import {mat4} from 'gl-matrix';


import vertexShaderSrc from './default.vs';
import fragmentShaderSrc from './default.fs';


export default class Renderer {
	public gl: WebGLRenderingContext;

	public vertexPosLoc!: number;
	public textureCoordLoc!: number;
	private viewportLoc!: WebGLUniformLocation;
	private translateLoc!: WebGLUniformLocation;
	public samplerLoc!: WebGLUniformLocation;

	private viewport: mat4 = mat4.create();

	private mkContext(): WebGLRenderingContext {
		let gl = (this.canvas.getContext('webgl') || this.canvas.getContext('experimental-webgl')) as WebGLRenderingContext|null;
		if (!gl)
			throw new Error('unable to initialize WebGL context');

		return gl;
	}

	getAttribLocation(program: WebGLProgram, name: string): number {
		let ret = this.gl.getAttribLocation(program, name);
		if (ret < 0)
			throw new Error('unable to get location of attribute \'' + name + '\'');

		return ret;
	}

	getUniformLocation(program: WebGLProgram, name: string): WebGLUniformLocation {
		let ret = this.gl.getUniformLocation(program, name);
		if (!ret)
			throw new Error('unable to get location of uniform \'' + name + '\'');

		return ret;
	}

	createBuffer(): WebGLBuffer {
		let ret = this.gl.createBuffer();
		if (!ret)
			throw new Error('unable to create buffer');

		return ret;
	}

	compileShader(type: number, src: string): WebGLShader {
		let shader = this.gl.createShader(type);
		if (!shader)
			throw new Error('Unable to create shader');

		this.gl.shaderSource(shader, src);
		this.gl.compileShader(shader);

		if (!this.gl.getShaderParameter(shader, this.gl.COMPILE_STATUS)) {
			let err = this.gl.getShaderInfoLog(shader);
			this.gl.deleteShader(shader);
			throw new Error('Unable to compile shader: ' + err);
		}

		return shader;
	}

	private initShaders(): void {
		let shaderProgram = this.gl.createProgram();
		if (!shaderProgram)
			throw new Error('Unable to create shader program');

		let vertexShader = this.compileShader(this.gl.VERTEX_SHADER, vertexShaderSrc);
		let fragmentShader = this.compileShader(this.gl.FRAGMENT_SHADER, fragmentShaderSrc);


		this.gl.attachShader(shaderProgram, vertexShader);
		this.gl.attachShader(shaderProgram, fragmentShader);

		this.gl.linkProgram(shaderProgram);
		if (!this.gl.getProgramParameter(shaderProgram, this.gl.LINK_STATUS)) {
			let err = this.gl.getProgramInfoLog(shaderProgram);

			this.gl.deleteShader(vertexShader);
			this.gl.deleteShader(fragmentShader);
			this.gl.deleteProgram(shaderProgram);

			throw new Error('Unable to link shader: ' + err);
		}

		this.gl.useProgram(shaderProgram);

		this.vertexPosLoc = this.getAttribLocation(shaderProgram, 'aVertexPos');
		this.gl.enableVertexAttribArray(this.vertexPosLoc);

		this.textureCoordLoc = this.getAttribLocation(shaderProgram, 'aTextureCoord');
		this.gl.enableVertexAttribArray(this.textureCoordLoc);

		this.viewportLoc = this.getUniformLocation(shaderProgram, 'uViewport');
		this.translateLoc = this.getUniformLocation(shaderProgram, 'uTranslate');
		this.samplerLoc = this.getUniformLocation(shaderProgram, 'uSampler');
	}

	private setSize(): void {
		let w = this.canvas.width;
		let h = this.canvas.height;

		this.gl.viewport(0, 0, w, h);
		this.gl.clear(this.gl.COLOR_BUFFER_BIT | this.gl.DEPTH_BUFFER_BIT);

		mat4.identity(this.viewport);
		mat4.scale(this.viewport, this.viewport, [2 * 64 / w, -2 * 64 / h, 1.0]);
		this.gl.uniformMatrix4fv(this.viewportLoc, false, this.viewport);

		this.gl.uniform2f(this.translateLoc, -5.0, -5.0);
	}

	constructor(private canvas: HTMLCanvasElement) {
		this.gl = this.mkContext();

		this.initShaders();

		this.gl.clearColor(0.0, 0.0, 0.0, 1.0);

		this.setSize();
	}
}