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defaults.go
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defaults.go
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package config
import (
"fmt"
"reflect"
"regexp"
"strconv"
"strings"
"time"
"google.golang.org/protobuf/encoding/protojson"
"google.golang.org/protobuf/types/known/durationpb"
"google.golang.org/protobuf/types/known/timestamppb"
"github.com/fluxninja/aperture/pkg/log"
)
// Most of the code ported from github.com/mcuadros/go-defaults
type fieldData struct {
Parent *fieldData
TagValue string
Value reflect.Value
Field reflect.StructField
}
type fillerFunc func(field *fieldData)
// filler contains all the functions to fill any struct field with any type allowing to define function by Kind, Type of field name.
type filler struct {
FuncByName map[string]fillerFunc
FuncByType map[typeHash]fillerFunc
FuncByKind map[reflect.Kind]fillerFunc
Tag string
}
// fill apply all the functions contained on Filler, setting all the possible
// values.
func (f *filler) fill(variable interface{}) {
fields := f.getFields(variable)
f.setDefaultValues(fields)
}
func (f *filler) getFields(variable interface{}) []*fieldData {
valueObject := reflect.ValueOf(variable).Elem()
return f.getFieldsFromValue(valueObject, nil)
}
func (f *filler) getFieldsFromValue(valueObject reflect.Value, parent *fieldData) []*fieldData {
typeObject := valueObject.Type()
count := valueObject.NumField()
var results []*fieldData
for i := 0; i < count; i++ {
value := valueObject.Field(i)
field := typeObject.Field(i)
if value.CanSet() {
results = append(results, &fieldData{
Value: value,
Field: field,
TagValue: field.Tag.Get(f.Tag),
Parent: parent,
})
}
}
return results
}
func (f *filler) setDefaultValues(fields []*fieldData) {
for _, field := range fields {
if f.isEmpty(field) {
f.setDefaultValue(field)
}
}
}
func (f *filler) isEmpty(field *fieldData) bool {
switch field.Value.Kind() {
case reflect.Bool:
return !field.Value.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return field.Value.Int() == 0
case reflect.Float32, reflect.Float64:
return field.Value.Float() == .0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return field.Value.Uint() == 0
case reflect.Slice:
switch field.Value.Type().Elem().Kind() {
case reflect.Struct, reflect.Ptr, reflect.Interface:
// always assume the structs, ptrs, interfaces in the slice is empty and can be filled
// the actually filling logic should take care of the rest
return true
default:
return field.Value.Len() == 0
}
case reflect.String:
return field.Value.String() == ""
}
return true
}
func (f *filler) setDefaultValue(field *fieldData) {
getters := []func(field *fieldData) fillerFunc{
f.getFunctionByName,
f.getFunctionByType,
f.getFunctionByKind,
}
for _, getter := range getters {
filler := getter(field)
if filler != nil {
filler(field)
return
}
}
}
func (f *filler) getFunctionByName(field *fieldData) fillerFunc {
if f, ok := f.FuncByName[field.Field.Name]; ok {
return f
}
return nil
}
func (f *filler) getFunctionByType(field *fieldData) fillerFunc {
if f, ok := f.FuncByType[getTypeHash(field.Field.Type)]; ok {
return f
}
return nil
}
func (f *filler) getFunctionByKind(field *fieldData) fillerFunc {
if f, ok := f.FuncByKind[field.Field.Type.Kind()]; ok {
return f
}
return nil
}
// typeHash is a string representing a reflect.Type following the next pattern:
// <package.name>.<type.name>.
type typeHash string
// getTypeHash returns the TypeHash for a given reflect.Type.
func getTypeHash(t reflect.Type) typeHash {
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
return typeHash(fmt.Sprintf("%s.%s", t.PkgPath(), t.Name()))
}
// SetDefaults applies the default values to the struct object, the struct type must have
// the StructTag with name "default" and the directed value.
// Example usage:
//
// type ExampleBasic struct {
// Foo bool `default:"true"`
// Bar string `default:"33"`
// Qux int8
// Dur time.Duration `default:"2m3s"`
// }
//
// foo := &ExampleBasic{}
// SetDefaults(foo)
func SetDefaults(variable interface{}) {
kind := reflect.ValueOf(variable).Elem().Kind()
if kind != reflect.Struct {
// Panic early with clear message to avoid cryptic errors from inner functions.
