/*
 * Copyright 2023 Comcast Cable Communications Management, LLC
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

import { getNormalizedRgbaComponents } from '../../lib/utils.js';
import {
  LinearGradientTemplate,
  type LinearGradientProps,
} from '../templates/LinearGradientTemplate.js';
import { genGradientColors } from '../../renderers/webgl/internal/ShaderUtils.js';
import type { WebGlRenderer } from '../../renderers/webgl/WebGlRenderer.js';
import type { WebGlShaderType } from '../../renderers/webgl/WebGlShaderNode.js';

export const LinearGradient: WebGlShaderType<LinearGradientProps> = {
  props: LinearGradientTemplate.props,
  update() {
    const props = this.props!;
    this.uniform1f('u_angle', props.angle - (Math.PI / 180) * 90);
    this.uniform1fv('u_stops', new Float32Array(props.stops));
    const colors: number[] = [];
    for (let i = 0; i < props.colors.length; i++) {
      const norm = getNormalizedRgbaComponents(props.colors[i]!);
      colors.push(norm[0], norm[1], norm[2], norm[3]);
    }
    this.uniform4fv('u_colors', new Float32Array(colors));
  },
  getCacheMarkers(props: LinearGradientProps) {
    return `colors:${props.colors.length}`;
  },
  fragment(renderer: WebGlRenderer, props: LinearGradientProps) {
    return `
    # ifdef GL_FRAGMENT_PRECISION_HIGH
    precision highp float;
    # else
    precision mediump float;
    # endif

    #define PI 3.14159265359
    #define MAX_STOPS ${props.colors.length}
    #define LAST_STOP ${props.colors.length - 1}

    uniform float u_alpha;
    uniform vec2 u_dimensions;

    uniform sampler2D u_texture;

    uniform float u_angle;
    uniform float u_stops[MAX_STOPS];
    uniform vec4 u_colors[MAX_STOPS];

    varying vec4 v_color;
    varying vec2 v_textureCoords;

    vec2 calcPoint(float d, float angle) {
      return d * vec2(cos(angle), sin(angle)) + (u_dimensions * 0.5);
    }

    vec4 getGradientColor(float dist) {
      dist = clamp(dist, 0.0, 1.0);

      if(dist <= u_stops[0]) {
        return u_colors[0];
      }

      if(dist >= u_stops[LAST_STOP]) {
        return u_colors[LAST_STOP];
      }

      for(int i = 0; i < LAST_STOP; i++) {
        float left = u_stops[i];
        float right = u_stops[i + 1];
        if(dist >= left && dist <= right) {
          float lDist = smoothstep(left, right, dist);
          return mix(u_colors[i], u_colors[i + 1], lDist);
        }
      }
    }

    void main() {
      vec4 color = texture2D(u_texture, v_textureCoords) * v_color;
      float a = u_angle;
      float lineDist = abs(u_dimensions.x * cos(a)) + abs(u_dimensions.y * sin(a));
      vec2 f = calcPoint(lineDist * 0.5, a);
      vec2 t = calcPoint(lineDist * 0.5, a + PI);
      vec2 gradVec = t - f;
      float dist = dot(v_textureCoords.xy * u_dimensions - f, gradVec) / dot(gradVec, gradVec);
      vec4 colorOut = getGradientColor(dist);
      vec3 blendedRGB = mix(color.rgb, colorOut.rgb, clamp(colorOut.a, 0.0, 1.0));
      gl_FragColor = vec4(blendedRGB, color.a);
    }
  `;
  },
};