tuna/frontend/src/services/PurchaseFlowService.ts

import { PricingCalculation } from './PricingService';

export interface PurchaseStep {
  id: string;
  title: string;
  description: string;
  completed: boolean;
  current: boolean;
  error?: string;
}

export interface PurchaseFlowState {
  currentStep: number;
  steps: PurchaseStep[];
  calculation: PricingCalculation | null;
  paymentIntentId: string | null;
  clientSecret: string | null;
  error: any;
  isProcessing: boolean;
}

export class PurchaseFlowService {
  private static readonly STEPS: Omit<PurchaseStep, 'completed' | 'current' | 'error'>[] = [
    {
      id: 'quantity-selection',
      title: 'Select Tokens',
      description: 'Choose the number of tokens you want to purchase'
    },
    {
      id: 'pricing-calculation',
      title: 'Calculate Price',
      description: 'Review pricing and available discounts'
    },
    {
      id: 'payment-method',
      title: 'Payment Method',
      description: 'Select your preferred payment method'
    },
    {
      id: 'payment-processing',
      title: 'Process Payment',
      description: 'Complete your payment securely'
    },
    {
      id: 'confirmation',
      title: 'Confirmation',
      description: 'Payment successful and tokens allocated'
    }
  ];

  /**
   * Initialize the purchase flow
   */
  static initializeFlow(): PurchaseFlowState {
    const steps = this.STEPS.map((step, index) => ({
      ...step,
      completed: false,
      current: index === 0,
      error: undefined
    }));

    return {
      currentStep: 0,
      steps,
      calculation: null,
      paymentIntentId: null,
      clientSecret: null,
      error: null,
      isProcessing: false
    };
  }

  /**
   * Move to the next step
   */
  static nextStep(state: PurchaseFlowState): PurchaseFlowState {
    const newState = { ...state };
    
    if (newState.currentStep < newState.steps.length - 1) {
      // Mark current step as completed
      newState.steps[newState.currentStep] = {
        ...newState.steps[newState.currentStep],
        completed: true,
        current: false
      };

      // Move to next step
      newState.currentStep += 1;
      newState.steps[newState.currentStep] = {
        ...newState.steps[newState.currentStep],
        current: true
      };
    }

    return newState;
  }

  /**
   * Move to the previous step
   */
  static previousStep(state: PurchaseFlowState): PurchaseFlowState {
    const newState = { ...state };
    
    if (newState.currentStep > 0) {
      // Mark current step as not current
      newState.steps[newState.currentStep] = {
        ...newState.steps[newState.currentStep],
        current: false
      };

      // Move to previous step
      newState.currentStep -= 1;
      newState.steps[newState.currentStep] = {
        ...newState.steps[newState.currentStep],
        current: true,
        completed: false // Allow editing previous step
      };
    }

    return newState;
  }

  /**
   * Jump to a specific step
   */
  static goToStep(state: PurchaseFlowState, stepIndex: number): PurchaseFlowState {
    const newState = { ...state };
    
    if (stepIndex >= 0 && stepIndex < newState.steps.length) {
      // Reset all steps
      newState.steps = newState.steps.map((step, index) => ({
        ...step,
        completed: index < stepIndex,
        current: index === stepIndex,
        error: undefined
      }));

      newState.currentStep = stepIndex;
    }

    return newState;
  }

  /**
   * Set error for current step
   */
  static setStepError(state: PurchaseFlowState, error: any): PurchaseFlowState {
    const newState = { ...state };
    
    newState.steps[newState.currentStep] = {
      ...newState.steps[newState.currentStep],
      error: error?.message || 'An error occurred'
    };

    newState.error = error;
    return newState;
  }

  /**
   * Clear error for current step
   */
  static clearStepError(state: PurchaseFlowState): PurchaseFlowState {
    const newState = { ...state };
    
    newState.steps[newState.currentStep] = {
      ...newState.steps[newState.currentStep],
      error: undefined
    };

    newState.error = null;
    return newState;
  }

  /**
   * Set processing state
   */
  static setProcessing(state: PurchaseFlowState, isProcessing: boolean): PurchaseFlowState {
    return {
      ...state,
      isProcessing
    };
  }

  /**
   * Set calculation data
   */
  static setCalculation(state: PurchaseFlowState, calculation: PricingCalculation): PurchaseFlowState {
    return {
      ...state,
      calculation
    };
  }

  /**
   * Set payment intent data
   */
  static setPaymentIntent(state: PurchaseFlowState, paymentIntentId: string, clientSecret: string): PurchaseFlowState {
    return {
      ...state,
      paymentIntentId,
      clientSecret
    };
  }

  /**
   * Complete the purchase flow
   */
  static completeFlow(state: PurchaseFlowState): PurchaseFlowState {
    const newState = { ...state };
    
    // Mark all steps as completed
    newState.steps = newState.steps.map(step => ({
      ...step,
      completed: true,
      current: false
    }));

    newState.isProcessing = false;
    newState.error = null;

    return newState;
  }

  /**
   * Reset the flow to initial state
   */
  static resetFlow(): PurchaseFlowState {
    return this.initializeFlow();
  }

  /**
   * Get current step info
   */
  static getCurrentStep(state: PurchaseFlowState): PurchaseStep | null {
    return state.steps[state.currentStep] || null;
  }

  /**
   * Check if flow can proceed to next step
   */
  static canProceed(state: PurchaseFlowState): boolean {
    const currentStep = this.getCurrentStep(state);
    if (!currentStep) return false;

    switch (currentStep.id) {
      case 'quantity-selection':
        return state.calculation !== null;
      case 'pricing-calculation':
        return state.calculation !== null;
      case 'payment-method':
        return true; // Payment method selection is always valid
      case 'payment-processing':
        return state.clientSecret !== null;
      case 'confirmation':
        return true; // Confirmation step is always valid
      default:
        return false;
    }
  }

  /**
   * Get progress percentage
   */
  static getProgress(state: PurchaseFlowState): number {
    const completedSteps = state.steps.filter(step => step.completed).length;
    return (completedSteps / state.steps.length) * 100;
  }

  /**
   * Check if flow is completed
   */
  static isCompleted(state: PurchaseFlowState): boolean {
    return state.steps.every(step => step.completed);
  }

  /**
   * Get step by ID
   */
  static getStepById(state: PurchaseFlowState, stepId: string): PurchaseStep | null {
    return state.steps.find(step => step.id === stepId) || null;
  }

  /**
   * Validate current step
   */
  static validateCurrentStep(state: PurchaseFlowState): {
    isValid: boolean;
    error?: string;
  } {
    const currentStep = this.getCurrentStep(state);
    if (!currentStep) {
      return { isValid: false, error: 'Invalid step' };
    }

    switch (currentStep.id) {
      case 'quantity-selection':
        if (!state.calculation) {
          return { isValid: false, error: 'Please select a quantity' };
        }
        break;
      case 'pricing-calculation':
        if (!state.calculation) {
          return { isValid: false, error: 'Please calculate pricing first' };
        }
        break;
      case 'payment-method':
        // Payment method selection is always valid
        break;
      case 'payment-processing':
        if (!state.clientSecret) {
          return { isValid: false, error: 'Payment intent not created' };
        }
        break;
      case 'confirmation':
        // Confirmation step is always valid
        break;
    }

    return { isValid: true };
  }
}