Errorpages/main.go

package main

import (
	"errors"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"strconv"
)

type StatusData struct {
	Code     string
	Message  string
	Response int
}

var Statuses = map[string]string{
	"401": "You are not authorized to access the resource",
	"404": "The requested resource couldn't be found",
	"403": "Access to the resource was denied for the server",
	"405": "Method not supported by the server",
	"407": "You are no authorized to access the resource",
	"408": "Request timed out",
	"410": "The requested content is permanently gone",
	"414": "Requested URI is too long",
	"415": "Unsupported media type",
	"500": "The server encountered an internal error",
	"501": "Method not supported by the server",
	"502": "Requested endpoint encountered an error",
	"503": "Service is currently unavailable",
	"504": "Requested endpoint is unreachable",
	"505": "Protocol version not supported",
	"511": "Requested endpoint requires authentication for proxy",
}

func isStatusCode(code string) (int, error) {
	num, err := strconv.Atoi(code)
	if err != nil {
		return 500, errors.New("not a number")
	}

	if num > 99 && num < 512 {
		return num, nil
	}

	return 500, errors.New("Invalid range")
}

func genStatus(request string) StatusData {
	// create and init page status
	var status StatusData
	status.Code = "500"
	status.Message = fmt.Sprintf("Invalid error response code recieved: %.5s[..]", request)
	status.Response = 500

	// check if we have a valid status code
	var code, err = isStatusCode(request)
	if err == nil {
		status.Code = request
		status.Message = fmt.Sprintf("Interrupted unsupported error response: %s", request)
		status.Response = code
	}

	// set custom status message if present
	description, ok := Statuses[request]
	if ok {
		status.Message = description
	}

	return status
}

func main() {
	// load template
	tmpl, err := template.ParseFiles("index-inlined-minified.html")
	if err != nil {
		log.Fatal(err)
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		status := genStatus(r.URL.Path[1:])
		// set status code to propagate http error code
		w.WriteHeader(status.Response)
		tmpl.Execute(w, status)
	})

	log.Fatal(http.ListenAndServe("127.0.0.1:8000", nil))
}