import * as I from 'immutable';

import {compose} from '@avocado/core';
import {simpleState, Trait} from '@avocado/entity';

const decorate = compose(
  simpleState('informSize'),
);

class InformedBase extends Trait {

  static defaultState() {
    return {
      informSize: [1280, 720],
    };
  }

  destroy() {
    delete this._socket.entity;
    delete this._socket;
  }

  initialize() {
    this._socket = undefined;
    this.lastNearby = I.Set();
  }

  reduceStateDiffForEntityList(diff) {
    // Reduce the entity list.
    const nearbyEntities = this.entity.entitiesToInform();
    const reducedEntityList = {};
    let nearby = I.Set();
    for (const entity of nearbyEntities) {
      nearby = nearby.add(entity);
      const uuid = entity.instanceUuid;
      if (this.lastNearby.has(entity)) {
        // Keep diff.
        if (diff.entityList[uuid]) {
          reducedEntityList[uuid] = diff.entityList[uuid];
        }
      }
      else {
        // Added.
        reducedEntityList[uuid] = entity.state().toJS();
      }
    }
    for (const entity of this.lastNearby.values()) {
      const uuid = entity.instanceUuid;
      if (!nearby.has(entity)) {
        // Removed.
        reducedEntityList[uuid] = false;
      }
    }
    // Track who's nearby.
    this.lastNearby = nearby;
    // Merge the reduction.
    diff = {
      ...diff,
      entityList: reducedEntityList,
    };
    // Remove dead update.
    if (0 === Object.keys(diff.entityList).length) {
      delete diff.entityList;
    }
    return diff;
  }

  get socket() {
    return this._socket;
  }

  set socket(socket) {
    this._socket = socket;
  }

  methods() {
    return {

      entitiesToInform: () => {
        const informSize = this.entity.informSize.toJS();
        return this.entity.nearbyEntities(informSize);
      },

      inform: (diff) => {
        // Remove dead updates.
        if (0 === Object.keys(diff).length) {
          return;
        }
        this._socket.send({
          type: 'state-update',
          payload: diff,
        });
      },

      reduceStateDiff: (diff) => {
        return this.reduceStateDiffForEntityList(diff);
      },

    };
  }

}

export class Informed extends decorate(InformedBase) {}