refactor(scheduling): simplify candidate slot updates

src/govoplan_scheduling/backend/service.py

@@ -2,8 +2,9 @@ from __future__ import annotations
 
 import hashlib
 import json
+from dataclasses import dataclass
 from datetime import datetime, timezone
-from typing import Any
+from typing import Any, cast
 
 from sqlalchemy.orm import Session, object_session
 
@@ -1416,6 +1417,121 @@ def update_scheduling_request(
     return request
 
 
+@dataclass(frozen=True, slots=True)
+class _CandidateSlotChanges:
+    label: str
+    description: str | None
+    start_at: datetime
+    end_at: datetime
+    timezone: str
+    location: str | None
+    metadata: dict[str, Any]
+    normalized_start: datetime
+    normalized_end: datetime
+
+
+def _candidate_slot_changes(
+    slot: SchedulingCandidateSlot,
+    payload: SchedulingCandidateSlotUpdateRequest,
+) -> _CandidateSlotChanges:
+    supplied = payload.model_fields_set
+    for field in ("label", "start_at", "end_at", "timezone"):
+        if field in supplied and getattr(payload, field) is None:
+            raise SchedulingError(f"{field} cannot be null")
+
+    label = cast(str, payload.label if "label" in supplied else slot.label)
+    description = payload.description if "description" in supplied else slot.description
+    start_at = cast(datetime, payload.start_at if "start_at" in supplied else slot.start_at)
+    end_at = cast(datetime, payload.end_at if "end_at" in supplied else slot.end_at)
+    timezone_name = cast(str, payload.timezone if "timezone" in supplied else slot.timezone)
+    location = payload.location if "location" in supplied else slot.location
+    metadata = (payload.metadata or {}) if "metadata" in supplied else (slot.metadata_ or {})
+    normalized_start = cast(datetime, response_datetime(start_at))
+    normalized_end = cast(datetime, response_datetime(end_at))
+    if normalized_end <= normalized_start:
+        raise SchedulingError("end_at must be after start_at")
+    return _CandidateSlotChanges(
+        label=label,
+        description=description,
+        start_at=start_at,
+        end_at=end_at,
+        timezone=timezone_name,
+        location=location,
+        metadata=metadata,
+        normalized_start=normalized_start,
+        normalized_end=normalized_end,
+    )
+
+
+def _candidate_slot_change_flags(
+    slot: SchedulingCandidateSlot,
+    changes: _CandidateSlotChanges,
+) -> tuple[bool, bool]:
+    temporal_or_location_changed = (
+        changes.normalized_start != response_datetime(slot.start_at)
+        or changes.normalized_end != response_datetime(slot.end_at)
+        or changes.timezone != slot.timezone
+        or changes.location != slot.location
+    )
+    changed = (
+        changes.label != slot.label
+        or changes.description != slot.description
+        or temporal_or_location_changed
+        or changes.metadata != (slot.metadata_ or {})
+    )
+    return changed, temporal_or_location_changed
+
+
+def _update_candidate_poll_option(
+    session: Session,
+    *,
+    tenant_id: str,
+    request: SchedulingRequest,
+    slot: SchedulingCandidateSlot,
+    changes: _CandidateSlotChanges,
+) -> None:
+    try:
+        _poll_provider().update_option(
+            session,
+            tenant_id=tenant_id,
+            poll_id=cast(str, request.poll_id),
+            option_id=cast(str, slot.poll_option_id),
+            command=PollOptionUpdateCommand(
+                label=changes.label,
+                description=changes.description,
+                value={
+                    "slot_id": slot.id,
+                    "start_at": changes.normalized_start.isoformat(),
+                    "end_at": changes.normalized_end.isoformat(),
+                    "timezone": changes.timezone,
+                    "location": changes.location,
+                },
+                metadata=changes.metadata,
+            ),
+        )
+    except PollCapabilityError as exc:
+        raise SchedulingError(str(exc)) from exc
+
+
+def _apply_candidate_slot_changes(
+    slot: SchedulingCandidateSlot,
+    changes: _CandidateSlotChanges,
+    *,
+    temporal_or_location_changed: bool,
+) -> None:
+    slot.label = changes.label
+    slot.description = changes.description
+    slot.start_at = changes.start_at
+    slot.end_at = changes.end_at
+    slot.timezone = changes.timezone
+    slot.location = changes.location
+    slot.metadata_ = changes.metadata
+    if temporal_or_location_changed:
+        slot.freebusy_checked_at = None
+        slot.freebusy_status = None
+        slot.freebusy_conflicts = []
+
+
 def update_scheduling_candidate_slot(
     session: Session,
     *,
@@ -1440,35 +1556,8 @@ def update_scheduling_candidate_slot(
     if slot.poll_option_id is None:
         raise SchedulingError("Scheduling slot has no backing poll option")
 
