persist app title + code refactoring

server/configurator/configurator.go

@@ -0,0 +1,104 @@
+package configurator
+
+import (
+	"log/slog"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/marcopiovanello/yt-dlp-web-ui/v3/server/config"
+	"gopkg.in/yaml.v3"
+)
+
+// A singleton holding configuration of the frontend component
+// with optional persistence on a file.
+type AppConfig struct {
+	Title          string `yaml:"title" json:"title"`
+	BaseURL        string `yaml:"base_url" json:"base_url"`
+	Language       string `yaml:"language" json:"language"`
+	RPCPollingTime int    `yaml:"rpc_polling_time" json:"rpc_polling_time"`
+}
+
+type Configurator struct {
+	mu     sync.RWMutex
+	Config AppConfig
+}
+
+var (
+	instance     *Configurator
+	instanceOnce sync.Once
+)
+
+func Instance() *Configurator {
+	instanceOnce.Do(func() {
+		if instance == nil {
+			instance = &Configurator{}
+
+			// TODO: move out of initialization
+			err := instance.Load()
+			if err != nil {
+				slog.Error("failed initializating configurator", slog.Any("err", err))
+			}
+		}
+	})
+	return instance
+}
+
+func (c *Configurator) Load() error {
+	fd, err := getConfigurationFile()
+	if err != nil {
+		return err
+	}
+	defer fd.Close()
+
+	if err := yaml.NewDecoder(fd).Decode(&c.Config); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Configurator) Persist() error {
+	fd, err := getConfigurationFile()
+	if err != nil {
+		return err
+	}
+	defer fd.Close()
+
+	if err := yaml.NewEncoder(fd).Encode(c.Config); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Configurator) setAppConfig(ac *AppConfig) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	// TODO: better validaitons
+	if ac.BaseURL != "" {
+		c.Config.BaseURL = ac.BaseURL
+	}
+	if ac.Language != "" {
+		c.Config.Language = ac.Language
+	}
+	if ac.Title != "" {
+		c.Config.Title = ac.Title
+	}
+	if ac.RPCPollingTime >= 250 && ac.RPCPollingTime <= 2000 {
+		c.Config.RPCPollingTime = ac.RPCPollingTime
+	}
+}
+
+func getConfigurationFile() (*os.File, error) {
+	fd, err := os.OpenFile(
+		filepath.Join(config.Instance().Dir(), "web_config.yml"),
+		os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return fd, nil
+}