sg-delivery-customer/app/store/commonreducers/cart/reducer.ts

import { createAction, createReducer } from '@reduxjs/toolkit';
import { CartItem, CatalogItem } from '../../../interfaces';

// ─── State ───────────────────────────────────────────────────────────────────

export interface CartState {
  items: CartItem[];
  couponCode: string | null;
  discount: number;
  providerId: string | null;
  providerName: string | null;
}

const initialState: CartState = {
  items: [],
  couponCode: null,
  discount: 0,
  providerId: null,
  providerName: null,
};

// ─── Actions ─────────────────────────────────────────────────────────────────

export const addItem = createAction<{
  providerId: string;
  providerName: string;
  item: CatalogItem;
}>('cart/addItem');

export const removeItem = createAction<string>('cart/removeItem');
export const clearCart = createAction('cart/clearCart');
export const applyCoupon = createAction<string>('cart/applyCoupon');
export const removeCoupon = createAction('cart/removeCoupon');

// ─── Selector ────────────────────────────────────────────────────────────────

export const selectCartTotal = (state: { cart: CartState }) => {
  const subtotal = state.cart.items.reduce(
    (sum, item) => sum + item.item.price * item.quantity,
    0,
  );
  const deliveryFee = 40;
  const platformFee = 10;
  const discount = state.cart.discount;
  return {
    subtotal,
    deliveryFee,
    platformFee,
    discount,
    total: Math.max(0, subtotal + deliveryFee + platformFee - discount),
    itemCount: state.cart.items.reduce((sum, item) => sum + item.quantity, 0),
  };
};

// ─── Reducer ─────────────────────────────────────────────────────────────────

const cartReducer = createReducer(initialState, builder => {
  builder
    .addCase(addItem, (state, action) => {
      const { providerId, providerName, item } = action.payload;

      // Clear cart if switching providers
      if (state.providerId && state.providerId !== providerId) {
        state.items = [];
      }

      state.providerId = providerId;
      state.providerName = providerName;

      const existing = state.items.find(i => i.item.id === item.id);
      if (existing) {
        existing.quantity += 1;
      } else {
        state.items.push({
          id: `${providerId}-${item.id}`,
          providerId,
          providerName,
          item,
          quantity: 1,
        });
      }
    })
    .addCase(removeItem, (state, action) => {
      const existing = state.items.find(i => i.item.id === action.payload);
      if (existing) {
        if (existing.quantity > 1) {
          existing.quantity -= 1;
        } else {
          state.items = state.items.filter(i => i.item.id !== action.payload);
        }
      }
      if (state.items.length === 0) {
        state.providerId = null;
        state.providerName = null;
      }
    })
    .addCase(clearCart, state => {
      state.items = [];
      state.couponCode = null;
      state.discount = 0;
      state.providerId = null;
      state.providerName = null;
    })
    .addCase(applyCoupon, (state, action) => {
      state.couponCode = action.payload;
      state.discount = 50;
    })
    .addCase(removeCoupon, state => {
      state.couponCode = null;
      state.discount = 0;
    });
});

export default cartReducer;