bind.go

package rest

import (
	"encoding"
	"encoding/xml"
	"errors"
	"fmt"
	"mime/multipart"
	"net/http"
	"reflect"
	"strconv"
	"strings"

	"github.com/labstack/echo/v4"
)

type CustomBinder struct{}

// Bind implements the `Binder#Bind` function.
// Binding is done in following order: 1) path params; 2) query params; 3) request body. Each step COULD override previous
// step binded values. For single source binding use their own methods BindBody, BindQueryParams, BindPathParams.
func (b *CustomBinder) Bind(i interface{}, c echo.Context) (err error) {
	if err := b.BindPathParams(c, i); err != nil {
		return err
	}
	if err := b.BindHeaders(c, i); err != nil {
		return err
	}
	if err := b.BindCookies(c, i); err != nil {
		return err
	}
	if err = b.BindQueryParams(c, i); err != nil {
		return err
	}
	return b.BindBody(c, i)
}

// BindHeaders binds HTTP headers to a bindable object
func (b *CustomBinder) BindHeaders(c echo.Context, i interface{}) error {
	if err := b.bindData(i, c.Request().Header, "header"); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
	}
	return nil
}

// BindQueryParams binds query params to bindable object
func (b *CustomBinder) BindQueryParams(c echo.Context, i interface{}) error {
	if err := b.bindData(i, c.QueryParams(), "query"); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
	}
	return nil
}

// BindBody binds request body contents to bindable object
// NB: then binding forms take note that this implementation uses standard library form parsing
// which parses form data from BOTH URL and BODY if content type is not MIMEMultipartForm
// See non-MIMEMultipartForm: https://golang.org/pkg/net/http/#Request.ParseForm
// See MIMEMultipartForm: https://golang.org/pkg/net/http/#Request.ParseMultipartForm
func (b *CustomBinder) BindBody(c echo.Context, i interface{}) (err error) {
	req := c.Request()
	if req.ContentLength == 0 {
		return
	}

	ctype := req.Header.Get(echo.HeaderContentType)
	switch {
	case strings.HasPrefix(ctype, echo.MIMEApplicationJSON):
		if err = c.Echo().JSONSerializer.Deserialize(c, i); err != nil {
			switch err.(type) {
			case *echo.HTTPError:
				return err
			default:
				return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
			}
		}
	case strings.HasPrefix(ctype, echo.MIMEApplicationXML), strings.HasPrefix(ctype, echo.MIMETextXML):
		if err = xml.NewDecoder(req.Body).Decode(i); err != nil {
			if ute, ok := err.(*xml.UnsupportedTypeError); ok {
				return echo.NewHTTPError(http.StatusBadRequest, fmt.Sprintf("Unsupported type error: type=%v, error=%v", ute.Type, ute.Error())).SetInternal(err)
			} else if se, ok := err.(*xml.SyntaxError); ok {
				return echo.NewHTTPError(http.StatusBadRequest, fmt.Sprintf("Syntax error: line=%v, error=%v", se.Line, se.Error())).SetInternal(err)
			}
			return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
		}
	case strings.HasPrefix(ctype, echo.MIMEApplicationForm):
		params, err := c.FormParams()
		if err != nil {
			return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
		}
		if err = b.bindData(i, params, "form"); err != nil {
			return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
		}
	case strings.HasPrefix(ctype, echo.MIMEMultipartForm):
		form, err := c.MultipartForm()
		if err != nil {
			return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
		}
		if err = b.bindData(i, form.Value, "formData"); err != nil {
			return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
		}
		if err = b.bindFile(i, form.File, "formData"); err != nil {
			return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
		}
	default:
		return echo.ErrUnsupportedMediaType
	}
	return nil
}

func (b *CustomBinder) bindFile(destination interface{}, data map[string][]*multipart.FileHeader, tag string) error {
	if destination == nil || len(data) == 0 {
		return nil
	}
	typ := reflect.TypeOf(destination).Elem()
	val := reflect.ValueOf(destination).Elem()

