import gradio as gr
import pandas as pd
import tempfile
from fpdf import FPDF
from datetime import datetime

# In-memory database (dictionary)
products_db = {}
bill_items_db = []

def add_product(name, qty, price):
    if not name:
        return gr.update(), gr.update(choices=[])
    
    try:
        qty = float(qty) if qty else 1.0
        price = float(price) if price else 0.0
    except Exception:
        qty = 1.0
        price = 0.0
    
    products_db[name] = {"qty": qty, "price": price}
    
    df = [[name, products_db[name]["qty"], products_db[name]["price"]] 
          for name in products_db.keys()]
    
    choices = list(products_db.keys())
    
    return gr.update(value=df), gr.update(choices=choices)

def delete_product(name):
    if name and name in products_db:
        del products_db[name]
    
    df = [[name, products_db[name]["qty"], products_db[name]["price"]] 
          for name in products_db.keys()]
    choices = list(products_db.keys())
    
    return gr.update(value=df), gr.update(choices=choices, value=None)

def add_to_bill(product_name, quantity):
    if not product_name or product_name not in products_db:
        # Return current bill items and empty preview
        df = [[item["name"], item["quantity"], item["unit_price"], item["total"]] 
              for item in bill_items_db]
        return gr.update(value=df), ""
    
    try:
        quantity = float(quantity) if quantity else 0.0
    except Exception:
        quantity = 0.0
    
    if quantity <= 0:
        df = [[item["name"], item["quantity"], item["unit_price"], item["total"]] 
              for item in bill_items_db]
        return gr.update(value=df), ""
    
    product = products_db[product_name]
    unit_price = product["price"]
    total = unit_price * quantity
    
    bill_items_db.append({
        "name": product_name,
        "quantity": quantity,
        "unit_price": unit_price,
        "total": total
    })
    
    df = [[item["name"], item["quantity"], item["unit_price"], item["total"]] 
          for item in bill_items_db]
    
    preview = generate_bill_preview()
    
    return gr.update(value=df), preview

def clear_bill():
    bill_items_db.clear()
    return gr.update(value=[]), ""

def generate_bill_preview():
    if not bill_items_db:
        return "No items in bill"
    
    preview = "=" * 60 + "\n"
    preview += "BILL PREVIEW\n"
    preview += f"Date: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}\n"
    preview += "=" * 60 + "\n\n"
    preview += f"{'Product':<20} {'Qty':>8} {'Unit Price':>12} {'Total':>12}\n"
    preview += "-" * 60 + "\n"
    
    grand_total = 0.0
    for item in bill_items_db:
        preview += f"{item['name']:<20} {item['quantity']:>8.2f} {item['unit_price']:>12.2f} {item['total']:>12.2f}\n"
        grand_total += item['total']
    
    preview += "-" * 60 + "\n"
    preview += f"{'GRAND TOTAL':<20} {' ':>8} {' ':>12} {grand_total:>12.2f}\n"
    preview += "=" * 60 + "\n"
    
    return preview

def generate_bill_pdf():
    """Generate PDF bill and return file path"""
    if not bill_items_db:
        return None
    
    pdf = FPDF()
    pdf.add_page()
    
    pdf.set_font("Arial", "B", 16)
    pdf.cell(0, 10, "INVOICE", ln=1, align='C')
    pdf.ln(5)
    
    pdf.set_font("Arial", "", 10)
    pdf.cell(0, 10, f"Date: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}", ln=1)
    pdf.ln(5)
    
    pdf.set_font("Arial", "B", 11)
    pdf.cell(70, 10, "Product", 1, 0, 'L')
    pdf.cell(30, 10, "Qty", 1, 0, 'C')
    pdf.cell(40, 10, "Unit Price", 1, 0, 'R')
    pdf.cell(40, 10, "Total", 1, 1, 'R')
    
    pdf.set_font("Arial", "", 10)
    grand_total = 0.0
    for item in bill_items_db:
        pdf.cell(70, 10, item['name'], 1, 0, 'L')
        pdf.cell(30, 10, f"{item['quantity']:.2f}", 1, 0, 'C')
        pdf.cell(40, 10, f"{item['unit_price']:.2f}", 1, 0, 'R')
        pdf.cell(40, 10, f"{item['total']:.2f}", 1, 1, 'R')
        grand_total += item['total']
    
