const ParticleImageDisplayer = function(tag_id, canvas_el, params) {
  "use strict";
  this.pImageConfig = {
    particles: {
      array: [],
      density: 100,
      color: '#fff',
      size: {
        value: 2,
        random: false,
      },
      movement: {
        speed: 1,
        restless: {
          enabled: false,
          value: 10,
        }
      },
      interactivity: {
        on_hover: {
          enabled: true,
          action: 'repulse'
        },
        on_click: {
          enabled: false,
          action: 'big_repulse'
        },
        on_touch: {
          enabled: true,
          action: 'repulse'
        },
        fn_array: []
      }
    },
    image: {
      src: {
        path: null,
        is_external: false
      },
      size: {
        canvas_pct: 60,
        min_px: 50,
        max_px: 800
      }
    },
    interactions: {
      repulse: {
        distance: 100,
        strength: 200
      },
      big_repulse: {
        distance: 100,
        strength: 500
      },
      grab: {
        distance: 100,
        line_width: 1,
      }
    },
    canvas: {
      el: canvas_el,
      w: canvas_el.offsetWidth,
      h: canvas_el.offsetHeight
    },
    functions: {
      particles: {},
      image: {},
      canvas: {},
      interactivity: {},
      utils: {}
    },
    mouse: {
      x: null,
      y: null,
      click_x: null,
      click_y: null
    },
  };

  const pImg = this.pImageConfig;
  if (params) {
    Object.deepExtend(pImg, params);
  }

  /*
  ========================================
  =           CANVAS FUNCTIONS           =
  ========================================
  */
  pImg.functions.canvas.init = function() {
    pImg.canvas.context = pImg.canvas.el.getContext('2d');
    pImg.canvas.el.width = pImg.canvas.w;
    pImg.canvas.el.height = pImg.canvas.h;
    pImg.canvas.aspect_ratio = pImg.canvas.w / pImg.canvas.h;
    window.addEventListener('resize', pImg.functions.utils.debounce(pImg.functions.canvas.onResize, 200));
  };

  pImg.functions.canvas.onResize = function() {
    pImg.canvas.w = pImg.canvas.el.offsetWidth;
    pImg.canvas.h = pImg.canvas.el.offsetHeight;
    pImg.canvas.el.width = pImg.canvas.w;
    pImg.canvas.el.height = pImg.canvas.h;
    pImg.canvas.aspect_ratio = pImg.canvas.w / pImg.canvas.h;
    pImg.particles.array = [];
    pImg.functions.image.resize();
    const image_pixels = pImg.functions.canvas.getImagePixels();
    pImg.functions.particles.createImageParticles(image_pixels, true);
  };

  pImg.functions.canvas.clear = function() {
    pImg.canvas.context.clearRect(0, 0, pImg.canvas.w, pImg.canvas.h);
  };

  pImg.functions.canvas.getImagePixels = function() {
    pImg.functions.canvas.clear();
    pImg.canvas.context.drawImage(pImg.image.obj, pImg.image.x, pImg.image.y, pImg.image.obj.width, pImg.image.obj.height);
    const pixel_data = pImg.canvas.context.getImageData(pImg.image.x, pImg.image.y, pImg.image.obj.width, pImg.image.obj.height);
    pImg.functions.canvas.clear();
    return pixel_data;
  };

  /*
  ========================================
  =           IMAGE FUNCTIONS            =
  ========================================
  */
  pImg.functions.image.resize = function() {
    if (pImg.image.aspect_ratio < pImg.canvas.aspect_ratio) {
      // canvas height constrains image size
      pImg.image.obj.height = pImg.functions.utils.clamp(Math.round(pImg.canvas.h * pImg.image.size.canvas_pct / 100), pImg.image.size.min_px, pImg.image.size.max_px);
      pImg.image.obj.width = Math.round(pImg.image.obj.height * pImg.image.aspect_ratio);
    } else {
      // canvas width constrains image size
      pImg.image.obj.width = pImg.functions.utils.clamp(Math.round(pImg.canvas.w * pImg.image.size.canvas_pct / 100), pImg.image.size.min_px, pImg.image.size.max_px);
      pImg.image.obj.height = Math.round(pImg.image.obj.width / pImg.image.aspect_ratio);
    }
    // set x,y coords to center image on canvas
    pImg.image.x = pImg.canvas.w  / 2 - pImg.image.obj.width / 2;
    pImg.image.y = pImg.canvas.h / 2 - pImg.image.obj.height / 2;
  };

