hook

README

hook

Package hook provides an interface for plugins to modify program behavior.

Documentation

Overview

Package hook provides an interface for plugins to modify program behavior.

Example

package main

import (
	"context"
	"io"
	"net/http"
	"net/http/httptest"
	"os"

	"golang.org/x/text/language"
	"golang.org/x/text/message"

	"github.com/BenLubar/hook"
)

func main() {
	var (
		beforeRequest func(*http.Request, http.Header) (*http.Request, error)
		BeforeRequest = hook.NewFilter(&beforeRequest).(func(func(*http.Request, http.Header) (*http.Request, error), int))
	)

	type printerValue struct{}
	matcher := language.NewMatcher([]language.Tag{language.AmericanEnglish, language.French, language.German, language.Spanish})
	_ = message.SetString(language.French, "Hello, world!\n", "Bonjour le monde!\n")
	_ = message.SetString(language.German, "Hello, world!\n", "Hallo Welt!\n")
	_ = message.SetString(language.Spanish, "Hello, world!\n", "¡Hola Mundo!\n")

	BeforeRequest(func(r *http.Request, headers http.Header) (*http.Request, error) {
		headers.Add("Vary", "Accept-Language")
		tags, _, err := language.ParseAcceptLanguage(r.Header.Get("Accept-Language"))
		if err != nil {
			return r, err
		}
		tag, _, _ := matcher.Match(tags...)
		return r.WithContext(context.WithValue(r.Context(), printerValue{}, message.NewPrinter(tag))), nil
	}, -100)

	PrinterForRequest := func(r *http.Request) *message.Printer {
		return r.Context().Value(printerValue{}).(*message.Printer)
	}

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		r, err := beforeRequest(r, w.Header())
		if err != nil {
			panic(err)
		}

		_, _ = PrinterForRequest(r).Fprintf(w, "Hello, world!\n")
	}))
	defer srv.Close()

	req, err := http.NewRequest("GET", srv.URL, nil)
	if err != nil {
		panic(err)
	}
	req.Header.Set("Accept-Language", "es")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer func() {
		err = resp.Body.Close()
		if err != nil {
			panic(err)
		}
	}()

	if resp.StatusCode != http.StatusOK {
		panic(resp.Status)
	}

	_, err = io.Copy(os.Stdout, resp.Body)
	if err != nil {
		panic(err)
	}

}

Output:

¡Hola Mundo!

Index

• type FilterFunc
• type FilterFuncPtr
• type FilterRegisterFunc
  • func NewFilter(apply FilterFuncPtr) (register FilterRegisterFunc)

Examples

• Package

Types

type FilterFunc

type FilterFunc interface{}

FilterFunc is func(T1, ..., A1, A2, A3, ...) (T1, ..., error)

type FilterFuncPtr

type FilterFuncPtr interface{}

FilterFuncPtr is *FilterFunc

type FilterRegisterFunc

type FilterRegisterFunc interface{}

FilterRegisterFunc is func(f FilterFunc, priority int)

func NewFilter

func NewFilter(apply FilterFuncPtr) (register FilterRegisterFunc)

NewFilter sets apply to a function that calls each FilterFunc given to register in order from lowest priority to highest priority, passing the result of the previous function call as the next function call's first arguments. If a non-nil error is returned by any of the FilterFuncs, apply returns the current result without continuing.