"""Calendar API router.

BE-CAL-004: MinimumWorkload CRUD endpoints.
BE-CAL-API-001: Single-slot creation endpoint.
BE-CAL-API-002: Day-view calendar query endpoint.
BE-CAL-API-003: Calendar slot edit endpoints (real + virtual).
BE-CAL-API-004: Calendar slot cancel endpoints (real + virtual).
BE-CAL-API-005: Plan schedule / plan list endpoints.
BE-CAL-API-006: Plan edit / plan cancel endpoints.
BE-CAL-API-007: Date-list endpoint.
"""

from datetime import date as date_type, datetime, timezone
from typing import Optional

from fastapi import APIRouter, Depends, Header, HTTPException, Query
from sqlalchemy.orm import Session

from app.api.deps import get_current_user
from app.core.config import get_db
from app.models.calendar import SchedulePlan, SlotStatus, SlotType, TimeSlot
from app.models.models import User
from app.models.agent import Agent, AgentStatus, ExhaustReason
from app.schemas.calendar import (
    AgentHeartbeatResponse,
    AgentStatusUpdateRequest,
    CalendarDayResponse,
    CalendarSlotItem,
    DateListResponse,
    MinimumWorkloadConfig,
    MinimumWorkloadResponse,
    MinimumWorkloadUpdate,
    SchedulePlanCancelResponse,
    SchedulePlanCreate,
    SchedulePlanEdit,
    SchedulePlanListResponse,
    SchedulePlanResponse,
    SlotStatusEnum,
    SlotConflictItem,
    SlotAgentUpdate,
    TimeSlotCancelResponse,
    TimeSlotCreate,
    TimeSlotCreateResponse,
    TimeSlotEdit,
    TimeSlotEditResponse,
    TimeSlotResponse,
)
from app.services.agent_heartbeat import get_pending_slots_for_agent
from app.services.agent_status import (
    record_heartbeat,
    transition_to_busy,
    transition_to_idle,
    transition_to_offline,
    transition_to_exhausted,
)
from app.services.discord_wakeup import create_private_wakeup_channel
from app.services.minimum_workload import (
    get_workload_config,
    get_workload_warnings_for_date,
    replace_workload_config,
    upsert_workload_config,
)
from app.services.overlap import check_overlap_for_create, check_overlap_for_edit
from app.services.plan_slot import (
    detach_slot_from_plan,
    get_virtual_slots_for_date,
    materialize_from_virtual_id,
    parse_virtual_slot_id,
)
from app.services.slot_immutability import (
    ImmutableSlotError,
    guard_cancel_real_slot,
    guard_cancel_virtual_slot,
    guard_edit_real_slot,
    guard_edit_virtual_slot,
    guard_plan_cancel_no_past_retroaction,
    guard_plan_edit_no_past_retroaction,
)
from app.models.role_permission import Permission, RolePermission

router = APIRouter(prefix="/calendar", tags=["Calendar"])


def _has_global_permission(db: Session, user: User, permission_name: str) -> bool:
    if user.is_admin:
        return True
    if not user.role_id:
        return False
    perm = db.query(Permission).filter(Permission.name == permission_name).first()
    if not perm:
        return False
    return db.query(RolePermission).filter(
        RolePermission.role_id == user.role_id,
        RolePermission.permission_id == perm.id,
    ).first() is not None


def _require_calendar_permission(db: Session, user: User, permission_name: str) -> User:
    if _has_global_permission(db, user, permission_name):
        return user
    raise HTTPException(status_code=403, detail=f"Calendar permission '{permission_name}' required")


def require_calendar_read(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    return _require_calendar_permission(db, current_user, "calendar.read")


def require_calendar_write(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    return _require_calendar_permission(db, current_user, "calendar.write")


def require_calendar_manage(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    return _require_calendar_permission(db, current_user, "calendar.manage")


# ---------------------------------------------------------------------------
# TimeSlot creation (BE-CAL-API-001)
# ---------------------------------------------------------------------------

def _slot_to_response(slot: TimeSlot) -> TimeSlotResponse:
    """Convert a TimeSlot ORM object to a response schema."""
    return TimeSlotResponse(
        id=slot.id,
        user_id=slot.user_id,
        date=slot.date,
        slot_type=slot.slot_type.value if hasattr(slot.slot_type, "value") else str(slot.slot_type),
        estimated_duration=slot.estimated_duration,
        scheduled_at=slot.scheduled_at.isoformat() if slot.scheduled_at else "",
        started_at=slot.started_at.isoformat() if slot.started_at else None,
        attended=slot.attended,
        actual_duration=slot.actual_duration,
        event_type=slot.event_type.value if slot.event_type and hasattr(slot.event_type, "value") else (str(slot.event_type) if slot.event_type else None),
        event_data=slot.event_data,
        priority=slot.priority,
        status=slot.status.value if hasattr(slot.status, "value") else str(slot.status),
        plan_id=slot.plan_id,
        created_at=slot.created_at,
        updated_at=slot.updated_at,
    )


@router.post(
    "/slots",
    response_model=TimeSlotCreateResponse,
    status_code=201,
    summary="Create a single calendar slot",
)
def create_slot(
    payload: TimeSlotCreate,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Create a one-off calendar slot.

