package crypto

import (
	"bytes"
	"crypto"
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/sha256"
	"io"
	"testing"
)

func TestECDSAPublicKeyDerivation_P256(t *testing.T) {
	d := []byte{
		0xc9, 0x80, 0x68, 0x98, 0xa0, 0x33, 0x49, 0x16, 0xc8, 0x60, 0x74, 0x88, 0x80, 0xa5, 0x41, 0xf0,
		0x93, 0xb5, 0x79, 0xa9, 0xb1, 0xf3, 0x29, 0x34, 0xd8, 0x6c, 0x36, 0x3c, 0x39, 0x80, 0x03, 0x57,
	}

	x := []byte{
		0xd0, 0x72, 0x0d, 0xc6, 0x91, 0xaa, 0x80, 0x09, 0x6b, 0xa3, 0x2f, 0xed, 0x1c, 0xb9, 0x7c, 0x2b,
		0x62, 0x06, 0x90, 0xd0, 0x6d, 0xe0, 0x31, 0x7b, 0x86, 0x18, 0xd5, 0xce, 0x65, 0xeb, 0x72, 0x8f,
	}

	y := []byte{
		0x96, 0x81, 0xb5, 0x17, 0xb1, 0xcd, 0xa1, 0x7d, 0x0d, 0x83, 0xd3, 0x35, 0xd9, 0xc4, 0xa8, 0xa9,
		0xa9, 0xb0, 0xb1, 0xb3, 0xc7, 0x10, 0x6d, 0x8f, 0x3c, 0x72, 0xbc, 0x50, 0x93, 0xdc, 0x27, 0x5f,
	}

	testKeyDerivation(t, elliptic.P256(), d, x, y)
}

func TestECDSAPublicKeyDerivation_P384(t *testing.T) {
	d := []byte{
		0x53, 0x94, 0xf7, 0x97, 0x3e, 0xa8, 0x68, 0xc5, 0x2b, 0xf3, 0xff, 0x8d, 0x8c, 0xee, 0xb4, 0xdb,
		0x90, 0xa6, 0x83, 0x65, 0x3b, 0x12, 0x48, 0x5d, 0x5f, 0x62, 0x7c, 0x3c, 0xe5, 0xab, 0xd8, 0x97,
		0x8f, 0xc9, 0x67, 0x3d, 0x14, 0xa7, 0x1d, 0x92, 0x57, 0x47, 0x93, 0x16, 0x62, 0x49, 0x3c, 0x37,
	}

	x := []byte{
		0xfd, 0x3c, 0x84, 0xe5, 0x68, 0x9b, 0xed, 0x27, 0x0e, 0x60, 0x1b, 0x3d, 0x80, 0xf9, 0x0d, 0x67,
		0xa9, 0xae, 0x45, 0x1c, 0xce, 0x89, 0x0f, 0x53, 0xe5, 0x83, 0x22, 0x9a, 0xd0, 0xe2, 0xee, 0x64,
		0x56, 0x11, 0xfa, 0x99, 0x36, 0xdf, 0xa4, 0x53, 0x06, 0xec, 0x18, 0x06, 0x67, 0x74, 0xaa, 0x24,
	}

	y := []byte{
		0xb8, 0x3c, 0xa4, 0x12, 0x6c, 0xfc, 0x4c, 0x4d, 0x1d, 0x18, 0xa4, 0xb6, 0xc2, 0x1c, 0x7f, 0x69,
		0x9d, 0x51, 0x23, 0xdd, 0x9c, 0x24, 0xf6, 0x6f, 0x83, 0x38, 0x46, 0xee, 0xb5, 0x82, 0x96, 0x19,
		0x6b, 0x42, 0xec, 0x06, 0x42, 0x5d, 0xb5, 0xb7, 0x0a, 0x4b, 0x81, 0xb7, 0xfc, 0xf7, 0x05, 0xa0,
	}

	testKeyDerivation(t, elliptic.P384(), d, x, y)
}

func TestECDSAKnownSigningValue_P256(t *testing.T) {
	d := []byte{
		0x51, 0x9b, 0x42, 0x3d, 0x71, 0x5f, 0x8b, 0x58, 0x1f, 0x4f, 0xa8, 0xee, 0x59, 0xf4, 0x77, 0x1a,
		0x5b, 0x44, 0xc8, 0x13, 0x0b, 0x4e, 0x3e, 0xac, 0xca, 0x54, 0xa5, 0x6d, 0xda, 0x72, 0xb4, 0x64,
	}