  pImg.functions.image.init = function() {
    pImg.image.obj = new Image();
    pImg.image.obj.addEventListener('load', function() {
      // get aspect ratio (only have to compute once on initial load)
      pImg.image.aspect_ratio = pImg.image.obj.width / pImg.image.obj.height;
      pImg.functions.image.resize();
      const img_pixels = pImg.functions.canvas.getImagePixels();
      pImg.functions.particles.createImageParticles(img_pixels);
      pImg.functions.particles.animateParticles();
    });
    pImg.image.obj.src = pImg.image.src.path;
    if (pImg.image.src.is_external) {
      pImg.image.obj.crossOrigin = "anonymous";
    }
  };

  /*
  ========================================
  =          PARTICLE FUNCTIONS          =
  ========================================
  */
  pImg.functions.particles.SingleImageParticle = function(init_xy, dest_xy) {
    this.x = init_xy.x;
    this.y = init_xy.y;
    this.dest_x = dest_xy.x;
    this.dest_y = dest_xy.y;
    this.vx = (Math.random() - 0.5) * pImg.particles.movement.speed;
    this.vy = (Math.random() - 0.5) * pImg.particles.movement.speed;
    this.acc_x = 0;
    this.acc_y = 0;
    this.friction = Math.random() * 0.01 + 0.92;
    this.restlessness = {
      max_displacement: Math.ceil(Math.random() * pImg.particles.movement.restless.value),
      x_jitter: pImg.functions.utils.randIntInRange(-3, 3),
      y_jitter: pImg.functions.utils.randIntInRange(-3, 3),
      on_curr_frame: false
    };
    if (pImg.particles.color instanceof Array) {
      this.color = pImg.particles.color[Math.floor(Math.random() * (pImg.particles.color.length + 1))];
    } else {
      this.color = pImg.particles.color;
    }
    this.radius = Math.round((pImg.particles.size.random ? Math.max(Math.random(), 0.5) : 1) * pImg.particles.size.value);
  };

  pImg.functions.particles.SingleImageParticle.prototype.draw = function() {
    pImg.canvas.context.fillStyle = this.color;
    pImg.canvas.context.beginPath();
    pImg.canvas.context.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false);
    pImg.canvas.context.fill();
  };

  pImg.functions.particles.createImageParticles = function(pixel_data, at_dest = false) {
    const increment = Math.round(pixel_data.width / pImg.particles.density);
    for (let i = 0; i < pixel_data.width; i += increment) {
      for (let j = 0; j < pixel_data.height; j += increment) {
        if (pixel_data.data[(i + j * pixel_data.width) * 4 + 3] > 128) {
          const dest_xy = {x: pImg.image.x + i, y: pImg.image.y + j};
          const init_xy = at_dest ? dest_xy : {x: Math.random() * pImg.canvas.w, y: Math.random() * pImg.canvas.h};
          pImg.particles.array.push(new pImg.functions.particles.SingleImageParticle(init_xy, dest_xy));
        }
      }
    }
  };

  pImg.functions.particles.updateParticles = function() {
    for (let p of pImg.particles.array) {
      if ((pImg.particles.movement.restless.enabled) && (p.restlessness.on_curr_frame)) {
        // if restless activity is enabled & particle is in restless mode, animate some random movement
        pImg.functions.particles.jitterParticle(p);
      } else {
        // otherwise, update position with approach to destination
        p.acc_x = (p.dest_x - p.x) / 500;
        p.acc_y = (p.dest_y - p.y) / 500;
        p.vx = (p.vx + p.acc_x) * p.friction;
        p.vy = (p.vy + p.acc_y) * p.friction;
        p.x += p.vx;
        p.y += p.vy;
      }

      pImg.functions.interactivity.interactWithClient(p);
    }
  };

  pImg.functions.particles.jitterParticle = function(p) {
    p.x += p.restlessness.x_jitter;
    p.y += p.restlessness.y_jitter;
    if (Math.sqrt((p.dest_x - p.x) ** 2 + (p.dest_y - p.y) ** 2) >= pImg.particles.movement.restless.value) {
      p.restlessness.on_curr_frame = false;
    }
  };

  pImg.functions.particles.animateParticles = function() {
    pImg.functions.canvas.clear()
    pImg.functions.particles.updateParticles();
    for (let p of pImg.particles.array) {
      p.draw();
    }
    requestAnimFrame(pImg.functions.particles.animateParticles);
  };

