAX) + 2 * outputSize * (lodOut > LOD_MAX - LOD_MIN ? lodOut - LOD_MAX + LOD_MIN : 0);

		_setViewport(targetOut, x, y, 3 * outputSize, 2 * outputSize);
		renderer.setRenderTarget(targetOut);
		renderer.render(blurMesh, _flatCamera);
	}
}

function _createPlanes() {
	const _lodPlanes = [];
	const _sizeLods = [];
	const _sigmas = [];

	let lod = LOD_MAX;

	for (let i = 0; i < TOTAL_LODS; i++) {
		const sizeLod = Math.pow(2, lod);
		_sizeLods.push(sizeLod);
		let sigma = 1.0 / sizeLod;

		if (i > LOD_MAX - LOD_MIN) {
			sigma = EXTRA_LOD_SIGMA[i - LOD_MAX + LOD_MIN - 1];
		} else if (i === 0) {
			sigma = 0;
		}

		_sigmas.push(sigma);

		const texelSize = 1.0 / (sizeLod - 1);
		const min = -texelSize / 2;
		const max = 1 + texelSize / 2;
		const uv1 = [min, min, max, min, max, max, min, min, max, max, min, max];

		const cubeFaces = 6;
		const vertices = 6;
		const positionSize = 3;
		const uvSize = 2;
		const faceIndexSize = 1;

		const position = new Float32Array(positionSize * vertices * cubeFaces);
		const uv = new Float32Array(uvSize * vertices * cubeFaces);
		const faceIndex = new Float32Array(faceIndexSize * vertices * cubeFaces);

		for (let face = 0; face < cubeFaces; face++) {
			const x = ((face % 3) * 2) / 3 - 1;
			const y = face > 2 ? 0 : -1;
			const coordinates = [x, y, 0, x + 2 / 3, y, 0, x + 2 / 3, y + 1, 0, x, y, 0, x + 2 / 3, y + 1, 0, x, y + 1, 0];
			position.set(coordinates, positionSize * vertices * face);
			uv.set(uv1, uvSize * vertices * face);
			const fill = [face, face, face, face, face, face];
			faceIndex.set(fill, faceIndexSize * vertices * face);
		}

		const planes = new BufferGeometry();
		planes.setAttribute('position', new BufferAttribute(position, positionSize));
		planes.setAttribute('uv', new BufferAttribute(uv, uvSize));
		planes.setAttribute('faceIndex', new BufferAttribute(faceIndex, faceIndexSize));
		_lodPlanes.push(planes);

		if (lod > LOD_MIN) {
			lod--;
		}
	}

	return { _lodPlanes, _sizeLods, _sigmas };
}

function _createRenderTarget(params) {
	const cubeUVRenderTarget = new WebGLRenderTarget(3 * SIZE_MAX, 3 * SIZE_MAX, params);
	cubeUVRenderTarget.texture.mapping = CubeUVReflectionMapping;
	cubeUVRenderTarget.texture.name = 'PMREM.cubeUv';
	cubeUVRenderTarget.scissorTest = true;
	return cubeUVRenderTarget;
}

function _setViewport(target, x, y, width, height) {
	target.viewport.set(x, y, width, height);
	target.scissor.set(x, y, width, height);
}

function _getBlurShader(maxSamples) {
	const weights = new Float32Array(maxSamples);
	const poleAxis = new Vector3(0, 1, 0);
	const shaderMaterial = new RawShaderMaterial({
		name: 'SphericalGaussianBlur',

		defines: { n: maxSamples },

		uniforms: {
			envMap: { value: null },
			samples: { value: 1 },
			weights: { value: weights },
			latitudinal: { value: false },
			dTheta: { value: 0 },
			mipInt: { value: 0 },
			poleAxis: { value: poleAxis },
		},

		vertexShader: _getCommonVertexShader(),

		fragmentShader: /* glsl */ `

			precision mediump float;
			precision mediump int;

			varying vec3 vOutputDirection;

			uniform sampler2D envMap;
			uniform int samples;
			uniform float weights[ n ];
			uniform bool latitudinal;
			uniform float dTheta;
			uniform float mipInt;
			uniform vec3 poleAxis;

			#define ENVMAP_TYPE_CUBE_UV
			#include <cube_uv_reflection_fragment>

			vec3 getSample( float theta, vec3 axis ) {

				float cosTheta = cos( theta );
				// Rodrigues' axis-angle rotation
				vec3 sampleDirection = vOutputDirection * cosTheta
					+ cross( axis, vOutputDirection ) * sin( theta )
					+ axis * dot( axis, vOutputDirection ) * ( 1.0 - cosTheta );

				return bilinearCubeUV( envMap, sampleDirection, mipInt );

