feat: add config loading with YAML, env override, and hot-reload

internal/config/config.go

@@ -0,0 +1,53 @@
+package config
+
+import (
+	"sync/atomic"
+)
+
+// DoubaoConfig holds 火山引擎豆包 ASR credentials.
+type DoubaoConfig struct {
+	AppKey     string `yaml:"app_key"`
+	AccessKey  string `yaml:"access_key"`
+	ResourceID string `yaml:"resource_id"`
+}
+
+// ServerConfig holds server settings.
+type ServerConfig struct {
+	Port    int  `yaml:"port"`
+	TLSAuto bool `yaml:"tls_auto"`
+}
+
+// Config is the top-level configuration.
+type Config struct {
+	Doubao DoubaoConfig `yaml:"doubao"`
+	Server ServerConfig `yaml:"server"`
+}
+
+// defaults returns a Config with default values.
+func defaults() Config {
+	return Config{
+		Doubao: DoubaoConfig{
+			ResourceID: "volc.seedasr.sauc.duration",
+		},
+		Server: ServerConfig{
+			Port:    8443,
+			TLSAuto: true,
+		},
+	}
+}
+
+// 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)
+	}
+	return defaults()
+}
+
+// store updates the global config.
+func store(cfg Config) {
+	global.Store(cfg)
+}

internal/config/load.go

@@ -0,0 +1,125 @@
+package config
+
+import (
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strconv"
+
+	"github.com/fsnotify/fsnotify"
+	"gopkg.in/yaml.v3"
+)
+
+// Load reads config from file (optional), applies env overrides, validates, and stores globally.
+// If configPath is empty, it tries "config.yaml" in the working directory.
+func Load(configPath string) (Config, error) {
+	cfg := defaults()
+
+	// Try loading YAML file
+	if configPath == "" {
+		configPath = "config.yaml"
+	}
+	if data, err := os.ReadFile(configPath); err == nil {
+		if err := yaml.Unmarshal(data, &cfg); err != nil {
+			return cfg, fmt.Errorf("parse config %s: %w", configPath, err)
+		}
+		slog.Info("loaded config file", "path", configPath)
+	}
+
+	// Env overrides
+	applyEnv(&cfg)
+
+	// Validate
+	if err := validate(cfg); err != nil {
+		return cfg, err
+	}
+
+	store(cfg)
+	return cfg, nil
+}
+
+// applyEnv overrides config fields with environment variables.
+func applyEnv(cfg *Config) {
+	if v := os.Getenv("DOUBAO_APP_KEY"); v != "" {
+		cfg.Doubao.AppKey = v
+	}
+	if v := os.Getenv("DOUBAO_ACCESS_KEY"); v != "" {
+		cfg.Doubao.AccessKey = v
+	}
+	if v := os.Getenv("DOUBAO_RESOURCE_ID"); v != "" {
+		cfg.Doubao.ResourceID = v
+	}
+	if v := os.Getenv("PORT"); v != "" {
+		if port, err := strconv.Atoi(v); err == nil {
+			cfg.Server.Port = port
+		}
+	}
+	if v := os.Getenv("TLS_AUTO"); v != "" {
+		cfg.Server.TLSAuto = v == "true" || v == "1"
+	}
+}
+
+// validate checks required fields.
+func validate(cfg Config) error {
+	if cfg.Doubao.AppKey == "" {
+		return fmt.Errorf("doubao.app_key is required (set DOUBAO_APP_KEY or config.yaml)")
+	}
+	if cfg.Doubao.AccessKey == "" {
+		return fmt.Errorf("doubao.access_key is required (set DOUBAO_ACCESS_KEY or config.yaml)")
+	}
+	return nil
+}
+
+// WatchAndReload watches the config file for changes and hot-reloads.
+func WatchAndReload(configPath string) {
+	if configPath == "" {
+		configPath = "config.yaml"
+	}
+
+	absPath, err := filepath.Abs(configPath)
+	if err != nil {
+		slog.Warn("cannot resolve config path for watching", "error", err)
+		return
+	}
+
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		slog.Warn("cannot create file watcher", "error", err)
+		return
+	}
+
+	dir := filepath.Dir(absPath)
+	if err := watcher.Add(dir); err != nil {
+		slog.Warn("cannot watch config directory", "error", err)
+		watcher.Close()
+		return
+	}
+
+	slog.Info("watching config for changes", "path", absPath)
+
+	go func() {
+		defer watcher.Close()
+		for {
+			select {
+			case event, ok := <-watcher.Events:
+				if !ok {
+					return
+				}
+				if filepath.Clean(event.Name) == absPath && (event.Has(fsnotify.Write) || event.Has(fsnotify.Create)) {
+					slog.Info("config file changed, reloading")
+					if _, err := Load(configPath); err != nil {
+						slog.Error("failed to reload config", "error", err)
+					} else {
+						slog.Info("config reloaded successfully")
+					}
+				}
+			case err, ok := <-watcher.Errors:
+				if !ok {
+					return
+				}
+				slog.Error("config watcher error", "error", err)
+			}
+		}
+	}()
+}