<template>
  <div ref="canvasContainer" id="canvasContainer"></div>
</template>

<script>
  import p5 from 'p5';

  export default {
    mounted() {
      this.p5Instance = new p5(this.sketch, this.$refs.canvasContainer);
    },
    beforeDestroy() {
      if (this.p5Instance) {
        this.p5Instance.remove();
      }
    },
    methods: {
      sketch(p) {
        let brushStrokes = [];
        const fadingTime = 2000;
        const brushDensity = 30;
        const textureDensity = 2;
        const brushSize = 4;

        p.setup = () => {
          p.createCanvas(p.windowWidth, p.windowHeight);
          p.clear();
          p.colorMode(p.HSL);
          p.noStroke();
        };

        p.draw = () => {
          p.clear();
          for (let i = brushStrokes.length - 1; i >= 0; i--) {
            let brushStroke = brushStrokes[i];
            let elapsedTime = p.millis() - brushStroke.startTime;
            if (elapsedTime > fadingTime) {
              brushStrokes.splice(i, 1);
              continue;
            }

            let isSwiperOpen;
            let swipers = document.querySelectorAll('.swiper');
            for (let swiper of swipers) {
              if (swiper.style.opacity == 1) isSwiperOpen = true;
            }



            if (!isSwiperOpen) {
              let alpha = p.map(elapsedTime, 0, fadingTime, 1, 0);
              
              
              for (let j = 0; j < brushStroke.dots.length; j++) {
                p.fill(
                  brushStroke.dots[j].color.h,
                  brushStroke.dots[j].color.s,
                  brushStroke.dots[j].color.l,
                  alpha);
  
                p.ellipse(
                  brushStroke.dots[j].x,
                  brushStroke.dots[j].y,
                  brushStroke.dots[j].size,
                  brushStroke.dots[j].size
                );
              }
            }
            }
            
        };

        p.mouseMoved = () => {
          let dots = [];
          for (let j = 0; j < brushDensity; j++) {
            let angle = p.random(p.TWO_PI);
            let r = p.sqrt(p.pow(p.random(1), 2)) * gaussian(brushSize, 3);
            let x = p.mouseX + r * p.cos(angle);
            let y = p.mouseY + r * p.sin(angle);
            dots.push({ 
              x: x,
              y: y,
              size: p.random(1) * textureDensity,
              color: {
                h: 178,
                s: 20,
                l: constrainedGaussian(22, 10, 10, 100)
              }
            });
          }
          brushStrokes.push({
            x: p.mouseX,
            y: p.mouseY,
            startTime: p.millis(),
            dots: dots
          });
        }

        function gaussian(mean, sd) {
          let u1 = p.random();
          let u2 = p.random();
          let z0 = p.sqrt(-2.0 * p.log(u1)) * p.cos(p.TWO_PI * u2);
          return z0 * sd + mean;
        }

        function constrainedGaussian(mean, sd, min, max) {
          let value;
          do {
            value = gaussian(mean, sd);
          } while (value < min || value > max);
          return value;
        }
      }

    },

  }  
</script>

<style scoped>
    #canvasContainer {
        pointer-events: none;
        top: 0;
        left: 0;
        z-index: 2;
        position: fixed;
        width: 100vw;
        height: 100vh;
    }
</style>