    pdf.set_font("Arial", "B", 11)
    pdf.cell(140, 10, "GRAND TOTAL", 1, 0, 'R')
    pdf.cell(40, 10, f"{grand_total:.2f}", 1, 1, 'R')
    
    tmp = tempfile.NamedTemporaryFile(delete=False, suffix=".pdf")
    pdf.output(tmp.name)
    tmp.close()
    
    return tmp.name

with gr.Blocks(title="Billing System - A Likitha") as demo:
    gr.Markdown("# 🧾 Billing System - by A Likitha")
    gr.Markdown("Manage products and generate bills with ease autocalculated with pdf exports!")
    
    with gr.Tab("📦 Products"):
        gr.Markdown("### Add/Update Products")
        gr.Markdown("Enter product details below. Quantity represents the base unit (e.g., 1 kg, 1 piece, etc.)")
        
        with gr.Row():
            product_name = gr.Textbox(label="Product Name", placeholder="e.g., Idly, Sugar")
            product_qty = gr.Number(label="Quantity (Base Unit)", value=1, precision=0)
            product_price = gr.Number(label="Price per Unit", value=0, precision=2)
        
        add_product_btn = gr.Button("➕ Add/Update Product", variant="primary")
        
        gr.Markdown("### Product List")
        product_table = gr.Dataframe(
            headers=["Name", "Qty", "Price"],
            datatype=["str", "number", "number"],
            row_count=0,
            interactive=False,
            label="Current Products"
        )
        
        gr.Markdown("### Delete Product")
        with gr.Row():
            delete_dropdown = gr.Dropdown(choices=[], label="Select Product to Delete")
            delete_product_btn = gr.Button("🗑️ Delete Product", variant="stop")
        
        add_product_btn.click(
            fn=add_product,
            inputs=[product_name, product_qty, product_price],
            outputs=[product_table, delete_dropdown]
        )
        
        delete_product_btn.click(
            fn=delete_product,
            inputs=[delete_dropdown],
            outputs=[product_table, delete_dropdown]
        )
    
    with gr.Tab("💰 Bills"):
        gr.Markdown("### Create New Bill")
        gr.Markdown("Select a product and enter the quantity to add to the bill")
        
        with gr.Row():
            bill_product_dropdown = gr.Dropdown(
                choices=list(products_db.keys()),
                label="Select Product"
            )
            bill_quantity = gr.Number(label="Quantity", value=1, precision=2)
            add_to_bill_btn = gr.Button("➕ Add to Bill", variant="primary")
        
        clear_bill_btn = gr.Button("🗑️ Clear Bill", variant="secondary")
        
        gr.Markdown("### Current Bill Items")
        bill_table = gr.Dataframe(
            headers=["Product", "Quantity", "Unit Price", "Total"],
            datatype=["str", "number", "number", "number"],
            row_count=0,
            interactive=False,
            label="Bill Items"
        )
        
        gr.Markdown("### Bill Preview")
        bill_preview = gr.Textbox(
            label="Preview",
            lines=15,
            interactive=False,
            placeholder="Add items to see bill preview..."
        )
        
        generate_pdf_btn = gr.Button("📄 Generate & Download PDF", variant="primary", size="lg")
        pdf_output = gr.File(label="Download Bill PDF")
        
        add_to_bill_btn.click(
            fn=add_to_bill,
            inputs=[bill_product_dropdown, bill_quantity],
            outputs=[bill_table, bill_preview]
        )
        
        clear_bill_btn.click(
            fn=clear_bill,
            inputs=[],
            outputs=[bill_table, bill_preview]
        )
        
        generate_pdf_btn.click(
            fn=generate_bill_pdf,
            inputs=[],
            outputs=[pdf_output]
        )
        
        add_product_btn.click(
            fn=lambda: gr.update(choices=list(products_db.keys())),
            inputs=[],
            outputs=[bill_product_dropdown]
        )

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