[bugfix] Fix setting immediate expires_at value on filter endpoints (#3513)

* [bugfix] Fix setting immediate `expires_at` value on filter endpoints

* update wording

* update wording

* oh my

internal/api/util/parseform.go

@@ -0,0 +1,70 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package util
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// ParseDuration parses the given raw interface belonging to
+// the given fieldName as an integer duration.
+//
+// Will return nil, nil if rawI is the zero value of its type.
+func ParseDuration(rawI any, fieldName string) (*int, error) {
+	var (
+		asInteger int
+		err       error
+	)
+
+	switch raw := rawI.(type) {
+	case float64:
+		// Submitted as JSON number
+		// (casts to float64 by default).
+		asInteger = int(raw)
+
+	case string:
+		// Submitted as JSON string or form field.
+		asInteger, err = strconv.Atoi(raw)
+		if err != nil {
+			err = fmt.Errorf(
+				"could not parse %s value %s as integer: %w",
+				fieldName, raw, err,
+			)
+		}
+
+	default:
+		// Submitted as god-knows-what.
+		err = fmt.Errorf(
+			"could not parse %s type %T as integer",
+			fieldName, rawI,
+		)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Someone submitted 0,
+	// don't point to this.
+	if asInteger == 0 {
+		return nil, nil
+	}
+
+	return &asInteger, nil
+}