package kmsvc

import (
	"errors"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// Sentinel errors callers can match with errors.Is, so they never need to
// import google.golang.org/grpc/status themselves.
var (
	ErrQueueNotFound   = errors.New("kmsvc: queue not found")
	ErrAlreadyExists   = errors.New("kmsvc: already exists")
	ErrInvalidArgument = errors.New("kmsvc: invalid argument")
	ErrUnauthenticated = errors.New("kmsvc: unauthenticated")
	ErrMessageTooLarge = errors.New("kmsvc: message body too large")
)

// mapError wraps a gRPC error with the matching sentinel above (when one
// applies) so errors.Is works for callers, while preserving the original
// error via %w for inspection/logging.
func mapError(err error) error {
	if err == nil {
		return nil
	}

	st, ok := status.FromError(err)
	if !ok {
		return err
	}

	switch st.Code() {
	case codes.NotFound:
		return joinSentinel(ErrQueueNotFound, err)
	case codes.AlreadyExists:
		return joinSentinel(ErrAlreadyExists, err)
	case codes.InvalidArgument:
		return joinSentinel(ErrInvalidArgument, err)
	case codes.Unauthenticated:
		return joinSentinel(ErrUnauthenticated, err)
	case codes.ResourceExhausted:
		return joinSentinel(ErrMessageTooLarge, err)
	default:
		return err
	}
}

func joinSentinel(sentinel, original error) error {
	return &sentinelError{sentinel: sentinel, original: original}
}

type sentinelError struct {
	sentinel error
	original error
}

func (e *sentinelError) Error() string { return e.original.Error() }
func (e *sentinelError) Unwrap() error { return e.original }
func (e *sentinelError) Is(target error) bool {
	return target == e.sentinel
}