"""
A collection of functions to calculate key health and valuation metrics
for a SaaS / micro-SaaS business based on a provided set of formulas.
"""

import gradio as gr


def calculate_arr(mrr: float) -> float:
    """
    Calculates Annual Recurring Revenue (ARR) from Monthly Recurring Revenue (MRR).
    (Formula 1)

    Args:
        mrr: Monthly Recurring Revenue.

    Returns:
        The calculated Annual Recurring Revenue.
    """
    return mrr * 12


def calculate_valuation_revenue(arr: float, multiple: float) -> float:
    """
    Calculates a simple revenue-based valuation.
    (Formula 2)

    Args:
        arr: Annual Recurring Revenue.
        multiple: The valuation multiple (e.g., 3.0 for 3x).

    Returns:
        The calculated revenue-based valuation.
    """
    return arr * multiple


def calculate_sde(
    revenue: float, owner_comp: float, cogs: float, op_ex: float
) -> float:
    """
    Calculates Seller's Discretionary Earnings (SDE).
    (Formula 3)

    Args:
        revenue: Total revenue for the period.
        owner_comp: Owner compensation to be added back.
        cogs: Cost of Goods Sold.
        op_ex: Operating Expenses.

    Returns:
        The calculated Seller's Discretionary Earnings.
    """
    return (revenue + owner_comp) - (cogs + op_ex)


def calculate_valuation_sde(sde: float, multiple: float) -> float:
    """
    Calculates an SDE-based valuation.
    (Formula 3)

    Args:
        sde: Seller's Discretionary Earnings.
        multiple: The SDE valuation multiple.

    Returns:
        The calculated SDE-based valuation.
    """
    return sde * multiple


def calculate_valuation_ebitda(ebitda: float, multiple: float) -> float:
    """
    Calculates an EBITDA-based valuation.
    (Formula 4)

    Args:
        ebitda: Earnings Before Interest, Taxes, Depreciation, and Amortization.
        multiple: The EBITDA valuation multiple.

    Returns:
        The calculated EBITDA-based valuation.
    """
    return ebitda * multiple


def calculate_customer_churn_rate(
    churned_customers: int, start_customers: int
) -> float:
    """
    Calculates the customer churn rate for a period.
    (Formula 5)

    Args:
        churned_customers: Number of customers lost during the period.
        start_customers: Number of customers at the start of the period.

    Returns:
        The customer churn rate as a decimal (e.g., 0.05 for 5%).
    """
    if start_customers == 0:
        return 0.0
    return churned_customers / start_customers


def calculate_gross_revenue_churn_rate(
    churned_revenue: float, mrr_start: float
) -> float:
    """
    Calculates the gross revenue churn rate for a period.
    (Formula 6)

    Args:
        churned_revenue: MRR lost from cancellations and downgrades.
        mrr_start: MRR at the start of the period.

    Returns:
        The gross revenue churn rate as a decimal.
    """
    if mrr_start == 0:
        return 0.0
    return churned_revenue / mrr_start


def calculate_net_revenue_churn_rate(
    churned_revenue: float, expansion_revenue: float, mrr_start: float
) -> float:
    """
    Calculates the net revenue churn rate for a period. Can be negative.
    (Formula 7)

    Args:
        churned_revenue: MRR lost from cancellations and downgrades.
        expansion_revenue: MRR gained from upgrades and upsells.
        mrr_start: MRR at the start of the period.

    Returns:
        The net revenue churn rate as a decimal.
    """
    if mrr_start == 0:
        return 0.0
    return (churned_revenue - expansion_revenue) / mrr_start


def calculate_nrr(
    mrr_start: float, expansion_revenue: float, churn_revenue: float
) -> float:
    """
    Calculates Net Revenue Retention (NRR).
    Note: 'churn_revenue' here includes all lost revenue (cancellations + contractions).
    (Formula 8)

    Args:
        mrr_start: MRR at the start of the period.
        expansion_revenue: MRR gained from existing customers.
        churn_revenue: MRR lost from existing customers.

