/**
 * Represents a WebGL shader object and provides a mechanism to load shaders from HTML
 * script tags.
 */

export default class ShaderCompiler {
    /**
     * @param {WebGLRenderingContext}gl
     * @param {{type: string, source: string}}script
     * @return {WebGLShader}
     */
    static compile(gl: WebGLRenderingContext, script: { type: string; source: string }): WebGLShader | null {
        let shader: WebGLShader | null;
        // Now figure out what type of shader script we have, based on its MIME type.
        if (script.type === 'x-shader/x-fragment') {
            shader = gl.createShader(gl.FRAGMENT_SHADER);
        } else if (script.type === 'x-shader/x-vertex') {
            shader = gl.createShader(gl.VERTEX_SHADER);
        } else {
            throw new Error('Unknown shader type: ' + script.type);
        }
        if (!shader) {
            throw new Error('Failed to create shader');
        }

        // Send the source to the shader object.
        gl.shaderSource(shader, script.source);

        // Compile the shader program.
        gl.compileShader(shader);

        // See if it compiled successfully.
        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            throw new Error('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));
        }

        return shader;
    }
}