import { gl_Colors_template } from "./render-utils";

class ShaderMaker {
    /**
     * 
     * @param {'VERTEX_SHADER' | 'FRAGMENT_SHADER'} type 
     * @param {string} source 
     */
    constructor(type, source) {
        this.type = type;
        this.source = source;
    }

    /**
     * @param {WebGL2RenderingContext} gl
     * @return {WebGLShader}
     */
    make(gl) {
        const shader = gl.createShader(gl[this.type]);
        gl.shaderSource(shader, this.source);
        gl.compileShader(shader);
        const ok = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
        if (!ok) {
            console.log('创建类型为 ' + type + ' 的着色器失败！');
        }
        return shader;
    }
}

const colorsLength = gl_Colors_template.length << 1;

const vertexShader = new ShaderMaker('VERTEX_SHADER', `#version 300 es
in uvec4 pos;
out vec4 v_color;
uniform vec2 scale;
uniform vec2 offset;
uniform vec4 colors[${colorsLength}];
uniform vec2 shifts[7];          // 基础八位图偏移量，为了性能，pos 只传入整数，需要的坐标负数由该值提供
uniform vec2 widthShifts[8];     // 用于构造线宽的偏移

void main() {
  v_color = colors[pos.z];
  vec2 shift = shifts[pos.y];
  vec2 widthShift = widthShifts[pos.w];
  gl_Position = vec4(
    float(pos.x) * scale.x + offset.x + float(widthShift.x) + shift.y,
    float(shift.x) * scale.y + offset.y + float(widthShift.y),
    1, 1
  );
}`);

const fragmentShader = new ShaderMaker('FRAGMENT_SHADER', `#version 300 es
precision mediump float;
in vec4 v_color;
out vec4 outColor;
void main() {
    outColor = v_color;
}`);


export {
    vertexShader,
    fragmentShader
}