Add initial framework of configuration.

feat: configuration file system of app.

Note: still work in progress.

internal/config/config.go

@@ -0,0 +1,74 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"time"
+)
+
+type Config struct {
+	Server   ServerConfig   `mapstructure:"server"`
+	Database DatabaseConfig `mapstructure:"database"`
+	Storage  StorageConfig  `mapstructure:"storage"`
+	JWT      JWTConfig      `mapstructure:"jwt"`
+}
+
+type ServerConfig struct {
+	Host string `mapstructure:"host"`
+	Port int    `mapstructure:"port"`
+}
+
+type DatabaseConfig struct {
+	Driver string `mapstructure:"driver"`
+	Path   string `mapstructure:"path"`
+}
+
+type StorageConfig struct {
+	Driver string             `mapstructure:"driver"`
+	Local  LocalStorageConfig `mapstructure:"local"`
+}
+
+type LocalStorageConfig struct {
+	Path string `mapstructure:"path"`
+}
+
+type JWTConfig struct {
+	Secret     string        `mapstructure:"secret"`
+	AccessTTL  time.Duration `mapstructure:"access_ttl"`
+	RefreshTTL time.Duration `mapstructure:"refresh_ttl"`
+}
+
+func (c *Config) Validate() error {
+	var errs []error
+
+	if c.Server.Port < 1 || c.Server.Port > 65535 {
+		errs = append(errs, fmt.Errorf("server.port: %d out of range [1, 65535]", c.Server.Port))
+	}
+
+	if addr := net.ParseIP(c.Server.Host); c.Server.Host != "" && addr == nil {
+		errs = append(errs, fmt.Errorf("server.host: %q is not a valid IP address", c.Server.Host))
+	}
+
+	if c.Database.Path == "" {
+		errs = append(errs, errors.New("database.path: must not be empty"))
+	}
+
+	if c.Storage.Local.Path == "" {
+		errs = append(errs, errors.New("storage.local.path: must not be empty"))
+	}
+
+	if c.JWT.Secret == "" {
+		errs = append(errs, errors.New("jwt.secret: must not be empty"))
+	}
+
+	if c.JWT.AccessTTL <= 0 {
+		errs = append(errs, fmt.Errorf("jwt.access_ttl: %v must be positive", c.JWT.AccessTTL))
+	}
+
+	if c.JWT.RefreshTTL <= 0 {
+		errs = append(errs, fmt.Errorf("jwt.refresh_ttl: %v must be positive", c.JWT.RefreshTTL))
+	}
+
+	return errors.Join(errs...)
+}