job-search/internal/config/modify.go

package config

import (
	"errors"
	"fmt"
	"reflect"
	"strconv"

	"github.com/spf13/viper"
)

// StoreValue parses value as the type of key, checks conf accepts it, sets it
// in conf and Viper and writes it to the config file Viper is using. Only the
// file's own settings are written back, not defaults or environment
// variables. It returns the stored value (as ValueOf gives it) and its kind.
func StoreValue(
	conf *JobSearchConfig, key, value string,
) (any, reflect.Kind, error) {
	return storeValue(conf, key, value)
}

// storeValue is StoreValue for any section, so key types that
// JobSearchConfig doesn't have yet can be tested.
func storeValue(
	section Section, key, value string,
) (any, reflect.Kind, error) {
	confType, err := section.TypeOf(key)
	if err != nil {
		return nil, confType, err
	}

	// Check the value is of the right kind first, for a clearer error than
	// SetValue gives.
	if _, err := parseValue(confType, value); err != nil {
		return nil, confType, fmt.Errorf(
			"config: value type not accepted, expected <%s>", confType,
		)
	}

	// SetValue parses the string into the field's own type (e.g. int8,
	// float32 or time.Duration) and rejects values the configuration itself
	// would not accept, e.g. an unknown log level or an unparseable duration.
	if err := section.SetValue(key, value); err != nil {
		return nil, confType, err
	}
	confValue, err := section.ValueOf(key)
	if err != nil {
		return nil, confType, err
	}

	viper.Set(key, confValue)
	file, err := readUsedConfigFile()
	if err != nil {
		return nil, confType, err
	}
	file.Set(key, confValue)
	if err := file.WriteConfig(); err != nil {
		return nil, confType, err
	}

	return confValue, confType, nil
}

// parseValue parses value as a value of kind, returning
// errors.ErrUnsupported for a kind it can't parse.
func parseValue(kind reflect.Kind, value string) (any, error) {
	switch kind {
	case reflect.Bool:
		return strconv.ParseBool(value)
	case reflect.String:
		return value, nil
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return strconv.ParseInt(value, 10, 64)
	case reflect.Uint,
		reflect.Uint8,
		reflect.Uint16,
		reflect.Uint32,
		reflect.Uint64:
		return strconv.ParseUint(value, 10, 64)
	case reflect.Float32, reflect.Float64:
		return strconv.ParseFloat(value, 64)
	case reflect.Slice:
		return splitList(value), nil
	}
	return nil, errors.ErrUnsupported
}

// PurgeValue rewrites the config file Viper is using without key. The
// file's other settings are kept as they are; defaults and environment
// variables are not written to it.
func PurgeValue(conf *JobSearchConfig, key string) error {
	if _, err := conf.TypeOf(key); err != nil {
		return err
	}

	file, err := readUsedConfigFile()
	if err != nil {
		return err
	}

	out := viper.New()
	out.SetConfigFile(file.ConfigFileUsed())
	for _, fileKey := range file.AllKeys() {
		if fileKey != key {
			out.Set(fileKey, file.Get(fileKey))
		}
	}

	return out.WriteConfig()
}

// readUsedConfigFile reads the config file Viper is using into a new Viper, so
// it holds only the file's settings.
func readUsedConfigFile() (*viper.Viper, error) {
	path := viper.ConfigFileUsed()
	if path == "" {
		return nil, errors.New("config: no configuration file in use")
	}

	file := viper.New()
	file.SetConfigFile(path)
	if err := file.ReadInConfig(); err != nil {
		return nil, err
	}

	return file, nil
}