fulldump/goconfig

package goconfig

import (
    "encoding/json"
    "errors"
    "io/ioutil"
    "reflect"
    "strings"
    "time"
)

func FillJson(c interface{}, filename string) error {

    if "" == filename {
        return nil
    }

    data, err := ioutil.ReadFile(filename)
    if nil != err {
        return err
    }

    return unmarshalJSON(data, c)
}

func unmarshalJSON(data []byte, c interface{}) error {
    if reflect.TypeOf(c).Implements(reflect.TypeOf(new(json.Unmarshaler)).Elem()) {
        if err := json.Unmarshal(data, c); err != nil {
            return errors.New("Bad json file: " + err.Error())
        }

    } else {
        var values map[string]json.RawMessage
        if err := json.Unmarshal(data, &values); err != nil {
            return errors.New("Bad json file: " + err.Error())
        }
        for k, v := range values {
            k = strings.ToLower(k)
            values[k] = v
        }

        traverse_json(c, func(i item) {
            tag := i.Tags.Get("json")
            if len(tag) > 0 {
                if i := strings.Index(tag, ","); i != -1 {
                    tag = tag[:i]
                }
            }

            var value json.RawMessage
            if v, ok := values[tag]; ok {
                value = v
            } else if v, ok := values[i.FieldName]; ok {
                value = v
            } else if v, ok := values[strings.ToLower(i.FieldName)]; ok {
                value = v
            } else {
                return
            }

            if reflect.TypeOf(i.Value.Type()).Implements(reflect.TypeOf(new(json.Unmarshaler)).Elem()) {
                unmarshalJSON(value, i.Ptr)

            } else if reflect.TypeOf(time.Duration(0)) == i.Value.Type() {
                var d time.Duration
                // try nanosecond int, then duration string
                if err := json.Unmarshal(value, &d); err != nil {
                    tmp := ""
                    if err := json.Unmarshal(value, &tmp); err != nil {
                        return
                    }

                    if d, err = unmarshalDurationString(tmp); err != nil {
                        return
                    }
                }

                v := int64(d)
                set(i.Ptr, &v)

            } else {
                json.Unmarshal(value, i.Ptr)
            }
        })
    }

    return nil
}