draft unified mechanisms for loading config files

tracker/config.go

@@ -0,0 +1,42 @@
+package tracker
+
+import (
+	"embed"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+
+	"gopkg.in/yaml.v2"
+)
+
+func ReadConfig(embedFS embed.FS, path string, out any) (warning error) {
+	bytes := must(fs.ReadFile(embedFS, path)) // the file _must_ exist in the embedded fs; panic on purpose if not
+	if err := yaml.UnmarshalStrict(bytes, out); err != nil {
+		panic(err) // also, the embedded default config file _must_ be strictly valid yaml; panic if not
+	}
+	// now, try to read the user config file, overlapping the default one.
+	// Notice that the return values are just warnings - there's always the
+	// default config there so no harm done if the user config is missing or
+	// invalid.
+	configDir, err := os.UserConfigDir()
+	if err != nil {
+		return fmt.Errorf("ReadConfig %v: %v", path, err)
+	}
+	configPath := filepath.Join(configDir, "sointu", path)
+	bytesUser, err := os.ReadFile(configPath)
+	if err != nil {
+		return fmt.Errorf("ReadConfig %v: %v", path, err)
+	}
+	if err := yaml.Unmarshal(bytesUser, out); err != nil {
+		return fmt.Errorf("ReadConfig %v: %v", path, err)
+	}
+	return nil
+}
+
+func must[T any](ic T, err error) T {
+	if err != nil {
+		panic(err)
+	}
+	return ic
+}