Remodel/packages/engine/src/remodel_engine/financial/pnl.py

"""25-year Profit & Loss statement.

Revenue
  - OpEx (O&M, insurance, land lease, AM fee, misc)
= EBITDA
  - Depreciation (book SLM)
= EBIT
  - Interest expense (from debt schedule)
= PBT
  - Current tax (115BAA)
= PAT
"""

from __future__ import annotations

from remodel_engine.schemas.financial import OpexConfig, PnLRow


def compute_ppa_units(
    gen_mwh_by_year: list[float],
    aux_pct: float,
    tx_loss_pct: float,
    dsm_loss_pct: float,
) -> list[float]:
    """Net PPA-billable units for each year in MWh."""
    return [
        round(mwh * (1 - aux_pct) * (1 - tx_loss_pct) * (1 - dsm_loss_pct), 2)
        for mwh in gen_mwh_by_year
    ]


def compute_revenue(
    ac_gen_mwh_by_year: list[float],
    tariff_inr_per_kwh: float,
    aux_pct: float,
    tx_loss_pct: float,
    dsm_loss_pct: float,
    bad_debt_pct: float = 0.0,
) -> list[float]:
    """Net revenue for each year in INR Crore.

    net_injection = generation * (1 - aux) * (1 - tx_loss) * (1 - dsm_loss)
    revenue = net_injection * tariff / 1000   (kWh from MWh: already in kWh via MWh*1000)
    """
    rev = []
    for mwh in ac_gen_mwh_by_year:
        net_kwh = mwh * 1000.0 * (1 - aux_pct) * (1 - tx_loss_pct) * (1 - dsm_loss_pct)
        gross_rev = net_kwh * tariff_inr_per_kwh / 1e7   # INR → Cr (1 Cr = 1e7 INR)
        rev.append(round(gross_rev * (1 - bad_debt_pct), 4))
    return rev


def compute_opex(
    revenue_by_year: list[float],
    solar_mw: float,
    wind_mw: float,
    bess_mwh: float,
    base_capex_cr: float,
    config: OpexConfig,
) -> list[float]:
    """Total opex for each year in INR Crore (excluding depreciation and interest)."""
    opex: list[float] = []
    for y, rev in enumerate(revenue_by_year):
        esc = (1.0 + config.om_escalation_pct) ** y
        om = (
            config.om_solar_cr_per_mw * solar_mw
            + config.om_wind_cr_per_mw * wind_mw
            + config.om_bess_cr_per_mwh * bess_mwh
        ) * esc
        insurance = config.insurance_pct_of_capex * base_capex_cr
        land = config.land_lease_cr * esc
        am_fee = config.am_fee_pct_of_revenue * rev
        misc = config.misc_cr * esc
        opex.append(round(om + insurance + land + am_fee + misc, 4))
    return opex


def build_pnl(
    revenue_by_year: list[float],
    gen_mwh_by_year: list[float],
    tariff_inr_per_kwh: float,
    mcp_revenue_by_year: list[float],
    mcp_units_by_year: list[float],
    opex_by_year: list[float],
    book_depr_by_year: list[float],
    interest_by_year: list[float],
    current_tax_by_year: list[float],
    deferred_tax_by_year: list[float],
    solar_mw: float,
    wind_mw: float,
    bess_mwh: float,
    base_capex_cr: float,
    config: OpexConfig,
) -> list[PnLRow]:
    """Build 25-year P&L row list."""
    n = len(revenue_by_year)
    rows: list[PnLRow] = []
    for y in range(n):
        ppa_rev = revenue_by_year[y]
        ppa_units = gen_mwh_by_year[y] if y < len(gen_mwh_by_year) else 0.0
        mcp_rev = mcp_revenue_by_year[y] if y < len(mcp_revenue_by_year) else 0.0
        mcp_units = mcp_units_by_year[y] if y < len(mcp_units_by_year) else 0.0
        total_rev = ppa_rev + mcp_rev

        esc = (1.0 + config.om_escalation_pct) ** y
        om = (
            config.om_solar_cr_per_mw * solar_mw
            + config.om_wind_cr_per_mw * wind_mw
            + config.om_bess_cr_per_mwh * bess_mwh
        ) * esc
        ins = config.insurance_pct_of_capex * base_capex_cr
        land = config.land_lease_cr * esc
        am = config.am_fee_pct_of_revenue * total_rev
        misc = config.misc_cr * esc

        opex_total = om + ins + land + am + misc
        ebitda = total_rev - opex_total
        depr = book_depr_by_year[y]
        ebit = ebitda - depr
        interest = interest_by_year[y]
        pbt = ebit - interest
        ct = current_tax_by_year[y]
        dt = deferred_tax_by_year[y]
        pat = pbt - ct

        rows.append(PnLRow(
            year=y + 1,
            revenue_cr=round(total_rev, 4),
            ppa_revenue_cr=round(ppa_rev, 4),
            mcp_revenue_cr=round(mcp_rev, 4),
            ppa_tariff_inr_per_kwh=tariff_inr_per_kwh,
            ppa_units_mwh=round(ppa_units, 2),
            mcp_units_mwh=round(mcp_units, 2),
            opex_total_cr=round(opex_total, 4),
            om_cr=round(om, 4),
            insurance_cr=round(ins, 4),
            land_lease_cr=round(land, 4),
            am_fee_cr=round(am, 4),
            misc_opex_cr=round(misc, 4),
            ebitda_cr=round(ebitda, 4),
            depreciation_book_cr=round(depr, 4),
            ebit_cr=round(ebit, 4),
            interest_cr=round(interest, 4),
            pbt_cr=round(pbt, 4),
            tax_cr=round(ct, 4),
            pat_cr=round(pat, 4),
            deferred_tax_cr=round(dt, 4),
        ))
    return rows