package config

import (
	"github.com/creasty/defaults"
	"github.com/fsnotify/fsnotify"
	"github.com/go-playground/validator/v10"
	"github.com/ngaut/log"
	"github.com/pingcap/errors"
	"github.com/spf13/viper"
	"go.uber.org/zap"
)

var (
	globalConf *GlobalConfig = &GlobalConfig{}
)

func Global() *GlobalConfig {
	return globalConf
}

// use defaults <- pulumi config (config file) <- remote config <- secrets
// defaults for tag default in the config struct.

// use a single instance of Validate, it caches struct info
var validate = validator.New()

func NormalizeConfigDefaults(config *GlobalConfig) error {
	return defaults.Set(config)
}

func NormalizeConfigSetup(config *GlobalConfig) error {
	err := viper.Unmarshal(config)
	if err != nil {
		return errors.Annotate(err, "failed unmarshal from viper")
	}

	return nil
}

func NormalizeConfigValidate(config *GlobalConfig) error {
	// validate the values
	if err := validate.Struct(config); err != nil {
		return errors.Annotate(err, "failed to validate the config values")
	}

	return nil
}

func NormalizeConfig() error {
	config := &GlobalConfig{}

	err := NormalizeConfigDefaults(config)
	if err != nil {
		return err
	}
	err = NormalizeConfigSetup(config)
	if err != nil {
		return err
	}
	err = NormalizeConfigValidate(config)
	if err != nil {
		return err
	}
	globalConf = config
	return nil
}

// InitConfig parse the central configuration file and init the global config var
func InitConfig(path string) error {
	viper.SetConfigFile(path)
	viper.AutomaticEnv()
	err := viper.ReadInConfig()
	if err != nil {
		return err
	}
	err = NormalizeConfig()
	if err != nil {
		return err
	}
	// register config change watcher
	viper.WatchConfig()
	viper.OnConfigChange(func(e fsnotify.Event) {
		log.Info("config file changed", zap.String("path", e.Name))
		// reload and re-normalize config when file changes
		if err := NormalizeConfig(); err != nil {
			log.Error("failed to reload config after file change", zap.Error(err))
		} else {
			log.Info("config successfully reloaded")
		}
	})

	return nil
}