package config

import (
	"fmt"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/config"
	"github.com/spf13/viper"
)

// Config represents a group of named values structured
// by tree type.
//
// Sub-trees are named configuration sub-sections,
// leaves are named configuration values.
// Names are of string type.
type Config struct {
	v *viper.Viper

	opts opts

	defaultPath []string
	path        []string
}

const (
	separator = "."

	// EnvPrefix is a prefix of ENV variables related
	// to storage node configuration.
	EnvPrefix = "FROSTFS"

	// EnvSeparator is a section separator in ENV variables.
	EnvSeparator = "_"
)

// Prm groups required parameters of the Config.
type Prm struct{}

// New creates a new Config instance.
//
// If file option is provided (WithConfigFile),
// configuration values are read from it.
// Otherwise, Config is a degenerate tree.
func New(_ Prm, opts ...Option) *Config {
	v := viper.New()

	o := defaultOpts()
	for i := range opts {
		opts[i](o)
	}

	if o.envPrefix != "" {
		v.SetEnvPrefix(o.envPrefix)
		v.AutomaticEnv()
		v.SetEnvKeyReplacer(strings.NewReplacer(separator, EnvSeparator))
	}

	if o.path != "" {
		v.SetConfigFile(o.path)

		err := v.ReadInConfig()
		if err != nil {
			panic(fmt.Errorf("failed to read config: %w", err))
		}
	}

	if o.configDir != "" {
		if err := config.ReadConfigDir(v, o.configDir); err != nil {
			panic(fmt.Errorf("failed to read config dir: %w", err))
		}
	}

	return &Config{
		v:    v,
		opts: *o,
	}
}

// Reload reads configuration path if it was provided to New.
func (x *Config) Reload() error {
	if x.opts.path != "" {
		err := x.v.ReadInConfig()
		if err != nil {
			return fmt.Errorf("rereading configuration file: %w", err)
		}
	}

	if x.opts.configDir != "" {
		if err := config.ReadConfigDir(x.v, x.opts.configDir); err != nil {
			return fmt.Errorf("rereading configuration dir: %w", err)
		}
	}

	return nil
}