"""Read the deployed payslip-ingest schema for income + RSU vest cadence.

Read-only: we never write to `payslip_ingest.*`. The DB role
`pg-fire-planner` only needs SELECT on payslip_ingest.payslip and
payslip_ingest.rsu_vest_events.

Outputs feed scenario calibration:
- savings_per_year_gbp: median monthly net_pay × 12 less the £100k
  baseline spend (the planner allocates the surplus to portfolio).
- annual_rsu_gross_gbp: median annual RSU vest value, used to validate
  the savings rate against expected gross compensation.
"""
from __future__ import annotations

from dataclasses import dataclass
from datetime import date
from decimal import Decimal

from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession


@dataclass(frozen=True)
class IncomeSummary:
    median_monthly_net_pay_gbp: Decimal
    median_annual_rsu_gbp: Decimal
    earliest_date: date | None
    latest_date: date | None
    payslip_count: int
    rsu_count: int


async def read_income_summary(session: AsyncSession, months: int = 24) -> IncomeSummary:
    """Aggregate the most-recent `months` of payslips + RSU vests."""
    payslip_rows = (await session.execute(
        text(
            """
            SELECT pay_date, net_pay
              FROM payslip_ingest.payslip
             WHERE pay_date >= CURRENT_DATE - (:months || ' months')::interval
             ORDER BY pay_date DESC
            """, ),
        {"months": months},
    )).all()

    rsu_rows = (await session.execute(
        text(
            """
            SELECT vest_date, gross_value_gbp
              FROM payslip_ingest.rsu_vest_events
             WHERE vest_date >= CURRENT_DATE - (:months || ' months')::interval
             ORDER BY vest_date DESC
            """, ),
        {"months": months},
    )).all()

    monthly_nets = sorted(Decimal(str(r[1] or 0)) for r in payslip_rows)
    median_monthly_net = (monthly_nets[len(monthly_nets) // 2] if monthly_nets else Decimal("0"))

    rsu_total_gbp = sum((Decimal(str(r[1] or 0)) for r in rsu_rows), start=Decimal("0"))
    months_span = max(1, months)
    annual_rsu = rsu_total_gbp * 12 / months_span

    pay_dates = [r[0] for r in payslip_rows]
    rsu_dates = [r[0] for r in rsu_rows]
    all_dates = pay_dates + rsu_dates
    earliest = min(all_dates) if all_dates else None
    latest = max(all_dates) if all_dates else None

    return IncomeSummary(
        median_monthly_net_pay_gbp=median_monthly_net,
        median_annual_rsu_gbp=annual_rsu,
        earliest_date=earliest,
        latest_date=latest,
        payslip_count=len(payslip_rows),
        rsu_count=len(rsu_rows),
    )