import uuid
from datetime import datetime, timezone
from fastapi import APIRouter, Depends, HTTPException
from fastapi.responses import StreamingResponse
from pydantic import BaseModel
from sqlalchemy.orm import Session as DBSession

from app.db.database import get_db
from app.db.models import Session, Message
from app.core import memory as mem
from app.core import llm
from app.core.config import DEFAULT_MODEL

router = APIRouter(prefix="/chat", tags=["chat"])


class ChatRequest(BaseModel):
    session_id: str | None = None
    message: str
    model: str | None = None


class SessionResponse(BaseModel):
    id: str
    title: str
    model: str
    updated_at: datetime

    class Config:
        from_attributes = True


class MessageResponse(BaseModel):
    id: int
    role: str
    content: str
    created_at: datetime

    class Config:
        from_attributes = True


@router.get("/sessions", response_model=list[SessionResponse])
def list_sessions(db: DBSession = Depends(get_db)):
    return db.query(Session).order_by(Session.updated_at.desc()).all()


@router.get("/sessions/{session_id}/messages", response_model=list[MessageResponse])
def get_messages(session_id: str, db: DBSession = Depends(get_db)):
    session = db.get(Session, session_id)
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")
    return session.messages


@router.delete("/sessions/{session_id}", status_code=204)
def delete_session(session_id: str, db: DBSession = Depends(get_db)):
    session = db.get(Session, session_id)
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")
    db.delete(session)
    db.commit()


@router.post("/stream")
async def stream_chat(req: ChatRequest, db: DBSession = Depends(get_db)):
    # セッション取得 or 新規作成
    if req.session_id:
        session = db.get(Session, req.session_id)
        if not session:
            raise HTTPException(status_code=404, detail="Session not found")
    else:
        session = Session(
            id=str(uuid.uuid4()),
            title=req.message[:40],
            model=req.model or DEFAULT_MODEL,
        )
        db.add(session)
        db.commit()

    # ユーザーメッセージを保存
    user_msg = Message(session_id=session.id, role="user", content=req.message)
    db.add(user_msg)
    db.commit()

    context = mem.get_context_messages(db, session.id)

    async def generate():
        import json as _json

        def sse(payload: dict) -> str:
            return f"data: {_json.dumps(payload, ensure_ascii=False)}\n\n"

        # セッションIDをまず返す（新規セッション時にフロントへ通知）
        yield sse({"type": "session_id", "value": session.id})

        full_response = []
        try:
            async for chunk in llm.stream_chat(context, model=req.model or session.model, session_id=session.id):
                full_response.append(chunk)
                yield sse({"type": "chunk", "value": chunk})

            # アシスタントメッセージを保存
            assistant_content = "".join(full_response)
            db.add(Message(session_id=session.id, role="assistant", content=assistant_content))
            session.updated_at = datetime.now(timezone.utc)
            db.commit()

            # メモリ要約チェック
            await mem.maybe_summarize(db, session)

            yield sse({"type": "done"})

        except Exception as e:
            yield sse({"type": "error", "value": str(e)})

    return StreamingResponse(
        generate(),
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "X-Accel-Buffering": "no",
            "Connection": "keep-alive",
        },
    )