package sr25519

import (
	"bytes"
	"fmt"

	"github.com/tendermint/tendermint/crypto"
	"github.com/tendermint/tendermint/crypto/tmhash"

	schnorrkel "github.com/ChainSafe/go-schnorrkel"
)

var _ crypto.PubKey = PubKey{}

// PubKeySize is the number of bytes in an Sr25519 public key.
const PubKeySize = 32

// PubKeySr25519 implements crypto.PubKey for the Sr25519 signature scheme.
type PubKey []byte

// Address is the SHA256-20 of the raw pubkey bytes.
func (pubKey PubKey) Address() crypto.Address {
	return crypto.Address(tmhash.SumTruncated(pubKey[:]))
}

// Bytes marshals the PubKey using amino encoding.
func (pubKey PubKey) Bytes() []byte {
	return []byte(pubKey)
}

func (pubKey PubKey) VerifyBytes(msg []byte, sig []byte) bool {
	// make sure we use the same algorithm to sign
	if len(sig) != SignatureSize {
		return false
	}
	var sig64 [SignatureSize]byte
	copy(sig64[:], sig)

	publicKey := &(schnorrkel.PublicKey{})
	var p [PubKeySize]byte
	copy(p[:], pubKey)
	err := publicKey.Decode(p)
	if err != nil {
		return false
	}

	signingContext := schnorrkel.NewSigningContext([]byte{}, msg)

	signature := &(schnorrkel.Signature{})
	err = signature.Decode(sig64)
	if err != nil {
		return false
	}

	return publicKey.Verify(signature, signingContext)
}

func (pubKey PubKey) String() string {
	return fmt.Sprintf("PubKeySr25519{%X}", []byte(pubKey))
}

// Equals - checks that two public keys are the same time
// Runs in constant time based on length of the keys.
func (pubKey PubKey) Equals(other crypto.PubKey) bool {
	if otherEd, ok := other.(PubKey); ok {
		return bytes.Equal(pubKey[:], otherEd[:])
	}
	return false
}