internal/util: introduce temp dir/path helpers

In most of the reconcilers we have a repetative pattern of using part of
the object metadata to construct a temporary file path.

This commit introduces helpers as an abstraction, for both the creation
of a temporary directory based on `client.Object` type and object
metadata, and the generation of an arbitrary random temporary path
string.

Signed-off-by: Hidde Beydals <hello@hidde.co>

internal/util/temp.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2021 The Flux authors
+
+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 util
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+// TempDirForObj creates a new temporary directory in the directory dir
+// in the format of 'Kind-Namespace-Name-*', and returns the
+// pathname of the new directory.
+func TempDirForObj(dir string, obj client.Object) (string, error) {
+	return os.MkdirTemp(dir, pattern(obj))
+}
+
+// TempPathForObj creates a temporary file path in the format of
+// '<dir>/Kind-Namespace-Name-<random bytes><suffix>'.
+// If the given dir is empty, os.TempDir is used as a default.
+func TempPathForObj(dir, suffix string, obj client.Object) string {
+	if dir == "" {
+		dir = os.TempDir()
+	}
+	randBytes := make([]byte, 16)
+	rand.Read(randBytes)
+	return filepath.Join(dir, pattern(obj)+hex.EncodeToString(randBytes)+suffix)
+}
+
+func pattern(obj client.Object) (p string) {
+	kind := strings.ToLower(obj.GetObjectKind().GroupVersionKind().Kind)
+	return fmt.Sprintf("%s-%s-%s-", kind, obj.GetNamespace(), obj.GetName())
+}

internal/util/temp_test.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2021 The Flux authors
+
+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 util
+
+import (
+	"os"
+	"testing"
+
+	. "github.com/onsi/gomega"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+func TestTempDirForObj(t *testing.T) {
+	g := NewWithT(t)
+
+	got, err := TempDirForObj("", mockObj())
+	g.Expect(err).ToNot(HaveOccurred())
+	g.Expect(got).To(BeADirectory())
+	defer os.RemoveAll(got)
+
+	got2, err := TempDirForObj(got, mockObj())
+	g.Expect(err).ToNot(HaveOccurred())
+	g.Expect(got2).To(BeADirectory())
+	defer os.RemoveAll(got2)
+	g.Expect(got2).To(ContainSubstring(got))
+}
+
+func TestTempPathForObj(t *testing.T) {
+	tests := []struct {
+		name   string
+		dir    string
+		suffix string
+		want   string
+	}{
+		{
+			name: "default",
+			want: os.TempDir() + "/secret-default-foo-",
+		},
+		{
+			name: "with directory",
+			dir:  "/foo",
+			want: "/foo/secret-default-foo-",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			g := NewWithT(t)
+			got := TempPathForObj(tt.dir, tt.suffix, mockObj())
+			g.Expect(got[:len(got)-32]).To(Equal(tt.want))
+		})
+	}
+}
+
+func Test_pattern(t *testing.T) {
+	g := NewWithT(t)
+	g.Expect(pattern(mockObj())).To(Equal("secret-default-foo-"))
+}
+
+func mockObj() client.Object {
+	return &corev1.Secret{
+		TypeMeta: metav1.TypeMeta{
+			Kind: "Secret",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "foo",
+			Namespace: "default",
+		},
+	}
+}