"""Scenario — the named retrofit brief the Modelling stage scores against.

Built by a user in the scenario-builder UI and persisted before any modelling
fires; the pipeline is handed only its id and reads it back via a
`ScenarioRepository`. This is the thin slice the Modelling stage uses today:
the goal + budget that the Optimiser will consume (#1160) and `is_default`
(which drives `plan.is_default`). The legacy file-path / portfolio-aggregate
columns are not modelled. Carries no phases — multi-phase is deferred
(ADR-0005). See CONTEXT.md.
"""

from dataclasses import dataclass
from typing import Optional

from domain.modelling.measure_type import MeasureType

_NO_EXCLUSIONS: frozenset[MeasureType] = frozenset()


@dataclass(frozen=True)
class Scenario:
    """A retrofit brief: its goal, optional budget, and whether it is the
    Property's default Scenario. `goal` / `goal_value` are the lodged target
    (e.g. "INCREASING_EPC" → band "C"); carried for the Optimiser, not yet
    enforced.

    `exclusions` are the measure types the brief bars from the run (the only
    measure-scoping the live ``scenario`` table persists — there is no
    inclusions column). Empty means nothing is barred."""

    id: int
    goal: str
    goal_value: str
    budget: Optional[float]
    is_default: bool
    exclusions: frozenset[MeasureType] = _NO_EXCLUSIONS

    def considered_measures(self) -> Optional[frozenset[MeasureType]]:
        """The measure-type allowlist the Scenario's exclusions imply: every
        modelled measure minus the excluded ones, or None (consider every
        measure) when nothing is excluded."""
        if not self.exclusions:
            return None
        return frozenset(MeasureType) - self.exclusions