import { Shader, ShaderAttrs } from "./shader";
import { GlType, GlLocatable } from "./primitives";
import { WgglProgram, WgglProgramShaders, AttrPointers } from "./program";

export class Wggl {
  public canvas: HTMLCanvasElement;
  public gl: WebGLRenderingContext;

  // Programs become dynamic properties on the Wggl instance, this just prevents
  // unwanted types from becoming properties.
  [key: string]:
    | HTMLCanvasElement
    | WebGLRenderingContext
    | WgglProgram
    | Function;

  constructor(
    canvas: HTMLCanvasElement,
    vertShader: Shader,
    fragShader: Shader
  );
  constructor(canvas: HTMLCanvasElement, vertShader: any, fragShader?: Shader) {
    this.canvas = canvas;
    this.gl = canvas.getContext("webgl") as WebGLRenderingContext;

    let programs: WgglProgramShaders;
    if (vertShader && fragShader) {
      programs = { default: [vertShader, fragShader] };
    } else {
      programs = vertShader;
    }

    // do things with programs
    this.setupPrograms(programs);

    this.reset();

    // If there is a default program, "hoist" its methods to the Wggl instance
    // wggl.default.draw() ==> wggl.draw();
    // wggl.default.drawTo() ==> wggl.drawTo();
    if (this.default) {
      const defaultProgram = this.default as WgglProgram;
      this.draw = defaultProgram.draw.bind(this.default);
      this.drawTo = defaultProgram.drawTo.bind(this.default);
    }
  }

  setupPrograms(programs: WgglProgramShaders): void {
    Object.keys(programs).forEach(programName => {
      const [vShader, fShader] = programs[programName];
      const gl = this.gl;

      if (this[programName] != null) {
        console.warn(
          `Skipping program ${programName}. It is either a duplicate program or uses a reserved name`
        );
      }

      const bindPointers: AttrPointers = {};
      const vs = createShader(gl, gl.VERTEX_SHADER, vShader.src);
      const fs = createShader(gl, gl.FRAGMENT_SHADER, fShader.src);
      let program = createProgram(gl, vs, fs);

      mergeAttrs(gl, program, bindPointers, vShader.attrs);
      mergeAttrs(gl, program, bindPointers, fShader.attrs);

      Object.keys(bindPointers).forEach(key => {
        const value = bindPointers[key];
        if (value.parameters.glType === GlType.attribute) {
          value.buffer = gl.createBuffer() as WebGLBuffer;
        }
      });

      this[programName] = new WgglProgram(this.canvas, bindPointers, program);
    });
  }

  public reset(): void {
    const { gl, canvas } = this;
    const scale = Math.min(window.devicePixelRatio, 2);
    canvas.width = Math.floor(canvas.clientWidth * scale);
    canvas.height = Math.floor(canvas.clientHeight * scale);
    gl.viewport(0, 0, canvas.width, canvas.height);
    gl.clearColor(0, 0, 0, 0);
    gl.clear(gl.COLOR_BUFFER_BIT);
  }
}

function mergeAttrs(
  gl: WebGLRenderingContext,
  program: WebGLProgram,
  source: AttrPointers,
  attrs: ShaderAttrs
): void {
  Object.keys(attrs).forEach(attr => {
    if (source[attr] != null) {
      console.warn(
        `Attribute ${attr} is being bound multiple times. Variable names should be unique across shaders and primitives`
      );
    }
    source[attr] = {
      location: locationForAttr(gl, program, attr, attrs[attr]),
      parameters: attrs[attr]
    };
  });
}

function locationForAttr(
  gl: WebGLRenderingContext,
  program: WebGLProgram,
  key: string,
  value: GlLocatable
): WebGLUniformLocation | number {
  switch (value.glType) {
    case GlType.attribute:
      return gl.getAttribLocation(program, key);
    case GlType.uniform:
      return gl.getUniformLocation(program, key) as WebGLUniformLocation;
  }
}

function createShader(
  gl: WebGLRenderingContext,
  type: number,
  source: string
): WebGLShader {
  let shader = gl.createShader(type) as WebGLShader;
  gl.shaderSource(shader, source);
  gl.compileShader(shader);

  const isCompiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);

  if (!isCompiled) {
    const err = gl.getShaderInfoLog(shader) as string;
    gl.deleteShader(shader);
    throw new Error(err);
  }

  return shader;
}

function createProgram(
  gl: WebGLRenderingContext,
  vertexShader: WebGLShader,
  fragmentShader: WebGLShader
): WebGLProgram {
  let program = gl.createProgram() as WebGLProgram;
  gl.attachShader(program, vertexShader);
  gl.attachShader(program, fragmentShader);
  gl.linkProgram(program);

  const isLinked = gl.getProgramParameter(program, gl.LINK_STATUS);

  if (!isLinked) {
    const err = gl.getProgramInfoLog(program) as string;
    gl.deleteProgram(program);
    throw new Error(err);
  }

  return program;
}