-    supplied = payload.model_fields_set
-    for field in ("label", "start_at", "end_at", "timezone"):
-        if field in supplied and getattr(payload, field) is None:
-            raise SchedulingError(f"{field} cannot be null")
-
-    label = payload.label if "label" in supplied else slot.label
-    description = payload.description if "description" in supplied else slot.description
-    start_at = payload.start_at if "start_at" in supplied else slot.start_at
-    end_at = payload.end_at if "end_at" in supplied else slot.end_at
-    timezone_name = payload.timezone if "timezone" in supplied else slot.timezone
-    location = payload.location if "location" in supplied else slot.location
-    metadata = (payload.metadata or {}) if "metadata" in supplied else (slot.metadata_ or {})
-    normalized_start = response_datetime(start_at)
-    normalized_end = response_datetime(end_at)
-    if normalized_end <= normalized_start:
-        raise SchedulingError("end_at must be after start_at")
-
-    temporal_or_location_changed = (
-        normalized_start != response_datetime(slot.start_at)
-        or normalized_end != response_datetime(slot.end_at)
-        or timezone_name != slot.timezone
-        or location != slot.location
-    )
-    changed = (
-        label != slot.label
-        or description != slot.description
-        or temporal_or_location_changed
-        or metadata != (slot.metadata_ or {})
-    )
+    changes = _candidate_slot_changes(slot, payload)
+    changed, temporal_or_location_changed = _candidate_slot_change_flags(slot, changes)
     if not changed:
         return request
     if temporal_or_location_changed and slot.tentative_hold_event_id:
@@ -1476,27 +1565,13 @@ def update_scheduling_candidate_slot(
             "A slot with a tentative calendar hold cannot change time, timezone, or location"
         )
 
-    try:
-        _poll_provider().update_option(
-            session,
-            tenant_id=tenant_id,
-            poll_id=request.poll_id,
-            option_id=slot.poll_option_id,
-            command=PollOptionUpdateCommand(
-                label=label,
-                description=description,
-                value={
-                    "slot_id": slot.id,
-                    "start_at": normalized_start.isoformat(),
-                    "end_at": normalized_end.isoformat(),
-                    "timezone": timezone_name,
-                    "location": location,
-                },
-                metadata=metadata,
-            ),
-        )
-    except PollCapabilityError as exc:
-        raise SchedulingError(str(exc)) from exc
+    _update_candidate_poll_option(
+        session,
+        tenant_id=tenant_id,
+        request=request,
+        slot=slot,
+        changes=changes,
+    )
 
     refresh_participant_response_state(
         session,
@@ -1504,17 +1579,11 @@ def update_scheduling_candidate_slot(
         reset_missing=True,
     )
 
-    slot.label = label
-    slot.description = description
-    slot.start_at = start_at
-    slot.end_at = end_at
-    slot.timezone = timezone_name
-    slot.location = location
-    slot.metadata_ = metadata
-    if temporal_or_location_changed:
-        slot.freebusy_checked_at = None
-        slot.freebusy_status = None
-        slot.freebusy_conflicts = []
+    _apply_candidate_slot_changes(
+        slot,
+        changes,
+        temporal_or_location_changed=temporal_or_location_changed,
+    )
     session.flush()
     return request