BILLING SYSTEM

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Define structures to represent customer and product
struct Customer {
    int id;
    char name[50];
};

struct Product {
    int id;
    char name[50];
    float price;
};

// Define structures to represent a line item in an invoice
struct InvoiceItem {
    struct Product product;
    int quantity;
};

// Define a structure for an invoice
struct Invoice {
    struct Customer customer;
    struct InvoiceItem items[10];  // Assume a maximum of 10 items per invoice
    int itemCount;
};

// Function prototypes
void displayMenu();
void addCustomer();
void addProduct();
void generateInvoice();

// Global arrays to store customers and products
struct Customer customers[10];
struct Product products[10];
int customerCount = 0;
int productCount = 0;

int main() {
    int choice;

    do {
        displayMenu();
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                addCustomer();
                break;
            case 2:
                addProduct();
                break;
            case 3:
                generateInvoice();
                break;
            case 4:
                printf("Exiting the billing system. Goodbye!\n");
                break;
            default:
                printf("Invalid choice. Please enter a valid option.\n");
        }
    } while (choice != 4);

    return 0;
}

void displayMenu() {
    printf("\n=== Billing System Menu ===\n");
    printf("1. Add Customer\n");
    printf("2. Add Product\n");
    printf("3. Generate Invoice\n");
    printf("4. Exit\n");
}

void addCustomer() {
    if (customerCount < 10) {
        printf("Enter customer name: ");
        scanf("%s", customers[customerCount].name);
        customers[customerCount].id = customerCount + 1;
        customerCount++;
        printf("Customer added successfully.\n");
    } else {
        printf("Maximum number of customers reached.\n");
    }
}

void addProduct() {
    if (productCount < 10) {
        printf("Enter product name: ");
        scanf("%s", products[productCount].name);
        printf("Enter product price: ");
        scanf("%f", &products[productCount].price);
        products[productCount].id = productCount + 1;
        productCount++;
        printf("Product added successfully.\n");
    } else {
        printf("Maximum number of products reached.\n");
    }
}

void generateInvoice() {
    struct Invoice invoice;
    int customerId, productId, quantity;

    printf("Enter customer ID: ");
    scanf("%d", &customerId);

    // Find customer by ID
    int customerIndex = -1;
    for (int i = 0; i < customerCount; i++) {
        if (customers[i].id == customerId) {
            customerIndex = i;
            break;
        }
    }

    if (customerIndex == -1) {
        printf("Customer not found.\n");
        return;
    }

    // Set customer for the invoice
    invoice.customer = customers[customerIndex];
    invoice.itemCount = 0;

    // Add products to the invoice
    do {
        printf("Enter product ID (0 to finish): ");
        scanf("%d", &productId);

        if (productId != 0) {
            // Find product by ID
            int productIndex = -1;
            for (int i = 0; i < productCount; i++) {
                if (products[i].id == productId) {
                    productIndex = i;
                    break;
                }
            }

            if (productIndex != -1) {
                // Set product and quantity for the invoice item
                invoice.items[invoice.itemCount].product = products[productIndex];
                printf("Enter quantity: ");
                scanf("%d", &quantity);
                invoice.items[invoice.itemCount].quantity = quantity;
                invoice.itemCount++;
            } else {
                printf("Product not found.\n");
            }
        }
    } while (productId != 0);

    // Display the generated invoice
    printf("\n=== Invoice ===\n");
    printf("Customer: %s\n", invoice.customer.name);
    printf("------------------------------\n");
    printf("Product\t\tQuantity\tPrice\n");
    float totalAmount = 0;

    for (int i = 0; i < invoice.itemCount; i++) {
        struct InvoiceItem item = invoice.items[i];
        printf("%s\t\t%d\t\t%.2f\n", item.product.name, item.quantity, item.product.price);
        totalAmount += item.quantity * item.product.price;
    }

    printf("------------------------------\n");
    printf("Total Amount: %.2f\n", totalAmount);
}