Invoice Template Generator in C++

This document provides a simple and efficient C++ implementation of an invoice template generator. The solution includes necessary imports, function documentation, input validation, inline comments, and a usage example.

Overview

An invoice typically contains information about the buyer, seller, items purchased, prices, and totals. The provided function will generate a structured invoice in a text format.

Code Implementation

Necessary Imports

#include 
#include 
#include 
#include 

Invoice Struct

Define a struct to hold invoice information efficiently.

struct Item {
    std::string description;
    double price;
    int quantity;

    double total() const; // Computes total price for this item
};

Total Calculation Method

Implement the total price calculation for an item.

double Item::total() const {
    return price * quantity;
}

Invoice Class Definition

Define a class for generating and displaying the invoice.

class Invoice {
public:
    Invoice(const std::string& seller, const std::string& buyer);
    void addItem(const std::string& description, double price, int quantity);
    void generateInvoice() const;

private:
    std::string seller;
    std::string buyer;
    std::vector items;

    void validateInput(const std::string& description, double price, int quantity);
};

Constructor Implementation

Initialize the invoice with seller and buyer details.

Invoice::Invoice(const std::string& seller, const std::string& buyer)
    : seller(seller), buyer(buyer) {}

Add Item Function

This function adds items to the invoice with input validation.

void Invoice::addItem(const std::string& description, double price, int quantity) {
    validateInput(description, price, quantity); // Validate inputs
    items.push_back({description, price, quantity}); // Add item to the invoice
}

Validate Input Method

Ensure inputs are valid before adding them to the invoice.

void Invoice::validateInput(const std::string& description, double price, int quantity) {
    if (description.empty()) {
        throw std::invalid_argument("Item description cannot be empty.");
    }
    if (price < 0) {
        throw std::invalid_argument("Price cannot be negative.");
    }
    if (quantity <= 0) {
        throw std::invalid_argument("Quantity must be a positive integer.");
    }
}

Generate Invoice Function

This function generates and prints the invoice.

void Invoice::generateInvoice() const {
    std::cout << "Invoice\n";
    std::cout << "Seller: " << seller << "\n";
    std::cout << "Buyer: " << buyer << "\n\n";
    std::cout << std::setw(20) << "Description" 
              << std::setw(10) << "Price" 
              << std::setw(10) << "Quantity" 
              << std::setw(10) << "Total" << "\n";
    
    double grandTotal = 0;
    for (const auto& item : items) {
        double itemTotal = item.total();
        std::cout << std::setw(20) << item.description 
                  << std::setw(10) << std::fixed << std::setprecision(2) << item.price 
                  << std::setw(10) << item.quantity 
                  << std::setw(10) << itemTotal << "\n";
        grandTotal += itemTotal; // Aggregate the total
    }
    
    std::cout << std::setw(30) << "Grand Total:" 
              << std::setw(10) << std::fixed << std::setprecision(2) << grandTotal << "\n";
}

Complete Program Example

Here’s a complete example demonstrating the use of the Invoice class.

int main() {
    try {
        Invoice invoice("ABC Corp.", "John Doe");
        invoice.addItem("Widget", 25.50, 2);
        invoice.addItem("Gadget", 15.75, 1);
        invoice.addItem("Doodad", 5.99, 4);
        
        invoice.generateInvoice(); // Generate and print the invoice

    } catch (const std::invalid_argument& e) {
        std::cerr << "Error: " << e.what() << std::endl; // Handle input validation errors
    }

    return 0;
}

Code Usage Example

The example above creates an invoice for a fictitious company leveraging the 'Invoice' class. The invoice captures several items with their descriptions, prices, and quantities, and calculates the total effectively.

Key Points

• Input validation is enforced to ensure data integrity.
• Structure is established for easy maintenance and scalability.
• The program adheres to standard C++ practices and includes thorough documentation.

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