			}

			void main() {

				vec3 axis = latitudinal ? poleAxis : cross( poleAxis, vOutputDirection );

				if ( all( equal( axis, vec3( 0.0 ) ) ) ) {

					axis = vec3( vOutputDirection.z, 0.0, - vOutputDirection.x );

				}

				axis = normalize( axis );

				gl_FragColor = vec4( 0.0, 0.0, 0.0, 1.0 );
				gl_FragColor.rgb += weights[ 0 ] * getSample( 0.0, axis );

				for ( int i = 1; i < n; i++ ) {

					if ( i >= samples ) {

						break;

					}

					float theta = dTheta * float( i );
					gl_FragColor.rgb += weights[ i ] * getSample( -1.0 * theta, axis );
					gl_FragColor.rgb += weights[ i ] * getSample( theta, axis );

				}

			}
		`,

		blending: NoBlending,
		depthTest: false,
		depthWrite: false,
	});

	return shaderMaterial;
}

function _getEquirectShader() {
	const texelSize = new Vector2(1, 1);
	const shaderMaterial = new RawShaderMaterial({
		name: 'EquirectangularToCubeUV',

		uniforms: {
			envMap: { value: null },
			texelSize: { value: texelSize },
		},

		vertexShader: _getCommonVertexShader(),

		fragmentShader: /* glsl */ `

			precision mediump float;
			precision mediump int;

			varying vec3 vOutputDirection;

			uniform sampler2D envMap;
			uniform vec2 texelSize;

			#include <common>

			void main() {

				gl_FragColor = vec4( 0.0, 0.0, 0.0, 1.0 );

				vec3 outputDirection = normalize( vOutputDirection );
				vec2 uv = equirectUv( outputDirection );

				vec2 f = fract( uv / texelSize - 0.5 );
				uv -= f * texelSize;
				vec3 tl = texture2D ( envMap, uv ).rgb;
				uv.x += texelSize.x;
				vec3 tr = texture2D ( envMap, uv ).rgb;
				uv.y += texelSize.y;
				vec3 br = texture2D ( envMap, uv ).rgb;
				uv.x -= texelSize.x;
				vec3 bl = texture2D ( envMap, uv ).rgb;

				vec3 tm = mix( tl, tr, f.x );
				vec3 bm = mix( bl, br, f.x );
				gl_FragColor.rgb = mix( tm, bm, f.y );

			}
		`,

		blending: NoBlending,
		depthTest: false,
		depthWrite: false,
	});

	return shaderMaterial;
}

function _getCubemapShader() {
	const shaderMaterial = new RawShaderMaterial({
		name: 'CubemapToCubeUV',

		uniforms: {
			envMap: { value: null },
			flipEnvMap: { value: -1 },
		},

		vertexShader: _getCommonVertexShader(),

		fragmentShader: /* glsl */ `

			precision mediump float;
			precision mediump int;

			uniform float flipEnvMap;

			varying vec3 vOutputDirection;

			uniform samplerCube envMap;

			void main() {

				gl_FragColor = textureCube( envMap, vec3( flipEnvMap * vOutputDirection.x, vOutputDirection.yz ) );

			}
		`,

		blending: NoBlending,
		depthTest: false,
		depthWrite: false,
	});

	return shaderMaterial;
}

function _getCommonVertexShader() {
	return /* glsl */ `

		precision mediump float;
		precision mediump int;

		attribute vec3 position;
		attribute vec2 uv;
		attribute float faceIndex;

		varying vec3 vOutputDirection;

		// RH coordinate system; PMREM face-indexing convention
		vec3 getDirection( vec2 uv, float face ) {

			uv = 2.0 * uv - 1.0;

			vec3 direction = vec3( uv, 1.0 );

			if ( face == 0.0 ) {

				direction = direction.zyx; // ( 1, v, u ) pos x

			} else if ( face == 1.0 ) {

				direction = direction.xzy;
				direction.xz *= -1.0; // ( -u, 1, -v ) pos y

			} else if ( face == 2.0 ) {

				direction.x *= -1.0; // ( -u, v, 1 ) pos z

			} else if ( face == 3.0 ) {

				direction = direction.zyx;
				direction.xz *= -1.0; // ( -1, v, -u ) neg x

			} else if ( face == 4.0 ) {

				direction = direction.xzy;
				direction.xy *= -1.0; // ( -u, -1, v ) neg y

			} else if ( face == 5.0 ) {

				direction.z *= -1.0; // ( u, v, -1 ) neg z

			}

			return direction;

		}

		void main() {

			vOutputDirection = getDirection( uv, faceIndex );
			gl_Position = vec4( position, 1.0 );

		}
	`;
}

export { PMREMGenerator };