# File: backend/app/api/v1/endpoints/messages.py (New)
# Description: API endpoint for fetching messages

from fastapi import APIRouter, Depends, HTTPException, status, Query
from typing import List
from sqlalchemy.ext.asyncio import AsyncSession
from app.db.database import get_db_session
from app.models.pydantic_models import MessageRead
from app.db.models import MessageModel # Import DB model
from sqlalchemy.future import select

router = APIRouter()

@router.get("/session/{session_id}", response_model=List[MessageRead])
async def read_messages_for_session(
    session_id: str,
    db: AsyncSession = Depends(get_db_session),
    skip: int = Query(0, ge=0), # Offset for pagination
    limit: int = Query(100, ge=1, le=500) # Limit number of messages
):
    """获取指定会话的消息列表 (按时间顺序)"""
    # TODO: Add check if session exists
    stmt = (
        select(MessageModel)
        .filter(MessageModel.session_id == session_id)
        .order_by(MessageModel.order.asc()) # Fetch in chronological order
        .offset(skip)
        .limit(limit)
    )
    result = await db.execute(stmt)
    messages = result.scalars().all()
    # Validate using Pydantic model before returning
    return [MessageRead.model_validate(msg) for msg in messages]