feat: get next link from repsonse helper func for pagination

internal/helper/pagination.go

@@ -0,0 +1,52 @@
+// sparrow
+// (C) 2024, Deutsche Telekom IT GmbH
+//
+// Deutsche Telekom IT GmbH and all other contributors /
+// copyright owners license this file to you 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 helper
+
+import (
+	"net/http"
+	"strings"
+)
+
+const (
+	linkHeader = "Link"
+	linkNext   = "next"
+)
+
+// getNextLink returns the url to the next page of
+// a paginated http response provided in the passed response header.
+func GetNextLink(header http.Header) string {
+	link := header.Get("Link")
+	if link == "" {
+		return ""
+	}
+
+	for _, link := range strings.Split(link, ",") {
+		linkParts := strings.Split(link, ";")
+		if len(linkParts) != 2 {
+			continue
+		}
+		linkType := strings.Trim(strings.Split(linkParts[1], "=")[1], "\"")
+
+		if linkType != linkNext {
+			continue
+		}
+		return strings.Trim(linkParts[0], "< >")
+	}
+	return ""
+}

internal/helper/pagination_test.go

@@ -0,0 +1,79 @@
+// sparrow
+// (C) 2024, Deutsche Telekom IT GmbH
+//
+// Deutsche Telekom IT GmbH and all other contributors /
+// copyright owners license this file to you 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 helper
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetNextLink(t *testing.T) {
+	type header struct {
+		noLinkHeader bool
+		key          string
+		value        string
+	}
+	tests := []struct {
+		name   string
+		header header
+		want   string
+	}{
+		{
+			"no link header present",
+			header{
+				noLinkHeader: true,
+			},
+			"",
+		},
+		{
+			"no next link in link header present",
+			header{
+				key:   "link",
+				value: "<https://link.first.de>; rel=\"first\", <https://link.last.de>; rel=\"last\"",
+			},
+			"",
+		},
+		{
+			"link header syntax not valid",
+			header{
+				key:   "link",
+				value: "no link here",
+			},
+			"",
+		},
+		{
+			"valid next link",
+			header{
+				key:   "link",
+				value: "<https://link.next.de>; rel=\"next\", <https://link.first.de>; rel=\"first\", <https://link.last.de>; rel=\"last\"",
+			},
+			"https://link.next.de",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			testHeader := http.Header{}
+			testHeader.Add(tt.header.key, tt.header.value)
+
+			assert.Equal(t, tt.want, GetNextLink(testHeader))
+		})
+	}
+}