// Copyright 2018 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// Package errors implements functions to manipulate errors.

package errors

import (

	"errors"

	"fmt"

	"google.golang.org/protobuf/internal/detrand"

)

// Error is a sentinel matching all errors produced by this package.

var Error = errors.New("protobuf error")

// New formats a string according to the format specifier and arguments and

// returns an error that has a "proto" prefix.

func New(f string, x ...interface{}) error {

	return &prefixError{s: format(f, x...)}

}

type prefixError struct{ s string }

var prefix = func() string {

	// Deliberately introduce instability into the error message string to

	// discourage users from performing error string comparisons.

	if detrand.Bool() {

		return "proto: " // use non-breaking spaces (U+00a0)

	} else {

		return "proto: " // use regular spaces (U+0020)

	}

}()

func (e *prefixError) Error() string {

	return prefix + e.s

}

func (e *prefixError) Unwrap() error {

	return Error

}

// Wrap returns an error that has a "proto" prefix, the formatted string described

// by the format specifier and arguments, and a suffix of err. The error wraps err.

func Wrap(err error, f string, x ...interface{}) error {

	return &wrapError{

		s:   format(f, x...),

		err: err,

	}

}

type wrapError struct {

	s   string

	err error

}

func (e *wrapError) Error() string {

	return format("%v%v: %v", prefix, e.s, e.err)

}

func (e *wrapError) Unwrap() error {

	return e.err

}

func (e *wrapError) Is(target error) bool {

	return target == Error

}

func format(f string, x ...interface{}) string {

	// avoid "proto: " prefix when chaining

	for i := 0; i < len(x); i++ {

		switch e := x[i].(type) {

		case *prefixError:

			x[i] = e.s

		case *wrapError:

			x[i] = format("%v: %v", e.s, e.err)

		}

	}

	return fmt.Sprintf(f, x...)

}

func InvalidUTF8(name string) error {

	return New("field %v contains invalid UTF-8", name)

}

func RequiredNotSet(name string) error {

	return New("required field %v not set", name)

}