puffin-app/src/hooks/useCalculatorState.ts

/**
 * useCalculatorState Hook
 *
 * Persists calculator state in localStorage to survive page reloads,
 * browser navigation, and Stripe checkout redirects.
 *
 * State automatically expires after 1 hour to prevent stale data.
 */

import { useState, useEffect } from 'react';

export interface CalculatorState {
  // Calculation type
  calculationType: 'fuel' | 'distance' | 'custom';

  // Distance-based inputs
  distance: string;
  speed: string;
  fuelRate: string;

  // Fuel-based inputs
  fuelAmount: string;
  fuelUnit: 'liters' | 'gallons';

  // Custom amount input
  customAmount: string;

  // Offset order settings
  offsetPercentage: number;
  portfolioId?: number;

  // Metadata
  timestamp: number; // Used for auto-expiry
}

const STORAGE_KEY = 'puffin_calculator_state';
const EXPIRY_MS = 60 * 60 * 1000; // 1 hour (per user preference)

/**
 * Custom hook for calculator state persistence
 *
 * @returns Object with state, saveState, and clearState functions
 */
export function useCalculatorState() {
  const [state, setState] = useState<CalculatorState | null>(null);
  const [isLoaded, setIsLoaded] = useState(false);

  // Load from localStorage on mount
  useEffect(() => {
    const stored = localStorage.getItem(STORAGE_KEY);

    if (stored) {
      try {
        const parsed = JSON.parse(stored) as CalculatorState;
        const age = Date.now() - parsed.timestamp;

        // Check if state has expired
        if (age < EXPIRY_MS) {
          setState(parsed);
        } else {
          // State expired, clean up
          localStorage.removeItem(STORAGE_KEY);
        }
      } catch (err) {
        // Corrupted data, clean up
        console.warn('Failed to parse calculator state from localStorage:', err);
        localStorage.removeItem(STORAGE_KEY);
      }
    }

    setIsLoaded(true);
  }, []);

  /**
   * Save partial or complete state to localStorage
   * Merges with existing state
   */
  const saveState = (newState: Partial<CalculatorState>) => {
    const updated: CalculatorState = {
      ...(state || {
        calculationType: 'fuel',
        distance: '',
        speed: '12',
        fuelRate: '100',
        fuelAmount: '',
        fuelUnit: 'liters',
        customAmount: '',
        offsetPercentage: 100,
      }),
      ...newState,
      timestamp: Date.now(), // Always update timestamp
    };

    setState(updated);

    try {
      localStorage.setItem(STORAGE_KEY, JSON.stringify(updated));
    } catch (err) {
      console.error('Failed to save calculator state to localStorage:', err);
    }
  };

  /**
   * Clear calculator state from memory and localStorage
   * Call this after successful payment completion
   */
  const clearState = () => {
    setState(null);

    try {
      localStorage.removeItem(STORAGE_KEY);
    } catch (err) {
      console.error('Failed to clear calculator state from localStorage:', err);
    }
  };

  return {
    /** Current calculator state (null if none saved or expired) */
    state,

    /** Whether state has been loaded from localStorage */
    isLoaded,

    /** Save new or partial state */
    saveState,

    /** Clear all saved state */
    clearState,
  };
}