"""用户数据服务 — 收藏、阅读状态、个人笔记、阅读列表查询。无账号体系，数据写入本地 SQLite。"""

from __future__ import annotations

from sqlalchemy import or_, select
from sqlalchemy.orm import Session, joinedload

from app.models import PAPER_FULL_LOAD, Paper, PaperTag, UserBookmark, UserNote, UserReadingStatus
from app.utils import utc_now

# ── 收藏 ──────────────────────────────────────────────────────────────


def toggle_bookmark(db: Session, arxiv_id: str) -> dict:
    """切换收藏状态。返回 {"bookmarked": bool, "arxiv_id": str}。"""
    paper = db.execute(select(Paper).where(Paper.arxiv_id == arxiv_id)).scalar_one_or_none()
    if not paper:
        return {"error": "not_found"}

    existing = db.execute(
        select(UserBookmark).where(UserBookmark.paper_id == paper.id)
    ).scalar_one_or_none()
    if existing:
        db.delete(existing)
        db.commit()
        return {"bookmarked": False, "arxiv_id": arxiv_id}
    else:
        bookmark = UserBookmark(
            paper_id=paper.id,
            created_at=utc_now(),
        )
        db.add(bookmark)
        db.commit()
        return {"bookmarked": True, "arxiv_id": arxiv_id}


# ── 阅读状态 ──────────────────────────────────────────────────────────

VALID_STATUSES = {"unread", "skimmed", "read_summary", "read_full"}


def set_reading_status(db: Session, arxiv_id: str, status: str) -> dict:
    """设置阅读状态。status 必须是 unread/skimmed/read_summary/read_full。"""
    if status not in VALID_STATUSES:
        return {"error": "invalid_status", "valid": sorted(VALID_STATUSES)}

    paper = db.execute(select(Paper).where(Paper.arxiv_id == arxiv_id)).scalar_one_or_none()
    if not paper:
        return {"error": "not_found"}

    now = utc_now()
    existing = db.execute(
        select(UserReadingStatus).where(UserReadingStatus.paper_id == paper.id)
    ).scalar_one_or_none()
    if existing:
        existing.status = status
        existing.updated_at = now
    else:
        db.add(
            UserReadingStatus(
                paper_id=paper.id,
                status=status,
                updated_at=now,
            )
        )
    db.commit()
    return {"arxiv_id": arxiv_id, "status": status}


# ── 笔记 ──────────────────────────────────────────────────────────────


def get_note(db: Session, arxiv_id: str) -> dict | None:
    """获取笔记。返回 {"arxiv_id", "content", "updated_at"} 或 None（论文不存在时）。"""
    paper = db.execute(select(Paper).where(Paper.arxiv_id == arxiv_id)).scalar_one_or_none()
    if not paper:
        return None

    note = db.execute(
        select(UserNote).where(UserNote.paper_id == paper.id)
    ).scalar_one_or_none()
    if not note:
        return {"arxiv_id": arxiv_id, "content": "", "updated_at": None}

    return {
        "arxiv_id": arxiv_id,
        "content": note.content,
        "updated_at": note.updated_at.isoformat() if note.updated_at else None,
    }


def save_note(db: Session, arxiv_id: str, content: str) -> dict:
    """创建或更新笔记。返回 {"arxiv_id", "content", "updated_at"}。"""
    paper = db.execute(select(Paper).where(Paper.arxiv_id == arxiv_id)).scalar_one_or_none()
    if not paper:
        return {"error": "not_found"}

    now = utc_now()
    existing = db.execute(
        select(UserNote).where(UserNote.paper_id == paper.id)
    ).scalar_one_or_none()
    if existing:
        existing.content = content
        existing.updated_at = now
    else:
        db.add(
            UserNote(
                paper_id=paper.id,
                content=content,
                created_at=now,
                updated_at=now,
            )
        )
    db.commit()
    return {
        "arxiv_id": arxiv_id,
        "content": content,
        "updated_at": now.isoformat(),
    }


# ── 阅读列表 ──────────────────────────────────────────────────────────


def query_reading_list(
    db: Session,
    filter_type: str,
    tag: str | None,
) -> list[Paper]:
    """根据筛选条件查询阅读列表。"""
    # 基础：有任意用户数据的论文
    stmt = select(Paper).where(
        or_(
            Paper.bookmark.has(),
            Paper.reading_status.has(),
            Paper.note.has(),
        )
    )

    # 应用筛选
    if filter_type == "has_note":
        stmt = stmt.where(Paper.note.has())
    elif filter_type in ("unread", "skimmed", "read_summary", "read_full"):
        stmt = stmt.where(
            Paper.reading_status.has(UserReadingStatus.status == filter_type)
        )

    # 应用标签
    if tag:
        stmt = stmt.where(Paper.tags.any(PaperTag.tag == tag))

    return (
        db.execute(
            stmt.options(
                joinedload(Paper.note),
                *PAPER_FULL_LOAD,
            )
            .order_by(Paper.paper_date.desc(), Paper.upvotes.desc())
        )
        .unique()
        .scalars()
        .all()
    )