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package acme

import (
	"crypto"
	"crypto/ecdsa"
	"crypto/rsa"
	"encoding/base64"
	"io"
	"strings"

	"github.com/square/go-jose"
)

// KeySize is a default RSA key size
const KeySize = 2048

// Signer ...
type Signer struct {
	signer jose.Signer
	thumb  string
}

func NewSigner(privKey crypto.PrivateKey) (*Signer, error) {
	thumb := func(alg string, pubKey crypto.PublicKey) (string, error) {
		wk := &jose.JsonWebKey{Key: pubKey, Algorithm: alg}
		t, err := wk.Thumbprint(crypto.SHA256)
		return base64.RawURLEncoding.EncodeToString(t), err
	}
	switch k := privKey.(type) {
	case *rsa.PrivateKey:
		s, err := jose.NewSigner(jose.RS256, k)
		if err != nil {
			return nil, err
		}
		t, err := thumb("RSA", k.Public())
		if err != nil {
			return nil, err
		}
		return &Signer{signer: s, thumb: t}, nil
	case *ecdsa.PrivateKey:
		s, err := jose.NewSigner(jose.ES384, k)
		if err != nil {
			return nil, err
		}
		t, err := thumb("EC", k.Public())
		if err != nil {
			return nil, err
		}
		return &Signer{signer: s, thumb: t}, nil
	default:
		return nil, ErrKeyType
	}
}

// Sign implements Signer interface
func (s Signer) Sign(msg []byte, n jose.NonceSource) (io.Reader, error) {
	s.signer.SetNonceSource(n)
	obj, err := s.signer.Sign(msg)
	if err != nil {
		return nil, err
	}
	return strings.NewReader(obj.FullSerialize()), nil
}

func (s Signer) KeyAuth(token string) string {
	return token + "." + s.thumb
}