    - **Overlap detection**: rejects the request if the proposed slot
      overlaps with existing real or virtual slots on the same day.
    - **Workload warnings**: after successful creation, returns any
      minimum-workload warnings (advisory only, does not block creation).
    """
    target_date = payload.date or date_type.today()

    # --- Overlap check (hard reject) ---
    conflicts = check_overlap_for_create(
        db,
        user_id=current_user.id,
        target_date=target_date,
        scheduled_at=payload.scheduled_at,
        estimated_duration=payload.estimated_duration,
    )
    if conflicts:
        raise HTTPException(
            status_code=409,
            detail={
                "message": "Slot overlaps with existing schedule",
                "conflicts": [c.to_dict() for c in conflicts],
            },
        )

    # --- Create the slot ---
    slot = TimeSlot(
        user_id=current_user.id,
        date=target_date,
        slot_type=payload.slot_type.value,
        estimated_duration=payload.estimated_duration,
        scheduled_at=payload.scheduled_at,
        event_type=payload.event_type.value if payload.event_type else None,
        event_data=payload.event_data,
        priority=payload.priority,
        status=SlotStatus.NOT_STARTED,
    )
    db.add(slot)
    db.commit()
    db.refresh(slot)

    # --- Workload warnings (advisory) ---
    warnings = get_workload_warnings_for_date(db, current_user.id, target_date)

    return TimeSlotCreateResponse(
        slot=_slot_to_response(slot),
        warnings=warnings,
    )


# ---------------------------------------------------------------------------
# Day-view query (BE-CAL-API-002)
# ---------------------------------------------------------------------------

# Statuses that no longer occupy calendar time — hidden from default view.
_INACTIVE_STATUSES = {SlotStatus.SKIPPED.value, SlotStatus.ABORTED.value}


def _real_slot_to_item(slot: TimeSlot) -> CalendarSlotItem:
    """Convert a real TimeSlot ORM object to a CalendarSlotItem."""
    return CalendarSlotItem(
        id=slot.id,
        virtual_id=None,
        user_id=slot.user_id,
        date=slot.date,
        slot_type=slot.slot_type.value if hasattr(slot.slot_type, "value") else str(slot.slot_type),
        estimated_duration=slot.estimated_duration,
        scheduled_at=slot.scheduled_at.isoformat() if slot.scheduled_at else "",
        started_at=slot.started_at.isoformat() if slot.started_at else None,
        attended=slot.attended,
        actual_duration=slot.actual_duration,
        event_type=slot.event_type.value if slot.event_type and hasattr(slot.event_type, "value") else (str(slot.event_type) if slot.event_type else None),
        event_data=slot.event_data,
        priority=slot.priority,
        status=slot.status.value if hasattr(slot.status, "value") else str(slot.status),
        plan_id=slot.plan_id,
        created_at=slot.created_at,
        updated_at=slot.updated_at,
    )


def _virtual_slot_to_item(vs: dict) -> CalendarSlotItem:
    """Convert a virtual-slot dict to a CalendarSlotItem."""
    slot_type = vs["slot_type"]
    slot_type_str = slot_type.value if hasattr(slot_type, "value") else str(slot_type)

    event_type = vs.get("event_type")
    event_type_str = None
    if event_type is not None:
        event_type_str = event_type.value if hasattr(event_type, "value") else str(event_type)

    status = vs["status"]
    status_str = status.value if hasattr(status, "value") else str(status)

    scheduled_at = vs["scheduled_at"]
    scheduled_at_str = scheduled_at.isoformat() if hasattr(scheduled_at, "isoformat") else str(scheduled_at)

    return CalendarSlotItem(
        id=None,
        virtual_id=vs["virtual_id"],
        user_id=vs["user_id"],
        date=vs["date"],
        slot_type=slot_type_str,
        estimated_duration=vs["estimated_duration"],
        scheduled_at=scheduled_at_str,
        started_at=None,
        attended=vs.get("attended", False),
        actual_duration=vs.get("actual_duration"),
        event_type=event_type_str,
        event_data=vs.get("event_data"),
        priority=vs.get("priority", 0),
        status=status_str,
        plan_id=vs.get("plan_id"),
        created_at=None,
        updated_at=None,
    )


def _require_agent(db: Session, agent_id: str, claw_identifier: str) -> Agent:
    agent = (
        db.query(Agent)
        .filter(Agent.agent_id == agent_id, Agent.claw_identifier == claw_identifier)
        .first()
    )
    if agent is None:
        raise HTTPException(status_code=404, detail="Agent not found")
    return agent


def _apply_agent_slot_update(slot: TimeSlot, payload: SlotAgentUpdate) -> None:
    slot.status = payload.status.value
    if payload.started_at is not None:
        slot.started_at = payload.started_at
        slot.attended = True
    if payload.actual_duration is not None:
        slot.actual_duration = payload.actual_duration
    if payload.status == SlotStatusEnum.ONGOING:
        slot.attended = True


def _maybe_trigger_discord_wakeup(db: Session, slot: TimeSlot) -> dict | None:
    """Trigger Discord wakeup if slot became ONGOING and not already sent."""
    # Only trigger for ONGOING status and if not already sent
    if slot.status != SlotStatus.ONGOING or slot.wakeup_sent_at is not None:
        return None

