feat: project scaffold, config loading, skeleton main

internal/config/config.go

@@ -0,0 +1,100 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/spf13/viper"
+)
+
+type Config struct {
+	Server    ServerConfig    `mapstructure:"server"`
+	Database  DatabaseConfig  `mapstructure:"database"`
+	Redis     RedisConfig     `mapstructure:"redis"`
+	SMTP      SMTPConfig      `mapstructure:"smtp"`
+	RateLimit RateLimitConfig `mapstructure:"rate_limit"`
+}
+
+type ServerConfig struct {
+	Port     int    `mapstructure:"port"`
+	AdminKey string `mapstructure:"admin_key"`
+}
+
+type DatabaseConfig struct {
+	Host     string `mapstructure:"host"`
+	Port     int    `mapstructure:"port"`
+	User     string `mapstructure:"user"`
+	Password string `mapstructure:"password"`
+	Database string `mapstructure:"database"`
+}
+
+func (d DatabaseConfig) DSN() string {
+	return fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=utf8mb4&parseTime=true&loc=Local",
+		d.User, d.Password, d.Host, d.Port, d.Database)
+}
+
+type RedisConfig struct {
+	Host     string `mapstructure:"host"`
+	Port     int    `mapstructure:"port"`
+	Password string `mapstructure:"password"`
+	DB       int    `mapstructure:"db"`
+}
+
+func (r RedisConfig) Addr() string {
+	return fmt.Sprintf("%s:%d", r.Host, r.Port)
+}
+
+type SMTPConfig struct {
+	Host     string `mapstructure:"host"`
+	Port     int    `mapstructure:"port"`
+	User     string `mapstructure:"user"`
+	Password string `mapstructure:"password"`
+	From     string `mapstructure:"from"`
+}
+
+type RateLimitConfig struct {
+	Default int `mapstructure:"default"`
+}
+
+func Load(path string) (*Config, error) {
+	v := viper.New()
+	v.SetConfigFile(path)
+	v.SetEnvPrefix("NOTIFY")
+	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+	v.AutomaticEnv()
+
+	if err := v.ReadInConfig(); err != nil {
+		return nil, fmt.Errorf("read config: %w", err)
+	}
+
+	// Expand ${ENV_VAR} placeholders in config values
+	for _, key := range v.AllKeys() {
+		val := v.GetString(key)
+		if strings.Contains(val, "${") {
+			expanded := expandEnv(val)
+			v.Set(key, expanded)
+		}
+	}
+
+	var cfg Config
+	if err := v.Unmarshal(&cfg); err != nil {
+		return nil, fmt.Errorf("unmarshal config: %w", err)
+	}
+	return &cfg, nil
+}
+
+func expandEnv(s string) string {
+	return os.Expand(s, func(key string) string {
+		// support ${VAR:-default}
+		if i := strings.Index(key, ":-"); i >= 0 {
+			name := key[:i]
+			def := key[i+2:]
+			if v, ok := os.LookupEnv(name); ok {
+				return v
+			}
+			return def
+		}
+		return os.Getenv(key)
+	})
+}