/**
 * Sigma.js WebGL Renderer Node Program
 * =====================================
 *
 * Simple program rendering nodes as discs, shaped by triangles using the
 * `gl.TRIANGLES` display mode. So, to draw one node, it will need to store
 * three times the center of the node, with the color, the size and an angle
 * indicating which "corner" of the triangle to draw.
 * It does not extend AbstractNodeProgram, which works very differently, and
 * really targets the gl.POINTS drawing methods.
 * @module
 */
import { NodeDisplayData } from "../../../types";
import { floatColor } from "../../../utils";
import vertexShaderSource from "../shaders/node.vert.glsl";
import fragmentShaderSource from "../shaders/node.frag.glsl";
import { AbstractProgram, RenderParams } from "./common/program";

const POINTS = 3;
const ATTRIBUTES = 5;

const ANGLE_1 = 0;
const ANGLE_2 = (2 * Math.PI) / 3;
const ANGLE_3 = (4 * Math.PI) / 3;

export default class NodeProgram extends AbstractProgram {
  positionLocation: GLint;
  sizeLocation: GLint;
  colorLocation: GLint;
  angleLocation: GLint;

  matrixLocation: WebGLUniformLocation;
  sqrtZoomRatioLocation: WebGLUniformLocation;
  correctionRatioLocation: WebGLUniformLocation;

  constructor(gl: WebGLRenderingContext) {
    super(gl, vertexShaderSource, fragmentShaderSource, POINTS, ATTRIBUTES);

    // Locations
    this.positionLocation = gl.getAttribLocation(this.program, "a_position");
    this.sizeLocation = gl.getAttribLocation(this.program, "a_size");
    this.colorLocation = gl.getAttribLocation(this.program, "a_color");
    this.angleLocation = gl.getAttribLocation(this.program, "a_angle");

    // Uniform Location
    const matrixLocation = gl.getUniformLocation(this.program, "u_matrix");
    if (matrixLocation === null) throw new Error("AbstractNodeProgram: error while getting matrixLocation");
    this.matrixLocation = matrixLocation;

    const sqrtZoomRatioLocation = gl.getUniformLocation(this.program, "u_sqrtZoomRatio");
    if (sqrtZoomRatioLocation === null) throw new Error("NodeProgram: error while getting sqrtZoomRatioLocation");
    this.sqrtZoomRatioLocation = sqrtZoomRatioLocation;

    const correctionRatioLocation = gl.getUniformLocation(this.program, "u_correctionRatio");
    if (correctionRatioLocation === null) throw new Error("NodeProgram: error while getting correctionRatioLocation");
    this.correctionRatioLocation = correctionRatioLocation;

    this.bind();
  }

  bind(): void {
    const gl = this.gl;

    gl.enableVertexAttribArray(this.positionLocation);
    gl.enableVertexAttribArray(this.sizeLocation);
    gl.enableVertexAttribArray(this.colorLocation);
    gl.enableVertexAttribArray(this.angleLocation);

    gl.vertexAttribPointer(
      this.positionLocation,
      2,
      gl.FLOAT,
      false,
      this.attributes * Float32Array.BYTES_PER_ELEMENT,
      0,
    );
    gl.vertexAttribPointer(this.sizeLocation, 1, gl.FLOAT, false, this.attributes * Float32Array.BYTES_PER_ELEMENT, 8);
    gl.vertexAttribPointer(
      this.colorLocation,
      4,
      gl.UNSIGNED_BYTE,
      true,
      this.attributes * Float32Array.BYTES_PER_ELEMENT,
      12,
    );
    gl.vertexAttribPointer(
      this.angleLocation,
      1,
      gl.FLOAT,
      false,
      this.attributes * Float32Array.BYTES_PER_ELEMENT,
      16,
    );
  }

  process(data: NodeDisplayData, hidden: boolean, offset: number): void {
    const array = this.array;
    let i = offset * POINTS * ATTRIBUTES;

    if (hidden) {
      for (let l = i + POINTS * ATTRIBUTES; i < l; i++) array[i] = 0;
      return;
    }

    const color = floatColor(data.color);

    array[i++] = data.x;
    array[i++] = data.y;
    array[i++] = data.size;
    array[i++] = color;
    array[i++] = ANGLE_1;

    array[i++] = data.x;
    array[i++] = data.y;
    array[i++] = data.size;
    array[i++] = color;
    array[i++] = ANGLE_2;

    array[i++] = data.x;
    array[i++] = data.y;
    array[i++] = data.size;
    array[i++] = color;
    array[i] = ANGLE_3;
  }

  render(params: RenderParams): void {
    if (this.hasNothingToRender()) return;

    const gl = this.gl;
    const program = this.program;

    gl.useProgram(program);

    gl.uniformMatrix3fv(this.matrixLocation, false, params.matrix);
    gl.uniform1f(this.sqrtZoomRatioLocation, Math.sqrt(params.ratio));
    gl.uniform1f(this.correctionRatioLocation, params.correctionRatio);

    gl.drawArrays(gl.TRIANGLES, 0, this.array.length / ATTRIBUTES);
  }
}