class Shaders {
    constructor(gl) {
        this.gl = gl;
        this.shaderNames = [];
        this.shaders = {};
        this.programs = {};
    }

    async loadShader(name, path) {
        this.shaderNames.push(name);
        await this.load(name, path + name + ".vert", this.gl.VERTEX_SHADER);
        await this.load(name, path + name + ".frag", this.gl.FRAGMENT_SHADER);
    }

    async load(name, url, type) {
        let realName = name + "_" + type;
        if (!this.shaders[realName]) {
            let data = await fetch(url);
            let shader = this.createShader(await data.text(), type);
            if (shader) {
                this.shaders[realName] = shader;
            }
        }
        return !!this.shaders[realName];
    }

    getShader(name, type) {
        let realName = name + "_" + type;
        return this.shaders[realName];
    }

    getAllShaders() {
        return this.shaderNames;
    }

    async createProgramForEach(arr) {
        arr = arr || this.shaderNames;
        for (let i = 0; i < arr.length; i++) {
            let shader = arr[i];
            let v = await shaderHandler.createProgram(shader, [shader])
            if (!v) {
                return false;
            }
        }
        return true;
    }

    createShader(source, type) {
        let gl = this.gl;
        let shader = gl.createShader(type);
        gl.shaderSource(shader, source);
        gl.compileShader(shader);
        if (gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            return shader;
        }
        console.error(gl.getShaderInfoLog(shader));
        gl.deleteShader(shader);
        return null;
    }

    createProgram(name, shaders) {
        let gl = this.gl;
        let pro = gl.createProgram();
        for (let i = 0; i < shaders.length; i++) {
            gl.attachShader(pro, this.getShader(shaders[i], gl.VERTEX_SHADER));
            gl.attachShader(pro, this.getShader(shaders[i], gl.FRAGMENT_SHADER));
        }
        gl.linkProgram(pro);
        var success = gl.getProgramParameter(pro, gl.LINK_STATUS);
        if (success) {
            this.programs[name] = pro;
            return pro;
        }

        console.log(gl.getProgramInfoLog(pro));
        gl.deleteProgram(pro);
        return null;
    }

    getProgram(name) {
        return this.programs[name];
    }
}