myth/binding/binding.go

// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package binding

import "net/http"

// Content-Type MIME of the most common data formats.
const (
	MIMEJSON              = "application/json"
	MIMEHTML              = "text/html"
	MIMEXML               = "application/xml"
	MIMEXML2              = "text/xml"
	MIMEPlain             = "text/plain"
	MIMEPOSTForm          = "application/x-www-form-urlencoded"
	MIMEMultipartPOSTForm = "multipart/form-data"
	MIMEPROTOBUF          = "application/x-protobuf"
	MIMEMSGPACK           = "application/x-msgpack"
	MIMEMSGPACK2          = "application/msgpack"
	MIMEYAML              = "application/x-yaml"
)

// Binding describes the interface which needs to be implemented for binding the
// data present in the request such as JSON request body, query parameters or
// the form POST.
type Binding interface {
	Name() string
	Bind(*http.Request, interface{}) error
}

// BindingBody adds BindBody method to Binding. BindBody is similar with Bind,
// but it reads the body from supplied bytes instead of req.Body.
type BindingBody interface {
	Binding
	BindBody([]byte, interface{}) error
}

// BindingUri adds BindUri method to Binding. BindUri is similar with Bind,
// but it read the Params.
type BindingUri interface {
	Name() string
	BindUri(map[string][]string, interface{}) error
}

// StructValidator is the minimal interface which needs to be implemented in
// order for it to be used as the validator engine for ensuring the correctness
// of the request. Gin provides a default implementation for this using
// https://github.com/go-playground/validator/tree/v8.18.2.
type StructValidator interface {
	// ValidateStruct can receive any kind of type and it should never panic, even if the configuration is not right.
	// If the received type is not a struct, any validation should be skipped and nil must be returned.
	// If the received type is a struct or pointer to a struct, the validation should be performed.
	// If the struct is not valid or the validation itself fails, a descriptive error should be returned.
	// Otherwise nil must be returned.
	ValidateStruct(interface{}) error

	// Engine returns the underlying validator engine which powers the
	// StructValidator implementation.
	Engine() interface{}
}

// Validator is the default validator which implements the StructValidator
// interface. It uses https://github.com/go-playground/validator/tree/v8.18.2
// under the hood.
//var Validator StructValidator = &defaultValidator{}

// These implement the Binding interface and can be used to bind the data
// present in the request to struct instances.
var (
	JSON          = jsonBinding{}
	XML           = xmlBinding{}
	Form          = formBinding{}
	Query         = queryBinding{}
	FormPost      = formPostBinding{}
	FormMultipart = formMultipartBinding{}
	ProtoBuf      = protobufBinding{}
	MsgPack       = msgpackBinding{}
	YAML          = yamlBinding{}
	Uri           = uriBinding{}
)

// Default returns the appropriate Binding instance based on the HTTP method
// and the content type.
func Default(method, contentType string) Binding {
	if method == "GET" {
		return Form
	}

	switch contentType {
	case MIMEJSON:
		return JSON
	case MIMEXML, MIMEXML2:
		return XML
	case MIMEPROTOBUF:
		return ProtoBuf
	case MIMEMSGPACK, MIMEMSGPACK2:
		return MsgPack
	case MIMEYAML:
		return YAML
	case MIMEMultipartPOSTForm:
		return FormMultipart
	default: // case MIMEPOSTForm:
		return Form
	}
}

func validate(obj interface{}) error {
	return nil
	/*
		if Validator == nil {
			return nil
		}
		return Validator.ValidateStruct(obj)
		// */
}

// Bind checks the Content-Type to select a binding engine automatically,
// Depending the "Content-Type" header different bindings are used:
//     "application/json" --> JSON binding
//     "application/xml"  --> XML binding
// otherwise --> returns an error.
// It parses the request's body as JSON if Content-Type == "application/json" using JSON or XML as a JSON input.
// It decodes the json payload into the struct specified as a pointer.
// It writes a 400 error and sets Content-Type header "text/plain" in the response if input is not valid.
func Bind(req *http.Request, obj interface{}) error {
	b := Default(req.Method, ContentType(req))
	return MustBindWith(req, obj, b)
}

// BindQuery query to struct
func BindQuery(req *http.Request, obj interface{}) error {
	return MustBindWith(req, obj, Form)
}

// MustBindWith binds the passed struct pointer using the specified binding engine.
// It will abort the request with HTTP 400 if any error occurs.
// See the binding package.
func MustBindWith(req *http.Request, obj interface{}, b Binding) (err error) {
	return b.Bind(req, obj)
}

// ContentType returns the Content-Type header of the request.
func ContentType(req *http.Request) string {
	return filterFlags(req.Header.Get("Content-Type"))
}

func filterFlags(content string) string {
	for i, char := range content {
		if char == ' ' || char == ';' {
			return content[:i]
		}
	}
	return content
}