import * as I from 'immutable';
import isPlainObject from 'is-plain-object';

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

const decorate = compose(
);

export class Informed extends decorate(Trait) {

  initialize() {
    this.entityReducer = this.createIndexedReducer();
    this._informState = I.Map();
    this._sentSelf = false;
    this._socket = undefined;
    this.lastNearby = I.Set();
  }

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

  collapseStateDiff(diff) {
    for (const index in diff) {
      const value = diff[index];
      if (isPlainObject(value)) {
        if (!this.collapseStateDiff(value)) {
          delete diff[index];
        }
      }
    }
    if (0 === Object.keys(diff).length) {
      return null;
    }
    return diff;
  }

  createIndexedReducer() {
    let previous = {};
    return (diff, indexed) => {
      const reducedDiff = {};
      const current = {};
      for (const index in indexed) {
        const item = indexed[index];
        current[index] = item;
        // Diff.
        if (previous[index]) {
          if (diff[index]) {
            reducedDiff[index] = diff[index];
          }
        }
        // Added.
        else {
          reducedDiff[index] = item.state.toJS();
        }
      }
      // Removed.
      for (const index in previous) {
        if (!current[index]) {
          reducedDiff[index] = false;
        }
      }
      previous = current;
      return reducedDiff;
    };
  }

  reduceStateDiff(diff) {
    if (!diff || !diff.room || !diff.room.layers) {
      return diff
    }
    const room = this.entity.room;
    const camera = this.entity.camera;
    for (const index in diff.room.layers) {
      // Index entities.
      const layer = room.layer(index);
      const visibleEntities = layer.visibleEntities(
        camera.rectangle
      );
      const indexedEntities = {};
      for (const entity of visibleEntities) {
        indexedEntities[entity.instanceUuid] = entity;
      }
      // Reduce entities.
      diff.room.layers[index].entityList = this.entityReducer(
        diff.room.layers[index].entityList || {},
        indexedEntities,
      );
    }
    return this.collapseStateDiff(diff);
  }

  get socket() {
    return this._socket;
  }

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

  methods() {
    return {

      inform: (stateSynchronizer) => {
        // Take diff.
        let diff = stateSynchronizer.diff(this._informState);
        diff = this.reduceStateDiff(diff);
        diff = diff ? diff : {};
        this._informState = stateSynchronizer.state;
        // Let the client know who they are.
        if (!this._sentSelf) {
          diff.selfEntity = this.entity.instanceUuid;
          this._sentSelf = true;
        }
        // Remove dead updates.
        if (0 === Object.keys(diff).length) {
          return;
        }
        // Emit!
        this._socket.send({type: 'state-update', payload: diff});
      },

    };
  }

}