Use only one Config struct

This commit switches from a GlobalConfig struct with named sub-structs
to a single struct definition with anonymous sub-structs. The advantage
is that there are not so many names the reader has to understand.

A custom UnmarshalJSON() function on the Config struct level ensures
that the error checking can be embedded into the parsing process and
native Go types like net.HardwareAddr can be used in the struct
definition while the string-based struct for JSON unmarshaling is an
implementation detail of the custom UnmarshalJSON() function.

In general the user of this type and its method only has to parse the
config with json.Unmarshal(), handle error at this step and can rely on
validated configuration data with native Go types from that point on.

2 files changed, 48 insertions, 29 deletions

diff --git a/config.go b/config.go
index e187827..d04c423 100644
--- a/config.go
+++ b/config.go
@@ -10,62 +10,81 @@ import (
 
 const configPathRelative = `.config/soundbox/config.json`
 
-type MacAddress net.HardwareAddr
+type Config struct {
+	Soundboxes []struct {
+		Name string
+		Mac  net.HardwareAddr
+	}
+	URLs []struct {
+		Name string
+		Url  string
+	}
+}
 
-func (m *MacAddress) UnmarshalJSON(data []byte) error {
-	var macStr string
-	err := json.Unmarshal(data, &macStr)
-	if err != nil {
-		return err
+func (config *Config) UnmarshalJSON(data []byte) error {
+	var buffer struct {
+		Soundboxes []struct {
+			Name string
+			Mac  string
+		}
+		URLs []struct {
+			Name string
+			Url  string
+		}
 	}
 
-	hwAddr, err := net.ParseMAC(macStr)
+	err := json.Unmarshal(data, &buffer)
 	if err != nil {
 		return err
 	}
 
-	*m = MacAddress(hwAddr)
-	return nil
-}
+	parsed := Config{}
 
-type SoundboxConfig struct {
-	Name string     `json:"name"`
-	Mac  MacAddress `json:"mac"`
-}
+	for _, soundbox := range buffer.Soundboxes {
+		hwAddr, err := net.ParseMAC(soundbox.Mac)
+		if err != nil {
+			return err
+		}
+		parsed.Soundboxes = append(parsed.Soundboxes, struct {
+			Name string
+			Mac  net.HardwareAddr
+		}{soundbox.Name, hwAddr})
+	}
 
-type URLConfig struct {
-	Name string `json:"name"`
-	Url  string `json:"url"`
-}
+	for _, url := range buffer.URLs {
+		parsed.URLs = append(parsed.URLs, struct {
+			Name string
+			Url  string
+		}{url.Name, url.Url})
+	}
 
-type GlobalConfig struct {
-	Soundboxes []SoundboxConfig `json:"soundboxes"`
-	URLs       []URLConfig      `json:"urls"`
+	*config = parsed
+	return nil
 }
 
-func loadConfig() (GlobalConfig, error) {
+func loadConfig() (Config, error) {
 	home, err := os.UserHomeDir()
 	if err != nil {
-		return GlobalConfig{}, err
+		return Config{}, err
 	}
 
 	path := filepath.Join(home, configPathRelative)
 
 	file, err := os.Open(path)
 	if err != nil {
-		return GlobalConfig{}, err
+		return Config{}, err
 	}
 	defer file.Close()
 
 	bytes, err := io.ReadAll(file)
 	if err != nil {
-		return GlobalConfig{}, err
+		return Config{}, err
 	}
 
-	var config GlobalConfig
+	var config Config
 	err = json.Unmarshal(bytes, &config)
 	if err != nil {
-		return GlobalConfig{}, err
+		return Config{}, err
 	}
 
 	return config, nil
diff --git a/main.go b/main.go
index 8302155..20ee049 100644
--- a/main.go
+++ b/main.go
@@ -38,7 +38,7 @@ func main() {
 
 type State struct {
 	sync.Mutex
-	Config              GlobalConfig
+	Config              Config
 	Theme               *material.Theme
 	Title               string
 	UrlEditor           widget.Editor
@@ -53,7 +53,7 @@ type Ui struct {
 	State  State
 }
 
-func NewUi(config GlobalConfig) *Ui {
+func NewUi(config Config) *Ui {
 	ui := Ui{}
 
 	ui.State.Config = config