    Returns:
        The Net Revenue Retention rate as a decimal (e.g., 1.05 for 105%).
    """
    if mrr_start == 0:
        return 0.0
    return (mrr_start + expansion_revenue - churn_revenue) / mrr_start


def calculate_cac(sm_spend: float, new_customers: int) -> float:
    """
    Calculates Customer Acquisition Cost (CAC).
    (Formula 9)

    Args:
        sm_spend: Total sales and marketing spend for the period.
        new_customers: Number of new customers acquired in the period.

    Returns:
        The average Customer Acquisition Cost.
    """
    if new_customers == 0:
        # Returning infinity is mathematically correct for 0 new customers
        # with non-zero spend, representing an infinitely high cost.
        return float("inf") if sm_spend > 0 else 0.0
    return sm_spend / new_customers


def calculate_arpa(mrr: float, active_accounts: int) -> float:
    """
    Calculates Average Revenue Per Account (ARPA).
    (Formula 10)

    Args:
        mrr: Monthly Recurring Revenue.
        active_accounts: Number of active accounts.

    Returns:
        The Average Revenue Per Account.
    """
    if active_accounts == 0:
        return 0.0
    return mrr / active_accounts


def calculate_customer_lifetime(customer_churn_rate: float) -> float:
    """
    Calculates the approximate customer lifetime in periods.
    (Formula 11)

    Args:
        customer_churn_rate: The per-period customer churn rate as a decimal.

    Returns:
        The average customer lifetime in number of periods.
    """
    if customer_churn_rate <= 0:
        # A churn rate of 0 implies infinite lifetime.
        return float("inf")
    return 1 / customer_churn_rate


def calculate_ltv(arpa: float, gross_margin: float, revenue_churn_rate: float) -> float:
    """
    Calculates the margin-adjusted Customer Lifetime Value (LTV).
    (Formula 12)

    Args:
        arpa: Average Revenue Per Account.
        gross_margin: The gross margin as a decimal (e.g., 0.80 for 80%).
        revenue_churn_rate: The revenue churn rate as a decimal.

    Returns:
        The margin-adjusted Customer Lifetime Value.
    """
    if revenue_churn_rate <= 0:
        # A churn rate of 0 implies infinite LTV.
        return float("inf")
    return (arpa * gross_margin) / revenue_churn_rate


def calculate_ltv_cac_ratio(ltv: float, cac: float) -> float:
    """
    Calculates the LTV to CAC ratio.
    (Formula 13)

    Args:
        ltv: Customer Lifetime Value.
        cac: Customer Acquisition Cost.

    Returns:
        The LTV to CAC ratio.
    """
    if cac == 0:
        # An LTV with zero acquisition cost is technically an infinite return.
        return float("inf") if ltv > 0 else 0.0
    return ltv / cac


def calculate_cac_payback_period(cac: float, arpa: float, gross_margin: float) -> float:
    """
    Calculates the CAC payback period in months (assuming ARPA is monthly).
    (Formula 14)

    Args:
        cac: Customer Acquisition Cost.
        arpa: Average Revenue Per Account (monthly).
        gross_margin: Gross margin as a decimal.

    Returns:
        The number of months to pay back CAC.
    """
    monthly_gross_profit_per_customer = arpa * gross_margin
    if monthly_gross_profit_per_customer <= 0:
        # If there's no gross profit, CAC is never paid back.
        return float("inf")
    return cac / monthly_gross_profit_per_customer


def calculate_gross_margin(revenue: float, cogs: float) -> float:
    """
    Calculates the gross margin.
    (Formula 15)

    Args:
        revenue: Total revenue.
        cogs: Cost of Goods Sold.

    Returns:
        The gross margin as a decimal.
    """
    if revenue == 0:
        return 0.0
    return (revenue - cogs) / revenue


def calculate_yoy_growth(arr_current: float, arr_prior: float) -> float:
    """
    Calculates Year-over-Year (YoY) growth rate.
    (Formula 16)

    Args:
        arr_current: ARR for the current year.
        arr_prior: ARR for the prior year.

    Returns:
        The YoY growth rate as a decimal.
    """
    if arr_prior == 0:
        return float("inf") if arr_current > 0 else 0.0
    return (arr_current - arr_prior) / arr_prior


def calculate_rule_of_40(growth_rate: float, ebitda_margin: float) -> float:
    """
    Calculates the Rule of 40 score.
    (Formula 17)

    Args:
        growth_rate: The growth rate as a percentage (e.g., 30 for 30%).
        ebitda_margin: The EBITDA margin as a percentage (e.g., 15 for 15%).

