import gradio as gr

# -----------------------------
# Module 1: Data Structures (USD)
# -----------------------------

Inventory = [
    (101, "Hammer", 1.20),
    (102, "Screwdriver Set", 3.50),
    (103, "Drill Machine", 25.00),
    (104, "Pliers", 1.80),
    (105, "Wrench", 2.20),
]

# Lookup dictionary for fast access
inventory_lookup = {item[0]: {"name": item[1], "price": item[2]} for item in Inventory}

# Cart holds item IDs
My_Cart = []


# -----------------------------
# Module 2: Business Logic
# -----------------------------

def add_to_cart(item_id):
    if item_id in inventory_lookup:
        My_Cart.append(item_id)
        return f"Added: {inventory_lookup[item_id]['name']}"
    return "Invalid item ID."

def remove_from_cart(item_id):
    if item_id in My_Cart:
        My_Cart.remove(item_id)
        return f"Removed: {inventory_lookup[item_id]['name']}"
    return "Item not in cart."

def get_cart_contents():
    if not My_Cart:
        return "Cart is empty."
    lines = []
    for item_id in My_Cart:
        item = inventory_lookup[item_id]
        lines.append(f"{item_id} - {item['name']} - ${item['price']:.2f}")
    return "\n".join(lines)

def calculate_total():
    total = sum(inventory_lookup[item_id]["price"] for item_id in My_Cart)
    return f"Total Amount: ${total:.2f}"


# -----------------------------
# Module 3: Helpers for Dropdown Text
# -----------------------------

def extract_id(choice_text):
    # Dropdown text looks like: "101 - Hammer - $1.20"
    return int(choice_text.split(" - ")[0])


# -----------------------------
# Module 4: Gradio Callbacks
# -----------------------------

def handle_add(selected_text):
    item_id = extract_id(selected_text)
    msg = add_to_cart(item_id)
    return get_cart_contents(), msg

def handle_remove(selected_text):
    item_id = extract_id(selected_text)
    msg = remove_from_cart(item_id)
    return get_cart_contents(), msg

def handle_total():
    return calculate_total()


# -----------------------------
# Module 5: Gradio Interface
# -----------------------------

with gr.Blocks(title="Hardware Store Billing System (USD)") as demo:

    gr.Markdown("## 🧰 Hardware Store Billing System (USD)")

    # Dropdowns show: "101 - Hammer - $1.20"
    formatted_choices = [
        f"{item[0]} - {item[1]} - ${item[2]:.2f}" for item in Inventory
    ]

    with gr.Row():
        add_dropdown = gr.Dropdown(
            choices=formatted_choices,
            label="Select Item to Add"
        )
        add_button = gr.Button("Add Tool")

    with gr.Row():
        remove_dropdown = gr.Dropdown(
            choices=formatted_choices,
            label="Select Item to Remove"
        )
        remove_button = gr.Button("Remove Tool")

    cart_display = gr.Textbox(label="Cart Contents", lines=8)
    message_display = gr.Textbox(label="Status Message")

    total_button = gr.Button("Calculate Total")
    total_output = gr.Textbox(label="Total Amount")

    # Bind callbacks
    add_button.click(handle_add, inputs=add_dropdown, outputs=[cart_display, message_display])
    remove_button.click(handle_remove, inputs=remove_dropdown, outputs=[cart_display, message_display])
    total_button.click(handle_total, outputs=total_output)

if __name__ == "__main__":
    demo.launch()