config

var (
	// ConfigEnvPrefix defines the environment variable prefix for reading server configuration from the environment.
	// This can be overridden to provide a customised default environment prefix for an app.
	ConfigEnvPrefix = "APP_"
	// ErrLoadConfig is the sentinel error returned when there was an issue loading the config.
	ErrLoadConfig = errors.New("error loading config")
	// ErrInvalidConfig is the sentinel error returned when the config was loaded but contains invalid values.
	ErrInvalidConfig = errors.New("invalid config")
)

var LoadAppConfig = sync.OnceValues(func() (*AppConfig, error) {
	cfg := &AppConfig{
		Environment: EnvDevelopment,
		Version:     "_UNKNOWN_",
	}
	var vcsRevision string
	// var vcsTime string
	var vcsModified bool
	var vcsSystem string
	if info, ok := debug.ReadBuildInfo(); ok {
		for buildInfo := range slices.Values(info.Settings) {
			switch buildInfo.Key {
			case "vcs":
				vcsSystem = buildInfo.Value
			case "vcs.revision":
				vcsRevision = buildInfo.Value

			case "vcs.modified":
				vcsModified = buildInfo.Value == "true"
			}
		}
		cfg.Version = strings.Join([]string{vcsSystem, vcsRevision}, "-")
		if vcsModified {
			cfg.Version += "-dirty"
		}
	}

	if err := Load(ConfigEnvPrefix, cfg); err != nil {
		return nil, fmt.Errorf("load base config: %w", err)
	}

	if err := validation.Validate.Struct(cfg); err != nil {
		return nil, fmt.Errorf("validate base config: %w", err)
	}

	return cfg, nil
})