"""Client-overlay pins — identity at the composite, linear per-driver
scaling, growth re-basing, and copy semantics."""

import dataclasses

import pytest

from teicalc import (
    BENEFIT_DRIVERS,
    BENEFITS_VERBATIM,
    COMPOSITE,
    COST_DRIVERS,
    COSTS_VERBATIM,
    ClientDrivers,
    compute_summary,
    growth_multiplier,
    overlay_rows,
    scale_factor,
)


def _row(rows, key):
    return next(r for r in rows if r["field_key"] == key)


def test_identity_at_composite():
    """overlay_rows(COMPOSITE) reproduces the verbatim study to the cent."""
    ob, oc = overlay_rows(COMPOSITE)
    got = compute_summary(ob, oc, 0.10)
    want = compute_summary(BENEFITS_VERBATIM, COSTS_VERBATIM, 0.10)
    assert got["benefits_pv"] == pytest.approx(want["benefits_pv"], abs=0.01)
    assert got["costs_pv"] == pytest.approx(want["costs_pv"], abs=0.01)
    assert got["npv"] == pytest.approx(want["npv"], abs=0.01)


def test_driver_map_covers_every_row():
    assert set(BENEFIT_DRIVERS) == {r["field_key"] for r in BENEFITS_VERBATIM}
    assert set(COST_DRIVERS) == {r["field_key"] for r in COSTS_VERBATIM}


def test_scale_factor():
    d = ClientDrivers(agents_fte=1_000, annual_contacts_y1=40_000_000)
    assert scale_factor("agents", d) == pytest.approx(0.5)
    assert scale_factor("contacts", d) == pytest.approx(2.0)
    assert scale_factor("fixed", d) == 1.0
    with pytest.raises(KeyError):
        scale_factor("revenue", d)


def test_half_agents_halves_agent_rows_only():
    ob, oc = overlay_rows(ClientDrivers(agents_fte=1_000))
    assert _row(ob, "ai_forecasting_supervision")["year_values"]["1"] == \
        pytest.approx(6_651_680 / 2)
    assert _row(ob, "legacy_solution_savings")["year_values"]["1"] == \
        pytest.approx(6_177_600 / 2)
    # Contact-driven and fixed rows unmoved.
    assert _row(ob, "ai_contact_resolution")["year_values"]["1"] == \
        pytest.approx(13_911_040)
    assert _row(oc, "amazon_connect_usage")["year_values"]["1"] == \
        pytest.approx(6_456_448)
    assert _row(oc, "implementation_migration")["initial"] == 1_087_500


def test_double_contacts_doubles_usage_only():
    _, oc = overlay_rows(ClientDrivers(annual_contacts_y1=40_000_000))
    assert _row(oc, "amazon_connect_usage")["year_values"]["1"] == \
        pytest.approx(6_456_448 * 2)
    assert _row(oc, "implementation_migration")["year_values"]["1"] == \
        pytest.approx(188_333)
    assert _row(oc, "ongoing_management")["year_values"]["1"] == \
        pytest.approx(256_200)


def test_growth_rebase():
    assert growth_multiplier(1, 0.0) == 1.0                       # Y1 always 1.0
    assert growth_multiplier(2, 0.0) == pytest.approx(1 / 1.3)
    assert growth_multiplier(3, 0.0) == pytest.approx((1 / 1.3) ** 2)
    assert growth_multiplier(3, 0.30) == 1.0                      # composite growth = identity

    ob, oc = overlay_rows(ClientDrivers(growth_rate=0.0))
    row = _row(ob, "ai_contact_resolution")
    assert row["year_values"]["1"] == pytest.approx(13_911_040)
    assert row["year_values"]["2"] == pytest.approx(23_932_480 / 1.3)
    assert row["year_values"]["3"] == pytest.approx(37_797_760 / 1.3**2)
    # Fixed rows ignore the growth re-base too.
    assert _row(oc, "ongoing_management")["year_values"]["2"] == pytest.approx(187_200)


def test_drivers_frozen_and_rows_are_copies():
    with pytest.raises(dataclasses.FrozenInstanceError):
        COMPOSITE.agents_fte = 1  # type: ignore[misc]
    ob, oc = overlay_rows(COMPOSITE)
    ob[0]["year_values"]["1"] = -1
    oc[0]["year_values"]["1"] = -1
    assert BENEFITS_VERBATIM[0]["year_values"]["1"] == 13_911_040
    assert COSTS_VERBATIM[0]["year_values"]["1"] == 6_456_448