herrors.go

package herrors

import (
	"errors"
	"net/http"
)

var (
	// 4xx errors
	ErrBadRequest           = New(http.StatusBadRequest)
	ErrUnauthorized         = New(http.StatusUnauthorized)
	ErrPaymentRequired      = New(http.StatusPaymentRequired)
	ErrForbidden            = New(http.StatusForbidden)
	ErrNotFound             = New(http.StatusNotFound)
	ErrMethodNotAllowed     = New(http.StatusMethodNotAllowed)
	ErrNotAcceptable        = New(http.StatusNotAcceptable)
	ErrProxyAuthRequired    = New(http.StatusProxyAuthRequired)
	ErrRequestTimeout       = New(http.StatusRequestTimeout)
	ErrConflict             = New(http.StatusConflict)
	ErrResourceGone         = New(http.StatusGone)
	ErrLengthRequired       = New(http.StatusLengthRequired)
	ErrPreconditionFailed   = New(http.StatusPreconditionFailed)
	ErrEntityTooLarge       = New(http.StatusRequestEntityTooLarge)
	ErrURITooLong           = New(http.StatusRequestURITooLong)
	ErrUnsupportedMediaType = New(http.StatusUnsupportedMediaType)
	ErrRangeNotSatisfiable  = New(http.StatusRequestedRangeNotSatisfiable)
	ErrExpectationFailed    = New(http.StatusExpectationFailed)
	ErrMisdirectedRequest   = New(http.StatusMisdirectedRequest)
	ErrUnprocessableEntity  = New(http.StatusUnprocessableEntity)
	ErrLocked               = New(http.StatusLocked)
	ErrFailedDependency     = New(http.StatusFailedDependency)
	ErrTooEarly             = New(http.StatusTooEarly)
	ErrPreconditionRequired = New(http.StatusPreconditionRequired)
	ErrTooManyRequests      = New(http.StatusTooManyRequests)
	ErrHeaderFieldsTooLarge = New(http.StatusRequestHeaderFieldsTooLarge)
	ErrIllegal              = New(http.StatusUnavailableForLegalReasons)

	// 5xx errors
	ErrInternalServer                = New(http.StatusInternalServerError)
	ErrNotImplemented                = New(http.StatusNotImplemented)
	ErrBadGateway                    = New(http.StatusBadGateway)
	ErrServiceUnavailable            = New(http.StatusServiceUnavailable)
	ErrGatewayTimeout                = New(http.StatusGatewayTimeout)
	ErrHTTPVersionNotSupported       = New(http.StatusHTTPVersionNotSupported)
	ErrVariantAlsoNegotiates         = New(http.StatusVariantAlsoNegotiates)
	ErrInsufficientStorage           = New(http.StatusInsufficientStorage)
	ErrLoopDetected                  = New(http.StatusLoopDetected)
	ErrNotExtended                   = New(http.StatusNotExtended)
	ErrNetworkAuthenticationRequired = New(http.StatusNetworkAuthenticationRequired)
)

// New constructs an ErrHttp error with the code and message populated
func New(statusCode uint) error {
	e := &ErrHttp{
		code: statusCode,
	}

	e.msg = http.StatusText(int(e.Code()))

	return e
}

// Wrap will create a new ErrHttp and place the provided error
// inside of it. There is a complementary errors.Unwrap to retrieve
// the wrapped error.
func Wrap(err error, statusCode uint) error {
	e := &ErrHttp{
		code:  statusCode,
		cause: err,
	}

	e.msg = http.StatusText(int(e.Code()))

	return e
}

// Write sets the response status code to the provided
// error code. When unable to find an ErrHttp error in
// the error chain then a 500 internal error is output.
func Write(w http.ResponseWriter, err error) {
	if err == nil {
		return
	}

	var target hasCode
	// don't allow unknown errors to surface to user
	if !errors.As(err, &target) {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	w.WriteHeader(int(target.Code()))
}

type ErrHttp struct {
	msg   string
	code  uint
	cause error
}

// Code returns http status code that the error represents
func (e *ErrHttp) Code() uint {
	if e.code == 0 {
		return http.StatusInternalServerError
	}

	return e.code
}

// Error returns http friendly error message
func (e *ErrHttp) Error() string {
	return e.msg
}

// Unwrap will return the first wrapped error if there is one
func (e *ErrHttp) Unwrap() error {
	return e.cause
}

// Is used by errors.Is for comparing ErrHttp
func (e *ErrHttp) Is(target error) bool {
	h, ok := target.(hasCode)
	if !ok {
		return false
	}

	return e.Code() == h.Code()
}

type hasCode interface {
	Code() uint
}