app.py

import gradio as gr
import pandas as pd

# ---------- Inventory ----------
# ID -> (Name, Price per KG)
INVENTORY = {
    1: ("Apples", 250),
    2: ("Cherry", 650),
    3: ("Chickoo", 50),
    4: ("Grapes", 90),
    5: ("Mangoes", 150),
}

def inventory_markdown():
    items = "\n".join([f"({pid}) **{name}**, {price}"
                        for pid, (name, price) in INVENTORY.items()])
    return f"### Inventory\n{items}"

# ---------- Cart helpers ----------
def summarize_cart(cart):
    """Return (DataFrame, total_cost) for the cart.
    Cart structure: list of dicts with keys: id, name, unit_price, qty
    """
    if not cart:
        return pd.DataFrame(columns=["Index","Name","Quantity","Price Per KG"]), 0
    rows = []
    total = 0
    for idx, item in enumerate(cart):
        rows.append({
            "Index": idx,
            "Name": item["name"],
            "Quantity": item["qty"],
            "Price Per KG": f"${item['unit_price']:.2f}",
        })
        total += item["qty"] * item["unit_price"]
    df = pd.DataFrame(rows)
    return df, total

def add_item_to_cart(pid, cart):
    add_msg = ""
    if pid is None:
        return *summarize_cart(cart), add_msg, ""
    if pid not in INVENTORY:
        add_msg = f":warning: Invalid ID {pid}. Please use one of: {list(INVENTORY.keys())}"
        return *summarize_cart(cart), add_msg, ""
    name, price = INVENTORY[pid]
    # Check if already in cart -> increment quantity
    for item in cart:
        if item["id"] == pid:
            item["qty"] += 1
            df, total = summarize_cart(cart)
            add_msg = f">>>>>>>>>> The item '{name}' has been added to the cart. <<<<<<<<<<"
            return df, total, add_msg, ""
    # Otherwise append new
    cart.append({"id": pid, "name": name, "unit_price": float(price), "qty": 1})
    df, total = summarize_cart(cart)
    add_msg = f">>>>>>>>>> The item '{name}' has been added to the cart. <<<<<<<<<<"
    return df, total, add_msg, ""

def remove_item_from_cart(index, cart):
    rm_msg = ""
    if index is None:
        return *summarize_cart(cart), "", rm_msg
    if not cart:
        rm_msg = ":warning: Cart is empty."
        return *summarize_cart(cart), "", rm_msg
    if index < 0 or index >= len(cart):
        rm_msg = f":warning: Invalid index {index}. Must be 0..{max(0,len(cart)-1)}"
        return *summarize_cart(cart), "", rm_msg
    removed = cart.pop(index)
    df, total = summarize_cart(cart)
    rm_msg = f"Removed '{removed['name']}' from the cart."
    return df, total, "", rm_msg

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

    # App state: the cart
    cart_state = gr.State([])

    with gr.Row():
        with gr.Column(scale=2):
            pid_in = gr.Number(label="Enter Product ID to Add to Cart", value=2, precision=0)
        with gr.Column(scale=2):
            rm_index_in = gr.Number(label="Enter Index ID to Remove from Cart", value=0, precision=0)
        with gr.Column(scale=1):
            add_btn = gr.Button("Add to Cart", variant="primary")
        with gr.Column(scale=1):
            rm_btn = gr.Button("Remove from Cart", variant="secondary")

    with gr.Row():
        with gr.Column(scale=3):
            gr.Markdown("### Your Cart\n_Use 0-based index for removal_ :shopping_trolley:")
            cart_df = gr.Dataframe(headers=["Index","Name","Quantity","Price Per KG"],
                                   interactive=False,
                                   wrap=True,
                                   height=220)
            add_msg_out = gr.Textbox(label="Add Item Message", interactive=False)
            rm_msg_out = gr.Textbox(label="Remove Item Message", interactive=False)
            total_cost_out = gr.Textbox(label="Total Cost", interactive=False)
        with gr.Column(scale=2):
            inv_md = gr.Markdown(inventory_markdown())
            gr.Markdown("""
### Business Requirements
1. **Add Products to the Shopping Cart**: Add by ID from the inventory; quantities aggregate automatically.  
2. **Remove Unwanted Items**: Remove by 0-based index shown in the cart table.  
3. **Calculate the Total Bill**: Total updates automatically after each action.
""")

    def handle_add(pid, cart):
        df, total, add_msg, rm_msg = add_item_to_cart(int(pid), cart)
        total_str = f"$ {total:,.2f}"
        return df, add_msg, rm_msg, total_str, cart

    def handle_remove(index, cart):
        df, total, add_msg, rm_msg = remove_item_from_cart(int(index), cart)
        total_str = f"$ {total:,.2f}"
        return df, add_msg, rm_msg, total_str, cart

    add_btn.click(
        handle_add,
        inputs=[pid_in, cart_state],
        outputs=[cart_df, add_msg_out, rm_msg_out, total_cost_out, cart_state]
    )

    rm_btn.click(
        handle_remove,
        inputs=[rm_index_in, cart_state],
        outputs=[cart_df, add_msg_out, rm_msg_out, total_cost_out, cart_state]
    )

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