import { mat4, vec3 } from 'gl-matrix';
import { System } from '@serpentity/serpentity';
import Drawable from '../nodes/drawable';
import Configurable from '../nodes/configurable';
import Cameras from '../nodes/cameras';
import { initializeShaderProgram, initializeBuffers } from '../webgl_utils';

const internals = {
  kDefaultLineLength: 1000,
  kCameraRadius: 5,
  kCameraAngularVelocity: Math.PI / 180,
  kFieldOfView: 45, // degrees
  kNearLimit: 0.1,
  kFarLimit: 100,
  kWidthRatio: 1.5,
  kHeightRatio: 1,
  kTargetVerticalResolution: 1024,
  kVertexShader: `

    attribute vec4 aVertexPosition;
    attribute vec4 aColor;

    varying vec4 vColor;

    uniform mat4 uViewMatrix;
    uniform mat4 uProjectionMatrix;

    void main() {

        gl_Position = uProjectionMatrix * uViewMatrix * aVertexPosition;
        vColor = aColor;
        gl_PointSize = 10.0; // Set the point size
    }
  `,

  kFragmentShader: `

    precision mediump float;
    varying vec4 vColor;

    void main() {

        gl_FragColor = vColor;
    }
  `
};

/**
  * Does all the WebGL rendering. I'm not super familiar with WebGL so I need
  * to revisit this in a while and see how I would restructure this.
  */
export default class WebGLRenderer extends System {

  constructor(canvas) {

    super();
    this.canvas = canvas;
  }

  added(engine){

    // Set up canvas
    const { canvas } = this;
    window.addEventListener('resize', () => this._resizeCanvas(canvas));

    // Set up WebGL
    const gl = canvas.getContext('webgl', {
      preserveDrawingBuffer: true
    });
    this.gl = gl;

    gl.clearColor(0.05882, 0.14902, 0.12157, 1);
    gl.enable(gl.DEPTH_TEST);
    gl.depthFunc(gl.LEQUAL);

    this.colorBuffer = gl.createBuffer();

    const shaderProgram = initializeShaderProgram(
      gl,
      internals.kVertexShader,
      internals.kFragmentShader
    );

    this.programInfo = {
      program: shaderProgram,
      attribLocations: {
        vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
        vertexColor: gl.getAttribLocation(shaderProgram, 'aColor')
      },
      uniformLocations: {
        projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
        viewMatrix: gl.getUniformLocation(shaderProgram, 'uViewMatrix')
      }
    };

    this.buffers = initializeBuffers(gl);
    this._resizeCanvas(canvas);

    this.points = engine.getNodes(Drawable);
    this.positions = [];
    this.colors = [];

    this.configurations = engine.getNodes(Configurable);
    this.cameras = engine.getNodes(Cameras);
  }

  removed(engine){

    delete this.gl;
    delete this.points;
    delete this.colorBuffer;
    delete this.buffers;
    delete this.positions;
    delete this.colors;
    delete this.configurations;
    delete this.cameras;
  }

  update(){

    const {gl, programInfo, buffers} = this;

    gl.useProgram(programInfo.program);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    const fieldOfView = internals.kFieldOfView * Math.PI / 180;
    const aspectRatio = internals.kWidthRatio / internals.kHeightRatio;
    const projectionMatrix = mat4.create();

    mat4.perspective(
      projectionMatrix,
      fieldOfView,
      aspectRatio,
      internals.kNearLimit,
      internals.kFarLimit
    );

    gl.uniformMatrix4fv(
      programInfo.uniformLocations.projectionMatrix,
      false,
      projectionMatrix
    );

    // We only support one camera for now.
    const camera = this.cameras.nodes[0];
    if (camera != undefined) {
      const eye = vec3.fromValues(camera.position.x, camera.position.y, camera.position.z);
      const center = vec3.fromValues(0, 0, 0);
      const up = vec3.fromValues(camera.up.x, camera.up.y, camera.up.z);
      const viewMatrix = mat4.create();
      mat4.lookAt(viewMatrix, eye, center, up);
      gl.uniformMatrix4fv(
        programInfo.uniformLocations.viewMatrix,
        false,
        viewMatrix
      );
    }

    let i = 0;
    for (const point of this.points) {
      this.positions[i] = this.positions[i] || [];
      this.positions[i].push(point.position.x, point.position.y, point.position.z, 1);
      this.positions[i].push(
        point.position.prevX || point.position.x,
        point.position.prevY || point.position.y,
        point.position.prevZ || point.position.z,
        1
      );
      point.position.prevX = point.position.x;
      point.position.prevY = point.position.y;
      point.position.prevZ = point.position.z;

      this.colors[i] = this.colors[i] || [];
      this.colors[i].push(
        0.5 + point.position.z / 4 + point.position.x / 4,
        0.5 + point.position.z / 4 + point.position.y / 4,
        0.75 + point.position.z / 4, 1,
        0.5 + point.position.prevZ / 4 + point.position.prevX / 4,
        0.5 + point.position.prevZ / 4 + point.position.prevY / 4,
        0.75 + point.position.prevZ / 4,1);

      ++i;
    }

    gl.bindBuffer(gl.ARRAY_BUFFER, this.colorBuffer);
    const colors = this.colors.flat();
    gl.bufferData(gl.ARRAY_BUFFER,
      new Float32Array(colors),
      gl.STATIC_DRAW);

    {
      const numberOfComponents = 4;
      const type = gl.FLOAT;
      const normalize = false;
      const stride = 0;
      const offset = 0;

      gl.bindBuffer(gl.ARRAY_BUFFER, this.colorBuffer);
      gl.vertexAttribPointer(
        programInfo.attribLocations.vertexColor,
        numberOfComponents,
        type,
        normalize,
        stride,
        offset
      );
      gl.enableVertexAttribArray(programInfo.attribLocations.vertexColor);
    }

    gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
    const positions = this.positions.flat();
    gl.bufferData(gl.ARRAY_BUFFER,
      new Float32Array(positions),
      gl.STATIC_DRAW);

    {
      const numberOfComponents = 4;
      const type = gl.FLOAT;
      const normalize = false;
      const stride = 0;
      const offset = 0;

      gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
      gl.vertexAttribPointer(
        programInfo.attribLocations.vertexPosition,
        numberOfComponents,
        type,
        normalize,
        stride,
        offset
      );
      gl.enableVertexAttribArray(programInfo.attribLocations.vertexPosition);
    }

    {
      gl.lineWidth(2);
      gl.drawArrays(gl.LINES, 0, positions.length / 4);
    }

    this._cullLines();
  }

  _resizeCanvas(canvas) {

    let width = window.innerWidth;
    let height = Math.round(width * internals.kHeightRatio / internals.kWidthRatio);

    if (window.innerHeight < height) {
      height = window.innerHeight;
      width = Math.round(height * internals.kWidthRatio / internals.kHeightRatio);
    }

    canvas.style.width = `${width}px`;
    canvas.style.height = `${height}px`;

    canvas.width = internals.kTargetVerticalResolution * internals.kWidthRatio;
    canvas.height = internals.kTargetVerticalResolution;

    this.gl.viewport(0, 0, canvas.width, canvas.height);
  }

  _cullLines() {
    const lineLength = this.configurations.nodes[0]?.configuration.lineLength || internals.kDefaultLineLength;

    for (const [i, position] of Object.entries(this.positions)) {
      this.positions[i] = position.slice(-lineLength * 8);
    }

    for (const [i, color] of Object.entries(this.colors)) {
      this.colors[i] = color.slice(-lineLength * 8);
    }
  }
};