import { Tool } from '../tool.js';
import { 
  ZOOM_IN_FACTOR,
  ZOOM_OUT_FACTOR,
} from '../config.js';

export class Zoom extends Tool {
  constructor(toolbar) {
    super(toolbar);

    const zoomOut = document.createElement('button');
    const zoomIn = document.createElement('button');
    const zoomAll = document.createElement('button');
    const zeroNetMomentum = document.createElement('button');

    this.div.appendChild(zoomOut);
    this.div.appendChild(zoomIn);
    this.div.appendChild(document.createElement('br'));
    this.div.appendChild(zoomAll);
    this.div.appendChild(document.createElement('br'));
    this.div.appendChild(zeroNetMomentum);

    zoomAll.classList.add('wide');
    zeroNetMomentum.classList.add('wide');

    zoomOut.innerHTML = '<h2>Zoom<br>Out</h2>';
    zoomIn.innerHTML = '<h2>Zoom<br>In</h2>';
    zoomAll.innerHTML = '<h2>Zoom to Fit</h2>';
    zeroNetMomentum.innerHTML = '<h2>Zero Net Momentum</h2>';

    zoomOut.addEventListener('click', (e) => {
      // Aim at center of view
      const x = this.sim.display.width * this.sim.display.scale / 2;
      const y = this.sim.display.height * this.sim.display.scale / 2;
      this.sim.scheduleZoom({x, y}, ZOOM_OUT_FACTOR);
    });

    zoomIn.addEventListener('click', (e) => {
      // Aim at center of view
      const x = this.sim.display.width * this.sim.display.scale / 2;
      const y = this.sim.display.height * this.sim.display.scale / 2;
      this.sim.scheduleZoom({x, y}, ZOOM_IN_FACTOR);
    });

    zoomAll.addEventListener('click', (e) => {
      // Determine bounding box
      const box = this.sim.objects.boundingBox;
      const x = (box.start.x + box.end.x) / 2;
      const y = (box.start.y + box.end.y) / 2;
      if (box.start.x !== box.end.x && box.start.y !== box.end.y) {
        const widthRatio = Math.abs(box.start.x - box.end.x) / this.sim.display.width;
        const heightRatio = Math.abs(box.start.y - box.end.y) / this.sim.display.height;
        const biggerRatio = Math.max(widthRatio, heightRatio);
        if (biggerRatio <= 1) {
          const base2Ratio = Math.log(1/biggerRatio) / Math.log(2);
          this.sim.scheduleZoom({x, y}, Math.floor(base2Ratio));
        } else {
          const base2Ratio = Math.log(1/biggerRatio) / Math.log(2);
          this.sim.scheduleZoom({x, y}, Math.ceil(base2Ratio));
        }
      }
    });

    zeroNetMomentum.addEventListener('click', (e) => {
      const { objects } = this.sim.objects;

      // Find total momentum
      let totalMomentum = objects.reduce((total, obj) => {
        const px = obj.mass * obj.velocity.x;
        const py = obj.mass * obj.velocity.y;
        return {
          x: total.x + px,
          y: total.y + py,
        };
      }, {x: 0, y: 0});

      // Find average momentum
      let averageMomentum = {
        x: totalMomentum.x / objects.length,
        y: totalMomentum.y / objects.length,
      };

      // Subtract average from each
      for (let i = 0; i < objects.length; i++) {
        const obj = objects[i];
        obj.velocity.x -= averageMomentum.x / obj.mass;
        obj.velocity.y -= averageMomentum.y / obj.mass;
      }
    });
  }
}