// Note: Perhaps we can lift this limitation.
panic(fmt.Sprintf("SetDefaults can be used only on structs, got %v", kind))
}
defaultFiller.fill(variable)
}
var defaultFiller *filler = newDefaultFiller()
func newDefaultFiller() *filler {
filler := &filler{}
var setPtrDefaults func(val reflect.Value)
setPtrDefaults = func(val reflect.Value) {
// handle all non-nil pointers
if val.IsNil() {
return
}
if val.Elem().Kind() == reflect.Struct {
filler.fill(val.Interface())
} else if val.Elem().Kind() == reflect.Ptr || val.Elem().Kind() == reflect.Interface {
setPtrDefaults(val.Elem())
}
}
funcs := make(map[reflect.Kind]fillerFunc, 0)
funcs[reflect.Bool] = func(field *fieldData) {
value, _ := strconv.ParseBool(field.TagValue)
field.Value.SetBool(value)
}
funcs[reflect.Int] = func(field *fieldData) {
value, _ := strconv.ParseInt(field.TagValue, 10, 64)
field.Value.SetInt(value)
}
funcs[reflect.Int8] = funcs[reflect.Int]
funcs[reflect.Int16] = funcs[reflect.Int]
funcs[reflect.Int32] = funcs[reflect.Int]
funcs[reflect.Int64] = func(field *fieldData) {
if field.Field.Type == reflect.TypeOf(time.Second) {
value, _ := time.ParseDuration(field.TagValue)
field.Value.Set(reflect.ValueOf(value))
} else {
value, _ := strconv.ParseInt(field.TagValue, 10, 64)
field.Value.SetInt(value)
}
}
funcs[reflect.Float32] = func(field *fieldData) {
value, _ := strconv.ParseFloat(field.TagValue, 64)
field.Value.SetFloat(value)
}
funcs[reflect.Float64] = funcs[reflect.Float32]
funcs[reflect.Uint] = func(field *fieldData) {
value, _ := strconv.ParseUint(field.TagValue, 10, 64)
field.Value.SetUint(value)
}
funcs[reflect.Uint8] = funcs[reflect.Uint]
funcs[reflect.Uint16] = funcs[reflect.Uint]
funcs[reflect.Uint32] = funcs[reflect.Uint]
funcs[reflect.Uint64] = funcs[reflect.Uint]
funcs[reflect.String] = func(field *fieldData) {
tagValue := parseDateTimeString(field.TagValue)
field.Value.SetString(tagValue)
}
funcs[reflect.Struct] = func(field *fieldData) {
fields := filler.getFieldsFromValue(field.Value, nil)
filler.setDefaultValues(fields)
}
funcs[reflect.Ptr] = func(field *fieldData) {
val := field.Value
setPtrDefaults(val)
}
funcs[reflect.Interface] = func(field *fieldData) {
val := field.Value
setPtrDefaults(val)
}
types := make(map[typeHash]fillerFunc, 5)
types["time.Duration"] = func(field *fieldData) {
d, _ := time.ParseDuration(field.TagValue)
field.Value.Set(reflect.ValueOf(d))
}
types[getTypeHash(reflect.TypeOf(Duration{}))] = func(field *fieldData) {
if value, ok := field.Value.Interface().(Duration); ok {
if value.AsDuration() != 0 {
return
}
if field.TagValue != "" {
durationJSON, _ := json.Marshal(field.TagValue)
dur := Duration{}
dur.duration = durationpb.New(0)
err := json.Unmarshal(durationJSON, &dur)
if err != nil {
log.Error().Err(err).Msg("Unable to unmarshal default duration")
}
field.Value.Set(reflect.ValueOf(dur))
}
}
}
types[getTypeHash(reflect.TypeOf(durationpb.New(0)))] = func(field *fieldData) {
iface := field.Value.Interface()
if value, ok := iface.(*durationpb.Duration); ok {
if value.AsDuration() != 0 {
return
}
if field.TagValue != "" {
durationJSON, _ := json.Marshal(field.TagValue)
dur := durationpb.New(0)
err := protojson.Unmarshal(durationJSON, dur)
if err != nil {
log.Error().Err(err).Msg("Unable to unmarshal duration default")
}
field.Value.Set(reflect.ValueOf(dur))
}
}
}
types[getTypeHash(reflect.TypeOf(Time{}))] = func(field *fieldData) {
if value, ok := field.Value.Interface().(Time); ok {
if field.TagValue != "" {
nullTime := time.Time{}
if value.timestamp.AsTime() != nullTime {
return
}
timestampJSON, _ := json.Marshal(field.TagValue)
t := &Time{
timestamp: timestamppb.Now(),
}