    Returns:
        The Rule of 40 score.
    """
    return growth_rate + ebitda_margin


with gr.Blocks(title="SaaS Metrics Calculator") as demo:
    gr.Markdown("# SaaS Metrics Calculator")
    gr.Markdown(
        "Calculate various key health and valuation metrics for your SaaS business. Each metric is in its own section below."
    )

    with gr.Accordion("Annual Recurring Revenue (ARR)", open=False):
        mrr_input = gr.Number(label="Monthly Recurring Revenue (MRR)")
        arr_output = gr.Number(label="Annual Recurring Revenue (ARR)")
        btn = gr.Button("Calculate")
        btn.click(calculate_arr, inputs=[mrr_input], outputs=[arr_output])

    with gr.Accordion("Revenue-Based Valuation", open=False):
        arr_input = gr.Number(label="Annual Recurring Revenue (ARR)")
        multiple_input = gr.Number(label="Valuation Multiple (e.g., 3.0 for 3x)")
        valuation_output = gr.Number(label="Revenue-Based Valuation")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_valuation_revenue,
            inputs=[arr_input, multiple_input],
            outputs=[valuation_output],
        )

    with gr.Accordion("Seller's Discretionary Earnings (SDE)", open=False):
        revenue_input = gr.Number(label="Total Revenue")
        owner_comp_input = gr.Number(label="Owner Compensation")
        cogs_input = gr.Number(label="Cost of Goods Sold (COGS)")
        op_ex_input = gr.Number(label="Operating Expenses")
        sde_output = gr.Number(label="Seller's Discretionary Earnings (SDE)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_sde,
            inputs=[revenue_input, owner_comp_input, cogs_input, op_ex_input],
            outputs=[sde_output],
        )

    with gr.Accordion("SDE-Based Valuation", open=False):
        sde_input = gr.Number(label="Seller's Discretionary Earnings (SDE)")
        multiple_input = gr.Number(label="SDE Valuation Multiple")
        valuation_output = gr.Number(label="SDE-Based Valuation")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_valuation_sde,
            inputs=[sde_input, multiple_input],
            outputs=[valuation_output],
        )

    with gr.Accordion("EBITDA-Based Valuation", open=False):
        ebitda_input = gr.Number(label="EBITDA")
        multiple_input = gr.Number(label="EBITDA Valuation Multiple")
        valuation_output = gr.Number(label="EBITDA-Based Valuation")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_valuation_ebitda,
            inputs=[ebitda_input, multiple_input],
            outputs=[valuation_output],
        )

    with gr.Accordion("Customer Churn Rate", open=False):
        churned_customers_input = gr.Number(label="Churned Customers")
        start_customers_input = gr.Number(label="Starting Customers")
        churn_rate_output = gr.Number(label="Customer Churn Rate (decimal)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_customer_churn_rate,
            inputs=[churned_customers_input, start_customers_input],
            outputs=[churn_rate_output],
        )

    with gr.Accordion("Gross Revenue Churn Rate", open=False):
        churned_revenue_input = gr.Number(label="Churned Revenue (MRR lost)")
        mrr_start_input = gr.Number(label="Starting MRR")
        churn_rate_output = gr.Number(label="Gross Revenue Churn Rate (decimal)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_gross_revenue_churn_rate,
            inputs=[churned_revenue_input, mrr_start_input],
            outputs=[churn_rate_output],
        )

    with gr.Accordion("Net Revenue Churn Rate", open=False):
        churned_revenue_input = gr.Number(label="Churned Revenue (MRR lost)")
        expansion_revenue_input = gr.Number(label="Expansion Revenue (MRR gained)")
        mrr_start_input = gr.Number(label="Starting MRR")
        churn_rate_output = gr.Number(label="Net Revenue Churn Rate (decimal)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_net_revenue_churn_rate,
            inputs=[churned_revenue_input, expansion_revenue_input, mrr_start_input],
            outputs=[churn_rate_output],
        )

