import { AnyAction, Reducer, Store as IStore, StoreListener } from '../interfaces/store';
import { StateChangeSet, State } from '../interfaces/state';
import { ChoiceFull } from '../interfaces/choice-full';
import { GroupFull } from '../interfaces/group-full';
import items from '../reducers/items';
import groups from '../reducers/groups';
import choices from '../reducers/choices';

type ReducerList = { [K in keyof State]: Reducer<State[K]> };

const reducers: ReducerList = {
  groups,
  items,
  choices,
} as const;

export default class Store<T> implements IStore {
  _state: State = this.defaultState;

  _listeners: StoreListener[] = [];

  _txn: number = 0;

  _changeSet?: StateChangeSet;

  _context: T;

  constructor(context: T) {
    this._context = context;
  }

  // eslint-disable-next-line class-methods-use-this
  get defaultState(): State {
    return {
      groups: [],
      items: [],
      choices: [],
    };
  }

  // eslint-disable-next-line class-methods-use-this
  changeSet(init: boolean): StateChangeSet {
    return {
      groups: init,
      items: init,
      choices: init,
    };
  }

  reset(): void {
    this._state = this.defaultState;
    const changes = this.changeSet(true);
    if (this._txn) {
      this._changeSet = changes;
    } else {
      this._listeners.forEach((l) => l(changes));
    }
  }

  subscribe(onChange: StoreListener): this {
    this._listeners.push(onChange);

    return this;
  }

  dispatch(action: AnyAction): void {
    const state = this._state;
    let hasChanges = false;
    const changes = this._changeSet || this.changeSet(false);

    Object.keys(reducers).forEach((key: string) => {
      const stateUpdate = (reducers[key] as Reducer<unknown>)(state[key], action, this._context);
      if (stateUpdate.update) {
        hasChanges = true;
        changes[key] = true;
        state[key] = stateUpdate.state;
      }
    });

    if (hasChanges) {
      if (this._txn) {
        this._changeSet = changes;
      } else {
        this._listeners.forEach((l) => l(changes));
      }
    }
  }

  withTxn(func: () => void): void {
    this._txn++;
    try {
      func();
    } finally {
      this._txn = Math.max(0, this._txn - 1);

      if (!this._txn) {
        const changeSet = this._changeSet;
        if (changeSet) {
          this._changeSet = undefined;
          this._listeners.forEach((l) => l(changeSet));
        }
      }
    }
  }

  /**
   * Get store object
   */
  get state(): State {
    return this._state;
  }

  /**
   * Get items from store
   */
  get items(): ChoiceFull[] {
    return this.state.items;
  }

  /**
   * Get highlighted items from store
   */
  get highlightedActiveItems(): ChoiceFull[] {
    return this.items.filter((item) => !item.disabled && item.active && item.highlighted);
  }

  /**
   * Get choices from store
   */
  get choices(): ChoiceFull[] {
    return this.state.choices;
  }

  /**
   * Get active choices from store
   */
  get activeChoices(): ChoiceFull[] {
    return this.choices.filter((choice) => choice.active);
  }

  /**
   * Get choices that can be searched (excluding placeholders)
   */
  get searchableChoices(): ChoiceFull[] {
    return this.choices.filter((choice) => !choice.disabled && !choice.placeholder);
  }

  /**
   * Get groups from store
   */
  get groups(): GroupFull[] {
    return this.state.groups;
  }

  /**
   * Get active groups from store
   */
  get activeGroups(): GroupFull[] {
    return this.state.groups.filter((group) => {
      const isActive = group.active && !group.disabled;
      const hasActiveOptions = this.state.choices.some((choice) => choice.active && !choice.disabled);

      return isActive && hasActiveOptions;
    }, []);
  }

  inTxn(): boolean {
    return this._txn > 0;
  }

  /**
   * Get single choice by it's ID
   */
  getChoiceById(id: number): ChoiceFull | undefined {
    return this.activeChoices.find((choice) => choice.id === id);
  }

  /**
   * Get group by group id
   */
  getGroupById(id: number): GroupFull | undefined {
    return this.groups.find((group) => group.id === id);
  }
}
