src/case_zero/engine/game_state.py

"""Immutable runtime state for a play session.

Nothing here is mutated in place. Reducers in ``state_update`` return new instances
via ``model_copy``, so the UI can hold snapshots safely and history is never clobbered.
"""

from __future__ import annotations

from enum import StrEnum

from pydantic import BaseModel, ConfigDict, Field

from ..schemas.accusation import Verdict


class Exchange(BaseModel):
    model_config = ConfigDict(frozen=True)

    turn_index: int
    question: str
    answer: str


class NotebookKind(StrEnum):
    CLUE = "clue"
    CONTRADICTION = "contradiction"
    LEAD = "lead"
    NOTE = "note"


class NotebookEntry(BaseModel):
    model_config = ConfigDict(frozen=True)

    kind: NotebookKind
    text: str
    turn_index: int
    suspect_id: str | None = None
    clue_id: str | None = None


class SuspectState(BaseModel):
    """Per-suspect mutable-by-copy interrogation state."""

    model_config = ConfigDict(frozen=True)

    sus_id: str
    stress: float = Field(default=0.0, ge=0.0, le=1.0)
    rapport: float = Field(default=0.0, ge=-1.0, le=1.0)
    turns: int = 0
    transcript: tuple[Exchange, ...] = ()
    revealed_fact_ids: frozenset[str] = frozenset()
    evidence_shown: frozenset[str] = frozenset()
    broken_lie_ids: frozenset[str] = frozenset()
    contradictions: tuple[str, ...] = ()


class GameState(BaseModel):
    """The whole session snapshot."""

    model_config = ConfigDict(frozen=True)

    case_id: str
    suspect_states: dict[str, SuspectState]
    discovered_clue_ids: frozenset[str] = frozenset()
    current_suspect_id: str | None = None
    turn_count: int = 0
    notebook: tuple[NotebookEntry, ...] = ()
    solved: bool = False
    verdict: Verdict | None = None

    def state_for(self, sus_id: str) -> SuspectState:
        return self.suspect_states[sus_id]


def new_game_state(case_id: str, suspect_ids: tuple[str, ...]) -> GameState:
    return GameState(
        case_id=case_id,
        suspect_states={sid: SuspectState(sus_id=sid) for sid in suspect_ids},
        current_suspect_id=suspect_ids[0] if suspect_ids else None,
    )