import { ExchangeRate } from '@arrow/bom/core';
import { CartHandoverService } from '@arrow/bom/core';
import { ConfigService } from '@arrow/bom/config';
import { Utils } from '@arrow/bom/core';
import { Pipe, PipeTransform, OnDestroy } from '@angular/core';
import { DecimalPipe } from '@angular/common';
import { Observable, of, BehaviorSubject, Subscription } from 'rxjs';

@Pipe({
  name: 'currencyConverter'
})
export class CurrencyConverterPipe implements PipeTransform, OnDestroy {
  private exchangeRates: Array<ExchangeRate> = [];
  private exchangeRate: ExchangeRate;
  private subscriptions: Subscription[] = [];
  private decimalFormat: string = null;

  constructor(
    private cartHandover: CartHandoverService,
    private config: ConfigService,
    private decimalPipe: DecimalPipe,
    private utils: Utils
  ) {}

  ngOnDestroy(): void {
    this.subscriptions.forEach(sub => sub.unsubscribe());
  }

  private _getFinalString(curSymbol: string, convertedPrice: number): string {
    // Sometimes we get a null/invalid number. This prevents a "$NULL" string from showing up
    if (convertedPrice > 0) {
      return (
        curSymbol +
        this.decimalPipe.transform(convertedPrice, this.decimalFormat)
      );
    } else {
      return '...';
    }
  }

  private _setExchangeRate(): void {
    this.exchangeRate = this.exchangeRates.find(
      (rate: ExchangeRate) =>
        rate.currencyCode === this.config.userSelectedCurrency
    );
  }

  private _getConvertedValue(defaultCurrencyVal: number): number {
    return this.exchangeRate.exchangeRate * defaultCurrencyVal;
  }

  /**
   *
   * @param val the value in default currency (USD)
   * @param format how to format the number, this gets fed directly into the Angular "DecimalPipe"
   * @param showCurrencyCode  whether to show the 3 letter currency code or just the
   *                          symbol (e.g. if the currency is USD and this is false, then the
   *                          output of this pipe will be "$ X.XX" rather than "USD X.XX")
   */
  transform(
    val: number,
    format: string,
    showCurrencyCode = true
  ): Observable<string | number> {
    this.decimalFormat = format;

    if (this.config.getTarget() === 'myarrow') {
      const displayCurrency = this.utils.getCurrencySymbol(
        this.config.userSelectedCurrency
      );
      const finalString = this._getFinalString(displayCurrency, val);
      return of(showCurrencyCode ? finalString : val);
    }

    // If currency is default (USD). No conversion needed.
    if (this.config.userSelectedCurrency === this.config.defaultCurrency) {
      const displayCurrency = this.utils.getCurrencySymbol(
        this.config.defaultCurrency
      );
      return of(
        showCurrencyCode ? this._getFinalString(displayCurrency, val) : val
      );
    }

    const returnSubject: BehaviorSubject<string | number> = new BehaviorSubject<
      string | number
    >('');
    const returnObservable$: Observable<
      string | number
    > = returnSubject.asObservable();

    this.subscriptions.push(
      this.cartHandover.exchangeRatesBehaveSub.subscribe(
        (response: ExchangeRate[]) => {
          this.exchangeRates = response;
          if (this.exchangeRates && this.exchangeRates.length > 0) {
            this._setExchangeRate();
            const convertedVal = this._getConvertedValue(val);
            const displayCurrency = this.utils.getCurrencySymbol(
              this.exchangeRate.currencyCode
            );
            const finalValue = showCurrencyCode
              ? this._getFinalString(displayCurrency, convertedVal)
              : convertedVal;
            returnSubject.next(finalValue);
          } else {
            returnSubject.next('...');
          }
        },
        () => {
          const displayCurrency = this.utils.getCurrencySymbol(
            this.config.defaultCurrency
          );
          const finalValue = showCurrencyCode
            ? this._getFinalString(displayCurrency, val)
            : val;
          returnSubject.next(finalValue);
        }
      )
    );

    return returnObservable$;
  }

  private getDisplayCurrency(
    currencyCode: string,
    showCurrencyCode: boolean
  ): string {
    if (showCurrencyCode) {
      return currencyCode;
    } else {
      return this.utils.getCurrencySymbol(currencyCode);
    }
  }
}