import TempNode from '../core/TempNode.js';
import { add } from '../math/OperatorNode.js';
import { bitangentView } from '../accessors/BitangentNode.js';
import { modelNormalMatrix } from '../accessors/ModelNode.js';
import { normalView } from '../accessors/NormalNode.js';
import { positionView } from '../accessors/PositionNode.js';
import { tangentView } from '../accessors/TangentNode.js';
import { uv } from '../accessors/UVNode.js';
import { faceDirection } from './FrontFacingNode.js';
import { addNodeClass } from '../core/Node.js';
import { tslFn, nodeProxy, vec3, mat3 } from '../shadernode/ShaderNode.js';

import { TangentSpaceNormalMap, ObjectSpaceNormalMap } from 'three';

// Normal Mapping Without Precomputed Tangents
// http://www.thetenthplanet.de/archives/1180

const perturbNormal2Arb = tslFn( ( inputs ) => {

	const { eye_pos, surf_norm, mapN, uv } = inputs;

	const q0 = eye_pos.dFdx();
	const q1 = eye_pos.dFdy();
	const st0 = uv.dFdx();
	const st1 = uv.dFdy();

	const N = surf_norm; // normalized

	const q1perp = q1.cross( N );
	const q0perp = N.cross( q0 );

	const T = q1perp.mul( st0.x ).add( q0perp.mul( st1.x ) );
	const B = q1perp.mul( st0.y ).add( q0perp.mul( st1.y ) );

	const det = T.dot( T ).max( B.dot( B ) );
	const scale = faceDirection.mul( det.inverseSqrt() );

	return add( T.mul( mapN.x, scale ), B.mul( mapN.y, scale ), N.mul( mapN.z ) ).normalize();

} );

class NormalMapNode extends TempNode {

	constructor( node, scaleNode = null ) {

		super( 'vec3' );

		this.node = node;
		this.scaleNode = scaleNode;

		this.normalMapType = TangentSpaceNormalMap;

	}

	construct( builder ) {

		const { normalMapType, scaleNode } = this;

		let normalMap = this.node.mul( 2.0 ).sub( 1.0 );

		if ( scaleNode !== null ) {

			normalMap = vec3( normalMap.xy.mul( scaleNode ), normalMap.z );

		}

		let outputNode = null;

		if ( normalMapType === ObjectSpaceNormalMap ) {

			outputNode = modelNormalMatrix.mul( normalMap ).normalize();

		} else if ( normalMapType === TangentSpaceNormalMap ) {

			const tangent = builder.hasGeometryAttribute( 'tangent' );

			if ( tangent === true ) {

				outputNode = TBNViewMatrix.mul( normalMap ).normalize();

			} else {

				outputNode = perturbNormal2Arb( {
					eye_pos: positionView,
					surf_norm: normalView,
					mapN: normalMap,
					uv: uv()
				} );

			}

		}

		return outputNode;

	}

}

export default NormalMapNode;

export const normalMap = nodeProxy( NormalMapNode );

export const TBNViewMatrix = mat3( tangentView, bitangentView, normalView );

addNodeClass( NormalMapNode );
