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struct2csv.go
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struct2csv.go
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package struct2csv
import (
"errors"
"fmt"
"reflect"
"strconv"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/reflect/protoreflect"
)
// HeaderConverter will convert the path string of the original struct field
// to the custom of KeyType
type HeaderConverter interface {
ConvertHeader(string) KeyType
}
// compile time checks
var _ HeaderConverter = (*HeaderAutoIncrementConv)(nil)
var _ HeaderConverter = (*HeaderOriginalStringConv)(nil)
type Option func(opts *Options)
func loadOptions(options ...Option) *Options {
opts := defaultOpts()
for _, option := range options {
option(opts)
}
return opts
}
func WithOptions(options Options) Option {
return func(opts *Options) {
*opts = options
}
}
type Options struct {
resultCap int // pre-allocated for []KeyValue
isObjArray bool // if u know the input data is must the map|struct of slice, set it true
strBuilderCap int // pre-allocated for strings.Builder Cap size, call the Grow function
rowSize int // pre-allocated for KeyValue map size
}
func WithResultCap(p int) Option {
return func(opts *Options) {
opts.resultCap = p
}
}
func WithIsObjArray(p bool) Option {
return func(opts *Options) {
opts.isObjArray = p
}
}
func WithStrBuilderCap(p int) Option {
return func(opts *Options) {
opts.strBuilderCap = p
}
}
func WithRowSize(p int) Option {
return func(opts *Options) {
opts.rowSize = p
}
}
func defaultOpts() *Options {
return &Options{
resultCap: 50,
isObjArray: true,
strBuilderCap: 100,
rowSize: 18000,
}
}
type StructConverter struct {
kvs *KVs
opts *Options
headerConv HeaderConverter
}
// NewStructConverter a converter can convert struct to csv kv
func NewStructConverter(headerConv HeaderConverter, opts ...Option) (*StructConverter, error) {
if headerConv == nil {
return nil, errors.New("HeaderConverter can not be nil")
}
sc := &StructConverter{
opts: loadOptions(opts...),
headerConv: headerConv,
}
sc.kvs = NewKVs(sc.opts.resultCap, sc.opts.rowSize)
return sc, nil
}
// Convert converts Struct to CSV key value
func (s *StructConverter) Convert(data interface{}) (*KVs, error) {
v := valueOf(data)
sliceIterator := func() error {
for i := 0; i < v.Len(); i++ {
_, err := s.doFlatten(v.Index(i), i)
if err != nil {
return err
}
}
return nil
}
if s.opts.isObjArray {
if err := sliceIterator(); err != nil {
return nil, err
}
return s.kvs, nil
}
switch v.Kind() {
case reflect.Map:
if v.Len() > 0 {
result, err := s.doFlatten(v, -1)
if err != nil {
return nil, err
}
s.kvs.appendElem(result)
}
case reflect.Slice:
if isObjectArray(v) {
if err := sliceIterator(); err != nil {
return nil, err
}
} else if v.Len() > 0 {
result, err := s.doFlatten(v, -1)
if err != nil {
return nil, err
}
if result != nil {
s.kvs.appendElem(result)
}
}
case reflect.Struct:
result, err := s.doFlatten(v, -1)
if err != nil {
return nil, err
}
s.kvs.appendElem(result)
case reflect.Ptr:
if v.Elem().Kind() == reflect.Struct {
result, err := s.doFlatten(v, -1)
if err != nil {
return nil, err
}
s.kvs.appendElem(result)
}
default:
return nil, fmt.Errorf("Unsupported struct structure, kind = %s", v.Kind().String())
}
return s.kvs, nil
}
func isObjectArray(obj interface{}) bool {
value := valueOf(obj)
if value.Kind() != reflect.Slice {
return false
}
l := value.Len()
if l == 0 {
return false
}
kind := valueOf(value.Index(0)).Kind()
if kind != reflect.Map && kind != reflect.Ptr && kind != reflect.Struct {
return false
}
return true
}
func valueOf(obj interface{}) reflect.Value {
v, ok := obj.(reflect.Value)
if !ok {
v = reflect.ValueOf(obj)
}
for v.Kind() == reflect.Interface && !v.IsNil() {
v = v.Elem()
}
return v
}
func toString(obj interface{}) string {
switch v := obj.(type) {
case int:
return strconv.Itoa(v)
case int8:
return strconv.Itoa(int(v))
case int16:
return strconv.Itoa(int(v))
case int32:
return strconv.Itoa(int(v))
case int64:
return strconv.Itoa(int(v))
case uint:
return strconv.Itoa(int(v))
case uint8:
return strconv.Itoa(int(v))
case uint16:
return strconv.Itoa(int(v))
case uint32:
return strconv.Itoa(int(v))
case uint64:
return strconv.Itoa(int(v))
case float32:
return strconv.FormatFloat(float64(v), 'f', 10, 32)
case float64:
return strconv.FormatFloat(v, 'f', 10, 64)
case string:
return v
default:
return fmt.Sprintf("%v", obj)
}
}
func protoMessage(i interface{}) (protoreflect.Value, bool) {
msg, ok := i.(proto.Message)
if !ok {
return protoreflect.Value{}, false
}
v := protoreflect.ValueOf(msg.ProtoReflect())
return v, true
}