	testKnownSigningValue(t, elliptic.P256(), d)
}

func TestECDSAKnownSigningValue_P384(t *testing.T) {
	d := []byte{
		0x53, 0x94, 0xf7, 0x97, 0x3e, 0xa8, 0x68, 0xc5, 0x2b, 0xf3, 0xff, 0x8d, 0x8c, 0xee, 0xb4, 0xdb,
		0x90, 0xa6, 0x83, 0x65, 0x3b, 0x12, 0x48, 0x5d, 0x5f, 0x62, 0x7c, 0x3c, 0xe5, 0xab, 0xd8, 0x97,
		0x8f, 0xc9, 0x67, 0x3d, 0x14, 0xa7, 0x1d, 0x92, 0x57, 0x47, 0x93, 0x16, 0x62, 0x49, 0x3c, 0x37,
	}

	testKnownSigningValue(t, elliptic.P384(), d)
}

func testKeyDerivation(t *testing.T, curve elliptic.Curve, d, expectedX, expectedY []byte) {
	privKey := ECDSAKey(curve, d)

	if e, a := d, privKey.D.Bytes(); bytes.Compare(e, a) != 0 {
		t.Errorf("expected % x, got % x", e, a)
	}

	if e, a := expectedX, privKey.X.Bytes(); bytes.Compare(e, a) != 0 {
		t.Errorf("expected % x, got % x", e, a)
	}

	if e, a := expectedY, privKey.Y.Bytes(); bytes.Compare(e, a) != 0 {
		t.Errorf("expected % x, got % x", e, a)
	}
}

func testKnownSigningValue(t *testing.T, curve elliptic.Curve, d []byte) {
	signingKey := ECDSAKey(curve, d)

	message := []byte{
		0x59, 0x05, 0x23, 0x88, 0x77, 0xc7, 0x74, 0x21, 0xf7, 0x3e, 0x43, 0xee, 0x3d, 0xa6, 0xf2, 0xd9,
		0xe2, 0xcc, 0xad, 0x5f, 0xc9, 0x42, 0xdc, 0xec, 0x0c, 0xbd, 0x25, 0x48, 0x29, 0x35, 0xfa, 0xaf,
		0x41, 0x69, 0x83, 0xfe, 0x16, 0x5b, 0x1a, 0x04, 0x5e, 0xe2, 0xbc, 0xd2, 0xe6, 0xdc, 0xa3, 0xbd,
		0xf4, 0x6c, 0x43, 0x10, 0xa7, 0x46, 0x1f, 0x9a, 0x37, 0x96, 0x0c, 0xa6, 0x72, 0xd3, 0xfe, 0xb5,
		0x47, 0x3e, 0x25, 0x36, 0x05, 0xfb, 0x1d, 0xdf, 0xd2, 0x80, 0x65, 0xb5, 0x3c, 0xb5, 0x85, 0x8a,
		0x8a, 0xd2, 0x81, 0x75, 0xbf, 0x9b, 0xd3, 0x86, 0xa5, 0xe4, 0x71, 0xea, 0x7a, 0x65, 0xc1, 0x7c,
		0xc9, 0x34, 0xa9, 0xd7, 0x91, 0xe9, 0x14, 0x91, 0xeb, 0x37, 0x54, 0xd0, 0x37, 0x99, 0x79, 0x0f,
		0xe2, 0xd3, 0x08, 0xd1, 0x61, 0x46, 0xd5, 0xc9, 0xb0, 0xd0, 0xde, 0xbd, 0x97, 0xd7, 0x9c, 0xe8,
	}

	sha256Hash := sha256.New()
	_, err := io.Copy(sha256Hash, bytes.NewReader(message))
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	msgHash := sha256Hash.Sum(nil)
	msgSignature, err := signingKey.Sign(rand.Reader, msgHash, crypto.SHA256)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	verified, err := VerifySignature(&signingKey.PublicKey, msgHash, msgSignature)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	if !verified {
		t.Fatalf("failed to verify message msgSignature")
	}
}

func TestECDSAInvalidSignature_P256(t *testing.T) {
	testInvalidSignature(t, elliptic.P256())
}

func TestECDSAInvalidSignature_P384(t *testing.T) {
	testInvalidSignature(t, elliptic.P384())
}

func TestECDSAGenKeySignature_P256(t *testing.T) {
	testGenKeySignature(t, elliptic.P256())
}

func TestECDSAGenKeySignature_P384(t *testing.T) {
	testGenKeySignature(t, elliptic.P384())
}

func testInvalidSignature(t *testing.T, curve elliptic.Curve) {
	privateKey, err := ecdsa.GenerateKey(curve, rand.Reader)
	if err != nil {
		t.Fatalf("failed to generate key: %v", err)
	}

