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decode.go
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decode.go
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package csvdecoder
import (
"encoding/csv"
"errors"
"fmt"
"io"
"os"
"reflect"
"strconv"
"time"
"cloud.google.com/go/civil"
)
var (
ErrInvalidInterface = errors.New("invalid interface")
ErrParse = errors.New("parse error")
)
func Decode(filepath string, out interface{}) error {
r, err := os.Open(filepath)
if err != nil {
return err
}
v := reflect.ValueOf(out)
if v.Kind() != reflect.Ptr {
return fmt.Errorf("%w; out must be pointer", ErrInvalidInterface)
}
v = v.Elem()
if v.Kind() != reflect.Slice {
return fmt.Errorf("%w; out must be slice", ErrInvalidInterface)
}
csvreader := csv.NewReader(r)
column, err := csvreader.Read()
if err != nil {
return err
}
for {
values, err := csvreader.Read()
if err == io.EOF {
break
} else if err != nil {
return err
}
elem := reflect.New(v.Type().Elem()).Elem()
if err := decode(elem, column, values); err != nil {
return err
}
v.Set(reflect.Append(v, elem))
}
return nil
}
func decode(v reflect.Value, column, values []string) error {
if v.Kind() == reflect.Ptr {
v.Set(reflect.New(v.Type().Elem()))
return decode(v.Elem(), column, values)
}
if v.Kind() != reflect.Struct {
return fmt.Errorf("%w; v must be slice but have %s", ErrInvalidInterface, v.Kind())
}
valueMap := map[string]string{}
if len(column) != len(values) {
return fmt.Errorf("%w; column must have %d elems", ErrParse, len(column))
}
for i, key := range column {
valueMap[key] = values[i]
}
return decodeStruct(v, valueMap)
}
func decodeStruct(v reflect.Value, values map[string]string) error {
for i := 0; i < v.NumField(); i++ {
value := v.Field(i)
str := getStrFromMap(v.Type().Field(i), values)
if str == "" {
continue
}
if err := parseField(value, str); err != nil {
return err
}
}
return nil
}
func getStrFromMap(field reflect.StructField, values map[string]string) string {
str, ok := values[field.Tag.Get("json")]
if ok && str != "" {
return str
}
str, ok = values[field.Name]
if ok && str != "" {
return str
}
return ""
}
func parseField(value reflect.Value, str string) error {
if value.Kind() == reflect.Ptr {
value.Set(reflect.New(value.Type().Elem()))
return parseField(value.Elem(), str)
}
switch value.Interface().(type) {
case int, int8, int16, int32, int64:
ret, err := strconv.ParseInt(str, 10, 64)
if err != nil {
return err
}
value.SetInt(ret)
case uint, uint8, uint16, uint32, uint64:
ret, err := strconv.ParseUint(str, 10, 64)
if err != nil {
return err
}
value.SetUint(ret)
case float32, float64:
ret, err := strconv.ParseFloat(str, 64)
if err != nil {
return err
}
value.SetFloat(ret)
case bool:
ret, err := strconv.ParseBool(str)
if err != nil {
return err
}
value.SetBool(ret)
case string:
value.SetString(str)
case time.Time:
ret, err := time.Parse(time.RFC3339, str)
if err != nil {
return err
}
value.Set(reflect.ValueOf(ret))
case civil.Date:
ret, err := civil.ParseDate(str)
if err != nil {
return err
}
value.Set(reflect.ValueOf(ret))
}
return nil
}