feat: add recurrence_rule validation and recurrence-preview endpoint in tasks routes

src/fabledassistant/routes/tasks.py

@@ -1,4 +1,5 @@
 import asyncio
+from datetime import date
 
 from quart import Blueprint, jsonify, request
 
@@ -14,9 +15,32 @@ from fabledassistant.services.notes import (
     list_notes,
     update_note,
 )
+from fabledassistant.services.recurrence import calculate_next_due, validate_recurrence_rule
 
 tasks_bp = Blueprint("tasks", __name__, url_prefix="/api/tasks")
 
+_UNSET = object()
+
+
+def _parse_recurrence_rule(data: dict) -> tuple[object, tuple | None]:
+    """Extract and validate recurrence_rule from request data.
+
+    Returns (rule_or_UNSET, error_response_or_None):
+      _UNSET  → key not present, do nothing
+      None    → key present and null, clear the rule
+      dict    → key present and valid, set the rule
+    """
+    if "recurrence_rule" not in data:
+        return _UNSET, None
+    rule = data["recurrence_rule"]
+    if rule is None:
+        return None, None
+    try:
+        validate_recurrence_rule(rule)
+    except ValueError as exc:
+        return _UNSET, (jsonify({"error": str(exc)}), 400)
+    return rule, None
+
 
 @tasks_bp.route("", methods=["GET"])
 @login_required
@@ -24,8 +48,8 @@ async def list_tasks_route():
     uid = get_current_user_id()
     q = request.args.get("q")
     tag = request.args.getlist("tag")
-    status = request.args.get("status")
-    priority = request.args.get("priority")
+    status = request.args.getlist("status") or None
+    priority = request.args.getlist("priority") or None
     sort = request.args.get("sort", "updated_at")
     order = request.args.get("order", "desc")
     limit, offset = parse_pagination()
@@ -80,6 +104,10 @@ async def create_task_route():
     except ValueError:
         return jsonify({"error": f"Invalid priority: {data['priority']}"}), 400
 
+    recurrence_rule, recurrence_err = _parse_recurrence_rule(data)
+    if recurrence_err:
+        return recurrence_err
+
     project_id = data.get("project_id")
     if project_id is None and data.get("project"):
         from fabledassistant.services.projects import get_project_by_title as _gpbt
@@ -98,6 +126,7 @@ async def create_task_route():
         project_id=project_id,
         milestone_id=data.get("milestone_id"),
         parent_id=data.get("parent_id"),
+        recurrence_rule=recurrence_rule if recurrence_rule is not _UNSET else None,
     )
     text = f"{task.title}\n{task.body}".strip() if task.body else (task.title or "")
     if text:
@@ -163,6 +192,12 @@ async def update_task_route(task_id: int):
         if key in data:
             fields[key] = data[key]
 
+    recurrence_rule, recurrence_err = _parse_recurrence_rule(data)
+    if recurrence_err:
+        return recurrence_err
+    if recurrence_rule is not _UNSET:
+        fields["recurrence_rule"] = recurrence_rule
+
     task = await update_note(uid, task_id, **fields)
     if task is None:
         return not_found("Task")
@@ -192,6 +227,27 @@ async def patch_task_status(task_id: int):
     return jsonify(task.to_dict())
 
 
+@tasks_bp.route("/<int:task_id>/recurrence-preview", methods=["GET"])
+@login_required
+async def recurrence_preview_route(task_id: int):
+    uid = get_current_user_id()
+    result = await get_note_for_user(uid, task_id)
+    if result is None:
+        return not_found("Task")
+    task, _ = result
+    if not task.recurrence_rule:
+        return jsonify({"error": "Task has no recurrence rule"}), 400
+
+    count = min(request.args.get("count", 5, type=int), 10)
+    base = task.due_date or date.today()
+    dates = []
+    current = base
+    for _ in range(count):
+        current = calculate_next_due(task.recurrence_rule, current)
+        dates.append(current.isoformat())
+    return jsonify({"dates": dates})
+
+
 @tasks_bp.route("/<int:task_id>", methods=["DELETE"])
 @login_required
 async def delete_task_route(task_id: int):