	message := []byte{
		0x59, 0x05, 0x23, 0x88, 0x77, 0xc7, 0x74, 0x21, 0xf7, 0x3e, 0x43, 0xee, 0x3d, 0xa6, 0xf2, 0xd9,
		0xe2, 0xcc, 0xad, 0x5f, 0xc9, 0x42, 0xdc, 0xec, 0x0c, 0xbd, 0x25, 0x48, 0x29, 0x35, 0xfa, 0xaf,
		0x41, 0x69, 0x83, 0xfe, 0x16, 0x5b, 0x1a, 0x04, 0x5e, 0xe2, 0xbc, 0xd2, 0xe6, 0xdc, 0xa3, 0xbd,
		0xf4, 0x6c, 0x43, 0x10, 0xa7, 0x46, 0x1f, 0x9a, 0x37, 0x96, 0x0c, 0xa6, 0x72, 0xd3, 0xfe, 0xb5,
		0x47, 0x3e, 0x25, 0x36, 0x05, 0xfb, 0x1d, 0xdf, 0xd2, 0x80, 0x65, 0xb5, 0x3c, 0xb5, 0x85, 0x8a,
		0x8a, 0xd2, 0x81, 0x75, 0xbf, 0x9b, 0xd3, 0x86, 0xa5, 0xe4, 0x71, 0xea, 0x7a, 0x65, 0xc1, 0x7c,
		0xc9, 0x34, 0xa9, 0xd7, 0x91, 0xe9, 0x14, 0x91, 0xeb, 0x37, 0x54, 0xd0, 0x37, 0x99, 0x79, 0x0f,
		0xe2, 0xd3, 0x08, 0xd1, 0x61, 0x46, 0xd5, 0xc9, 0xb0, 0xd0, 0xde, 0xbd, 0x97, 0xd7, 0x9c, 0xe8,
	}

	sha256Hash := sha256.New()
	_, err = io.Copy(sha256Hash, bytes.NewReader(message))
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	msgHash := sha256Hash.Sum(nil)
	msgSignature, err := privateKey.Sign(rand.Reader, msgHash, crypto.SHA256)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	byteToFlip := 15
	switch msgSignature[byteToFlip] {
	case 0:
		msgSignature[byteToFlip] = 0x0a
	default:
		msgSignature[byteToFlip] &^= msgSignature[byteToFlip]
	}

	verified, err := VerifySignature(&privateKey.PublicKey, msgHash, msgSignature)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	if verified {
		t.Fatalf("expected message verification to fail")
	}
}

func testGenKeySignature(t *testing.T, curve elliptic.Curve) {
	privateKey, err := ecdsa.GenerateKey(curve, rand.Reader)
	if err != nil {
		t.Fatalf("failed to generate key: %v", err)
	}

	message := []byte{
		0x59, 0x05, 0x23, 0x88, 0x77, 0xc7, 0x74, 0x21, 0xf7, 0x3e, 0x43, 0xee, 0x3d, 0xa6, 0xf2, 0xd9,
		0xe2, 0xcc, 0xad, 0x5f, 0xc9, 0x42, 0xdc, 0xec, 0x0c, 0xbd, 0x25, 0x48, 0x29, 0x35, 0xfa, 0xaf,
		0x41, 0x69, 0x83, 0xfe, 0x16, 0x5b, 0x1a, 0x04, 0x5e, 0xe2, 0xbc, 0xd2, 0xe6, 0xdc, 0xa3, 0xbd,
		0xf4, 0x6c, 0x43, 0x10, 0xa7, 0x46, 0x1f, 0x9a, 0x37, 0x96, 0x0c, 0xa6, 0x72, 0xd3, 0xfe, 0xb5,
		0x47, 0x3e, 0x25, 0x36, 0x05, 0xfb, 0x1d, 0xdf, 0xd2, 0x80, 0x65, 0xb5, 0x3c, 0xb5, 0x85, 0x8a,
		0x8a, 0xd2, 0x81, 0x75, 0xbf, 0x9b, 0xd3, 0x86, 0xa5, 0xe4, 0x71, 0xea, 0x7a, 0x65, 0xc1, 0x7c,
		0xc9, 0x34, 0xa9, 0xd7, 0x91, 0xe9, 0x14, 0x91, 0xeb, 0x37, 0x54, 0xd0, 0x37, 0x99, 0x79, 0x0f,
		0xe2, 0xd3, 0x08, 0xd1, 0x61, 0x46, 0xd5, 0xc9, 0xb0, 0xd0, 0xde, 0xbd, 0x97, 0xd7, 0x9c, 0xe8,
	}

