import * as I from 'immutable';

import {Resource} from '@avocado/resource';
import {Vector} from '@avocado/math';
import {Property} from '@avocado/mixins';

export class Trait {

  constructor(entity, params, state) {
    this.entity = entity;
    this.params = I.fromJS(this.constructor.defaultParams()).merge(params);
    this.state = I.fromJS(this.constructor.defaultState()).merge(state);
  }

  acceptStateChange(change) {
    if (!change.state) {
      return;
    }
    const undefinedProperties = {};
    for (const key in change.state) {
      const value = change.state[key];
      if (key in this.entity) {
        this.entity[key] = value;
      }
      else {
        undefinedProperties[key] = value;
      }
    }
    this.state = this.state.merge(undefinedProperties);
  }

  destroy() {}

  hooks() {
    return {};
  }

  hydrate() {
    return Promise.resolve();
  }

  initialize() {}

  label() {
    return this.constructor.name;
  }

  listeners() {
    return {};
  }

  methods() {
    return {};
  }

  toJSON() {
    return {
      params: this.params.toJS(),
      state: this.state.toJS(),
    };
  }

  static contextType() {
    return {};
  }

  static defaultParams() {
    return {};
  }

  static defaultState() {
    return {};
  }

  static dependencies() {
    return [];
  }

  static type() {
    return this.name.toLowerCase();
  }

}

export function StateProperty(key, meta = {}) {
  return (Superclass) => {
    meta.emit = meta.emit || function(...args) {
      this.entity.emit(...args);
    };
    meta.get = meta.get || function(value) {
      return this.state.get(key);
    };
    meta.set = meta.set || function(value) {
      this.state = this.state.set(key, value);
    };
    return Property(key, meta)(Superclass);
  }
}

StateProperty.Vector = (vector, x, y, meta = {}) => {
  return (Superclass) => {
    meta.default = undefined;
    meta.emit = meta.emit || function(...args) {
      this.entity.emit(...args);
    };
    meta.get = meta.get || function() {
      return [
        this.state.get(x),
        this.state.get(y),
      ];
    };
    meta.set = meta.set || function(vector) {
      if (meta.track && meta.emit) {
        if (this.state.get(x) !== vector[0]) {
          meta.emit.call(this, `${x}Changed`, this.state.get(x), vector[0]);
        }
        if (this.state.get(y) !== vector[1]) {
          meta.emit.call(this, `${y}Changed`, this.state.get(y), vector[1]);
        }
      }
      this.state = this.state.merge({
        [x]: vector[0],
        [y]: vector[1],
      });
    };
    return Vector.Mixin(vector, x, y, meta)(Superclass);
  };
}