    # Get user and check for discord_user_id
    user = db.query(User).filter(User.id == slot.user_id).first()
    if not user or not user.discord_user_id:
        return None

    # Get agent for this user
    agent = db.query(Agent).filter(Agent.user_id == user.id).first()
    agent_id_str = agent.agent_id if agent else "unknown"

    # Build wakeup message
    title = f"HarborForge Slot: {slot.event_type.value if slot.event_type else 'work'}"
    message = (
        f"🎯 **Slot started**\n"
        f"Agent: `{agent_id_str}`\n"
        f"Type: {slot.slot_type.value}\n"
        f"Duration: {slot.estimated_duration}min\n"
        f"Priority: {slot.priority}\n"
        f"Use `hf calendar slot {slot.id}` for details."
    )

    try:
        result = create_private_wakeup_channel(
            discord_user_id=user.discord_user_id,
            title=title,
            message=message,
        )
        slot.wakeup_sent_at = datetime.now(timezone.utc)
        return {"ok": True, "channel_id": result.get("channel_id")}
    except Exception as e:
        # Log but don't fail the slot update
        return {"ok": False, "error": str(e)}


@router.api_route(
    "/agent/heartbeat",
    methods=["GET", "POST"],
    response_model=AgentHeartbeatResponse,
    summary="Get all due slots for the calling agent",
)
def agent_heartbeat(
    x_agent_id: str = Header(..., alias="X-Agent-ID"),
    x_claw_identifier: str = Header(..., alias="X-Claw-Identifier"),
    db: Session = Depends(get_db),
):
    agent = _require_agent(db, x_agent_id, x_claw_identifier)
    record_heartbeat(db, agent)
    slots = get_pending_slots_for_agent(db, agent.user_id, now=datetime.now(timezone.utc))
    db.commit()
    return AgentHeartbeatResponse(
        slots=[_real_slot_to_item(slot) for slot in slots],
        agent_status=agent.status.value if hasattr(agent.status, 'value') else str(agent.status),
        message=f"{len(slots)} due slot(s)",
    )


@router.patch(
    "/slots/{slot_id}/agent-update",
    response_model=TimeSlotEditResponse,
    summary="Agent updates a real slot status",
)
def agent_update_real_slot(
    slot_id: int,
    payload: SlotAgentUpdate,
    x_agent_id: str = Header(..., alias="X-Agent-ID"),
    x_claw_identifier: str = Header(..., alias="X-Claw-Identifier"),
    db: Session = Depends(get_db),
):
    agent = _require_agent(db, x_agent_id, x_claw_identifier)
    slot = db.query(TimeSlot).filter(TimeSlot.id == slot_id, TimeSlot.user_id == agent.user_id).first()
    if slot is None:
        raise HTTPException(status_code=404, detail="Slot not found")
    _apply_agent_slot_update(slot, payload)
    _maybe_trigger_discord_wakeup(db, slot)
    db.commit()
    db.refresh(slot)
    return TimeSlotEditResponse(slot=_slot_to_response(slot), warnings=[])


@router.patch(
    "/slots/virtual/{virtual_id}/agent-update",
    response_model=TimeSlotEditResponse,
    summary="Agent materializes and updates a virtual slot status",
)
def agent_update_virtual_slot(
    virtual_id: str,
    payload: SlotAgentUpdate,
    x_agent_id: str = Header(..., alias="X-Agent-ID"),
    x_claw_identifier: str = Header(..., alias="X-Claw-Identifier"),
    db: Session = Depends(get_db),
):
    agent = _require_agent(db, x_agent_id, x_claw_identifier)
    slot = materialize_from_virtual_id(db, virtual_id)
    if slot.user_id != agent.user_id:
        db.rollback()
        raise HTTPException(status_code=404, detail="Slot not found")
    _apply_agent_slot_update(slot, payload)
    _maybe_trigger_discord_wakeup(db, slot)
    db.commit()
    db.refresh(slot)
    return TimeSlotEditResponse(slot=_slot_to_response(slot), warnings=[])


