package nebula

import (
	"crypto/ed25519"
	"crypto/rand"
	"fmt"
)

var (
	sigPrivKeyPrefix = []byte("s0")
	sigPubKeyPrefix  = []byte("S0")
)

// SigningPrivateKey wraps an ed25519.PrivateKey to provide convenient text
// (un)marshaling methods.
type SigningPrivateKey ed25519.PrivateKey

// MarshalText implements the encoding.TextMarshaler interface.
func (k SigningPrivateKey) MarshalText() ([]byte, error) {
	return encodeWithPrefix(sigPrivKeyPrefix, k), nil
}

// UnmarshalText implements the encoding.TextUnmarshaler interface.
func (k *SigningPrivateKey) UnmarshalText(b []byte) error {
	b, err := decodeWithPrefix(sigPrivKeyPrefix, b)
	if err != nil {
		return fmt.Errorf("unmarshaling: %w", err)
	}

	*k = SigningPrivateKey(b)
	return nil
}

func (k SigningPrivateKey) String() string {
	b, err := k.MarshalText()
	if err != nil {
		panic(err)
	}
	return string(b)
}

// SigningPublicKey wraps an ed25519.PublicKey to provide convenient text
// (un)marshaling methods.
type SigningPublicKey ed25519.PublicKey

// MarshalText implements the encoding.TextMarshaler interface.
func (pk SigningPublicKey) MarshalText() ([]byte, error) {
	return encodeWithPrefix(sigPubKeyPrefix, pk), nil
}

// UnmarshalText implements the encoding.TextUnmarshaler interface.
func (pk *SigningPublicKey) UnmarshalText(b []byte) error {
	b, err := decodeWithPrefix(sigPubKeyPrefix, b)
	if err != nil {
		return fmt.Errorf("unmarshaling: %w", err)
	}

	*pk = SigningPublicKey(b)
	return nil
}

func (pk SigningPublicKey) String() string {
	b, err := pk.MarshalText()
	if err != nil {
		panic(err)
	}
	return string(b)
}

// GenerateSigningPair generates and returns a new key pair which can be used
// for signing arbitrary blobs of bytes.
func GenerateSigningPair() (SigningPublicKey, SigningPrivateKey) {
	pub, priv, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		panic(fmt.Errorf("generating ed25519 key: %w", err))
	}
	return SigningPublicKey(pub), SigningPrivateKey(priv)
}