import { dot, max, mix } from '../math/MathNode.js';
import { add } from '../math/OperatorNode.js';
import { Fn, If, float, vec3, vec4 } from '../tsl/TSLBase.js';
import { ColorManagement } from '../../math/ColorManagement.js';
import { Vector3 } from '../../math/Vector3.js';
import { LinearSRGBColorSpace } from '../../constants.js';

/**
 * Computes a grayscale value for the given RGB color value.
 *
 * @tsl
 * @function
 * @param {Node<vec3>} color - The color value to compute the grayscale for.
 * @return {Node<vec3>} The grayscale color.
 */
export const grayscale = /*@__PURE__*/ Fn( ( [ color ] ) => {

	return luminance( color.rgb );

} );

/**
 * Super-saturates or desaturates the given RGB color.
 *
 * @tsl
 * @function
 * @param {Node<vec3>} color - The input color.
 * @param {Node<float>} [adjustment=1] - Specifies the amount of the conversion. A value under `1` desaturates the color, a value over `1` super-saturates it.
 * @return {Node<vec3>} The saturated color.
 */
export const saturation = /*@__PURE__*/ Fn( ( [ color, adjustment = float( 1 ) ] ) => {

	return adjustment.mix( luminance( color.rgb ), color.rgb );

} );

/**
 * Selectively enhance the intensity of less saturated RGB colors. Can result
 * in a more natural and visually appealing image with enhanced color depth
 * compared to {@link ColorAdjustment#saturation}.
 *
 * @tsl
 * @function
 * @param {Node<vec3>} color - The input color.
 * @param {Node<float>} [adjustment=1] - Controls the intensity of the vibrance effect.
 * @return {Node<vec3>} The updated color.
 */
export const vibrance = /*@__PURE__*/ Fn( ( [ color, adjustment = float( 1 ) ] ) => {

	const average = add( color.r, color.g, color.b ).div( 3.0 );

	const mx = color.r.max( color.g.max( color.b ) );
	const amt = mx.sub( average ).mul( adjustment ).mul( - 3.0 );

	return mix( color.rgb, mx, amt );

} );

/**
 * Updates the hue component of the given RGB color while preserving its luminance and saturation.
 *
 * @tsl
 * @function
 * @param {Node<vec3>} color - The input color.
 * @param {Node<float>} [adjustment=1] - Defines the degree of hue rotation in radians. A positive value rotates the hue clockwise, while a negative value rotates it counterclockwise.
 * @return {Node<vec3>} The updated color.
 */
export const hue = /*@__PURE__*/ Fn( ( [ color, adjustment = float( 1 ) ] ) => {

	const k = vec3( 0.57735, 0.57735, 0.57735 );

	const cosAngle = adjustment.cos();

	return vec3( color.rgb.mul( cosAngle ).add( k.cross( color.rgb ).mul( adjustment.sin() ).add( k.mul( dot( k, color.rgb ).mul( cosAngle.oneMinus() ) ) ) ) );

} );

/**
 * Computes the luminance for the given RGB color value.
 *
 * @tsl
 * @function
 * @param {Node<vec3>} color - The color value to compute the luminance for.
 * @param {?Node<vec3>} luminanceCoefficients - The luminance coefficients. By default predefined values of the current working color space are used.
 * @return {Node<float>} The luminance.
 */
export const luminance = (
	color,
	luminanceCoefficients = vec3( ColorManagement.getLuminanceCoefficients( new Vector3() ) )
) => dot( color, luminanceCoefficients );

/**
 * Color Decision List (CDL) v1.2
 *
 * Compact representation of color grading information, defined by slope, offset, power, and
 * saturation. The CDL should be typically be given input in a log space (such as LogC, ACEScc,
 * or AgX Log), and will return output in the same space. Output may require clamping >=0.
 *
 * @tsl
 * @function
 * @param {Node<vec4>} color Input (-Infinity < input < +Infinity)
 * @param {Node<vec3>} slope Slope (0 ≤ slope < +Infinity)
 * @param {Node<vec3>} offset Offset (-Infinity < offset < +Infinity; typically -1 < offset < 1)
 * @param {Node<vec3>} power Power (0 < power < +Infinity)
 * @param {Node<float>} saturation Saturation (0 ≤ saturation < +Infinity; typically 0 ≤ saturation < 4)
 * @param {Node<vec3>} luminanceCoefficients Luminance coefficients for saturation term, typically Rec. 709
 * @return {Node<vec4>} Output, -Infinity < output < +Infinity
 *
 * References:
 * - ASC CDL v1.2
 * - {@link https://blender.stackexchange.com/a/55239/43930}
 * - {@link https://docs.acescentral.com/specifications/acescc/}
 */
export const cdl = /*@__PURE__*/ Fn( ( [
	color,
	slope = vec3( 1 ),
	offset = vec3( 0 ),
	power = vec3( 1 ),
	saturation = float( 1 ),
	// ASC CDL v1.2 explicitly requires Rec. 709 luminance coefficients.
	luminanceCoefficients = vec3( ColorManagement.getLuminanceCoefficients( new Vector3(), LinearSRGBColorSpace ) )
] ) => {

	// NOTE: The ASC CDL v1.2 defines a [0, 1] clamp on the slope+offset term, and another on the
	// saturation term. Per the ACEScc specification and Filament, limits may be omitted to support
	// values outside [0, 1], requiring a workaround for negative values in the power expression.

	const luma = color.rgb.dot( vec3( luminanceCoefficients ) );

	const v = max( color.rgb.mul( slope ).add( offset ), 0.0 ).toVar();
	const pv = v.pow( power ).toVar();

	If( v.r.greaterThan( 0.0 ), () => { v.r.assign( pv.r ); } ); // eslint-disable-line
	If( v.g.greaterThan( 0.0 ), () => { v.g.assign( pv.g ); } ); // eslint-disable-line
	If( v.b.greaterThan( 0.0 ), () => { v.b.assign( pv.b ); } ); // eslint-disable-line

	v.assign( luma.add( v.sub( luma ).mul( saturation ) ) );

	return vec4( v.rgb, color.a );

} );
