import gradio as gr

# ---- Inventory (ID, Name, PricePerUnit) ----
INVENTORY = [
    (1, "Apples", 250),
    (2, "Cherry", 650),
    (3, "Chickoo", 50),
    (4, "Grapes", 90),
    (5, "Mangoes", 150),
]
INV_MAP = {pid: (name, price) for pid, name, price in INVENTORY}


def add_item(cart, item_id):
    """
    Add one unit of item_id to the cart.
    cart: dict {product_id: quantity}
    """
    # Validate item_id
    if item_id is None:
        return cart, "Please enter a Product ID to add.", ""
    try:
        item_id = int(item_id)
    except (TypeError, ValueError):
        return cart, "Product ID must be an integer.", ""

    if item_id not in INV_MAP:
        return cart, f"Invalid Product ID: {item_id}", ""

    new_cart = dict(cart) if cart else {}
    new_cart[item_id] = new_cart.get(item_id, 0) + 1
    name, _ = INV_MAP[item_id]
    return new_cart, f">>>>> '{name}' added to cart. <<<<<\n", ""


def remove_item(cart, item_id):
    """
    Remove one unit of item_id from the cart (if present).
    """
    if not cart:
        return cart, "", "Cart is empty."

    if item_id is None:
        return cart, "", "Please enter a Product ID to remove."
    try:
        item_id = int(item_id)
    except (TypeError, ValueError):
        return cart, "", "Product ID must be an integer."

    if item_id not in cart or cart[item_id] <= 0:
        return cart, "", f"Item ID {item_id} is not in the cart."

    new_cart = dict(cart)
    new_cart[item_id] -= 1
    if new_cart[item_id] <= 0:
        del new_cart[item_id]
    name, _ = INV_MAP[item_id]
    return new_cart, "", f">>>>> One '{name}' removed. <<<<<\n"


def render_cart(cart):
    """
    Pretty-print the cart and compute total.
    cart: dict {product_id: quantity}
    """
    if not cart:
        return ">>>>>>>> Your cart is empty! Why not buy fruits from us? <<<<<<<<\n", "Total cost: $0.00"

    lines = []
    lines.append("+" * 62)
    lines.append(f"{'Your Cart':^62}")
    lines.append("+" * 62)
    lines.append(f"{'ProdID':<8} {'Name':<20} {'Qty':<6} {'Price/Unit':<12} {'Line Total':<12}")
    lines.append("-" * 62)

    grand = 0
    # Stable order by product id
    for pid in sorted(cart.keys()):
        qty = cart[pid]
        name, price = INV_MAP[pid]
        line_total = price * qty
        grand += line_total
        lines.append(f"{pid:<8} {name:<20} {qty:<6} ${price/100:>10.2f} ${line_total/100:>10.2f}")

    lines.append("-" * 62)
    lines.append(f"{'Grand Total':<48} ${grand/100:>10.2f}")

    return "\n".join(lines), f"Total cost: ${grand/100:.2f}"


def add_handler(cart_state, item_id):
    cart, add_msg, _ = add_item(cart_state, item_id)
    cart_txt, total_txt = render_cart(cart)
    return cart, cart_txt, add_msg, "" , total_txt


def remove_handler(cart_state, item_id):
    cart, _, remove_msg = remove_item(cart_state, item_id)
    cart_txt, total_txt = render_cart(cart)
    return cart, cart_txt, "" , remove_msg, total_txt


def clear_cart():
    cart = {}
    cart_txt, total_txt = render_cart(cart)
    return cart, cart_txt, "", "", total_txt


def launch_gradio():
    with gr.Blocks() as demo:
        gr.Markdown("### Fruit Shopping Cart System")

        # Persist cart per user session
        cart_state = gr.State({})

        with gr.Row():
            add_id = gr.Number(label="Product ID to Add", precision=0)
            rem_id = gr.Number(label="Product ID to Remove", precision=0)

        with gr.Row():
            add_btn = gr.Button("Add to Cart")
            rem_btn = gr.Button("Remove from Cart")
            clr_btn = gr.Button("Clear Cart")

        cart_display = gr.Textbox(label="Your Cart", interactive=False, lines=12)
        add_msg_box = gr.Textbox(label="Add Item Message", interactive=False)
        rem_msg_box = gr.Textbox(label="Remove Item Message", interactive=False)
        total_box = gr.Textbox(label="Total Cost", interactive=False)

        # Show inventory reference
        inv_md = "#### Inventory\n"
        inv_md += "| ID | Name    | Price (USD) |\n|---:|---------|-------------:|\n"
        for pid, name, price in INVENTORY:
            inv_md += f"| {pid} | {name} | ${price/100:.2f} |\n"
        gr.Markdown(inv_md)

        # Wire up events
        add_btn.click(
            add_handler,
            inputs=[cart_state, add_id],
            outputs=[cart_state, cart_display, add_msg_box, rem_msg_box, total_box],
        )

        rem_btn.click(
            remove_handler,
            inputs=[cart_state, rem_id],
            outputs=[cart_state, cart_display, add_msg_box, rem_msg_box, total_box],
        )

        clr_btn.click(
            clear_cart,
            inputs=[],
            outputs=[cart_state, cart_display, add_msg_box, rem_msg_box, total_box],
        )

        # Initial render
        demo.load(lambda: render_cart({}), inputs=None, outputs=[cart_display, total_box])

    demo.launch()


if __name__ == "__main__":
    launch_gradio()