@router.post(
    "/agent/status",
    summary="Update agent runtime status from plugin",
)
def update_agent_status(
    payload: AgentStatusUpdateRequest,
    db: Session = Depends(get_db),
):
    agent = _require_agent(db, payload.agent_id, payload.claw_identifier)
    target = (payload.status or '').lower().strip()
    if target == AgentStatus.IDLE.value:
        transition_to_idle(db, agent)
    elif target == AgentStatus.BUSY.value:
        transition_to_busy(db, agent, slot_type=SlotType.WORK)
    elif target == AgentStatus.ON_CALL.value:
        transition_to_busy(db, agent, slot_type=SlotType.ON_CALL)
    elif target == AgentStatus.OFFLINE.value:
        transition_to_offline(db, agent)
    elif target == AgentStatus.EXHAUSTED.value:
        reason = ExhaustReason.BILLING if payload.exhaust_reason == 'billing' else ExhaustReason.RATE_LIMIT
        transition_to_exhausted(db, agent, reason=reason, recovery_at=payload.recovery_at)
    else:
        raise HTTPException(status_code=400, detail="Unsupported agent status")
    db.commit()
    return {"ok": True, "agent_id": agent.agent_id, "status": agent.status.value if hasattr(agent.status, 'value') else str(agent.status)}


@router.get(
    "/day",
    response_model=CalendarDayResponse,
    summary="Get all calendar slots for a given day",
)
def get_calendar_day(
    date: Optional[date_type] = Query(None, description="Target date (defaults to today)"),
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_read),
):
    """Return all calendar slots for the authenticated user on the given date.

    The response merges:
    1. **Real (materialized) slots** — rows from the ``time_slots`` table.
    2. **Virtual (plan-generated) slots** — synthesized from active
       ``SchedulePlan`` rules that match the date but have not yet been
       materialized.

    All slots are sorted by ``scheduled_at`` ascending.  Inactive slots
    (skipped / aborted) are excluded by default.
    """
    target_date = date or date_type.today()

    # 1. Fetch real slots for the day
    real_slots = (
        db.query(TimeSlot)
        .filter(
            TimeSlot.user_id == current_user.id,
            TimeSlot.date == target_date,
            TimeSlot.status.notin_(list(_INACTIVE_STATUSES)),
        )
        .all()
    )

    items: list[CalendarSlotItem] = [_real_slot_to_item(s) for s in real_slots]

    # 2. Synthesize virtual plan slots for the day
    virtual_slots = get_virtual_slots_for_date(db, current_user.id, target_date)
    items.extend(_virtual_slot_to_item(vs) for vs in virtual_slots)

    # 3. Sort by scheduled_at ascending
    items.sort(key=lambda item: item.scheduled_at)

    return CalendarDayResponse(
        date=target_date,
        user_id=current_user.id,
        slots=items,
    )


# ---------------------------------------------------------------------------
# Slot edit (BE-CAL-API-003)
# ---------------------------------------------------------------------------

def _apply_edit_fields(slot: TimeSlot, payload: TimeSlotEdit) -> None:
    """Apply non-None fields from *payload* to a TimeSlot ORM object."""
    if payload.slot_type is not None:
        slot.slot_type = payload.slot_type.value
    if payload.scheduled_at is not None:
        slot.scheduled_at = payload.scheduled_at
    if payload.estimated_duration is not None:
        slot.estimated_duration = payload.estimated_duration
    if payload.event_type is not None:
        slot.event_type = payload.event_type.value
    if payload.event_data is not None:
        slot.event_data = payload.event_data
    if payload.priority is not None:
        slot.priority = payload.priority


@router.patch(
    "/slots/{slot_id}",
    response_model=TimeSlotEditResponse,
    summary="Edit a real (materialized) calendar slot",
)
def edit_real_slot(
    slot_id: int,
    payload: TimeSlotEdit,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Edit an existing real (materialized) slot.

    - **Immutability**: rejects edits to past slots.
    - **Overlap detection**: if time/duration changed, rejects on overlap
      (excluding the slot being edited).
    - **Plan detach**: if the slot was materialized from a plan, editing
      detaches it (sets ``plan_id`` to NULL).
    - **Workload warnings**: returned after successful edit (advisory only).
    """
    slot = (
        db.query(TimeSlot)
        .filter(TimeSlot.id == slot_id, TimeSlot.user_id == current_user.id)
        .first()
    )
    if slot is None:
        raise HTTPException(status_code=404, detail="Slot not found")

    # --- Past-slot guard ---
    try:
        guard_edit_real_slot(db, slot)
    except ImmutableSlotError as e:
        raise HTTPException(status_code=422, detail=str(e))

    # --- Determine effective time/duration for overlap check ---
    effective_scheduled_at = payload.scheduled_at if payload.scheduled_at is not None else slot.scheduled_at
    effective_duration = payload.estimated_duration if payload.estimated_duration is not None else slot.estimated_duration

    # --- Overlap check (if time or duration changed) ---
    time_changed = (
        (payload.scheduled_at is not None and payload.scheduled_at != slot.scheduled_at)
        or (payload.estimated_duration is not None and payload.estimated_duration != slot.estimated_duration)
    )
    if time_changed:
        conflicts = check_overlap_for_edit(
            db,
            user_id=current_user.id,
            slot_id=slot.id,
            target_date=slot.date,
            scheduled_at=effective_scheduled_at,
            estimated_duration=effective_duration,
        )
        if conflicts:
            raise HTTPException(
                status_code=409,
                detail={
                    "message": "Edited slot overlaps with existing schedule",
                    "conflicts": [c.to_dict() for c in conflicts],
                },
            )

