feat(config): create example configuration file on first launch

internal/config/data/config.example.yml

@@ -0,0 +1,24 @@
+# Octoplex is a live stream multiplexer.
+---
+#
+sources:
+  # Currently the only source type is RTMP server.
+  rtmp:
+    enabled: yes
+    # Your local stream key. Defaults to "live".
+    #
+    # rtmp://localhost:1935/live
+    streamkey: live
+#
+logfile:
+  # Change to yes to log to system location.
+  enabled: no
+  # Or, log to this absolute path:
+  # path: octoplex.log
+#
+# Define your destinations here.
+destinations:
+  # - name: YouTube
+  #   url: rtmp://rtmp.youtube.com/myYoutubeStreamKey
+  # - name: Twitch
+  #   url: rtmp://ingest.global-contribute.live-video.net/app/myTwitchStreamKey

internal/config/service.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	_ "embed"
 	"errors"
 	"fmt"
 	"os"
@@ -11,6 +12,9 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+//go:embed data/config.example.yml
+var exampleConfig []byte
+
 // Service provides configuration services.
 type Service struct {
 	userConfigDir string
@@ -85,23 +89,16 @@ func (s *Service) readConfig() (cfg Config, _ error) {
 	return cfg, nil
 }
 
-func (s *Service) createConfig() (cfg Config, _ error) {
+func (s *Service) createConfig() (Config, error) {
 	if err := os.MkdirAll(s.appConfigDir, 0744); err != nil {
-		return cfg, fmt.Errorf("mkdir: %w", err)
+		return Config{}, fmt.Errorf("mkdir: %w", err)
 	}
 
-	s.setDefaults(&cfg)
-
-	yamlBytes, err := yaml.Marshal(cfg)
-	if err != nil {
-		return cfg, fmt.Errorf("marshal: %w", err)
+	if err := os.WriteFile(s.Path(), exampleConfig, 0644); err != nil {
+		return Config{}, fmt.Errorf("write file: %w", err)
 	}
 
-	if err = os.WriteFile(s.Path(), yamlBytes, 0644); err != nil {
-		return cfg, fmt.Errorf("write file: %w", err)
-	}
-
-	return cfg, nil
+	return Config{}, nil
 }
 
 func (s *Service) Path() string {

internal/config/service_test.go

@@ -33,16 +33,23 @@ var configMultipleInvalidDestinationURLs []byte
 
 func TestConfigServiceCreateConfig(t *testing.T) {
 	suffix := "read_or_create_" + shortid.New().String()
-	service, err := config.NewService(configDirFunc(suffix))
+	systemConfigDirFunc := buildSystemConfigDirFunc(suffix)
+	systemConfigDir, _ := systemConfigDirFunc()
+
+	service, err := config.NewService(systemConfigDirFunc)
 	require.NoError(t, err)
 
+	t.Cleanup(func() { require.NoError(t, os.RemoveAll(systemConfigDir)) })
+
 	cfg, err := service.ReadOrCreateConfig()
 	require.NoError(t, err)
 	require.Empty(t, cfg.LogFile, "expected no log file")
 
-	p := filepath.Join(configDir(suffix), "config.yaml")
-	_, err = os.Stat(p)
+	p := filepath.Join(systemConfigDir, "octoplex", "config.yaml")
+	cfgBytes, err := os.ReadFile(p)
 	require.NoError(t, err, "config file was not created")
+	// Ensure the example config file is written:
+	assert.Contains(t, string(cfgBytes), "# Octoplex is a live stream multiplexer.")
 }
 
 func TestConfigServiceReadConfig(t *testing.T) {
@@ -114,12 +121,17 @@ func TestConfigServiceReadConfig(t *testing.T) {
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			suffix := "read_or_create_" + shortid.New().String()
-			dir := configDir(suffix)
-			require.NoError(t, os.MkdirAll(dir, 0744))
-			configPath := filepath.Join(dir, "config.yaml")
+			systemConfigDirFunc := buildSystemConfigDirFunc(suffix)
+			systemConfigDir, _ := systemConfigDirFunc()
+			appConfigDir := buildAppConfigDir(suffix)
+
+			require.NoError(t, os.MkdirAll(appConfigDir, 0744))
+			t.Cleanup(func() { require.NoError(t, os.RemoveAll(systemConfigDir)) })
+
+			configPath := filepath.Join(appConfigDir, "config.yaml")
 			require.NoError(t, os.WriteFile(configPath, tc.configBytes, 0644))
 
-			service, err := config.NewService(configDirFunc(suffix))
+			service, err := config.NewService(buildSystemConfigDirFunc(suffix))
 			require.NoError(t, err)
 
 			cfg, err := service.ReadOrCreateConfig()
@@ -134,11 +146,15 @@ func TestConfigServiceReadConfig(t *testing.T) {
 	}
 }
 
-func configDir(suffix string) string {
+// buildAppConfigDir returns a temporary directory which mimics
+// $XDG_CONFIG_HOME/octoplex.
+func buildAppConfigDir(suffix string) string {
 	return filepath.Join(os.TempDir(), "config_test_"+suffix, "octoplex")
 }
 
-func configDirFunc(suffix string) func() (string, error) {
+// buildSystemConfigDirFunc returns a function that creates a temporary
+// directory which mimics $XDG_CONFIG_HOME.
+func buildSystemConfigDirFunc(suffix string) func() (string, error) {
 	return func() (string, error) {
 		return filepath.Join(os.TempDir(), "config_test_"+suffix), nil
 	}