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unmarshal.go
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unmarshal.go
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package crepe
import (
"bytes"
"fmt"
"reflect"
"strconv"
"github.com/PuerkitoBio/goquery"
"github.com/mkfsn/crepe/internal"
)
const (
tagName = "crepe"
)
func Unmarshal(b []byte, i interface{}) error {
reader := bytes.NewReader(b)
doc, err := goquery.NewDocumentFromReader(reader)
if err != nil {
return fmt.Errorf("failed to parse HTML document: %w", err)
}
return unmarshal(doc.Selection, i)
}
func unmarshal(s *goquery.Selection, i interface{}) error {
rValueOf := reflect.ValueOf(i)
if rValueOf.IsNil() {
return fmt.Errorf("%w: is nil", ErrInvalidValue)
}
switch rValueOf.Kind() {
case reflect.Ptr:
return unmarshalPtr(s, rValueOf)
}
return fmt.Errorf("%w: not a ptr", ErrInvalidValue)
}
func unmarshalPtr(s *goquery.Selection, rValueOf reflect.Value) error {
if rValueOf.Kind() != reflect.Ptr {
return fmt.Errorf("%w: not a ptr", ErrInvalidValue)
}
switch rValueOf := rValueOf.Elem(); rValueOf.Kind() {
case reflect.Struct:
return unmarshalStruct(s, rValueOf)
}
return fmt.Errorf("%w: not a ptr to struct", ErrInvalidValue)
}
func unmarshalStruct(s *goquery.Selection, rValueOf reflect.Value) error {
if rValueOf.Kind() != reflect.Struct {
return fmt.Errorf("%w: not a struct", ErrInvalidValue)
}
// Iterate over all available fields and read the tag value
for i := 0; i < rValueOf.NumField(); i++ {
rType, rValue := rValueOf.Type().Field(i), rValueOf.Field(i)
var err error
switch kind := rValue.Kind(); kind {
// Primitive type
case reflect.Bool, reflect.String, reflect.Float32, reflect.Float64,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
err = unmarshalPrimitive(s, rValue, rType)
case reflect.Slice:
err = unmarshalSlice(s, rValue, rType)
// Map is not supported
case reflect.Map, reflect.Interface:
err = fmt.Errorf("%w: %v", ErrUnimplemented, kind)
case reflect.Ptr:
err = unmarshalPtr(s, rValue)
// TODO
case reflect.Array:
fallthrough
// TODO
case reflect.Struct:
fallthrough
default:
err = fmt.Errorf("%w: %v", ErrUnimplemented, kind)
}
if err != nil {
return err
}
}
return nil
}
func unmarshalSlice(s *goquery.Selection, rValueOf reflect.Value, rField reflect.StructField) error {
tag := rField.Tag.Get(tagName)
if tag == "" {
return nil // Ignore this field
}
if !rValueOf.CanSet() {
return ErrUnexportedField
}
decoder, err := internal.NewSelectResolver(tag)
if err != nil {
return fmt.Errorf("failed to parse tag: %w", err)
}
s = decoder.Select(s)
slice := reflect.MakeSlice(rValueOf.Type(), rValueOf.Len(), rValueOf.Cap())
for i := 0; i < s.Length(); i++ {
var elem reflect.Value
switch typ := rValueOf.Type().Elem(); typ.Kind() {
case reflect.Ptr:
elem = reflect.New(typ.Elem())
if err := unmarshalStruct(s.Eq(i), elem.Elem()); err != nil {
return err
}
case reflect.Struct:
elem = reflect.New(typ).Elem()
if err := unmarshalStruct(s.Eq(i), elem); err != nil {
return err
}
default:
return ErrUnsupportedType
}
slice = reflect.Append(slice, elem)
}
rValueOf.Set(slice)
return nil
}
func unmarshalPrimitive(s *goquery.Selection, rValueOf reflect.Value, rField reflect.StructField) error {
tag := rField.Tag.Get(tagName)
if tag == "" {
return nil // Ignore this field
}
if !rValueOf.CanSet() {
return ErrUnexportedField
}
selector, err := internal.NewSelectResolver(tag)
if err != nil {
return fmt.Errorf("failed to parse tag: %w", err)
}
result, err := selector.Resolve(s)
if err != nil {
return err
}
switch rField.Type.Kind() {
case reflect.String:
rValueOf.SetString(result.Raw)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
v, err := strconv.ParseInt(result.Raw, 0, 64)
if err != nil {
return fmt.Errorf("failed to parse %v: %w", result.Raw, err)
}
rValueOf.SetInt(v)
case reflect.Float32, reflect.Float64:
v, err := strconv.ParseFloat(result.Raw, 64)
if err != nil {
return fmt.Errorf("failed to parse %v: %w", result.Raw, err)
}
rValueOf.SetFloat(v)
case reflect.Bool:
v, err := strconv.ParseBool(result.Raw)
if err != nil {
return fmt.Errorf("failed to parse %v: %w", result.Raw, err)
}
rValueOf.SetBool(v)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
v, err := strconv.ParseUint(result.Raw, 0, 64)
if err != nil {
return fmt.Errorf("failed to parse %v: %w", result.Raw, err)
}
rValueOf.SetUint(v)
default:
return fmt.Errorf("%w: not a primitive type: %v", ErrInvalidValue, rField.Type.Kind())
}
return nil
}