run.py

import json
import csv


def load_data():
    """
    Load inventory data from a JSON file.
    """
    try:
        with open("inventory.json", "r") as file:
            return json.load(file)
    except FileNotFoundError:
        print("Database not found, creating a new one...")
        return []
    except json.JSONDecodeError:
        print("Error reading database file. Starting with empty data.")
        return []


def save_data(data):
    """
    Save inventory data to a JSON file.
    """
    try:
        with open("inventory.json", "w") as file:
            json.dump(data, file, indent=4)
        print("Database saved successfully!")
    except Exception as e:
        print(f"Error saving database: {e}")


def show_menu():
    """
    Display the main menu options for the inventory manager.
    """
    print("\n=== Inventory Manager ===")
    print("1. Show inventory")
    print("2. Add product")
    print("3. Update product")
    print("4. Delete product")
    print("5. Search product")
    print("6. Export inventory to CSV")
    print("7. Import inventory from CSV")
    print("8. Save and exit")


def show_inventory(inventory):
    """
    Display all products in the inventory in a formatted way.
    """
    if not inventory:
        print("\nInventory is empty.")
        return

    print("\n=== Current Inventory ===")
    for item in inventory:
        print(
            f"ID: {item['id']} | Name: {item['name']} | "
            f"Quantity: {item['quantity']} | Price: €{item['price']}"
        )


def add_product(inventory):
    """
    Add a new product to the inventory with validated input.
    """
    print("\n=== Add New Product ===")
    name = input("Product name: ").strip()

    if not name:
        print("Product name cannot be empty.")
        return

    try:
        quantity = int(input("Quantity (integer): ").strip())
        price = float(input("Price (use . for decimals): ").strip())
    except ValueError:
        print(
            "Invalid input! Quantity must be an integer "
            "and price must be a number."
        )
        return

    if quantity < 0 or price < 0:
        print("Quantity and price must be positive values.")
        return

    # Generate a new ID
    if inventory:
        new_id = max(item["id"] for item in inventory) + 1
    else:
        new_id = 1

    new_product = {
        "id": new_id,
        "name": name,
        "quantity": quantity,
        "price": price,
    }

    inventory.append(new_product)
    print(f"Product '{name}' added successfully with ID {new_id}!")


def update_product(inventory):
    """
    Update quantity and/or price for an existing product.
    """
    if not inventory:
        print("\nInventory is empty. Nothing to update.")
        return

    print("\n=== Update Product ===")
    try:
        product_id = int(input("Enter product ID to update: ").strip())
    except ValueError:
        print("Invalid ID! ID must be an integer.")
        return

    # Search for the product
    product = next((item for item in inventory if item["id"] == product_id), None)

    if not product:
        print(f"No product found with ID {product_id}.")
        return

    print(
        f"Current product: {product['name']} | "
        f"Quantity: {product['quantity']} | Price: €{product['price']}"
    )

    # New quantity if the user wants
    new_quantity_input = input(
        "New quantity (leave blank to keep current): "
    ).strip()

    # New price if the user wants
    new_price_input = input(
        "New price (leave blank to keep current): "
    ).strip()

    try:
        if new_quantity_input:
            new_quantity = int(new_quantity_input)
            if new_quantity < 0:
                print("Quantity must be positive.")
                return
            product["quantity"] = new_quantity

        if new_price_input:
            new_price = float(new_price_input)
            if new_price < 0:
                print("Price must be positive.")
                return
            product["price"] = new_price

        print("Product updated successfully!")

    except ValueError:
        print(
            "Invalid value! Quantity must be integer and "
            "price must be a number."
        )


def delete_product(inventory):
    """
    Delete a product from the inventory by its ID.
    """
    if not inventory:
        print("\nInventory is empty. Nothing to delete.")
        return

    print("\n=== Delete Product ===")
    try:
        product_id = int(input("Enter product ID to delete: ").strip())
    except ValueError:
        print("Invalid ID! ID must be an integer.")
        return

