"""자료실 회독 카운트 API — append-only 로그 기반.

동작 규칙 (사용자 명시):
  - detail 페이지 진입만으로 자동 +1 금지. 명시 클릭 시에만 호출.
  - POST /api/documents/{id}/read       → row 1개 insert (회독 +1)
  - GET  /api/documents/{id}/read-stats → {read_count, last_read_at}
  - DELETE /api/documents/{id}/read/last → 현재 사용자의 그 문서 마지막 row 1개만 삭제

ownership:
  - documents 테이블에 user_id 없음 (single-user). document_reads.user_id 로
    사용자 분리. multi-user 전환 시 documents.user_id 추가 후 ownership check 필요.
"""

import logging
from datetime import datetime
from typing import Annotated

from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel
from sqlalchemy import delete, func, select
from sqlalchemy.ext.asyncio import AsyncSession

from core.auth import get_current_user
from core.database import get_session
from models.document import Document
from models.document_read import DocumentRead
from models.user import User

logger = logging.getLogger(__name__)
router = APIRouter()


class ReadStats(BaseModel):
    read_count: int
    last_read_at: datetime | None


async def _get_stats(
    session: AsyncSession, user_id: int, document_id: int
) -> ReadStats:
    row = await session.execute(
        select(
            func.count(DocumentRead.id),
            func.max(DocumentRead.read_at),
        ).where(
            DocumentRead.user_id == user_id,
            DocumentRead.document_id == document_id,
        )
    )
    count, last = row.one()
    return ReadStats(read_count=int(count or 0), last_read_at=last)


async def _verify_document_visible(
    session: AsyncSession, document_id: int
) -> Document:
    """문서 존재 + 미삭제 확인. ownership 은 single-user 가정으로 통과."""
    doc = await session.get(Document, document_id)
    if doc is None or getattr(doc, "deleted_at", None) is not None:
        raise HTTPException(status_code=404, detail="문서를 찾을 수 없습니다")
    return doc


@router.post("/{document_id}/read", response_model=ReadStats, status_code=201)
async def add_read(
    document_id: int,
    user: Annotated[User, Depends(get_current_user)],
    session: Annotated[AsyncSession, Depends(get_session)],
):
    """회독 +1 — 사용자 명시 클릭. 같은 날 여러 번 호출 가능 (각각 별개 회독)."""
    await _verify_document_visible(session, document_id)
    session.add(DocumentRead(user_id=user.id, document_id=document_id))
    await session.commit()
    return await _get_stats(session, user.id, document_id)


@router.get("/{document_id}/read-stats", response_model=ReadStats)
async def get_read_stats(
    document_id: int,
    user: Annotated[User, Depends(get_current_user)],
    session: Annotated[AsyncSession, Depends(get_session)],
):
    """현재 사용자의 그 문서 회독 통계."""
    await _verify_document_visible(session, document_id)
    return await _get_stats(session, user.id, document_id)


@router.delete("/{document_id}/read/last", response_model=ReadStats)
async def delete_last_read(
    document_id: int,
    user: Annotated[User, Depends(get_current_user)],
    session: Annotated[AsyncSession, Depends(get_session)],
):
    """현재 사용자의 그 문서 마지막 회독 row 1개만 삭제 (실수 클릭 취소)."""
    await _verify_document_visible(session, document_id)
    # 현재 사용자 + 해당 문서의 가장 최근 row 1건만.
    last = await session.execute(
        select(DocumentRead.id)
        .where(
            DocumentRead.user_id == user.id,
            DocumentRead.document_id == document_id,
        )
        .order_by(DocumentRead.read_at.desc(), DocumentRead.id.desc())
        .limit(1)
    )
    last_id = last.scalar_one_or_none()
    if last_id is not None:
        await session.execute(
            delete(DocumentRead).where(DocumentRead.id == last_id)
        )
        await session.commit()
    return await _get_stats(session, user.id, document_id)