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csv.go
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csv.go
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package csvhelper
import (
"bytes"
"encoding/csv"
"errors"
"reflect"
"strings"
)
type MarshalConfig struct {
SkipValidation bool
}
type ValidationConfig struct {
SkipValidation bool
}
var csvColumnNameTag = "csv_column_name"
var ErrInvalidHeaderSize = errors.New("invalid header size")
var ErrInvalidHeaderValues = errors.New("invalid header values")
var ErrMissingRequiredTag = errors.New("missing required tag")
var ErrDuplicatedTag = errors.New("duplicated tag")
var ErrUninitializedRecords = errors.New("uninitialized records")
type CsvHelper[T any] interface {
ReadAll(buffer *bytes.Buffer) CsvHelper[T]
Validate() (bool, error)
Records() ([][]string, error)
Error() error
Marshal(cfg MarshalConfig) ([]T, error)
}
type csvHelperImpl[T any] struct {
records [][]string
err error
}
func New[T any]() CsvHelper[T] {
return &csvHelperImpl[T]{}
}
func (c csvHelperImpl[T]) ReadAll(buffer *bytes.Buffer) CsvHelper[T] {
c.records, c.err = csv.NewReader(buffer).ReadAll()
return c
}
func (c csvHelperImpl[T]) Validate() (bool, error) {
if err := c.validate(ValidationConfig{}); err != nil {
return false, err
}
return true, nil
}
func (c csvHelperImpl[T]) Records() ([][]string, error) {
if err := c.validate(ValidationConfig{}); err != nil {
return nil, err
}
return c.records, c.err
}
func (c csvHelperImpl[T]) Error() error {
if err := c.validate(ValidationConfig{}); err != nil {
return err
}
return c.err
}
func (c csvHelperImpl[T]) Marshal(cfg MarshalConfig) ([]T, error) {
if err := c.validate(ValidationConfig{cfg.SkipValidation}); err != nil {
return nil, err
}
indexToFieldName, err := c.mapIndexToField(c.records)
if err != nil {
return nil, err
}
return c.assign(c.records, indexToFieldName)
}
func (c *csvHelperImpl[T]) validate(cfg ValidationConfig) error {
if err := c.validateIntegrity(); err != nil {
return err
}
if !cfg.SkipValidation {
if err := c.validateModelTags(); err != nil {
return err
}
var model T
csvHeaders := c.records[0]
modelSize := reflect.ValueOf(model).NumField()
if len(csvHeaders) != modelSize {
return ErrInvalidHeaderSize
}
}
return nil
}
func (c *csvHelperImpl[T]) validateIntegrity() error {
if c.err != nil {
return c.err
} else {
if len(c.records) == 0 {
return ErrUninitializedRecords
}
}
return nil
}
func (*csvHelperImpl[T]) validateModelTags() error {
var model T
tags := make(map[string]int)
modelSize := reflect.ValueOf(model).NumField()
for i := 0; i < modelSize; i++ {
tag := reflect.TypeOf(model).Field(i).Tag.Get(csvColumnNameTag)
if tag == "" {
return ErrMissingRequiredTag
} else {
tags[tag] = i
}
}
if len(tags) != modelSize {
return ErrDuplicatedTag
}
return nil
}
func (csvHelperImpl[T]) mapIndexToField(csv [][]string) (map[int]string, error) {
var model T
var modelFieldNames []string
modelFieldsToColumns := make(map[string]string)
csvHeaders := csv[0]
rv := reflect.ValueOf(model)
rt := reflect.TypeOf(model)
modelSize := rv.NumField()
indexToFieldName := make(map[int]string)
for i := 0; i < modelSize; i++ {
modelColumnName := rt.Field(i).Tag.Get(csvColumnNameTag)
modelFieldName := rt.Field(i).Name
modelFieldNames = append(modelFieldNames, modelFieldName)
modelFieldsToColumns[modelFieldName] = modelColumnName
}
for i := 0; i < len(modelFieldsToColumns); i++ {
for j, header := range csvHeaders {
if strings.EqualFold(modelFieldsToColumns[modelFieldNames[i]], header) {
indexToFieldName[j] = modelFieldNames[i]
}
}
}
return indexToFieldName, nil
}
func (csvHelperImpl[T]) assign(records [][]string, indexToFieldName map[int]string) ([]T, error) {
var output []T
for index, record := range records {
var model T
headerLine := 0
if index == headerLine {
continue
}
for index, data := range record {
modelField := indexToFieldName[index]
reflect.ValueOf(&model).Elem().FieldByName(modelField).SetString(data)
}
output = append(output, model)
}
return output, nil
}