"""Scheduled backup management."""
from __future__ import annotations

import asyncio

from fastapi import APIRouter, Depends, HTTPException, Request
from sqlmodel import Session, select

from auth import require_admin
from database import get_session
from models.backup_destination import BackupDestination
from models.backup_schedule import (
    FREQUENCIES,
    BackupSchedule,
    ScheduleCreate,
    ScheduleRead,
    ScheduleUpdate,
    describe_stacks,
    set_stacks,
    stacks_of,
    status_of,
)
from models.stack import Stack
from models.user import User
from services import audit_service, schedule_service

router = APIRouter(prefix="/api/backups/schedules", tags=["backups"])


def _ip(request: Request) -> str:
    return request.client.host if request.client else "unknown"


def _to_read(session: Session, s: BackupSchedule) -> ScheduleRead:
    dest = session.get(BackupDestination, s.destination_id)
    stack_ids = stacks_of(s)
    return ScheduleRead(
        id=s.id,
        stack_ids=stack_ids,
        all_stacks=s.all_stacks,
        stack_id=stack_ids[0] if len(stack_ids) == 1 and not s.all_stacks else "",
        destination_id=s.destination_id,
        destination_name=dest.name if dest else None,
        frequency=s.frequency,
        hour=s.hour,
        minute=s.minute,
        weekday=s.weekday,
        include_volumes=s.include_volumes,
        stop_first=s.stop_first,
        keep=s.keep,
        enabled=s.enabled,
        last_run=s.last_run,
        last_status=s.last_status,
        stack_status=status_of(s),
        running=schedule_service.is_running(s.id),
        next_run=s.next_run,
        created_at=s.created_at,
    )


def _get_or_404(session: Session, schedule_id: int) -> BackupSchedule:
    s = session.get(BackupSchedule, schedule_id)
    if not s:
        raise HTTPException(status_code=404, detail=f"Schedule {schedule_id} not found")
    return s


def _validate(session: Session, schedule: BackupSchedule) -> None:
    if schedule.frequency not in FREQUENCIES:
        raise HTTPException(status_code=400, detail=f"Unknown frequency '{schedule.frequency}'")
    if not session.get(BackupDestination, schedule.destination_id):
        raise HTTPException(status_code=404, detail=f"Destination {schedule.destination_id} not found")
    if schedule.all_stacks:
        return
    stack_ids = stacks_of(schedule)
    if not stack_ids:
        raise HTTPException(status_code=400, detail="Choose at least one stack, or all stacks")
    missing = [sid for sid in stack_ids if not session.get(Stack, sid)]
    if missing:
        raise HTTPException(status_code=404, detail=f"Stack(s) not found: {', '.join(missing)}")


@router.get("", response_model=list[ScheduleRead])
def list_schedules(
    session: Session = Depends(get_session),
    _user: User = Depends(require_admin),
) -> list[ScheduleRead]:
    rows = session.exec(select(BackupSchedule).order_by(BackupSchedule.id)).all()
    return [_to_read(session, s) for s in rows]


@router.post("", response_model=ScheduleRead, status_code=201)
def create_schedule(
    body: ScheduleCreate,
    request: Request,
    session: Session = Depends(get_session),
    user: User = Depends(require_admin),
) -> ScheduleRead:
    data = body.model_dump(exclude={"stack_ids", "stack_id"})
    s = BackupSchedule(**data)
    set_stacks(s, body.stack_ids or ([body.stack_id] if body.stack_id else []))
    _validate(session, s)
    s.next_run = schedule_service.compute_next_run(
        s.frequency, s.hour, s.minute, s.weekday, schedule_service._now()
    )
    session.add(s)
    session.commit()
    session.refresh(s)
    audit_service.record(
        session, user=user.username, action="schedule.create", target=describe_stacks(s),
        detail=f"{s.frequency} → dest {s.destination_id}", ip=_ip(request),
    )
    return _to_read(session, s)


@router.put("/{schedule_id}", response_model=ScheduleRead)
def update_schedule(
    schedule_id: int,
    body: ScheduleUpdate,
    request: Request,
    session: Session = Depends(get_session),
    user: User = Depends(require_admin),
) -> ScheduleRead:
    s = _get_or_404(session, schedule_id)
    data = body.model_dump(exclude_unset=True)
    stack_ids = data.pop("stack_ids", None)
    for k, v in data.items():
        setattr(s, k, v)
    if stack_ids is not None:
        set_stacks(s, stack_ids)
    _validate(session, s)
    # Recompute next run when timing fields change.
    if {"frequency", "hour", "minute", "weekday"} & set(data) or s.next_run is None:
        s.next_run = schedule_service.compute_next_run(
            s.frequency, s.hour, s.minute, s.weekday, schedule_service._now()
        )
    session.add(s)
    session.commit()
    session.refresh(s)
    audit_service.record(
        session, user=user.username, action="schedule.update", target=describe_stacks(s),
        ip=_ip(request),
    )
    return _to_read(session, s)


@router.delete("/{schedule_id}")
def delete_schedule(
    schedule_id: int,
    request: Request,
    session: Session = Depends(get_session),
    user: User = Depends(require_admin),
) -> dict:
    s = _get_or_404(session, schedule_id)
    target = describe_stacks(s)
    session.delete(s)
    session.commit()
    audit_service.record(
        session, user=user.username, action="schedule.delete", target=target,
        ip=_ip(request),
    )
    return {"ok": True}


#: Keeps "Run now" tasks referenced until they finish (asyncio only holds
#: weak references to tasks).
_tasks: set[asyncio.Task] = set()


@router.post("/{schedule_id}/run", status_code=202)
async def run_now(
    schedule_id: int,
    request: Request,
    session: Session = Depends(get_session),
    user: User = Depends(require_admin),
) -> dict:
    """Start the schedule in the background. Backing up several stacks takes
    far longer than a request may; the list shows ``running`` and then the
    per-stack results."""
    s = _get_or_404(session, schedule_id)
    if schedule_service.is_running(s.id):
        raise HTTPException(status_code=409, detail="This schedule is already running")
    task = asyncio.create_task(schedule_service.run_in_background(s.id))
    _tasks.add(task)
    task.add_done_callback(_tasks.discard)
    audit_service.record(
        session, user=user.username, action="schedule.run", target=describe_stacks(s),
        ip=_ip(request),
    )
    return {"started": True}