import * as I from 'immutable';

import {compose} from '@avocado/core';
import {EventEmitter} from '@avocado/mixins';

import {Layer} from './layer';

const decorate = compose(
  EventEmitter,
);

export class Layers extends decorate(class {}) {

  constructor() {
    super();
    this.layers = {};
    this._state = I.Map();
    this.onEntityAddedToLayers = this.onEntityAddedToLayers.bind(this);
    this.onEntityRemovedFromLayers = this.onEntityRemovedFromLayers.bind(this);
  }

  *[Symbol.iterator]() {
    for (const index in this.layers) {
      const layer = this.layers[index];
      yield {index, layer};
    }
  }

  acceptStateChange(change) {
    for (const index in change) {
      const layer = this.layers[index] ? this.layers[index] : new Layer();
      if (!this.layers[index]) {
        this.addLayer(index, layer);
      }
      layer.acceptStateChange(change[index]);
    }
  }

  addEntityToLayer(entity, layerIndex) {
    const layer = this.layers[layerIndex];
    if (!layer) {
      return;
    }
    layer.addEntity(entity);
  }

  addLayer(index, layer) {
    layer.on('entityAdded', this.onEntityAddedToLayers);
    layer.on('entityRemoved', this.onEntityRemovedFromLayers);
    this.layers[index] = layer;
    this.emit('layerAdded', layer, index);
  }

  destroy() {
    for (const index in this.layers) {
      const layer = this.layers[index];
      this.removeLayer(index);
      layer.destroy();
    }
  }

  findEntity(uuid) {
    for (const index in this.layers) {
      const layer = this.layers[index];
      const foundEntity = layer.findEntity(uuid);
      if (foundEntity) {
        return foundEntity;
      }
    }
  }

  fromJSON(json) {
    if (json) {
      for (const index in json) {
        const layerJSON = json[index];
        const layer = new Layer()
        this.addLayer(index, layer);
        layer.fromJSON(layerJSON);
      }
    }
    return this;
  }

  layer(index) {
    return this.layers[index];
  }

  onEntityAddedToLayers(entity) {
    this.emit('entityAdded', entity);
  }

  onEntityRemovedFromLayers(entity) {
    this.emit('entityRemoved', entity);
  }

  removeEntityFromLayer(entity, layerIndex) {
    const layer = this.layers[layerIndex];
    if (!layer) {
      return;
    }
    layer.removeEntity(entity);
  }

  removeLayer(index) {
    const layer = this.layers[index];
    if (!layer) {
      return;
    }
    layer.off('entityAdded', this.onEntityAddedToLayers);
    layer.off('entityRemoved', this.onEntityRemovedFromLayers);
    delete this.layers[index];
    this.emit('layerRemoved', layer, index);
  }

  get state() {
    return this._state;
  }

  tick(elapsed) {
    if (this.layers) {
      for (const index in this.layers) {
        const layer = this.layers[index];
        layer.tick(elapsed);
        this._state = this._state.set(index, layer.state);
      }
    }
  }

}