// Copyright (c) 2014 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package ecc_test

import (
	"encoding/hex"
	"fmt"
	"github.com/kaspanet/kaspad/util/daghash"

	"github.com/kaspanet/kaspad/ecc"
)

// This example demonstrates signing a message with a secp256k1 private key that
// is first parsed form raw bytes and serializing the generated signature.
func Example_signMessage() {
	// Decode a hex-encoded private key.
	pkBytes, err := hex.DecodeString("22a47fa09a223f2aa079edf85a7c2d4f87" +
		"20ee63e502ee2869afab7de234b80c")
	if err != nil {
		fmt.Println(err)
		return
	}
	privKey, pubKey := ecc.PrivKeyFromBytes(ecc.S256(), pkBytes)

	// Sign a message using the private key.
	message := "test message"
	messageHash := daghash.DoubleHashB([]byte(message))
	signature, err := privKey.Sign(messageHash)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Serialize and display the signature.
	fmt.Printf("Serialized Signature: %x\n", signature.Serialize())

	// Verify the signature for the message using the public key.
	verified := signature.Verify(messageHash, pubKey)
	fmt.Printf("Signature Verified? %v\n", verified)

	// Output:
	// Serialized Signature: 275d1c73a01b023377633cd1eaa6460e8cd0542ba089ad50450a8197246b3ef6d6836ef5a18226132c305e2b2060a699529cadc816fc98d63bc7d05771acec4d
	// Signature Verified? true
}

// This example demonstrates verifying a secp256k1 signature against a public
// key that is first parsed from raw bytes. The signature is also parsed from
// raw bytes.
func Example_verifySignature() {
	// Decode hex-encoded serialized public key.
	pubKeyBytes, err := hex.DecodeString("02a673638cb9587cb68ea08dbef685c" +
		"6f2d2a751a8b3c6f2a7e9a4999e6e4bfaf5")
	if err != nil {
		fmt.Println(err)
		return
	}
	pubKey, err := ecc.ParsePubKey(pubKeyBytes, ecc.S256())
	if err != nil {
		fmt.Println(err)
		return
	}

	// Decode hex-encoded serialized signature.
	sigBytes, err := hex.DecodeString("275d1c73a01b023377633cd1eaa6460e8cd0542ba" +
		"089ad50450a8197246b3ef6d6836ef5a18226132c305e2b2060a699529cadc816fc98d63bc7d05771acec4d")

	if err != nil {
		fmt.Println(err)
		return
	}
	signature, err := ecc.ParseSignature(sigBytes)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Verify the signature for the message using the public key.
	message := "test message"
	messageHash := daghash.DoubleHashB([]byte(message))
	verified := signature.Verify(messageHash, pubKey)
	fmt.Println("Signature Verified?", verified)

	// Output:
	// Signature Verified? true
}