1 files changed, 125 insertions, 0 deletions
diff --git a/tpl/collections/querify.go b/tpl/collections/querify.go
new file mode 100644
index 000000000..19e6d8afe
--- /dev/null
+++ b/tpl/collections/querify.go
@@ -0,0 +1,125 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collections
+
+import (
+	"errors"
+	"net/url"
+
+	"github.com/gohugoio/hugo/common/maps"
+	"github.com/spf13/cast"
+)
+
+var (
+	errWrongArgStructure = errors.New("expected a map, a slice with an even number of elements, or an even number of scalar values, and each key must be a string")
+	errKeyIsEmptyString  = errors.New("one of the keys is an empty string")
+)
+
+// Querify returns a URL query string composed of the given key-value pairs,
+// encoded and sorted by key.
+func (ns *Namespace) Querify(params ...any) (string, error) {
+	if len(params) == 0 {
+		return "", nil
+	}
+
+	if len(params) == 1 {
+		switch v := params[0].(type) {
+		case map[string]any: // created with collections.Dictionary
+			return mapToQueryString(v)
+		case maps.Params: // site configuration or page parameters
+			return mapToQueryString(v)
+		case []string:
+			return stringSliceToQueryString(v)
+		case []any:
+			s, err := interfaceSliceToStringSlice(v)
+			if err != nil {
+				return "", err
+			}
+			return stringSliceToQueryString(s)
+		default:
+			return "", errWrongArgStructure
+		}
+	}
+
+	if len(params)%2 != 0 {
+		return "", errWrongArgStructure
+	}
+
+	s, err := interfaceSliceToStringSlice(params)
+	if err != nil {
+		return "", err
+	}
+	return stringSliceToQueryString(s)
+}
+
+// mapToQueryString returns a URL query string derived from the given string
+// map, encoded and sorted by key. The function returns an error if it cannot
+// convert an element value to a string.
+func mapToQueryString[T map[string]any | maps.Params](m T) (string, error) {
+	if len(m) == 0 {
+		return "", nil
+	}
+
+	qs := url.Values{}
+	for k, v := range m {
+		if len(k) == 0 {
+			return "", errKeyIsEmptyString
+		}
+		vs, err := cast.ToStringE(v)
+		if err != nil {
+			return "", err
+		}
+		qs.Add(k, vs)
+	}
+	return qs.Encode(), nil
+}
+
+// sliceToQueryString returns a URL query string derived from the given slice
+// of strings, encoded and sorted by key. The function returns an error if
+// there are an odd number of elements.
+func stringSliceToQueryString(s []string) (string, error) {
+	if len(s) == 0 {
+		return "", nil
+	}
+	if len(s)%2 != 0 {
+		return "", errWrongArgStructure
+	}
+
+	qs := url.Values{}
+	for i := 0; i < len(s); i += 2 {
+		if len(s[i]) == 0 {
+			return "", errKeyIsEmptyString
+		}
+		qs.Add(s[i], s[i+1])
+	}
+	return qs.Encode(), nil
+}
+
+// interfaceSliceToStringSlice converts a slice of interfaces to a slice of
+// strings, returning an error if it cannot convert an element to a string.
+func interfaceSliceToStringSlice(s []any) ([]string, error) {
+	if len(s) == 0 {
+		return []string{}, nil
+	}
+
+	ss := make([]string, 0, len(s))
+	for _, v := range s {
+		vs, err := cast.ToStringE(v)
+		if err != nil {
+			return []string{}, err
+		}
+		ss = append(ss, vs)
+	}
+	return ss, nil
+}