import gradio as gr

def calculate_selling_price(daily_circulation, annual_expenses, days_sold):
    try:
        # Calculate the selling price per copy
        selling_price = annual_expenses / (daily_circulation * days_sold)
        return f"₹{selling_price:.2f} per copy"
    except ZeroDivisionError:
        return "Invalid input: Daily circulation and days sold must be greater than zero."

def concept_summary():
    summary = (
        "**Concept: Applying Print Economics to Digital News**\n\n"
        "In print media, unit economics are straightforward: \n"
        "Selling Price = Annual Expenses / (Daily Circulation × Days Sold).\n\n"
        "For digital news, while it eliminates printing costs, new challenges arise:\n"
        "- High fixed costs like servers and technology.\n"
        "- A smaller paying subscriber base.\n\n"
        "Example for Digital:\n"
        "If annual expenses are ₹500 crores and there are 10 lakh subscribers,\n"
        "Subscription Price = ₹500,00,00,000 / 10,00,000 = ₹5000/year (~₹417/month).\n\n"
        "Conclusion: Digital news is undoubtedly the future, but relying solely on subscription revenue is \n"
        "as impractical for digital as it is for print. Just as print media relies on a mix of subscription, \n"
        "advertising, and sponsorships, digital news platforms must adopt hybrid models \n"
        "(ads + subscription + partnerships) to remain sustainable."
    )
    return summary

# Gradio interface
interface = gr.Interface(
    fn=calculate_selling_price,
    inputs=[
        gr.Number(label="Daily Circulation (e.g., 1000000 for 10 lakh copies)"),
        gr.Number(label="Annual Expenses (in ₹, e.g., 900000000 for ₹900 crores)"),
        gr.Number(label="Days Sold (e.g., 360)")
    ],
    outputs=gr.Textbox(label="Selling Price per Copy"),
    examples=[[1000000, 900000000, 360]],
    title="Newspaper Selling Price Calculator",
    description=(
        "This calculator helps determine the selling price per copy of a newspaper based on its "
        "daily circulation, annual expenses, and the number of days it is sold in a year.\n\n"
        + concept_summary()
    )
)

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