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parse.go
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parse.go
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package config
import (
"errors"
"fmt"
"reflect"
"github.com/spf13/viper"
)
const tagPrefix = "viper"
// populateNucleusConfig is used to parse config read through viper
func populateNucleusConfig(config *NucleusConfig) (*NucleusConfig, error) {
err := recursivelySet(reflect.ValueOf(config), "")
if err != nil {
return nil, err
}
return config, nil
}
// populateSynapseConfig is used to parse config read through viper
func populateSynapseConfig(config *SynapseConfig) (*SynapseConfig, error) {
err := recursivelySet(reflect.ValueOf(config), "")
if err != nil {
return nil, err
}
return config, nil
}
// recursivelySet is used to recursively set conf read from
// files to golang structs. Since nested values are accessed using periods
// we need to recursively parse the values
func recursivelySet(val reflect.Value, prefix string) error {
if val.Kind() != reflect.Ptr {
return errors.New("WTF")
}
// dereference
val = reflect.Indirect(val)
if val.Kind() != reflect.Struct {
return errors.New("FML")
}
// grab the type for this instance
vType := reflect.TypeOf(val.Interface())
// go through child fields
for i := 0; i < val.NumField(); i++ {
thisField := val.Field(i)
thisType := vType.Field(i)
tags := getTags(thisType)
// try to fetch value for each key using multiple tags
for _, tag := range tags {
key := prefix + tag
switch thisField.Kind() {
case reflect.Struct:
if err := recursivelySet(thisField.Addr(), key+"."); err != nil {
return err
}
case reflect.Int:
fallthrough
case reflect.Int32:
fallthrough
case reflect.Int64:
// you can only set with an int64 -> int
configVal := int64(viper.GetInt(key))
// skip the update if tag is not set in viper
if viper.GetInt(key) == 0 && thisField.Int() != 0 {
continue
}
thisField.SetInt(configVal)
case reflect.String:
// skip the update if tag is not set in viper
if viper.GetString(key) == "" && thisField.String() != "" {
continue
}
thisField.SetString(viper.GetString(key))
case reflect.Bool:
// skip the update if tag is not set in viper
if !viper.GetBool(key) && thisField.Bool() {
continue
}
thisField.SetBool(viper.GetBool(key))
case reflect.Map:
continue
default:
return fmt.Errorf("unexpected type detected ~ aborting: %s", thisField.Kind())
}
}
}
return nil
}
func getTags(field reflect.StructField) []string {
// check if maybe we have a special magic tag
tag := field.Tag
values := []string{}
if tag != "" {
for _, prefix := range []string{tagPrefix, "yaml", "json", "env", "mapstructure"} {
if v := tag.Get(prefix); v != "" {
values = append(values, v)
}
}
return values
}
return []string{field.Name}
}