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[rbdr/sorting-hat-renderer] / lib / components / wave_renderer.js

import Vue from 'vue';
import DataService from '../services/data';

/* global window */

const internals = {

  // Constants

  kColors: {
    donatello: 'purple',
    leonardo: 'blue',
    michaelangelo: 'orange',
    raphael: 'red'
  },
  kFrequency: 100,
  kGradientFade: 0.1,
  kMinValue: 25,
  kMaxValue: 100,
  kRandomJitter: 10,
  kTargetFPS: 60,

  // Utility functions

  scale(value, min, max) {

    return ((value - min) / (max - min)) * (internals.kMaxValue - internals.kMinValue) - internals.kMinValue;
  }
};

/**
 * The wave renderer, draws some waves in a canvas to represent a set of
 * cateogirzed averages
 *
 * @class WaveRenderer
 */
export default Vue.component('waveRenderer', {
  template: '<transition name="fade">' +
    '<canvas v-show="state === 1" class="wave-renderer"></canvas>' +
    '</transition>',

  data: DataService.data,

  computed: {

    // Convert from the min / max value in the measurement to a
    // predefined min value between 0 and 100 (see kMinValue and
    // kMaxValue for actual values)

    scaledAverages() {

      const keys = Object.keys(this.runningAverages);

      const averages = keys.reduce((averagesObject, averageCategory) => {

        const runningAverage = this.runningAverages[averageCategory];
        averagesObject[averageCategory] = runningAverage.average;
        return averagesObject;
      }, {});

      const max = Math.max(...Object.values(averages));
      const min = Math.min(...Object.values(averages));

      const scaledAverages = Object.keys(averages).reduce((scaledAveragesObject, averageCategory) => {

        const value = averages[averageCategory];
        scaledAveragesObject[averageCategory] = internals.scale(value, min, max);
        return scaledAveragesObject;
      }, {});

      return scaledAverages;
    }
  },

  methods: {

    // Reset the size of the canvas on resize

    onResize() {

      this.$el.width = window.innerWidth;
      this.$el.height = window.innerHeight;
    }
  },

  // Initiates the animation loop

  mounted() {

    // Make sure we resize, do an initial sizing

    window.addEventListener('resize', this.onResize.bind(this));
    this.onResize();

    // Start the whole animation (Sorry it's a mess)

    const canvas = this.$el;

    const context = canvas.getContext('2d');
    const interval = 1000 / internals.kTargetFPS;

    let lastTimestamp = 0;

    const animationHandler = (timestamp) => {

      window.requestAnimationFrame(animationHandler);
      const delta = timestamp - lastTimestamp;

      if (delta > interval) {

        const keys = Object.keys(this.scaledAverages);
        const values = Object.values(this.scaledAverages);
        const segments = keys.length;
        const period = canvas.width / segments;

        const fillGradient = context.createLinearGradient(0, 0, canvas.width, 0);
        const gradientBandWidth = 1 / segments;

        // Position the drawing cursor left-center of screen

        context.clearRect(0, 0, canvas.width, canvas.height);
        context.beginPath();
        context.moveTo(0, canvas.height);
        context.lineTo(0, canvas.height / 2);

        // Iterate over the segments

        for (let i = 0; i < segments; ++i) {
          const segmentStart = i * period;

          const category = keys[i];
          const magnitude = values[i];
          const segmentHeight = Math.round(Math.random() * internals.kRandomJitter + magnitude * (canvas.height / 2) / 100);

          // Calculate the gradient using the correct color according to
          // scale

          const color = internals.kColors[category] || 'black';
          let currentGradientPosition = i * gradientBandWidth + internals.kGradientFade;
          fillGradient.addColorStop(currentGradientPosition, color);
          currentGradientPosition = (i + 1) * gradientBandWidth - internals.kGradientFade;
          fillGradient.addColorStop(currentGradientPosition, color);

          // This draws the sine wave

          for (let j = 0; j < 180; ++j) {
            const currentPixel = segmentStart + j * period / 180;
            const currentAngle = j + 180 * (i % 2);
            const currentRadians = currentAngle * Math.PI / 180;
            const currentHeight = segmentHeight * Math.sin(internals.kFrequency * currentRadians);

            context.lineTo(currentPixel, currentHeight + canvas.height / 2);
          }
        }

        context.lineTo(canvas.width, canvas.height / 2);
        context.lineTo(canvas.width, canvas.height);
        context.fillStyle = fillGradient;
        context.fill();

        lastTimestamp = timestamp;
      }
    };

    window.requestAnimationFrame(animationHandler);
  }
});