Implement opal-task Phase 3: Filter and Modifier Parsing

- Add filter.go: Parse filters (+tag, -tag, attribute:value, IDs)
- Implement Filter.ToSQL() for WHERE clause generation
- Add modifier.go: Parse modifiers (set/clear attributes, add/remove tags)
- Implement Modifier.Apply() to update existing tasks
- Add dateparse.go: Smart date parsing (ISO, today, tomorrow, weekdays)
- Implement nextWeekday logic (smart Sunday interpretation)
- Update GetTasks() to accept Filter parameter
- Add CreateTaskWithModifier() for task creation with modifiers
- Add comprehensive test suite (13 new tests, all passing)
- Support filtering by status, project, priority, tags, UUIDs, display IDs
- Support modifying priority, project, dates, recurrence, tags

opal-task/internal/engine/task.go

@@ -139,6 +139,11 @@ func sqlToUUIDPtr(v interface{}) *uuid.UUID {
 
 // CreateTask creates a new task with the given description
 func CreateTask(description string) (*Task, error) {
+	return CreateTaskWithModifier(description, nil)
+}
+
+// CreateTaskWithModifier creates a new task with the given description and applies modifiers
+func CreateTaskWithModifier(description string, mod *Modifier) (*Task, error) {
 	now := timeNow()
 	task := &Task{
 		UUID:        uuid.New(),
@@ -150,10 +155,26 @@ func CreateTask(description string) (*Task, error) {
 		Tags:        []string{},
 	}
 
+	// Apply modifiers before saving (for attributes)
+	if mod != nil {
+		if err := mod.ApplyToNew(task); err != nil {
+			return nil, err
+		}
+	}
+
 	if err := task.Save(); err != nil {
 		return nil, err
 	}
 
+	// Apply tags after saving (requires task.ID)
+	if mod != nil {
+		for _, tag := range mod.AddTags {
+			if err := task.AddTag(tag); err != nil {
+				return nil, err
+			}
+		}
+	}
+
 	return task, nil
 }
 
@@ -242,22 +263,33 @@ func GetTask(taskUUID uuid.UUID) (*Task, error) {
 	return task, nil
 }
 
-// GetTasks retrieves all tasks (filtering will be added later)
-func GetTasks() ([]*Task, error) {
+// GetTasks retrieves all tasks with optional filtering
+func GetTasks(filter *Filter) ([]*Task, error) {
 	db := GetDB()
 	if db == nil {
 		return nil, fmt.Errorf("database not initialized")
 	}
 
-	query := `
+	// Build WHERE clause from filter
+	whereClause := "1=1"
+	var args []interface{}
+	if filter != nil {
+		whereClause, args = filter.ToSQL()
+	}
+
+	query := fmt.Sprintf(`
 		SELECT id, uuid, status, description, project, priority,
 		       created, modified, start, end, due, scheduled, wait, until_date,
 		       recurrence_duration, parent_uuid
 		FROM tasks
-		ORDER BY due ASC, priority DESC
-	`
+		WHERE %s
+		ORDER BY 
+			CASE WHEN due IS NULL THEN 1 ELSE 0 END,
+			due ASC,
+			priority DESC
+	`, whereClause)
 
-	rows, err := db.Query(query)
+	rows, err := db.Query(query, args...)
 	if err != nil {
 		return nil, fmt.Errorf("failed to query tasks: %w", err)
 	}