	// Map
	if typ.Kind() == reflect.Map {
		for k, v := range data {
			val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v[0]))
		}
		return nil
	}
	for i := 0; i < typ.NumField(); i++ {
		typeField := typ.Field(i)
		structField := val.Field(i)
		if typeField.Anonymous {
			if structField.Kind() == reflect.Ptr {
				structField = structField.Elem()
			}
		}
		if !structField.CanSet() {
			continue
		}
		structFieldKind := structField.Kind()
		inputFieldName := typeField.Tag.Get(tag)
		if typeField.Anonymous && structField.Kind() == reflect.Struct && inputFieldName != "" {
			// if anonymous struct with query/param/form tags, report an error
			return errors.New("query/param/form tags are not allowed with anonymous struct field")
		}

		if inputFieldName == "" {
			continue
		}

		inputValue, exists := data[inputFieldName]
		if !exists {
			// Go json.Unmarshal supports case insensitive binding.  However the
			// url params are bound case sensitive which is inconsistent.  To
			// fix this we must check all of the map values in a
			// case-insensitive search.
			for k, v := range data {
				if strings.EqualFold(k, inputFieldName) {
					inputValue = v
					exists = true
					break
				}
			}
		}

		if !exists {
			continue
		}

		numElems := len(inputValue)
		if structFieldKind == reflect.Slice {
			val.Field(i).Set(reflect.ValueOf(inputValue))
		} else if numElems > 0 {
			val.Field(i).Set(reflect.ValueOf(inputValue[0]))
		}
	}
	return nil
}

// BindPathParams binds path params to bindable object
func (b *CustomBinder) BindPathParams(c echo.Context, i interface{}) error {
	names := c.ParamNames()
	values := c.ParamValues()
	params := map[string][]string{}
	for i, name := range names {
		params[name] = []string{values[i]}
	}
	if err := b.bindData(i, params, "path"); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
	}
	return nil
}

func (b *CustomBinder) BindCookies(c echo.Context, i interface{}) error {
	cookies := map[string][]string{}
	for _, cookie := range c.Cookies() {
		cookies[cookie.Name] = []string{cookie.Value}
	}
	if err := b.bindData(i, cookies, "cookie"); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
	}
	return nil
}

// get is an internal method and returns a map which satisfies conditions.
func (b *CustomBinder) getMap(m map[string][]string, key string) (map[string]string, bool) {
	dicts := make(map[string]string)
	exist := false
	for k, v := range m {
		if i := strings.IndexByte(k, '['); i >= 1 && k[0:i] == key {
			if j := strings.IndexByte(k[i+1:], ']'); j >= 1 {
				exist = true
				dicts[k[i+1:][:j]] = v[0]
			}
		}
	}
	return dicts, exist
}

// bindData will bind data ONLY fields in destination struct that have EXPLICIT tag
func (b *CustomBinder) bindData(destination interface{}, data map[string][]string, tag string) error {
	if destination == nil || len(data) == 0 {
		return nil
	}
	typ := reflect.TypeOf(destination).Elem()
	val := reflect.ValueOf(destination).Elem()

	// Map
	if typ.Kind() == reflect.Map {
		for k, v := range data {
			val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v[0]))
		}
		return nil
	}

	// !struct
	if typ.Kind() != reflect.Struct {
		if tag == "path" || tag == "query" || tag == "header" {
			// incompatible type, data is probably to be found in the body
			return nil
		}
		return errors.New("binding element must be a struct")
	}

	for i := 0; i < typ.NumField(); i++ {
		typeField := typ.Field(i)
		structField := val.Field(i)
		if typeField.Anonymous {
			if structField.Kind() == reflect.Ptr {
				structField = structField.Elem()
			}
		}
		if !structField.CanSet() {
			continue
		}
		structFieldKind := structField.Kind()
		inputFieldName := typeField.Tag.Get(tag)
		if typeField.Anonymous && structField.Kind() == reflect.Struct && inputFieldName != "" {
			// if anonymous struct with query/param/form tags, report an error
			return errors.New("query/param/form tags are not allowed with anonymous struct field")
		}

		if inputFieldName == "" {
			// If tag is nil, we inspect if the field is a not BindUnmarshaler struct and try to bind data into it (might contains fields with tags).
			// structs that implement BindUnmarshaler are binded only when they have explicit tag
			if _, ok := structField.Addr().Interface().(echo.BindUnmarshaler); !ok && structFieldKind == reflect.Struct {
				if err := b.bindData(structField.Addr().Interface(), data, tag); err != nil {
					return err
				}
			}
			// does not have explicit tag and is not an ordinary struct - so move to next field
			continue
		}

		if structFieldKind == reflect.Map &&
			structField.Type().Elem().Kind() == reflect.String {
			dists, _ := b.getMap(data, inputFieldName)
			structField.Set(reflect.ValueOf(dists))
			continue
		}

