Initial QSfera import

Server/vendor/github.com/lestrrat-go/jwx/v3/jwa/jwa.go

@@ -0,0 +1,68 @@
+//go:generate ../tools/cmd/genjwa.sh
+
+// Package jwa defines the various algorithm described in https://tools.ietf.org/html/rfc7518
+package jwa
+
+import (
+	"errors"
+	"fmt"
+)
+
+// KeyAlgorithm is a workaround for jwk.Key being able to contain different
+// types of algorithms in its `alg` field.
+//
+// Previously the storage for the `alg` field was represented as a string,
+// but this caused some users to wonder why the field was not typed appropriately
+// like other fields.
+//
+// Ideally we would like to keep track of Signature Algorithms and
+// Key Encryption Algorithms separately, and force the APIs to
+// type-check at compile time, but this allows users to pass a value from a
+// jwk.Key directly
+type KeyAlgorithm interface {
+	String() string
+	IsDeprecated() bool
+}
+
+var errInvalidKeyAlgorithm = errors.New(`invalid key algorithm`)
+
+func ErrInvalidKeyAlgorithm() error {
+	return errInvalidKeyAlgorithm
+}
+
+// KeyAlgorithmFrom takes either a string, `jwa.SignatureAlgorithm`,
+// `jwa.KeyEncryptionAlgorithm`, or `jwa.ContentEncryptionAlgorithm`.
+// and returns a `jwa.KeyAlgorithm`.
+//
+// If the value cannot be handled, it returns an `jwa.InvalidKeyAlgorithm`
+// object instead of returning an error. This design choice was made to allow
+// users to directly pass the return value to functions such as `jws.Sign()`
+func KeyAlgorithmFrom(v any) (KeyAlgorithm, error) {
+	switch v := v.(type) {
+	case SignatureAlgorithm:
+		return v, nil
+	case KeyEncryptionAlgorithm:
+		return v, nil
+	case ContentEncryptionAlgorithm:
+		return v, nil
+	case string:
+		salg, ok := LookupSignatureAlgorithm(v)
+		if ok {
+			return salg, nil
+		}
+
+		kalg, ok := LookupKeyEncryptionAlgorithm(v)
+		if ok {
+			return kalg, nil
+		}
+
+		calg, ok := LookupContentEncryptionAlgorithm(v)
+		if ok {
+			return calg, nil
+		}
+
+		return nil, fmt.Errorf(`invalid key value: %q: %w`, v, errInvalidKeyAlgorithm)
+	default:
+		return nil, fmt.Errorf(`invalid key type: %T: %w`, v, errInvalidKeyAlgorithm)
+	}
+}