Custom 🔌

You can extend httpin by adding your custom directives.

Firstly you should understand the concepts of Directive and Directive Executor.

To add your custom directive, you need to:

Steps

1. Create a Directive Executor

by implementing the httpin_core.DirectiveExecutor interface:

type DirectiveCaseFormatter struct {
	Transform func(string) string
}

func (f *DirectiveCaseFormatter) Decode(rtm *httpin_core.DirectiveRuntime) error {
	if rtm.Value.Type().Elem().Kind() != reflect.String {
		return errors.New("not a string")
	}

	currentValue := rtm.Value.Elem().String()
	newValue := f.Transform(currentValue)
	rtm.Value.Elem().SetString(newValue)
	return nil
}

func (f *DirectiveCaseFormatter) Encode(rtm *httpin_core.DirectiveRuntime) error {
	if rtm.Value.Type().Kind() != reflect.String {
		return errors.New("not a string")
	}

	currentValue := rtm.Value.String()
	newValue := f.Transform(currentValue)
	rtm.Value.SetString(newValue)
	return nil
}

2. Register your Directive to httpin

by calling httpin_core.RegisterDirective:

func init() {
	httpin_core.RegisterDirective("to_lowercase", DirectiveCaseFormatter{
		Transform: strings.ToLower,
	})

	httpin_core.RegisterDirective("to_uppercase", DirectiveCaseFormatter{
		Transform: strings.ToUpper,
	})
}

NB: make sure to register your directive executor before you start the server.

3. Use your Directive

type ListUsersInput struct {
	Username string `in:"query=username;to_lowercase"`
	Gender   string `in:"query=gender;to_uppercase"`
}

Runable Example

package main

import (
	"errors"
	"fmt"
	"net/http"
	"net/http/httptest"
	"reflect"
	"strings"

	"github.com/ggicci/httpin"
	httpin_core "github.com/ggicci/httpin/core"
	"github.com/go-chi/chi/v5"
)

type DirectiveCaseFormatter struct {
	Transform func(string) string
}

func (f *DirectiveCaseFormatter) Decode(rtm *httpin_core.DirectiveRuntime) error {
	if rtm.Value.Type().Elem().Kind() != reflect.String {
		return errors.New("not a string")
	}

	currentValue := rtm.Value.Elem().String()
	newValue := f.Transform(currentValue)
	rtm.Value.Elem().SetString(newValue)
	return nil
}

func (f *DirectiveCaseFormatter) Encode(rtm *httpin_core.DirectiveRuntime) error {
	if rtm.Value.Type().Kind() != reflect.String {
		return errors.New("not a string")
	}

	currentValue := rtm.Value.String()
	newValue := f.Transform(currentValue)
	rtm.Value.SetString(newValue)
	return nil
}

func init() {
	httpin_core.RegisterDirective("to_lowercase", &DirectiveCaseFormatter{
		Transform: strings.ToLower,
	})

	httpin_core.RegisterDirective("to_uppercase", &DirectiveCaseFormatter{
		Transform: strings.ToUpper,
	})
}

type ListUsersInput struct {
	Username string `in:"query=username;to_lowercase"`
	Gender   string `in:"query=gender;to_uppercase"`
}

func ListUsersHandler(rw http.ResponseWriter, r *http.Request) {
	input := r.Context().Value(httpin.Input).(*ListUsersInput)
	fmt.Printf("input: %#v\n", input)
}

func main() {
	router := chi.NewRouter()

	// Bind input struct with handler.
	router.With(
		httpin.NewInput(ListUsersInput{}),
	).Get("/users", ListUsersHandler)

	r, _ := http.NewRequest("GET", "/users?username=Ggicci&gender=male", nil)

	rw := httptest.NewRecorder()
	router.ServeHTTP(rw, r)
}