pomerium/internal/httputil/errors.go

package httputil // import "github.com/pomerium/pomerium/internal/httputil"

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"

	"github.com/pomerium/pomerium/internal/templates"
	"github.com/pomerium/pomerium/internal/version"
)

var (
	// ErrUserNotAuthorized is an error for unauthorized users.
	ErrUserNotAuthorized = errors.New("user not authorized")
)

// HTTPError stores the status code and a message for a given HTTP error.
type HTTPError struct {
	Code    int
	Message string
}

// Error fulfills the error interface, returning a string representation of the error.
func (h HTTPError) Error() string {
	return fmt.Sprintf("%d %s: %s", h.Code, http.StatusText(h.Code), h.Message)
}

// CodeForError maps an error type and returns a corresponding http.Status
func CodeForError(err error) int {
	switch err {
	case ErrTokenRevoked:
		return http.StatusUnauthorized
	}
	return http.StatusInternalServerError
}

// ErrorResponse renders an error page for errors given a message and a status code.
func ErrorResponse(rw http.ResponseWriter, req *http.Request, message string, code int) {
	if req.Header.Get("Accept") == "application/json" {
		var response struct {
			Error string `json:"error"`
		}
		response.Error = message
		writeJSONResponse(rw, code, response)
	} else {
		title := http.StatusText(code)
		rw.WriteHeader(code)
		t := struct {
			Code    int
			Title   string
			Message string
			Version string
		}{
			Code:    code,
			Title:   title,
			Message: message,
			Version: version.FullVersion(),
		}
		templates.New().ExecuteTemplate(rw, "error.html", t)
	}
}

// writeJSONResponse is a helper that sets the application/json header and writes a response.
func writeJSONResponse(rw http.ResponseWriter, code int, response interface{}) {
	rw.Header().Set("Content-Type", "application/json")
	rw.WriteHeader(code)

	err := json.NewEncoder(rw).Encode(response)
	if err != nil {
		io.WriteString(rw, err.Error())
	}
}