package main

import (
	"crypto"
	"crypto/aes"
	"crypto/cipher"
	"crypto/ed25519"
	"encoding/hex"
	"fmt"

	"github.com/dchest/bcrypt_pbkdf"
)

/*
Same key as private.ed25519 example.
*/

func main() {
	const (
		passphrase string = "test"
		rounds     int    = 100
		keySize    int    = 32
		lenPlain   int    = 160
	)
	var salt []byte
	var bcryptKey []byte
	var sk []byte
	var pk []byte
	var pubkey crypto.PublicKey
	var key ed25519.PrivateKey
	var decrypted []byte
	var aesCtx cipher.Block
	var encData []byte

	decrypted = make([]byte, lenPlain)
	encData = make([]byte, lenPlain)

	// Import salt
	if s, err := hex.DecodeString("50132f72900d68e0a31f9d75b6f0a5bc"); err != nil {
		fmt.Println(err)
		return
	} else {
		salt = s
	}

	// Import encrypted data
	if b, err := hex.DecodeString(
		"c49777cd0d1a7d37db77a1814991278f8ce99d572e2c666b93b99867425c60da" +
			"4652fddb8555098532b51beeee2959f9db5cf5a0905052720c5de25f2c4dd87e" +
			"bcc7bb5ea3d7bcbeacc6b732e4c39295d9991a97ef3f0838f8a9bfd43edb3403" +
			"189649088f6cfb78946fb914e358ac6abc64691072f5f2788534d9d42d7f406b" +
			"c5090b30df23cb7dd8c5cb938e41facd6e38e8845b8160bff840598118d447c2",
	); err != nil {
		fmt.Println(err)
		return
	} else {
		encData = b
	}

	// ED25519 keys
	// This is used to validate decrypted keys.
	if edk, err := hex.DecodeString(
		"ce6e2b8d638c9d5219dff455af1a90d0a5b72694cfcedfb93bc1e1b1816dee98" +
			"bfa2031aa5463113e40e16896af503c5299ead76b09cb63846f41cc4de1740f6",
	); err != nil {
		fmt.Println(err)
		return
	} else {
		key = edk
		// .Public() returns a crypto.PublicKey, which... is an interface that seemingly cannot be type asserted to anything.
		pubkey = key.Public()
	}
	sep := len(key) - ed25519.PublicKeySize
	pk = key[sep:]
	sk = key[0:sep]

	// Bcrypt_pbkdf2 derivation (used for deriving decryption key for AES encrypted private key)
	// if k, err := bcrypt_pbkdf.Key([]byte(passphrase), salt, rounds, keySize); err != nil {
	if k, err := bcrypt_pbkdf.Key([]byte(passphrase), salt, rounds, keySize+len(salt)); err != nil {
		fmt.Println(err)
		return
	} else {
		bcryptKey = k
	}
	realBcryptKey := bcryptKey[0:sep]
	realIV := bcryptKey[sep:]

	// Decrypter
	if a, err := aes.NewCipher(realBcryptKey); err != nil {
		fmt.Println(err)
		return
	} else {
		aesCtx = a
	}

	// Actual cipher setup. AES256-CBC
	// d := cipher.NewCBCDecrypter(aesCtx, realIV)
	// d.CryptBlocks(decrypted, encData)

	// Actual cipher setup. AES256-CTR
	d := cipher.NewCTR(aesCtx, realIV)
	d.XORKeyStream(decrypted, encData)

	/*
		if p, s, err := ed25519.GenerateKey(nil); err != nil {
			fmt.Println(err)
			return
		} else {
			pubkey = p
			key = s
			pk = key[(len(key) - ed25519.PublicKeySize):]
			sk = key[0:(len(key) - ed25519.PublicKeySize)]
		}
	*/

	fmt.Printf("ED25519 key: %v\n", hex.EncodeToString(key))
	fmt.Printf("Pubkey: %v\n", pubkey)
	fmt.Printf("SK: %v\n", hex.EncodeToString(sk))
	fmt.Printf("PK: %v\n", hex.EncodeToString(pk))
	fmt.Printf("Salt: %v\n", hex.EncodeToString(salt))
	fmt.Printf("Bcrypt Key: %v\n", hex.EncodeToString(bcryptKey))
	fmt.Printf("realBcryptKey: %v\n", hex.EncodeToString(realBcryptKey))
	fmt.Printf("realIV: %v\n", hex.EncodeToString(realIV))
	// fmt.Printf("Encrypted data: %v\n", hex.EncodeToString(encData))
	fmt.Printf("Decrypted data?: %v\n", hex.EncodeToString(decrypted))

}