import * as I from 'immutable';

import {compose} from '@avocado/core';
import {create as createEntity, EntityList} from '@avocado/entity';
import {EventEmitter, Property} from '@avocado/mixins';
import {StateSynchronizer} from '@avocado/state';

import {Tiles} from './tiles';

const decorate = compose(
  EventEmitter,
  Property('tilesetUri', {
    track: true,
  }),
);

export class Layer extends decorate(class {}) {

  constructor() {
    super();
    this.entityList = new EntityList();
    this._state = I.Map();
    this.tiles = new Tiles();
    // Listeners.
    this.onEntityAddedToLayer = this.onEntityAddedToLayer.bind(this);
    this.onEntityRemovedFromLayer = this.onEntityRemovedFromLayer.bind(this);
    this.entityList.on('entityAdded', this.onEntityAddedToLayer);
    this.entityList.on('entityRemoved', this.onEntityRemovedFromLayer);
    this.onTileDataChanged = this.onTileDataChanged.bind(this);
    this.tiles.on('dataChanged', this.onTileDataChanged);
  }

  addEntity(entity) {
    this.entityList.addEntity(entity);
  }

  destroy() {
    this.entityList.destroy();
    this.entityList.off('entityAdded', this.onEntityAddedToLayer);
    this.entityList.off('entityRemoved', this.onEntityRemovedFromLayer);
  }

  findEntity(uuid) {
    return this.entityList.findEntity(uuid);
  }

  fromJSON(json) {
    if (json.entities) {
      json.entities.forEach((entityJSON) => {
        const entity = createEntity();
        this.entityList.addEntity(entity.fromJSON(entityJSON));
      });
    }
    if (json.tiles) {
      this.tiles.fromJSON(json.tiles)
    }
    if (json.tilesetUri) {
      this.tilesetUri = json.tilesetUri;
    }
    return this;
  }

  onEntityAddedToLayer(entity) {
    entity.addTrait('layered');
    entity.layer = this;
    this.emit('entityAdded', entity)
  }

  onEntityRemovedFromLayer(entity) {
    if (entity.is('layered')) {
      entity.removeTrait('layered');
    }
    this.emit('entityRemoved', entity);
  }

  onTileDataChanged() {
    this.emit('tileDataChanged');
  }

  removeEntity(entity) {
    this.entityList.removeEntity(entity);
  }

  patchState(patch) {
    for (const step of patch) {
      const {op, path, value} = step;
      if ('/' === path) {
        if (value.entityList) {
          this.entityList.patchState([
            {
              op: 'replace',
              path: '/',
              value: value.entityList
            }
          ]);
        }
        if (value.tilesetUri) {
          this.tilesetUri = value.tilesetUri;
        }
        if (value.tiles) {
          this.tiles.patchState([
            {
              op: 'replace',
              path: '/',
              value: value.tiles
            }
          ]);
        }
      }
      else {
        const [key, substep] = StateSynchronizer.forwardStep(step);
        if ('entityList' === key) {
          this.entityList.patchState([substep]);
        }
        if ('tiles' === key) {
          this.tiles.patchState([substep]);
        }
      }
    }
  }

  setTileAt(x, y, tile) {
    this.tiles.setTileAt(x, y, tile);
  }

  get state() {
    return this._state;
  }

  tick(elapsed) {
    if (this.entityList) {
      this.entityList.tick(elapsed);
      this._state = this._state.set('entityList', this.entityList.state);
    }
    this._state = this._state.set('tilesetUri', this.tilesetUri);
    this.tiles.tick(elapsed);
    this._state = this._state.set('tiles', this.tiles.state);
  }

  visibleEntities(query) {
    return this.entityList.visibleEntities(query);
  }

}