  /*
  ========================================
  =        INTERACTIVITY FUNCTIONS       =
  ========================================
  */
  pImg.functions.interactivity.repulseParticle = function(p, args) {
    // compute distance to mouse
    const dx_mouse = p.x - pImg.mouse.x,
          dy_mouse = p.y - pImg.mouse.y,
          mouse_dist = Math.sqrt(dx_mouse * dx_mouse + dy_mouse * dy_mouse),
          inv_strength = pImg.functions.utils.clamp(300 - args.strength, 10, 300);
    if (mouse_dist <= args.distance) {
      p.acc_x = (p.x - pImg.mouse.x) / inv_strength;
      p.acc_y = (p.y - pImg.mouse.y) / inv_strength;
      p.vx += p.acc_x;
      p.vy += p.acc_y;
    }
  };

  pImg.functions.interactivity.grabParticle = function(p, args) {
    const dx_mouse = p.x - pImg.mouse.x,
          dy_mouse = p.y - pImg.mouse.y,
          mouse_dist = Math.sqrt(dx_mouse * dx_mouse + dy_mouse * dy_mouse);
    if (mouse_dist <= args.distance) {
      pImg.canvas.context.strokeStyle = p.color;
      pImg.canvas.context.lineWidth = Math.min(args.line_width, p.radius * 2);
      pImg.canvas.context.beginPath();
      pImg.canvas.context.moveTo(p.x, p.y);
      pImg.canvas.context.lineTo(pImg.mouse.x, pImg.mouse.y);
      pImg.canvas.context.stroke();
      pImg.canvas.context.closePath();
    }
  };

  pImg.functions.interactivity.onMouseMove = function(func, args, p) {
    if (pImg.mouse.x != null && pImg.mouse.y != null) {
      func(p, args);
    }
  };

  pImg.functions.interactivity.onMouseClick = function(func, args, p) {
    if (pImg.mouse.click_x != null && pImg.mouse.click_y != null) {
      func(p, args);
    }
  };

  pImg.functions.interactivity.addEventListeners = function() {
    if (pImg.particles.interactivity.on_hover.enabled || pImg.particles.interactivity.on_click.enabled) {
      pImg.canvas.el.addEventListener('mousemove', function(e) {
        let pos_x = e.offsetX || e.clientX,
            pos_y = e.offsetY || e.clientY;
        pImg.mouse.x = pos_x;
        pImg.mouse.y = pos_y;
      });
      pImg.canvas.el.addEventListener('mouseleave', function(e) {
        pImg.mouse.x = null;
        pImg.mouse.y = null;
      });
      pImg.functions.utils.addEventActions('on_hover');
    }
    if (pImg.particles.interactivity.on_click.enabled) {
      pImg.canvas.el.addEventListener('mousedown', function(e) {
        pImg.mouse.click_x = pImg.mouse.x;
        pImg.mouse.click_y = pImg.mouse.y;
      });
      pImg.canvas.el.addEventListener('mouseup', function(e) {
        pImg.mouse.click_x = null;
        pImg.mouse.click_y = null;
      });
      pImg.functions.utils.addEventActions('on_click');
    }
    if (pImg.particles.interactivity.on_touch.enabled) {
      pImg.canvas.el.addEventListener('touchmove', function(e) {
        let pos_x = e.touches[0].clientX,
            pos_y = e.touches[0].clientY;
        pImg.mouse.x = pos_x;
        pImg.mouse.y = pos_y;
      });
      pImg.canvas.el.addEventListener('touchend', function(e) {
        pImg.mouse.x = null;
        pImg.mouse.y = null;
      });
      pImg.functions.utils.addEventActions('on_touch');
    }
  };

  pImg.functions.interactivity.interactWithClient = function(p) {
    for (let func of pImg.particles.interactivity.fn_array) {
      func(p);
    }
  };