err := json.Unmarshal(timestampJSON, t)
if err != nil {
log.Error().Err(err).Msg("Unable to unmarshal default config.Timestamp")
}
field.Value.Set(reflect.ValueOf(t))
}
}
}
types[getTypeHash(reflect.TypeOf(timestamppb.Now()))] = func(field *fieldData) {
iface := field.Value.Interface()
if value, ok := iface.(*timestamppb.Timestamp); ok {
nullTime := time.Time{}
if value.AsTime() != nullTime {
return
}
if field.TagValue != "" {
timestampJSON, _ := json.Marshal(field.TagValue)
t := &Time{
timestamp: timestamppb.Now(),
}
err := json.Unmarshal(timestampJSON, t)
if err != nil {
log.Error().Err(err).Msg("Unable to unmarshal default timestamppb")
}
field.Value.Set(reflect.ValueOf(t))
}
}
}
funcs[reflect.Slice] = func(field *fieldData) {
k := field.Value.Type().Elem().Kind()
switch k {
case reflect.Uint8:
if field.Value.Bytes() != nil {
return
}
field.Value.SetBytes([]byte(field.TagValue))
case reflect.Struct:
count := field.Value.Len()
for i := 0; i < count; i++ {
fields := filler.getFieldsFromValue(field.Value.Index(i), nil)
filler.setDefaultValues(fields)
}
case reflect.Ptr, reflect.Interface:
count := field.Value.Len()
for i := 0; i < count; i++ {
val := field.Value.Index(i)
setPtrDefaults(val)
}
// FIXME: also descend into slice of slices
// FIXME: also descend into slice of maps
default:
reg := regexp.MustCompile(`^\[(.*)\]$`)
matches := reg.FindStringSubmatch(field.TagValue)
if len(matches) != 2 {
return
}
if matches[1] == "" {
field.Value.Set(reflect.MakeSlice(field.Value.Type(), 0, 0))
} else {
defaultValue := strings.Split(matches[1], ",")
result := reflect.MakeSlice(field.Value.Type(), len(defaultValue), len(defaultValue))
for i := 0; i < len(defaultValue); i++ {
itemValue := result.Index(i)
item := &fieldData{
Value: itemValue,
Field: reflect.StructField{},
TagValue: defaultValue[i],
Parent: nil,
}
funcs[k](item)
}
field.Value.Set(result)
}
}
}
funcs[reflect.Map] = func(field *fieldData) {
switch field.Field.Type.Elem().Kind() {
case reflect.Struct:
keys := field.Value.MapKeys()
for _, key := range keys {
// We need to pull the value from map, copy to a settable
// location, fill in defaults, and then put it back into map.
value := field.Value.MapIndex(key)
tmp := reflect.New(value.Type()).Elem()
tmp.Set(value)
fields := filler.getFieldsFromValue(tmp, nil)
filler.setDefaultValues(fields)
field.Value.SetMapIndex(key, tmp)
}
case reflect.Ptr, reflect.Interface:
iter := field.Value.MapRange()
for iter.Next() {
setPtrDefaults(iter.Value())
}
case reflect.Slice:
// FIXME: also descend into map of slices
case reflect.Map:
// FIXME: also descend into map of maps
}
// FIXME: handle actual default Tags on maps?
}
filler.FuncByKind = funcs
filler.FuncByType = types
filler.Tag = "default"
return filler
}
func parseDateTimeString(data string) string {
pattern := regexp.MustCompile(`\{\{(\w+\:(?:-|)\d*,(?:-|)\d*,(?:-|)\d*)\}\}`)
matches := pattern.FindAllStringSubmatch(data, -1) // matches is [][]string
for _, match := range matches {
tags := strings.Split(match[1], ":")
if len(tags) == 2 {
valueStrings := strings.Split(tags[1], ",")
if len(valueStrings) == 3 {
var values [3]int
for key, valueString := range valueStrings {
num, _ := strconv.ParseInt(valueString, 10, 64)
values[key] = int(num)
}
switch tags[0] {
case "date":
str := time.Now().AddDate(values[0], values[1], values[2]).Format("2006-01-02")
data = strings.ReplaceAll(data, match[0], str)
case "time":
str := time.Now().Add((time.Duration(values[0]) * time.Hour) +
(time.Duration(values[1]) * time.Minute) +
(time.Duration(values[2]) * time.Second)).Format("15:04:05")
data = strings.ReplaceAll(data, match[0], str)
}
}
}
}
return data
}