    with gr.Accordion("Net Revenue Retention (NRR)", open=False):
        mrr_start_input = gr.Number(label="Starting MRR")
        expansion_revenue_input = gr.Number(label="Expansion Revenue")
        churn_revenue_input = gr.Number(label="Churn Revenue (MRR lost)")
        nrr_output = gr.Number(label="Net Revenue Retention (decimal)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_nrr,
            inputs=[mrr_start_input, expansion_revenue_input, churn_revenue_input],
            outputs=[nrr_output],
        )

    with gr.Accordion("Customer Acquisition Cost (CAC)", open=False):
        sm_spend_input = gr.Number(label="Sales & Marketing Spend")
        new_customers_input = gr.Number(label="New Customers")
        cac_output = gr.Number(label="Customer Acquisition Cost (CAC)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_cac,
            inputs=[sm_spend_input, new_customers_input],
            outputs=[cac_output],
        )

    with gr.Accordion("Average Revenue Per Account (ARPA)", open=False):
        mrr_input = gr.Number(label="Monthly Recurring Revenue (MRR)")
        active_accounts_input = gr.Number(label="Active Accounts")
        arpa_output = gr.Number(label="Average Revenue Per Account (ARPA)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_arpa,
            inputs=[mrr_input, active_accounts_input],
            outputs=[arpa_output],
        )

    with gr.Accordion("Customer Lifetime", open=False):
        customer_churn_rate_input = gr.Number(label="Customer Churn Rate (decimal)")
        lifetime_output = gr.Number(label="Customer Lifetime (periods)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_customer_lifetime,
            inputs=[customer_churn_rate_input],
            outputs=[lifetime_output],
        )

    with gr.Accordion("Customer Lifetime Value (LTV)", open=False):
        arpa_input = gr.Number(label="ARPA")
        gross_margin_input = gr.Number(label="Gross Margin (decimal)")
        revenue_churn_rate_input = gr.Number(label="Revenue Churn Rate (decimal)")
        ltv_output = gr.Number(label="Customer Lifetime Value (LTV)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_ltv,
            inputs=[arpa_input, gross_margin_input, revenue_churn_rate_input],
            outputs=[ltv_output],
        )

    with gr.Accordion("LTV to CAC Ratio", open=False):
        ltv_input = gr.Number(label="LTV")
        cac_input = gr.Number(label="CAC")
        ratio_output = gr.Number(label="LTV to CAC Ratio")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_ltv_cac_ratio,
            inputs=[ltv_input, cac_input],
            outputs=[ratio_output],
        )

    with gr.Accordion("CAC Payback Period", open=False):
        cac_input = gr.Number(label="CAC")
        arpa_input = gr.Number(label="ARPA (monthly)")
        gross_margin_input = gr.Number(label="Gross Margin (decimal)")
        payback_output = gr.Number(label="CAC Payback Period (months)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_cac_payback_period,
            inputs=[cac_input, arpa_input, gross_margin_input],
            outputs=[payback_output],
        )

    with gr.Accordion("Gross Margin", open=False):
        revenue_input = gr.Number(label="Total Revenue")
        cogs_input = gr.Number(label="Cost of Goods Sold (COGS)")
        margin_output = gr.Number(label="Gross Margin (decimal)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_gross_margin,
            inputs=[revenue_input, cogs_input],
            outputs=[margin_output],
        )

    with gr.Accordion("Year-over-Year (YoY) Growth", open=False):
        arr_current_input = gr.Number(label="Current ARR")
        arr_prior_input = gr.Number(label="Prior ARR")
        growth_output = gr.Number(label="YoY Growth Rate (decimal)")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_yoy_growth,
            inputs=[arr_current_input, arr_prior_input],
            outputs=[growth_output],
        )

    with gr.Accordion("Rule of 40 Score", open=False):
        growth_rate_input = gr.Number(
            label="Growth Rate (percentage, e.g., 30 for 30%)"
        )
        ebitda_margin_input = gr.Number(
            label="EBITDA Margin (percentage, e.g., 15 for 15%)"
        )
        rule_output = gr.Number(label="Rule of 40 Score")
        btn = gr.Button("Calculate")
        btn.click(
            calculate_rule_of_40,
            inputs=[growth_rate_input, ebitda_margin_input],
            outputs=[rule_output],
        )

demo.launch()