		inputValue, exists := data[inputFieldName]
		if !exists {
			// Go json.Unmarshal supports case insensitive binding.  However the
			// url params are bound case sensitive which is inconsistent.  To
			// fix this we must check all of the map values in a
			// case-insensitive search.
			for k, v := range data {
				if strings.EqualFold(k, inputFieldName) {
					inputValue = v
					exists = true
					break
				}
			}
		}

		if !exists {
			continue
		}

		// Call this first, in case we're dealing with an alias to an array type
		if ok, err := unmarshalField(typeField.Type.Kind(), inputValue[0], structField); ok {
			if err != nil {
				return err
			}
			continue
		}

		numElems := len(inputValue)
		if structFieldKind == reflect.Slice && numElems > 0 {
			sliceOf := structField.Type().Elem().Kind()
			slice := reflect.MakeSlice(structField.Type(), numElems, numElems)
			for j := 0; j < numElems; j++ {
				if err := setWithProperType(sliceOf, inputValue[j], slice.Index(j)); err != nil {
					return err
				}
			}
			val.Field(i).Set(slice)
		} else if err := setWithProperType(typeField.Type.Kind(), inputValue[0], structField); err != nil {
			return err

		}
	}
	return nil
}

func setWithProperType(valueKind reflect.Kind, val string, structField reflect.Value) error {
	// But also call it here, in case we're dealing with an array of BindUnmarshalers
	if ok, err := unmarshalField(valueKind, val, structField); ok {
		return err
	}

	switch valueKind {
	case reflect.Ptr:
		return setWithProperType(structField.Elem().Kind(), val, structField.Elem())
	case reflect.Int:
		return setIntField(val, 0, structField)
	case reflect.Int8:
		return setIntField(val, 8, structField)
	case reflect.Int16:
		return setIntField(val, 16, structField)
	case reflect.Int32:
		return setIntField(val, 32, structField)
	case reflect.Int64:
		return setIntField(val, 64, structField)
	case reflect.Uint:
		return setUintField(val, 0, structField)
	case reflect.Uint8:
		return setUintField(val, 8, structField)
	case reflect.Uint16:
		return setUintField(val, 16, structField)
	case reflect.Uint32:
		return setUintField(val, 32, structField)
	case reflect.Uint64:
		return setUintField(val, 64, structField)
	case reflect.Bool:
		return setBoolField(val, structField)
	case reflect.Float32:
		return setFloatField(val, 32, structField)
	case reflect.Float64:
		return setFloatField(val, 64, structField)
	case reflect.String:
		structField.SetString(val)
	default:
		return errors.New("unknown type")
	}
	return nil
}

func unmarshalField(valueKind reflect.Kind, val string, field reflect.Value) (bool, error) {
	switch valueKind {
	case reflect.Ptr:
		return unmarshalFieldPtr(val, field)
	default:
		return unmarshalFieldNonPtr(val, field)
	}
}

func unmarshalFieldNonPtr(value string, field reflect.Value) (bool, error) {
	fieldIValue := field.Addr().Interface()
	if unmarshaler, ok := fieldIValue.(echo.BindUnmarshaler); ok {
		return true, unmarshaler.UnmarshalParam(value)
	}
	if unmarshaler, ok := fieldIValue.(encoding.TextUnmarshaler); ok {
		return true, unmarshaler.UnmarshalText([]byte(value))
	}

	return false, nil
}

func unmarshalFieldPtr(value string, field reflect.Value) (bool, error) {
	if field.IsNil() {
		// Initialize the pointer to a nil value
		field.Set(reflect.New(field.Type().Elem()))
	}
	return unmarshalFieldNonPtr(value, field.Elem())
}

func setIntField(value string, bitSize int, field reflect.Value) error {
	if value == "" {
		value = "0"
	}
	intVal, err := strconv.ParseInt(value, 10, bitSize)
	if err == nil {
		field.SetInt(intVal)
	}
	return err
}

func setUintField(value string, bitSize int, field reflect.Value) error {
	if value == "" {
		value = "0"
	}
	uintVal, err := strconv.ParseUint(value, 10, bitSize)
	if err == nil {
		field.SetUint(uintVal)
	}
	return err
}

func setBoolField(value string, field reflect.Value) error {
	if value == "" {
		value = "false"
	}
	boolVal, err := strconv.ParseBool(value)
	if err == nil {
		field.SetBool(boolVal)
	}
	return err
}

func setFloatField(value string, bitSize int, field reflect.Value) error {
	if value == "" {
		value = "0.0"
	}
	floatVal, err := strconv.ParseFloat(value, bitSize)
	if err == nil {
		field.SetFloat(floatVal)
	}
	return err
}