from datetime import date
from uuid import UUID
from sqlalchemy import select, func, and_
from sqlalchemy.ext.asyncio import AsyncSession
from app.models.leave import Leave
from app.models.user import User
from app.utils.timezone import today_cst
from app.services.dashboard import get_week_range


async def get_leaves(
    db: AsyncSession,
    user_id: str,
    role: str,
    manager_id: str | None = None,
    status: str | None = None,
    page: int = 1,
    page_size: int = 25,
) -> dict:
    """List leaves. Managers see only their own."""
    today = today_cst()

    query = select(Leave)
    count_q = select(func.count(Leave.id))

    # Role filter
    if role == "manager":
        query = query.where(Leave.manager_id == user_id)
        count_q = count_q.where(Leave.manager_id == user_id)
    elif manager_id:
        query = query.where(Leave.manager_id == manager_id)
        count_q = count_q.where(Leave.manager_id == manager_id)

    # Status filter
    if status == "active":
        query = query.where(and_(Leave.start_date <= today, Leave.end_date >= today))
        count_q = count_q.where(and_(Leave.start_date <= today, Leave.end_date >= today))
    elif status == "upcoming":
        query = query.where(Leave.start_date > today)
        count_q = count_q.where(Leave.start_date > today)
    elif status == "past":
        query = query.where(Leave.end_date < today)
        count_q = count_q.where(Leave.end_date < today)

    total = (await db.execute(count_q)).scalar() or 0

    query = query.order_by(Leave.start_date.desc())
    query = query.offset((page - 1) * page_size).limit(page_size)
    result = await db.execute(query)
    rows = result.scalars().all()

    # Resolve names
    user_ids = set()
    for r in rows:
        user_ids.add(r.manager_id)
        user_ids.add(r.submitted_by)
    users_result = await db.execute(select(User).where(User.id.in_(user_ids)))
    user_map = {u.id: u.name for u in users_result.scalars().all()}

    items = []
    for r in rows:
        days = ((r.end_date - r.start_date).days + 1) if r.start_date and r.end_date else 0
        items.append({
            "id": r.id,
            "manager_id": r.manager_id,
            "manager_name": user_map.get(r.manager_id, ""),
            "leave_type": r.leave_type,
            "start_date": str(r.start_date),
            "end_date": str(r.end_date),
            "days": days,
            "reason": r.reason or "",
            "submitted_by": r.submitted_by,
            "submitted_by_name": user_map.get(r.submitted_by, ""),
            "created_at": str(r.created_at) if r.created_at else None,
            "updated_at": str(r.updated_at) if r.updated_at else None,
        })

    return {"items": items, "total": total, "page": page, "page_size": page_size}


async def get_leave_by_id(db: AsyncSession, leave_id: UUID) -> Leave | None:
    result = await db.execute(select(Leave).where(Leave.id == leave_id))
    return result.scalar()


async def create_leave(
    db: AsyncSession,
    data: dict,
    submitted_by: UUID,
    role: str,
) -> Leave:
    """Create leave. Manager can only create for self; director can create for anyone."""
    if role == "manager":
        if str(data.get("manager_id")) != str(submitted_by):
            raise PermissionError("客户经理只能为自己提交请假")

    if data["start_date"] > data["end_date"]:
        raise ValueError("结束日期不能早于开始日期")

    leave = Leave(
        manager_id=data["manager_id"],
        leave_type=data.get("leave_type", "事假"),
        start_date=data["start_date"],
        end_date=data["end_date"],
        reason=data.get("reason", ""),
        submitted_by=submitted_by,
    )
    db.add(leave)
    await db.commit()
    await db.refresh(leave)
    return leave


async def update_leave(
    db: AsyncSession,
    leave_id: UUID,
    data: dict,
    user_id: UUID,
    role: str,
) -> Leave:
    """Update leave. Director can edit any; manager can edit own submitted leaves."""
    leave = await get_leave_by_id(db, leave_id)
    if not leave:
        raise ValueError("请假记录不存在")

    if role == "manager":
        if str(leave.submitted_by) != str(user_id):
            raise PermissionError("客户经理只能编辑自己提交的请假")

    for field in ("manager_id", "leave_type", "start_date", "end_date", "reason"):
        if field in data and data[field] is not None:
            setattr(leave, field, data[field])

    if leave.start_date > leave.end_date:
        raise ValueError("结束日期不能早于开始日期")

    await db.commit()
    await db.refresh(leave)
    return leave


async def delete_leave(
    db: AsyncSession,
    leave_id: UUID,
    user_id: UUID,
    role: str,
) -> bool:
    """Delete leave. Director can delete any; manager can delete own submitted leaves."""
    leave = await get_leave_by_id(db, leave_id)
    if not leave:
        return False

    if role == "manager":
        if str(leave.submitted_by) != str(user_id):
            raise PermissionError("客户经理只能删除自己提交的请假")

    await db.delete(leave)
    await db.commit()
    return True


async def get_leave_overview(
    db: AsyncSession,
    user_id: str,
    role: str,
    reference_date: date | None = None,
) -> dict:
    """Get leave overview for the dashboard card. Returns leaves overlapping with current week."""
    monday, sunday = get_week_range(reference_date)

    query = select(Leave).where(
        and_(Leave.start_date <= sunday, Leave.end_date >= monday)
    )
    if role == "manager":
        query = query.where(Leave.manager_id == user_id)

    result = await db.execute(query.order_by(Leave.start_date))
    rows = result.scalars().all()

    # Deduplicate by manager_id (one manager may have multiple leave records)
    user_ids = set(r.manager_id for r in rows)
    users_result = await db.execute(select(User).where(User.id.in_(user_ids)))
    user_map = {u.id: u.name for u in users_result.scalars().all()}

    manager_set = set()
    leave_list = []
    for r in rows:
        days = ((r.end_date - r.start_date).days + 1) if r.start_date and r.end_date else 0
        leave_list.append({
            "manager_id": str(r.manager_id),
            "manager_name": user_map.get(r.manager_id, ""),
            "leave_type": r.leave_type,
            "start_date": str(r.start_date),
            "end_date": str(r.end_date),
            "days": days,
        })
        manager_set.add(str(r.manager_id))

    return {
        "week_start": str(monday),
        "week_end": str(sunday),
        "total_on_leave": len(manager_set),
        "leave_list": leave_list,
    }