    # --- Detach from plan if applicable ---
    if slot.plan_id is not None:
        detach_slot_from_plan(slot)

    # --- Apply edits ---
    _apply_edit_fields(slot, payload)
    db.commit()
    db.refresh(slot)

    # --- Workload warnings ---
    warnings = get_workload_warnings_for_date(db, current_user.id, slot.date)

    return TimeSlotEditResponse(
        slot=_slot_to_response(slot),
        warnings=warnings,
    )


@router.patch(
    "/slots/virtual/{virtual_id}",
    response_model=TimeSlotEditResponse,
    summary="Edit a virtual (plan-generated) calendar slot",
)
def edit_virtual_slot(
    virtual_id: str,
    payload: TimeSlotEdit,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Edit a virtual (plan-generated) slot.

    This triggers **materialization**: the virtual slot is first converted
    into a real TimeSlot row, then the edits are applied, and the slot is
    detached from its plan (``plan_id`` set to NULL).

    - **Immutability**: rejects edits to past virtual slots.
    - **Overlap detection**: checks overlap with the edited time/duration
      against existing slots on the same day.
    - **Workload warnings**: returned after successful edit (advisory only).
    """
    # --- Validate virtual_id format ---
    parsed = parse_virtual_slot_id(virtual_id)
    if parsed is None:
        raise HTTPException(status_code=400, detail=f"Invalid virtual slot id: {virtual_id}")

    plan_id, slot_date = parsed

    # --- Past-slot guard ---
    try:
        guard_edit_virtual_slot(virtual_id)
    except ImmutableSlotError as e:
        raise HTTPException(status_code=422, detail=str(e))

    # --- Materialize ---
    try:
        slot = materialize_from_virtual_id(db, virtual_id)
    except ValueError as e:
        raise HTTPException(status_code=404, detail=str(e))

    # --- Verify ownership ---
    if slot.user_id != current_user.id:
        db.rollback()
        raise HTTPException(status_code=404, detail="Slot not found")

    # --- Determine effective time/duration for overlap check ---
    effective_scheduled_at = payload.scheduled_at if payload.scheduled_at is not None else slot.scheduled_at
    effective_duration = payload.estimated_duration if payload.estimated_duration is not None else slot.estimated_duration

    # --- Overlap check (exclude newly materialized slot) ---
    conflicts = check_overlap_for_edit(
        db,
        user_id=current_user.id,
        slot_id=slot.id,
        target_date=slot.date,
        scheduled_at=effective_scheduled_at,
        estimated_duration=effective_duration,
    )
    if conflicts:
        db.rollback()
        raise HTTPException(
            status_code=409,
            detail={
                "message": "Edited slot overlaps with existing schedule",
                "conflicts": [c.to_dict() for c in conflicts],
            },
        )

    # --- Detach from plan ---
    detach_slot_from_plan(slot)

    # --- Apply edits ---
    _apply_edit_fields(slot, payload)
    db.commit()
    db.refresh(slot)

    # --- Workload warnings ---
    warnings = get_workload_warnings_for_date(db, current_user.id, slot.date)

    return TimeSlotEditResponse(
        slot=_slot_to_response(slot),
        warnings=warnings,
    )


# ---------------------------------------------------------------------------
# Slot cancel (BE-CAL-API-004)
# ---------------------------------------------------------------------------

@router.post(
    "/slots/{slot_id}/cancel",
    response_model=TimeSlotCancelResponse,
    summary="Cancel a real (materialized) calendar slot",
)
def cancel_real_slot(
    slot_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Cancel an existing real (materialized) slot.

    - **Immutability**: rejects cancellation of past slots.
    - **Plan detach**: if the slot was materialized from a plan, cancelling
      detaches it (sets ``plan_id`` to NULL) so the plan no longer claims
      that date.
    - **Status**: sets the slot status to ``Skipped``.
    """
    slot = (
        db.query(TimeSlot)
        .filter(TimeSlot.id == slot_id, TimeSlot.user_id == current_user.id)
        .first()
    )
    if slot is None:
        raise HTTPException(status_code=404, detail="Slot not found")

    # --- Past-slot guard ---
    try:
        guard_cancel_real_slot(db, slot)
    except ImmutableSlotError as e:
        raise HTTPException(status_code=422, detail=str(e))

    # --- Detach from plan if applicable ---
    if slot.plan_id is not None:
        detach_slot_from_plan(slot)

    # --- Update status ---
    slot.status = SlotStatus.SKIPPED
    db.commit()
    db.refresh(slot)

    return TimeSlotCancelResponse(
        slot=_slot_to_response(slot),
        message="Slot cancelled successfully",
    )


@router.post(
    "/slots/virtual/{virtual_id}/cancel",
    response_model=TimeSlotCancelResponse,
    summary="Cancel a virtual (plan-generated) calendar slot",
)
def cancel_virtual_slot(
    virtual_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Cancel a virtual (plan-generated) slot.

