"""Small write/decision boundary for the journal MVP. Not a policy engine."""
from __future__ import annotations


from conversation_signals import similar_enough


class PolicyError(Exception):
    def __init__(self, code: str, message: str, status_code: int = 400):
        super().__init__(message)
        self.code = code
        self.message = message
        self.status_code = status_code


ENTRY_ORIGINS = {"user_edit", "accepted_draft", "restore"}


def require_explicit_generate(explicit: bool) -> None:
    if not explicit:
        raise PolicyError("generate_not_explicit", "Journal Drafts entstehen nur auf ausdrückliche Aktion.")


def consolidation_offer(conversations: list[dict] | int) -> bool:
    """Offer merge only when conversations look narratively compatible. User decides."""
    if isinstance(conversations, int):
        return False
    return similar_enough(conversations)


def source_conversation_ids(explicit_ids: list[str] | None, day_conversation_ids: list[str]) -> list[str]:
    """Missing selection never silently merges multiple conversations."""
    known = [item for item in day_conversation_ids if item]
    if explicit_ids:
        chosen = [item for item in explicit_ids if item in known]
        if not chosen:
            raise PolicyError("unknown_conversation", "Keine der angegebenen Conversations gehört zu diesem Tag.")
        return chosen
    if not known:
        raise PolicyError("no_source_dialogue", "Ohne Dialog gibt es nichts zu erzeugen.")
    return [known[-1]]


def draft_must_not_touch_entry() -> None:
    return None


def require_origin(origin: str) -> str:
    if origin not in ENTRY_ORIGINS:
        raise PolicyError("invalid_origin", "origin muss user_edit, accepted_draft oder restore sein")
    return origin