  /*
  ========================================
  =           UTILS FUNCTIONS            =
  ========================================
  */
  pImg.functions.utils.randIntInRange = function(min, max) {
    return Math.floor(Math.random() * (max - min + 1)) + min;
  };

  pImg.functions.utils.clamp = function(n, min, max) {
    return Math.min(Math.max(n, min), max);
  };

  pImg.functions.utils.debounce = function(func, min_interval) {
    let timer;
    return function(event) {
      if (timer) clearTimeout(timer);
      timer = setTimeout(func, min_interval, event);
    };
  };
  
  pImg.functions.utils.addEventActions = function(event) {
    const action_funcs = {
      repulse: pImg.functions.interactivity.repulseParticle,
      big_repulse: pImg.functions.interactivity.repulseParticle,
      grab: pImg.functions.interactivity.grabParticle
    };
    let event_wrapper = event === 'on_click' ? pImg.functions.interactivity.onMouseClick : pImg.functions.interactivity.onMouseMove;
    if (pImg.particles.interactivity[event].enabled) {
      const func = action_funcs[pImg.particles.interactivity[event].action],
            args = pImg.interactions[pImg.particles.interactivity[event].action];
      const partial_func = event_wrapper.bind(null, func, args);
      pImg.particles.interactivity.fn_array.push(partial_func);
    }
  };

  /*
  ========================================
  =           LAUNCH FUNCTIONS           =
  ========================================
  */
  pImg.functions.launch = function() {
    pImg.functions.interactivity.addEventListeners();
    pImg.functions.canvas.init();
    pImg.functions.image.init();
  };

  if (!pImg.disabled) {
    pImg.functions.launch();
  }
};

/*
========================================
=           GLOBAL FUNCTIONS           =
========================================
*/
Object.deepExtend = function(destination, source) {
  // credit: https://andrewdupont.net/2009/08/28/deep-extending-objects-in-javascript/
  for (let property in source) {
    if (source[property] && source[property].constructor &&
     source[property].constructor === Object) {
      destination[property] = destination[property] || {};
      arguments.callee(destination[property], source[property]);
    } else {
      destination[property] = source[property];
    }
  }
  return destination;
};

window.requestAnimFrame = (function() {
  return  window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame    ||
    window.oRequestAnimationFrame      ||
    window.msRequestAnimationFrame     ||
    function(callback) {
      window.setTimeout(callback, 1000 / 60);
    };
})();

window.cancelRequestAnimFrame = (function() {
  return window.cancelAnimationFrame         ||
    window.webkitCancelRequestAnimationFrame ||
    window.mozCancelRequestAnimationFrame    ||
    window.oCancelRequestAnimationFrame      ||
    window.msCancelRequestAnimationFrame     ||
    clearTimeout
})();

window.pImgDom = [];

window.particleImageDisplay = function(tag_id) {
  // get target element by ID, check for existing canvases
  const pImage_el = document.getElementById(tag_id),
      canvas_classname = 'particle-image-canvas-el',
      existing_canvases = pImage_el.getElementsByClassName(canvas_classname);

  // remove any existing canvases within div
  if (existing_canvases.length) {
    while(existing_canvases.length > 0){
      pImage_el.removeChild(existing_canvases[0]);
    }
  }

  // create canvas element, set size, append to target element
  const canvas_el = document.createElement('canvas');
  canvas_el.className = canvas_classname;
  canvas_el.style.width = "100%";
  canvas_el.style.height = "100%";
  const canvas = document.getElementById(tag_id).appendChild(canvas_el);


  if(canvas != null){
    // get params.json filepath from load parameters from element's data-params-src property
    const params_json = pImage_el.dataset.paramsSrc,
      xhr = new XMLHttpRequest();
    xhr.overrideMimeType("application/json")
    xhr.open("GET", params_json, false);
    xhr.onreadystatechange = function() {
      if (xhr.readyState === 4 && xhr.status === 200) {
        // parse parameters & launch display
        const params = JSON.parse(xhr.responseText);
        pImgDom.push(new ParticleImageDisplayer(tag_id, canvas, params));
      } else {
        console.log(`failed to load params.json. XMLHTTPRequest status: ${xhr.statusText}`);
      }
    };
    xhr.send();
  }
};

window.particleImageDisplay("particle-image");