    This triggers **materialization**: the virtual slot is first converted
    into a real TimeSlot row, then immediately set to ``Skipped`` status
    and detached from its plan (``plan_id`` set to NULL).

    - **Immutability**: rejects cancellation of past virtual slots.
    """
    # --- Validate virtual_id format ---
    parsed = parse_virtual_slot_id(virtual_id)
    if parsed is None:
        raise HTTPException(status_code=400, detail=f"Invalid virtual slot id: {virtual_id}")

    plan_id, slot_date = parsed

    # --- Past-slot guard ---
    try:
        guard_cancel_virtual_slot(virtual_id)
    except ImmutableSlotError as e:
        raise HTTPException(status_code=422, detail=str(e))

    # --- Materialize ---
    try:
        slot = materialize_from_virtual_id(db, virtual_id)
    except ValueError as e:
        raise HTTPException(status_code=404, detail=str(e))

    # --- Verify ownership ---
    if slot.user_id != current_user.id:
        db.rollback()
        raise HTTPException(status_code=404, detail="Slot not found")

    # --- Detach from plan ---
    detach_slot_from_plan(slot)

    # --- Update status ---
    slot.status = SlotStatus.SKIPPED
    db.commit()
    db.refresh(slot)

    return TimeSlotCancelResponse(
        slot=_slot_to_response(slot),
        message="Virtual slot materialized and cancelled successfully",
    )


# ---------------------------------------------------------------------------
# SchedulePlan (BE-CAL-API-005)
# ---------------------------------------------------------------------------

def _plan_to_response(plan: SchedulePlan) -> SchedulePlanResponse:
    """Convert a SchedulePlan ORM object to a response schema."""
    return SchedulePlanResponse(
        id=plan.id,
        user_id=plan.user_id,
        slot_type=plan.slot_type.value if hasattr(plan.slot_type, "value") else str(plan.slot_type),
        estimated_duration=plan.estimated_duration,
        at_time=plan.at_time.isoformat() if plan.at_time else "",
        on_day=plan.on_day.value if plan.on_day and hasattr(plan.on_day, "value") else (str(plan.on_day) if plan.on_day else None),
        on_week=plan.on_week,
        on_month=plan.on_month.value if plan.on_month and hasattr(plan.on_month, "value") else (str(plan.on_month) if plan.on_month else None),
        event_type=plan.event_type.value if plan.event_type and hasattr(plan.event_type, "value") else (str(plan.event_type) if plan.event_type else None),
        event_data=plan.event_data,
        is_active=plan.is_active,
        created_at=plan.created_at,
        updated_at=plan.updated_at,
    )


@router.post(
    "/plans",
    response_model=SchedulePlanResponse,
    status_code=201,
    summary="Create a recurring schedule plan",
)
def create_plan(
    payload: SchedulePlanCreate,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Create a new recurring schedule plan.

    The plan defines a template for virtual slots that are generated
    on matching dates.  Period-parameter hierarchy is enforced:
    ``on_month`` requires ``on_week``, which requires ``on_day``.
    ``at_time`` is always required.
    """
    plan = SchedulePlan(
        user_id=current_user.id,
        slot_type=payload.slot_type.value,
        estimated_duration=payload.estimated_duration,
        at_time=payload.at_time,
        on_day=payload.on_day.value if payload.on_day else None,
        on_week=payload.on_week,
        on_month=payload.on_month.value if payload.on_month else None,
        event_type=payload.event_type.value if payload.event_type else None,
        event_data=payload.event_data,
        is_active=True,
    )
    db.add(plan)
    db.commit()
    db.refresh(plan)

    return _plan_to_response(plan)


@router.get(
    "/plans",
    response_model=SchedulePlanListResponse,
    summary="List all schedule plans for the current user",
)
def list_plans(
    include_inactive: bool = Query(False, description="Include cancelled/inactive plans"),
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_read),
):
    """Return all schedule plans for the authenticated user.

    By default only active plans are returned.  Pass
    ``include_inactive=true`` to also include cancelled plans.
    """
    q = db.query(SchedulePlan).filter(SchedulePlan.user_id == current_user.id)
    if not include_inactive:
        q = q.filter(SchedulePlan.is_active.is_(True))
    q = q.order_by(SchedulePlan.created_at.desc())
    plans = q.all()

    return SchedulePlanListResponse(
        plans=[_plan_to_response(p) for p in plans],
    )


@router.get(
    "/plans/{plan_id}",
    response_model=SchedulePlanResponse,
    summary="Get a single schedule plan by ID",
)
def get_plan(
    plan_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_read),
):
    """Return a single schedule plan owned by the authenticated user."""
    plan = (
        db.query(SchedulePlan)
        .filter(SchedulePlan.id == plan_id, SchedulePlan.user_id == current_user.id)
        .first()
    )
    if plan is None:
        raise HTTPException(status_code=404, detail="Plan not found")
    return _plan_to_response(plan)


# ---------------------------------------------------------------------------
# Plan edit / cancel (BE-CAL-API-006)
# ---------------------------------------------------------------------------

def _validate_plan_hierarchy(
    on_day: str | None,
    on_week: int | None,
    on_month: str | None,
) -> None:
    """Enforce period-parameter hierarchy after merging edited values.

