from __future__ import annotations
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from services.db.conversation_repository import ConversationRepository
    from services.chat.compact_service import CompactService


class HistoryService:
    """대화 히스토리를 관리하는 서비스."""

    def __init__(
        self,
        system_prompt: str,
        max_turns: int,
        compact_threshold: int,
        repository: ConversationRepository | None = None,
        compact_service: CompactService | None = None,
    ):
        self._system_prompt = system_prompt
        self._max_turns = max_turns
        self._compact_threshold = compact_threshold
        self._repository = repository
        self._compact_service = compact_service
        self._summary: str | None = None
        self._turns: list[dict] = []
        self._conversation_id: int | None = None

        if repository:
            self._load_or_create()

    # ── DB 초기화 ────────────────────────────────────────────────

    def _load_or_create(self) -> None:
        conv_id = self._repository.get_latest_conversation_id()
        if conv_id:
            summary_id, summary = self._repository.get_latest_summary(conv_id)
            turns = self._repository.load_turns_after(
                conv_id, summary_id, self._compact_threshold * 2
            )
            self._summary = summary
            self._turns = turns
            self._conversation_id = conv_id
        else:
            self._conversation_id = self._repository.create_conversation()

    # ── 공개 인터페이스 ───────────────────────────────────────────

    def add(self, role: str, content: str) -> None:
        self._turns.append({"role": role, "content": content})
        if self._repository and self._conversation_id:
            self._repository.save_message(self._conversation_id, role, content)
        if role == "assistant":
            self._maybe_compact()

    def get(self) -> list[dict]:
        msgs = [{"role": "system", "content": self._system_prompt}]
        if self._summary:
            msgs.append({"role": "system", "content": f"[이전 대화 요약]\n{self._summary}"})
        msgs.extend(self._turns)
        return msgs

    def reset(self, new_conversation_id: int) -> None:
        self._summary = None
        self._turns = []
        self._conversation_id = new_conversation_id

    # ── 내부 ─────────────────────────────────────────────────────

    def _maybe_compact(self) -> None:
        if not self._compact_service or len(self._turns) <= self._compact_threshold:
            return

        mid = len(self._turns) // 2
        old_turns, self._turns = self._turns[:mid], self._turns[mid:]

        print("\n[대화 내용을 압축하는 중...]\n", flush=True)
        self._summary = self._compact_service.summarize(old_turns)

        if self._repository and self._conversation_id:
            self._repository.save_summary(self._conversation_id, self._summary)