1 files changed, 64 insertions, 0 deletions
diff --git a/internal/editor/editor.go b/internal/editor/editor.go
new file mode 100644
index 0000000..6a70fa0
--- /dev/null
+++ b/internal/editor/editor.go
@@ -0,0 +1,64 @@
+// Copyright 2020 Google LLC 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 editor implements a simple interface for interactive file editing.
+// It most likely does not work on windows.
+package editor
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+// Edit opens a temporary file in the default editor (per $EDITOR, falling back
+// to "vi") with the contents of the given io.Reader and a filename ending in
+// the given extension (to give a hint to the editor for syntax highlighting).
+//
+// The contents of the edited file are returned, and the temporary file removed.
+func Edit(input io.Reader, extension string) ([]byte, error) {
+	f, err := os.CreateTemp("", fmt.Sprintf("%s-edit.*.%s", filepath.Base(os.Args[0]), extension))
+	if err != nil {
+		return nil, err
+	}
+	defer os.Remove(f.Name())
+
+	if _, err := io.Copy(f, input); err != nil {
+		return nil, err
+	}
+	f.Close()
+
+	editor := "vi"
+	if env := os.Getenv("EDITOR"); env != "" {
+		editor = env
+	}
+
+	path, err := exec.LookPath(editor)
+	if err != nil {
+		return nil, err
+	}
+
+	cmd := exec.Command(path, f.Name())
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		return nil, err
+	}
+
+	return os.ReadFile(f.Name())
+}