    Raises HTTPException(422) if the hierarchy is violated.
    """
    if on_month is not None and on_week is None:
        raise HTTPException(
            status_code=422,
            detail="on_month requires on_week to be set",
        )
    if on_week is not None and on_day is None:
        raise HTTPException(
            status_code=422,
            detail="on_week requires on_day to be set",
        )


@router.patch(
    "/plans/{plan_id}",
    response_model=SchedulePlanResponse,
    summary="Edit a recurring schedule plan",
)
def edit_plan(
    plan_id: int,
    payload: SchedulePlanEdit,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Edit an existing schedule plan.

    - Only **future** virtual/materialized slots are affected; past
      materialized slots remain untouched.
    - Period-parameter hierarchy (``on_month`` → ``on_week`` → ``on_day``)
      is validated after merging edited values with existing plan values.
    - Inactive (cancelled) plans cannot be edited.
    """
    plan = (
        db.query(SchedulePlan)
        .filter(SchedulePlan.id == plan_id, SchedulePlan.user_id == current_user.id)
        .first()
    )
    if plan is None:
        raise HTTPException(status_code=404, detail="Plan not found")

    if not plan.is_active:
        raise HTTPException(status_code=422, detail="Cannot edit an inactive (cancelled) plan")

    # --- Identify past slots that must NOT be touched ---
    _past_ids = guard_plan_edit_no_past_retroaction(db, plan_id)

    # --- Apply clear flags first (set to NULL) ---
    if payload.clear_on_month:
        plan.on_month = None
    if payload.clear_on_week:
        plan.on_week = None
    if payload.clear_on_day:
        plan.on_day = None

    # --- Apply provided values ---
    if payload.slot_type is not None:
        plan.slot_type = payload.slot_type.value
    if payload.estimated_duration is not None:
        plan.estimated_duration = payload.estimated_duration
    if payload.at_time is not None:
        plan.at_time = payload.at_time
    if payload.on_day is not None:
        plan.on_day = payload.on_day.value
    if payload.on_week is not None:
        plan.on_week = payload.on_week
    if payload.on_month is not None:
        plan.on_month = payload.on_month.value
    if payload.event_type is not None:
        plan.event_type = payload.event_type.value
    if payload.event_data is not None:
        plan.event_data = payload.event_data

    # --- Validate hierarchy with merged values ---
    effective_on_day = plan.on_day
    effective_on_week = plan.on_week
    effective_on_month = plan.on_month
    _validate_plan_hierarchy(effective_on_day, effective_on_week, effective_on_month)

    # --- Detach future materialized slots so they keep old data ---
    # Future materialized slots with plan_id set are detached because
    # they were generated from the old plan template. New virtual slots
    # will reflect the updated plan going forward.
    from datetime import date as date_type
    today = date_type.today()
    future_materialized = (
        db.query(TimeSlot)
        .filter(
            TimeSlot.plan_id == plan_id,
            TimeSlot.date >= today,
        )
        .all()
    )
    for slot in future_materialized:
        slot.plan_id = None

    db.commit()
    db.refresh(plan)

    return _plan_to_response(plan)


@router.post(
    "/plans/{plan_id}/cancel",
    response_model=SchedulePlanCancelResponse,
    summary="Cancel a recurring schedule plan",
)
def cancel_plan(
    plan_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_write),
):
    """Cancel (soft-delete) a schedule plan.

    - Sets the plan's ``is_active`` flag to ``False``.
    - **Past** materialized slots are preserved untouched.
    - **Future** materialized slots that still reference this plan are
      detached (``plan_id`` set to NULL) so they remain on the calendar
      as standalone slots. If you want to also cancel those future slots,
      cancel them individually via the slot-cancel endpoints.
    """
    plan = (
        db.query(SchedulePlan)
        .filter(SchedulePlan.id == plan_id, SchedulePlan.user_id == current_user.id)
        .first()
    )
    if plan is None:
        raise HTTPException(status_code=404, detail="Plan not found")

    if not plan.is_active:
        raise HTTPException(status_code=422, detail="Plan is already cancelled")

    # --- Identify past slots that must NOT be touched ---
    past_ids = guard_plan_cancel_no_past_retroaction(db, plan_id)

    # --- Detach future materialized slots ---
    from datetime import date as date_type
    today = date_type.today()
    future_materialized = (
        db.query(TimeSlot)
        .filter(
            TimeSlot.plan_id == plan_id,
            TimeSlot.date >= today,
        )
        .all()
    )
    for slot in future_materialized:
        slot.plan_id = None

