import * as I from 'immutable';
import mapValues from 'lodash.mapvalues';

import {arrayUnique, compose} from '@avocado/core';
import {QuadTree, Rectangle, Vector} from '@avocado/math';
import {EventEmitter} from '@avocado/mixins';
import {Synchronized} from '@avocado/state';

import {create} from '../index';

const decorate = compose(
  EventEmitter,
);

export class EntityList extends decorate(Synchronized) {

  constructor() {
    super();
    this._entities = {};
    this._quadTree = new QuadTree();
    this._uuidMap = {};
  }

  *[Symbol.iterator]() {
    for (const uuid in this._entities) {
      const entity = this._entities[uuid];
      yield entity;
    }
  }

  addEntity(entity) {
    const uuid = entity.instanceUuid;
    this._entities[uuid] = entity;
    this.state = this.state.set(uuid, entity.state);
    entity.addTrait('listed');
    entity.list = this;
    entity.once('destroyed', () => {
      this.removeEntity(entity);
    });
    this.emit('entityAdded', entity);
  }

  destroy() {
    for (const entity of this) {
      entity.destroy();
    }
  }

  findEntity(uuid) {
    if (this._uuidMap[uuid]) {
      return this._entities[this._uuidMap[uuid]];
    }
    if (this._entities[uuid]) {
      return this._entities[uuid];
    }
  }

  patchStateStep(uuid, step) {
    const localUuid = this._uuidMap[uuid];
    const entity = this._entities[localUuid];
    if (entity) {
      if ('remove' === step.op) {
        // Entity removed.
        this.removeEntity(entity);
      }
      else {
        // Exists; patch.
        entity.patchState([step]);
      }
    }
    else {
      // New entity. Create with patch as traits.
      const newEntity = create().fromJSON({
        traits: step.value,
      });
      this._uuidMap[uuid] = newEntity.instanceUuid;
      this.addEntity(newEntity);
    }
  }

  get quadTree() {
    return this._quadTree;
  }

  removeEntity(entity) {
    const uuid = entity.instanceUuid;
    delete this._entities[uuid];
    this.state = this.state.delete(uuid);
    this.emit('entityRemoved', entity);
    if (entity.is('listed')) {
      entity.removeTrait('listed');
    }
  }

  tick(elapsed) {
    for (const uuid in this._entities) {
      const entity = this._entities[uuid];
      entity.tick(elapsed);
    }
    this.state = this.state.withMutations((state) => {
      for (const uuid in this._entities) {
        const entity = this._entities[uuid];
        state.set(uuid, entity.state);
      }
    });
  }

  visibleEntities(query) {
    const quadTree = this._quadTree;
    const entities = quadTree.search(query).map((node) => {
      return node.data[2];
    });
    // Hitting multiple points for each entity can return duplicates.
    return arrayUnique(entities);
  }

}

export {EntityListView} from './view';