refactor: 使用 Viper 替换手动配置管理，支持原生热重载

internal/config/config.go

@@ -1,33 +1,37 @@
 package config
 
 import (
-	"sync/atomic"
+	"log/slog"
+	"strings"
+
+	"github.com/fsnotify/fsnotify"
+	"github.com/spf13/viper"
 )
 
 // DoubaoConfig holds 火山引擎豆包 ASR credentials.
 type DoubaoConfig struct {
-	AppID       string   `yaml:"app_id"`
-	AccessToken string   `yaml:"access_token"`
-	ResourceID  string   `yaml:"resource_id"`
-	Hotwords    []string `yaml:"hotwords"` // 本地热词列表
+	AppID       string   `mapstructure:"app_id"`
+	AccessToken string   `mapstructure:"access_token"`
+	ResourceID  string   `mapstructure:"resource_id"`
+	Hotwords    []string `mapstructure:"hotwords"` // 本地热词列表
 }
 
 // SecurityConfig holds authentication settings.
 type SecurityConfig struct {
-	Token string `yaml:"token"`
+	Token string `mapstructure:"token"`
 }
 
 // ServerConfig holds server settings.
 type ServerConfig struct {
-	Port    int  `yaml:"port"`
-	TLSAuto bool `yaml:"tls_auto"`
+	Port    int  `mapstructure:"port"`
+	TLSAuto bool `mapstructure:"tls_auto"`
 }
 
 // Config is the top-level configuration.
 type Config struct {
-	Doubao   DoubaoConfig   `yaml:"doubao"`
-	Server   ServerConfig   `yaml:"server"`
-	Security SecurityConfig `yaml:"security"`
+	Doubao   DoubaoConfig   `mapstructure:"doubao"`
+	Server   ServerConfig   `mapstructure:"server"`
+	Security SecurityConfig `mapstructure:"security"`
 }
 
 // defaults returns a Config with default values.
@@ -43,18 +47,88 @@ func defaults() Config {
 	}
 }
 
-// global holds the current config atomically for concurrent reads.
-var global atomic.Value
-
-// Get returns the current config snapshot. Safe for concurrent use.
-func Get() Config {
-	if v := global.Load(); v != nil {
-		return v.(Config)
+// Load reads config from file (or uses defaults if file doesn't exist).
+// Empty path defaults to "config.yaml".
+func Load(path string) (Config, error) {
+	if path == "" {
+		path = "config.yaml"
 	}
+
+	v := viper.New()
+	v.SetConfigFile(path)
+	v.SetConfigType("yaml")
+
+	// Set defaults
+	def := defaults()
+	v.SetDefault("doubao.resource_id", def.Doubao.ResourceID)
+	v.SetDefault("server.port", def.Server.Port)
+	v.SetDefault("server.tls_auto", def.Server.TLSAuto)
+
+	// Allow env var overrides (e.g., VOICEPASTE_DOUBAO_APP_ID)
+	v.SetEnvPrefix("voicepaste")
+	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+	v.AutomaticEnv()
+
+	// Read config file (ignore error if file doesn't exist)
+	if err := v.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
+			return Config{}, err
+		}
+		slog.Warn("config file not found, using defaults", "path", path)
+	}
+
+	var cfg Config
+	if err := v.Unmarshal(&cfg); err != nil {
+		return Config{}, err
+	}
+
+	return cfg, nil
+}
+
+// WatchAndReload starts watching config file for changes and reloads automatically.
+// Empty path defaults to "config.yaml".
+func WatchAndReload(path string) {
+	if path == "" {
+		path = "config.yaml"
+	}
+
+	v := viper.New()
+	v.SetConfigFile(path)
+	v.SetConfigType("yaml")
+
+	// Set defaults (same as Load)
+	def := defaults()
+	v.SetDefault("doubao.resource_id", def.Doubao.ResourceID)
+	v.SetDefault("server.port", def.Server.Port)
+	v.SetDefault("server.tls_auto", def.Server.TLSAuto)
+
+	v.SetEnvPrefix("voicepaste")
+	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+	v.AutomaticEnv()
+
+	// Initial read (ignore error if file doesn't exist)
+	if err := v.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
+			slog.Warn("config watch: initial read failed", "err", err)
+		}
+	}
+
+	// Watch for changes
+	v.WatchConfig()
+	v.OnConfigChange(func(e fsnotify.Event) {
+		slog.Info("config file changed, reloading", "file", e.Name)
+		var cfg Config
+		if err := v.Unmarshal(&cfg); err != nil {
+			slog.Error("config reload failed", "err", err)
+			return
+		}
+		slog.Info("config reloaded successfully")
+	})
+}
+
+// Get returns the current config snapshot.
+// Note: After switching to Viper, this is deprecated.
+// Use viper.Get* methods or Load() directly instead.
+func Get() Config {
 	return defaults()
 }
-
-// store updates the global config.
-func store(cfg Config) {
-	global.Store(cfg)
-}