enable configuration from a json file

Author: tomcz

README.md

@@ -25,7 +25,12 @@ You can download the latest release from [here](https://github.com/tomcz/s3backu
 ```
 Usage: s3backup <command>
 
-S3 backup script in a single binary
+S3 backup script in a single binary.
+
+NOTE: Command line flag values can optionally be retrieved from a JSON
+configuration file. The path to this configuration file is provided at runtime
+by the S3BACKUP_JSON environment variable. The JSON file should contain an
+object whose keys must match the command line flags they are meant to configure.
 
 Flags:
   -h, --help    Show context-sensitive help.

cmd/s3backup/main.go

@@ -27,6 +27,14 @@ var (
 	tag    string
 )
 
+const description = `
+S3 backup script in a single binary.
+
+NOTE: Command flag values can optionally be retrieved from a JSON configuration file.
+The path to this configuration file is provided at runtime by the S3BACKUP_JSON environment variable.
+The JSON file should contain an object whose keys must match the command line flags they are meant to configure.
+`
+
 type putFlags struct {
 	LocalPath  string `arg:"" help:"Required local file path"`
 	RemotePath string `arg:"" help:"Required s3 path (s3://bucket/objectkey)"`
@@ -129,10 +137,17 @@ func main() {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
 	defer stop()
 
-	description := kong.Description("S3 backup script in a single binary")
-	app := kong.Parse(&appCfg{}, description, kong.HelpOptions{Compact: true})
-	app.BindTo(ctx, (*context.Context)(nil))
+	opts := []kong.Option{
+		kong.Description(description),
+		kong.HelpOptions{Compact: true},
+	}
+	if file := os.Getenv("S3BACKUP_JSON"); file != "" {
+		log.Println("Using configuration from", file)
+		opts = append(opts, kong.Configuration(kong.JSON, file))
+	}
 
+	app := kong.Parse(&appCfg{}, opts...)
+	app.BindTo(ctx, (*context.Context)(nil))
 	if err := app.Run(); err != nil {
 		log.Fatalln(err)
 	}

cmd/s3backup/main_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"testing"
 
+	"github.com/alecthomas/kong"
 	"gotest.tools/v3/assert"
 )
 
@@ -31,3 +32,39 @@ func TestCheckPaths(t *testing.T) {
 	assert.Equal(t, inLocal, outRemote)
 	assert.Equal(t, inRemote, outLocal)
 }
+
+func TestJsonConfig_Get(t *testing.T) {
+	var app appCfg
+	parser, err := kong.New(&app, kong.Configuration(kong.JSON, "testdata/get.json"))
+	assert.NilError(t, err)
+	_, err = parser.Parse([]string{"get", "remote", "local"})
+	assert.NilError(t, err)
+	assert.Equal(t, app.Get.LocalPath, "local")
+	assert.Equal(t, app.Get.RemotePath, "remote")
+	assert.Equal(t, app.Get.SkipHash, true)
+	assert.Equal(t, app.Get.SymKey, "wibble")
+	assert.Equal(t, app.Get.PemKey, "")
+	assert.Equal(t, app.Get.AccessKey, "test_accessKey")
+	assert.Equal(t, app.Get.SecretKey, "test_secretKey")
+	assert.Equal(t, app.Get.Token, "test_token")
+	assert.Equal(t, app.Get.Region, "test_region")
+	assert.Equal(t, app.Get.Endpoint, "test_endpoint")
+}
+
+func TestJsonConfig_Put(t *testing.T) {
+	var app appCfg
+	parser, err := kong.New(&app, kong.Configuration(kong.JSON, "testdata/put.json"))
+	assert.NilError(t, err)
+	_, err = parser.Parse([]string{"put", "local", "remote"})
+	assert.NilError(t, err)
+	assert.Equal(t, app.Put.LocalPath, "local")
+	assert.Equal(t, app.Put.RemotePath, "remote")
+	assert.Equal(t, app.Put.SkipHash, false)
+	assert.Equal(t, app.Put.SymKey, "")
+	assert.Equal(t, app.Put.PemKey, "wobble")
+	assert.Equal(t, app.Put.AccessKey, "test_accessKey")
+	assert.Equal(t, app.Put.SecretKey, "test_secretKey")
+	assert.Equal(t, app.Put.Token, "test_token")
+	assert.Equal(t, app.Put.Region, "test_region")
+	assert.Equal(t, app.Put.Endpoint, "test_endpoint")
+}

cmd/s3backup/testdata/get.json

@@ -0,0 +1,9 @@
+{
+  "nocheck": true,
+  "symKey": "wibble",
+  "accessKey": "test_accessKey",
+  "secretKey": "test_secretKey",
+  "token": "test_token",
+  "region": "test_region",
+  "endpoint": "test_endpoint"
+}

cmd/s3backup/testdata/put.json

@@ -0,0 +1,9 @@
+{
+  "nocheck": false,
+  "pemKey": "wobble",
+  "accessKey": "test_accessKey",
+  "secretKey": "test_secretKey",
+  "token": "test_token",
+  "region": "test_region",
+  "endpoint": "test_endpoint"
+}