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

export class Zoom extends Tool {
  get displayScale() {
    return this.sim.getScaleDisplay();
  }

  get displayScaleText() {
    return `Scale: ${this.displayScale}`;
  }

  constructor(toolbar) {
    super(toolbar);

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

    this.div.appendChild(currentScale);
    this.div.appendChild(zoomOut);
    this.div.appendChild(zoomIn);
    this.div.appendChild(zoomAll);
    this.div.appendChild(zeroVelocity);

    zoomAll.classList.add(WIDE_CLASSNAME);
    zeroVelocity.classList.add(WIDE_CLASSNAME);
    currentScale.classList.add(WIDE_CLASSNAME);
    currentScale.classList.add(TOOL_INFO_CLASSNAME);

    zoomOut.innerHTML = 'Zoom<br>Out';
    zoomIn.innerHTML = 'Zoom<br>In';
    zoomAll.innerHTML = 'Zoom to Fit';
    zeroVelocity.innerHTML = 'Zero Momentum';
    currentScale.innerHTML = this.displayScaleText;

    this.sim.onZoom(() => {
      currentScale.innerHTML = this.displayScaleText;
    });

    zoomOut.addEventListener('click', () => {
      // 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(this.sim.screenToSim(x, y), ZOOM_OUT_FACTOR);
    });

    zoomIn.addEventListener('click', () => {
      // 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(this.sim.screenToSim(x, y), ZOOM_IN_FACTOR);
    });

    zoomAll.addEventListener('click', () => {
      // 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;
      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);
      const base2factor = Math.log(1/biggerRatio) / Math.log(2) - 1;
      const factor = Math.floor(base2factor);
      // Determine average momentum and set panning velocity to match
      const netMomentum = {x: 0, y: 0};
      let totalMass = 0;
      let count = 0;
      this.sim.objects.forEachObject(obj => {
        count++;
        netMomentum.x += obj.mass * obj.velocity.x;
        netMomentum.y += obj.mass * obj.velocity.y;
        totalMass += obj.mass;
      });
      if (!count) {
        return;
      }
      const netVelocity = {
        x: netMomentum.x / totalMass,
        y: netMomentum.y / totalMass,
      };
      this.sim.scheduleZoom({x, y}, factor, netVelocity)
    });

    zeroVelocity.addEventListener('click', () => {
      // Determine average momentum
      const netMomentum = {x: 0, y: 0};
      let totalMass = 0;
      let count = 0;
      this.sim.objects.forEachObject(obj => {
        count++;
        netMomentum.x += obj.mass * obj.velocity.x;
        netMomentum.y += obj.mass * obj.velocity.y;
        totalMass += obj.mass;
      });
      if (!count) {
        return;
      }
      const netVelocity = {
        x: netMomentum.x / totalMass,
        y: netMomentum.y / totalMass,
      };
      // Apply offset to all object velocities
      this.sim.objects.forEachObject(obj => {
        obj.velocity.x -= netVelocity.x;
        obj.velocity.y -= netVelocity.y;
      });

      // TODO: Zero net angular momentum

      // Cancel panning
      this.sim.pointer.panning = undefined;
    });
  }
}