    # --- Deactivate the plan ---
    plan.is_active = False
    db.commit()
    db.refresh(plan)

    return SchedulePlanCancelResponse(
        plan=_plan_to_response(plan),
        message="Plan cancelled successfully",
        preserved_past_slot_ids=past_ids,
    )


# ---------------------------------------------------------------------------
# Date list (BE-CAL-API-007)
# ---------------------------------------------------------------------------

# Statuses considered inactive — slots with these statuses are excluded
# from the date-list result because they no longer occupy calendar time.
_DATE_LIST_EXCLUDED_STATUSES = {SlotStatus.SKIPPED.value, SlotStatus.ABORTED.value}


@router.get(
    "/dates",
    response_model=DateListResponse,
    summary="List future dates that have materialized slots",
)
def list_dates(
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_read),
):
    """Return a sorted list of future dates that have at least one
    materialized (real) slot.

    - Only dates **today or later** are included.
    - Only **active** slots are counted (skipped / aborted are excluded).
    - Pure plan-generated (virtual) dates that have not been materialized
      are **not** included.
    """
    today = date_type.today()

    rows = (
        db.query(TimeSlot.date)
        .filter(
            TimeSlot.user_id == current_user.id,
            TimeSlot.date >= today,
            TimeSlot.status.notin_(list(_DATE_LIST_EXCLUDED_STATUSES)),
        )
        .group_by(TimeSlot.date)
        .order_by(TimeSlot.date.asc())
        .all()
    )

    return DateListResponse(dates=[r[0] for r in rows])


# ---------------------------------------------------------------------------
# MinimumWorkload
# ---------------------------------------------------------------------------

@router.get(
    "/workload-config",
    response_model=MinimumWorkloadResponse,
    summary="Get current user's minimum workload configuration",
)
def get_my_workload_config(
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_manage),
):
    """Return the workload thresholds for the authenticated user.

    If no configuration has been saved yet, returns default (all-zero)
    thresholds.
    """
    cfg = get_workload_config(db, current_user.id)
    return MinimumWorkloadResponse(user_id=current_user.id, config=cfg)


@router.put(
    "/workload-config",
    response_model=MinimumWorkloadResponse,
    summary="Replace the current user's minimum workload configuration",
)
def put_my_workload_config(
    payload: MinimumWorkloadConfig,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_manage),
):
    """Full replacement of the workload configuration."""
    row = replace_workload_config(db, current_user.id, payload)
    db.commit()
    db.refresh(row)
    return MinimumWorkloadResponse(user_id=current_user.id, config=row.config)


@router.patch(
    "/workload-config",
    response_model=MinimumWorkloadResponse,
    summary="Partially update the current user's minimum workload configuration",
)
def patch_my_workload_config(
    payload: MinimumWorkloadUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_calendar_manage),
):
    """Partial update — only the provided periods are overwritten."""
    row = upsert_workload_config(db, current_user.id, payload)
    db.commit()
    db.refresh(row)
    return MinimumWorkloadResponse(user_id=current_user.id, config=row.config)


# ---------------------------------------------------------------------------
# Admin: manage another user's workload config
# ---------------------------------------------------------------------------

def _require_admin(current_user: User = Depends(get_current_user)):
    if not current_user.is_admin:
        raise HTTPException(status_code=403, detail="Admin required")
    return current_user


@router.get(
    "/workload-config/{user_id}",
    response_model=MinimumWorkloadResponse,
    summary="[Admin] Get a specific user's minimum workload configuration",
)
def get_user_workload_config(
    user_id: int,
    db: Session = Depends(get_db),
    _admin: User = Depends(_require_admin),
):
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    cfg = get_workload_config(db, user_id)
    return MinimumWorkloadResponse(user_id=user_id, config=cfg)


@router.put(
    "/workload-config/{user_id}",
    response_model=MinimumWorkloadResponse,
    summary="[Admin] Replace a specific user's minimum workload configuration",
)
def put_user_workload_config(
    user_id: int,
    payload: MinimumWorkloadConfig,
    db: Session = Depends(get_db),
    _admin: User = Depends(_require_admin),
):
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    row = replace_workload_config(db, user_id, payload)
    db.commit()
    db.refresh(row)
    return MinimumWorkloadResponse(user_id=user_id, config=row.config)


@router.patch(
    "/workload-config/{user_id}",
    response_model=MinimumWorkloadResponse,
    summary="[Admin] Partially update a specific user's minimum workload configuration",
)
def patch_user_workload_config(
    user_id: int,
    payload: MinimumWorkloadUpdate,
    db: Session = Depends(get_db),
    _admin: User = Depends(_require_admin),
):
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    row = upsert_workload_config(db, user_id, payload)
    db.commit()
    db.refresh(row)
    return MinimumWorkloadResponse(user_id=user_id, config=row.config)