import { unionBy, filter, isNumber, set, cloneDeep} from 'lodash';
import { ItemSelector, EntityItemCommon } from './interfaces';

// IDEA@Taemin: involvedItem에 대한 operation method는 한 번 결정되면 바뀌지 않으므로
//              involveditem과 operation을 한데 묶었다.
export default class Operation {
  method: 'ADD' | 'UPDATE' | 'DELETE';
  itemSelector: ItemSelector;
  requireRead: boolean;
  before: any;
  partialAfter: any;
  after: any;
  resolved: boolean;

  onResolved: (operation: Operation) => void;
  onSetBefore: (operation: Operation) => void;

  constructor(method: 'ADD'|'UPDATE'|'DELETE', itemSelector: ItemSelector, partialItem: Object = {}) {
    this.method = method;
    this.itemSelector = itemSelector;
    this.resolved = false;
    // ---------- ADD ----------
    if (method === 'ADD') {
      this.requireRead = false;
      this.before = {};
      this.partialAfter = partialItem;
      this.after = partialItem;
    // ---------- UPDATE ----------
    } else if (method === 'UPDATE') {
      this.requireRead = true;
      this.before = {};
      this.partialAfter = partialItem;
      this.after = partialItem;
    // ---------- DELETE ----------
    } else if (method === 'DELETE') {
      this.requireRead = true;
      this.before = {};
      this.partialAfter = {};
      this.after = {};
    } else {
      throw Error(`Can't handle method, ${method}`);
    }
  }

  connectToOperationManager(
    onResolved: (operation: Operation) => void,
    onSetBefore: (operation: Operation) => void
  ) {
    this.onResolved = onResolved;
    this.onSetBefore = onSetBefore;
  }

  // set this.before after read
  setBefore(beforeItem: Object) {
    this.before = beforeItem;
    this.updateAfter();
    this.requireRead = false;
    if (this.onSetBefore) this.onSetBefore(this);
  }

  markAsResolved() {
    this.resolved = true;
    if (this.onResolved) this.onResolved(this);
  }

  updateAfter() {
    if (this.method !== 'DELETE') {
      const newAfter = cloneDeep(this.before);
      Object.keys(this.partialAfter).forEach(key => {
        set(newAfter, key, this.partialAfter[key])
      });

      this.after = newAfter;
    }
  }

  throwErrorIfRequireRead(errorMessage: string) {
    if (this.requireRead) {
      throw Error(errorMessage);
    }
  }

  modify(partialItem: Object) {
    // this.throwErrorIfRequireRead("It's danger to modify operation before READ.");

    this.partialAfter = { ...this.partialAfter, ...partialItem };
    this.updateAfter();
  }

  addNumToProp(propKey: string, delta: number) {
    this.throwErrorIfRequireRead("It's danger to modify operation before READ.");

    const deltaNum = +delta; // type-casting for safety
    let beforeNum = +this.after[propKey];
    if (!isNumber(beforeNum) || isNaN(beforeNum)) beforeNum = 0;
    this.partialAfter = { ...this.partialAfter, [propKey]: beforeNum + deltaNum };
    this.updateAfter();
  }

  // newItem에 id가 없을 수도 있으므로 강제로 id를 넣어주기 위해 itemSelector를 받아낸다.
  setItemToProp(propKey: string, newItem: Object, newItemSelector:ItemSelector, limit: number) {
    this.throwErrorIfRequireRead("It's danger to modify operation before READ.");

    const newItemWithId = { ...newItem, id: newItemSelector.id };

    const itemList: Array<EntityItemCommon> = this.partialAfter[propKey] || this.before[propKey] || [];
    const newItemList = unionBy([newItemWithId], itemList, 'id');
    if (limit > 0 && newItemList.length > limit) {
      newItemList.pop();
    }
    this.partialAfter = { ...this.partialAfter, [propKey]: newItemList };
    this.updateAfter();
  }

  delItemFromProp(propKey: string, targetItemSelector:ItemSelector) {
    this.throwErrorIfRequireRead("It's danger to modify operation before READ.");

    const itemList: Array<EntityItemCommon> = this.partialAfter[propKey] || this.before[propKey] || [];
    const newItemList = filter(itemList, item => item.id !== targetItemSelector.id);
    this.partialAfter = { ...this.partialAfter, [propKey]: newItemList };
    this.updateAfter();
  }
}