	sha256Hash := sha256.New()
	_, err = io.Copy(sha256Hash, bytes.NewReader(message))
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	msgHash := sha256Hash.Sum(nil)
	msgSignature, err := privateKey.Sign(rand.Reader, msgHash, crypto.SHA256)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	verified, err := VerifySignature(&privateKey.PublicKey, msgHash, msgSignature)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	if !verified {
		t.Fatalf("expected message verification to fail")
	}
}

func TestECDSASignatureFormat(t *testing.T) {
	asn1Signature := []byte{
		0x30, 0x45, 0x02, 0x21, 0x00, 0xd7, 0xc5, 0xb9, 0x9e, 0x0b, 0xb1, 0x1a, 0x1f, 0x32, 0xda, 0x66, 0xe0, 0xff,
		0x59, 0xb7, 0x8a, 0x5e, 0xb3, 0x94, 0x9c, 0x23, 0xb3, 0xfc, 0x1f, 0x18, 0xcc, 0xf6, 0x61, 0x67, 0x8b, 0xf1,
		0xc1, 0x02, 0x20, 0x26, 0x4d, 0x8b, 0x7c, 0xaa, 0x52, 0x4c, 0xc0, 0x2e, 0x5f, 0xf6, 0x7e, 0x24, 0x82, 0xe5,
		0xfb, 0xcb, 0xc7, 0x9b, 0x83, 0x0d, 0x19, 0x7e, 0x7a, 0x40, 0x37, 0x87, 0xdd, 0x1c, 0x93, 0x13, 0xc4,
	}

	x := []byte{
		0x1c, 0xcb, 0xe9, 0x1c, 0x07, 0x5f, 0xc7, 0xf4, 0xf0, 0x33, 0xbf, 0xa2, 0x48, 0xdb, 0x8f, 0xcc,
		0xd3, 0x56, 0x5d, 0xe9, 0x4b, 0xbf, 0xb1, 0x2f, 0x3c, 0x59, 0xff, 0x46, 0xc2, 0x71, 0xbf, 0x83,
	}

	y := []byte{
		0xce, 0x40, 0x14, 0xc6, 0x88, 0x11, 0xf9, 0xa2, 0x1a, 0x1f, 0xdb, 0x2c, 0x0e, 0x61, 0x13, 0xe0,
		0x6d, 0xb7, 0xca, 0x93, 0xb7, 0x40, 0x4e, 0x78, 0xdc, 0x7c, 0xcd, 0x5c, 0xa8, 0x9a, 0x4c, 0xa9,
	}

	publicKey, err := ECDSAPublicKey(elliptic.P256(), x, y)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	message := []byte{
		0x59, 0x05, 0x23, 0x88, 0x77, 0xc7, 0x74, 0x21, 0xf7, 0x3e, 0x43, 0xee, 0x3d, 0xa6, 0xf2, 0xd9,
		0xe2, 0xcc, 0xad, 0x5f, 0xc9, 0x42, 0xdc, 0xec, 0x0c, 0xbd, 0x25, 0x48, 0x29, 0x35, 0xfa, 0xaf,
		0x41, 0x69, 0x83, 0xfe, 0x16, 0x5b, 0x1a, 0x04, 0x5e, 0xe2, 0xbc, 0xd2, 0xe6, 0xdc, 0xa3, 0xbd,
		0xf4, 0x6c, 0x43, 0x10, 0xa7, 0x46, 0x1f, 0x9a, 0x37, 0x96, 0x0c, 0xa6, 0x72, 0xd3, 0xfe, 0xb5,
		0x47, 0x3e, 0x25, 0x36, 0x05, 0xfb, 0x1d, 0xdf, 0xd2, 0x80, 0x65, 0xb5, 0x3c, 0xb5, 0x85, 0x8a,
		0x8a, 0xd2, 0x81, 0x75, 0xbf, 0x9b, 0xd3, 0x86, 0xa5, 0xe4, 0x71, 0xea, 0x7a, 0x65, 0xc1, 0x7c,
		0xc9, 0x34, 0xa9, 0xd7, 0x91, 0xe9, 0x14, 0x91, 0xeb, 0x37, 0x54, 0xd0, 0x37, 0x99, 0x79, 0x0f,
		0xe2, 0xd3, 0x08, 0xd1, 0x61, 0x46, 0xd5, 0xc9, 0xb0, 0xd0, 0xde, 0xbd, 0x97, 0xd7, 0x9c, 0xe8,
	}

	hash := sha256.New()
	_, err = io.Copy(hash, bytes.NewReader(message))
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	msgHash := hash.Sum(nil)

	verifySignature, err := VerifySignature(publicKey, msgHash, asn1Signature)
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	if !verifySignature {
		t.Fatalf("failed to verify signature")
	}
}