import {mat4} from 'gl-matrix';

import Shaders from './Shaders';

export default class Renderer {
	private readonly gl: WebGLRenderingContext;
	private readonly shaders: Shaders;
	private readonly viewport: mat4 = mat4.create();

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

		this.shaders = new Shaders(this.gl);

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

		this.setSize();
	}

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

		return ret;
	}

	public getContext(): WebGLRenderingContext {
		return this.gl;
	}

	public getVertexPosLoc(): number {
		return this.shaders.vertexPosLoc;
	}

	public getTextureCoordLoc(): number {
		return this.shaders.textureCoordLoc;
	}

	public getSamplerLoc(): WebGLUniformLocation {
		return this.shaders.samplerLoc;
	}

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

		return gl;
	}

	private setSize(): void {
		const w = this.canvas.width;
		const 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.shaders.viewportLoc, false, this.viewport);

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

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

		return ret;
	}

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

		return ret;
	}

	private compileShader(type: number, src: string): WebGLShader {
		const 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)) {
			const err = this.gl.getShaderInfoLog(shader);
			this.gl.deleteShader(shader);
			throw new Error('Unable to compile shader: ' + err);
		}

		return shader;
	}
}