    # Search for the product
    product = next((item for item in inventory if item["id"] == product_id), None)

    if not product:
        print(f"No product found with ID {product_id}.")
        return

    print(
        f"You are about to delete: {product['name']} "
        f"(Qty: {product['quantity']}, Price: €{product['price']})"
    )
    confirm = input("Are you sure? (y/n): ").strip().lower()

    if confirm == "y":
        inventory.remove(product)
        print("Product deleted successfully!")
    else:
        print("Delete cancelled.")


def search_product(inventory):
    """
    Search for products by name (case-insensitive).
    """
    if not inventory:
        print("\nInventory is empty. Nothing to search.")
        return

    print("\n=== Search Product ===")
    query = input("Enter product name to search: ").strip().lower()

    if not query:
        print("Search query cannot be empty.")
        return

    # Filter products
    results = [
        item for item in inventory
        if query in item["name"].lower()
    ]

    if not results:
        print(f"No products found matching: {query}")
        return

    print(f"\nFound {len(results)} matching product(s):")
    for item in results:
        print(
            f"ID: {item['id']} | Name: {item['name']} | "
            f"Quantity: {item['quantity']} | Price: €{item['price']}"
        )


def export_to_csv(inventory):
    """
    Export the current inventory to a CSV file.
    """
    if not inventory:
        print("\nInventory is empty. Nothing to export.")
        return

    filename = "inventory_export.csv"

    try:
        with open(filename, "w", newline="", encoding="utf-8") as file:
            writer = csv.writer(file)
            writer.writerow(["ID", "Name", "Quantity", "Price"])

            for item in inventory:
                writer.writerow(
                    [
                        item["id"],
                        item["name"],
                        item["quantity"],
                        item["price"],
                    ]
                )

        print(f"Inventory exported successfully to '{filename}'!")

    except Exception as e:
        print(f"Error exporting CSV: {e}")


def import_from_csv(inventory):
    """
    Import products from a CSV file and add them to the inventory.
    Expected columns: ID, Name, Quantity, Price.
    """
    filename = "inventory_import.csv"
    print(f"\nAttempting to import from '{filename}'...")

    try:
        with open(filename, "r", encoding="utf-8") as file:
            reader = csv.DictReader(file)

            imported_count = 0
            for row in reader:
                try:
                    name = row["Name"].strip()
                    quantity = int(row["Quantity"])
                    price = float(row["Price"])

                    if not name or quantity < 0 or price < 0:
                        print(f"Skipping invalid row: {row}")
                        continue

                    # Generate new ID
                    if inventory:
                        new_id = max(item["id"] for item in inventory) + 1
                    else:
                        new_id = 1

                    new_product = {
                        "id": new_id,
                        "name": name,
                        "quantity": quantity,
                        "price": price,
                    }
                    inventory.append(new_product)
                    imported_count += 1

                except (KeyError, ValueError):
                    print(f"Skipping invalid row: {row}")
                    continue

        print(f"Imported {imported_count} product(s) from CSV.")

    except FileNotFoundError:
        print(f"File '{filename}' not found. Create it before importing.")
    except Exception as e:
        print(f"Error importing CSV: {e}")


def main():
    """
    Main loop of the Inventory Manager CLI application.
    """
    inventory = load_data()

    print("Welcome to Inventory Manager CLI!")
    print(f"Loaded {len(inventory)} products from database.")

    while True:
        show_menu()
        choice = input("Choose an option (1-8): ").strip()

        if choice == "1":
            show_inventory(inventory)
        elif choice == "2":
            add_product(inventory)
        elif choice == "3":
            update_product(inventory)
        elif choice == "4":
            delete_product(inventory)
        elif choice == "5":
            search_product(inventory)
        elif choice == "6":
            export_to_csv(inventory)
        elif choice == "7":
            import_from_csv(inventory)
        elif choice == "8":
            save_data(inventory)
            print("Database saved. Goodbye!")
            break
        else:
            print("Invalid option, please choose a number between 1 and 8.")


if __name__ == "__main__":
    main()