import { apiService } from '@/services/api';
import { DEFAULT_MERCHANT, MERCHANT_IDS, type TMerchant } from '@/config/api';
import type {
  TCashierFlowState,
  IApiCurrency,
  IPaymentRequest,
  IFormMetadataField,
} from '../types';
import type { IPaymentMethod } from '@/features/payment-methods/types';
import { getCashierConfig } from '@/config/cashierConfig';

type StateChangeListener = (state: TCashierFlowState) => void;

class CashierService {
  private state: TCashierFlowState = 'loading';
  private methods: IPaymentMethod[] = [];
  private currencies: IApiCurrency[] = [];
  private selectedMethod: IPaymentMethod | null = null;
  private formMetadata: IFormMetadataField[] = [];
  private error: Error | null = null;
  private paymentUrl: string | null = null;
  private listeners: Set<StateChangeListener> = new Set();

  getState(): TCashierFlowState {
    return this.state;
  }

  getMethods(): IPaymentMethod[] {
    return this.methods;
  }

  getCurrencies(): IApiCurrency[] {
    return this.currencies;
  }

  getError(): Error | null {
    return this.error;
  }

  getPaymentUrl(): string | null {
    return this.paymentUrl;
  }

  getSelectedMethod(): IPaymentMethod | null {
    return this.selectedMethod;
  }

  getFormMetadata(): IFormMetadataField[] {
    return this.formMetadata;
  }

  async setSelectedMethod(
    method: IPaymentMethod | null,
    merchant: TMerchant = DEFAULT_MERCHANT
  ): Promise<void> {
    this.selectedMethod = method;
    this.formMetadata = [];

    if (method) {
      try {
        const config = getCashierConfig();
        console.log('config', config);
        const paymentType = config.paymentType || 'deposit';

        // Fetch form metadata and currencies for the selected method in parallel
        const [formMetadataData, currenciesData] = await Promise.all([
          apiService.getFormMetadata(method.code, paymentType, merchant),
          apiService.getCurrencies(merchant, method.code),
        ]);

        this.formMetadata = formMetadataData;
        this.currencies = currenciesData;
      } catch (err) {
        // If form metadata or currencies fetch fails, we still allow method selection
        // Error can be handled by the UI if needed
        console.error('Failed to fetch form metadata or currencies:', err);
      }
    } else {
      // Reset currencies when method is deselected
      // Optionally reload all currencies or keep empty
      this.currencies = [];
    }

    this.notifyListeners();
  }

  private setState(newState: TCashierFlowState): void {
    if (this.state !== newState) {
      this.state = newState;
      this.notifyListeners();
    }
  }

  subscribe(listener: StateChangeListener): () => void {
    this.listeners.add(listener);
    return () => {
      this.listeners.delete(listener);
    };
  }

  private notifyListeners(): void {
    this.listeners.forEach(listener => listener(this.state));
  }

  async loadData(merchant: TMerchant = DEFAULT_MERCHANT): Promise<void> {
    try {
      this.setState('loading');
      this.error = null;

      // Only fetch methods, currencies will be fetched when a method is selected
      const methodsData = await apiService.getMethods(merchant);

      this.methods = methodsData;
      this.currencies = []; // Currencies will be loaded when method is selected
      this.setState('ready');
    } catch (err) {
      this.error = err instanceof Error ? err : new Error('Failed to load cashier data');
      this.setState('error');
      throw this.error;
    }
  }

  async initiatePayment(
    paymentRequest: Omit<IPaymentRequest, 'merchant_id'>,
    merchant: TMerchant = DEFAULT_MERCHANT
  ): Promise<void> {
    try {
      this.setState('submitting');
      this.error = null;

      const fullRequest = {
        ...paymentRequest,
        merchant_id: MERCHANT_IDS[merchant],
      } as IPaymentRequest;

      const response = await apiService.initiatePayment(fullRequest, merchant);

      this.paymentUrl = response.redirect_url;
      this.setState('redirecting');
    } catch (err) {
      this.error = err instanceof Error ? err : new Error('Failed to initiate payment');
      this.setState('error');
      throw this.error;
    }
  }

  reset(): void {
    this.state = 'loading';
    this.selectedMethod = null;
    this.formMetadata = [];
    this.currencies = [];
    this.error = null;
    this.paymentUrl = null;
    this.notifyListeners();
  }

  goBack(): void {
    this.selectedMethod = null;
    this.formMetadata = [];
    this.currencies = [];
    this.error = null;
    // Reset to ready state if we have methods available, otherwise keep current state
    if (this.methods.length > 0) {
      this.setState('ready');
    } else {
      this.notifyListeners();
    }
  }
}

export const cashierService = new CashierService();