package cbk_test

import (
	"strings"
	"testing"

	"github.com/btcsuite/btcd/btcutil/hdkeychain"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"github.com/tyler-smith/go-bip39"

	"sneak.berlin/go/secret/pkg/bip85"
	"sneak.berlin/go/x/pkg/bip39wordlist"
	"sneak.berlin/go/x/pkg/cbk"
)

// The BIP85 specification publishes its test vectors against one master
// key. specMnemonic is the BIP39 phrase that produces that master key, so
// the whole mnemonic-to-entropy chain this package relies on can be
// checked against the specification.
const (
	specMnemonic = "install scatter logic circle pencil average fall shoe " +
		"quantum disease suspect usage"

	specMasterKey = "xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8" +
		"kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLjbKb"

	// specHex64 is the specification's HEX application vector for
	// m/83696968'/128169'/64'/0'.
	specHex64 = "492db4698cf3b73a5a24998aa3e9d7fa96275d85724a91e7" +
		"1aa2d645442f878555d078fd1f1f67e368976f04137b1f7a" +
		"0d19232136ca50c44614af72b5582a5c"
)

// The keys below are the keypair for specMnemonic at index 0, pinned when
// the BIP85 derivation was implemented. If this test starts failing, the
// derivation has changed and existing keys are no longer reproducible.
const (
	vectorPublicKeyHex = "dbef711b3f340d336eb99cd8d0dbd491e1edce8eaad71cd66be228032a9a743e"

	vectorPrivateKeyHex = "ea3ceb0b02ee8e587779c63f4b7b3a21e950a213f1ec53cab608d13e8796e6dc"
)

func TestSpecMnemonicProducesSpecMasterKey(t *testing.T) {
	t.Parallel()

	masterKey := specMasterKeyFromMnemonic(t)
	assert.Equal(t, specMasterKey, masterKey.String())

	hex64, err := bip85.DeriveHex(masterKey, 64, 0)
	require.NoError(t, err)
	assert.Equal(t, specHex64, hex64)
}

func TestNewMatchesPinnedVector(t *testing.T) {
	t.Parallel()

	keypair, err := cbk.FromMnemonic(specMnemonic)
	require.NoError(t, err)

	assert.Equal(t, vectorPublicKeyHex, keypair.PublicKeyHex())
	assert.Equal(t, vectorPrivateKeyHex, keypair.PrivateKeyHex())
}

func TestPrivateKeyIsBIP85HexApplicationOutput(t *testing.T) {
	t.Parallel()

	masterKey := specMasterKeyFromMnemonic(t)

	for _, index := range []uint32{0, 1, 7} {
		expected, err := bip85.DeriveHex(masterKey, cbk.KeySize, index)
		require.NoError(t, err)

		keypair, err := cbk.New(cbk.Params{Mnemonic: specMnemonic, Index: index})
		require.NoError(t, err)

		assert.Equal(t, expected, keypair.PrivateKeyHex(), "index %d", index)
	}
}

func TestNewIndexSelectsIndependentKeypairs(t *testing.T) {
	t.Parallel()

	first, err := cbk.New(cbk.Params{Mnemonic: specMnemonic, Index: 0})
	require.NoError(t, err)

	second, err := cbk.New(cbk.Params{Mnemonic: specMnemonic, Index: 1})
	require.NoError(t, err)

	assert.NotEqual(t, first.PublicKey, second.PublicKey)
	assert.NotEqual(t, first.PrivateKey, second.PrivateKey)

	fromMnemonic, err := cbk.FromMnemonic(specMnemonic)
	require.NoError(t, err)
	assert.Equal(t, first, fromMnemonic, "FromMnemonic uses index 0")
}

func TestNewRejectsIndexBeyondHardenedRange(t *testing.T) {
	t.Parallel()

	_, err := cbk.New(cbk.Params{Mnemonic: specMnemonic, Index: cbk.MaxIndex + 1})
	require.ErrorIs(t, err, cbk.ErrIndexTooLarge)

	_, err = cbk.New(cbk.Params{Mnemonic: specMnemonic, Index: cbk.MaxIndex})
	require.NoError(t, err)
}

func TestNewNormalizesMnemonic(t *testing.T) {
	t.Parallel()

	canonical, err := cbk.FromMnemonic(specMnemonic)
	require.NoError(t, err)

	words := strings.Fields(specMnemonic)
	messy := "  " + strings.ToUpper(words[0]) + "\t" +
		strings.Join(words[1:], "   ") + "\n"

	normalized, err := cbk.New(cbk.Params{Mnemonic: messy, Index: 0})
	require.NoError(t, err)

	assert.Equal(t, canonical, normalized)
}

func TestNewDifferentMnemonicsGiveDifferentKeys(t *testing.T) {
	t.Parallel()

	other, err := bip39wordlist.GenerateMnemonic(bip39wordlist.MaxWordCount)
	require.NoError(t, err)

	specKeypair, err := cbk.FromMnemonic(specMnemonic)
	require.NoError(t, err)

	otherKeypair, err := cbk.FromMnemonic(other)
	require.NoError(t, err)

	assert.NotEqual(t, specKeypair.PublicKey, otherKeypair.PublicKey)
	assert.NotEqual(t, specKeypair.PrivateKey, otherKeypair.PrivateKey)
}

func TestNewRejectsInvalidMnemonic(t *testing.T) {
	t.Parallel()

	_, err := cbk.FromMnemonic("abandon bogus about")
	require.ErrorIs(t, err, bip39wordlist.ErrInvalidWordCount)

	words := strings.Fields(specMnemonic)
	words[len(words)-1] = "bogus"

	_, err = cbk.FromMnemonic(strings.Join(words, " "))
	require.ErrorIs(t, err, bip39wordlist.ErrUnknownWord)
}

func TestKeyAccessors(t *testing.T) {
	t.Parallel()

	keypair, err := cbk.FromMnemonic(specMnemonic)
	require.NoError(t, err)

	assert.Equal(t, keypair.PublicKey[:], keypair.PublicKeyBytes())
	assert.Equal(t, keypair.PrivateKey[:], keypair.PrivateKeyBytes())
	assert.Len(t, keypair.PublicKeyBytes(), cbk.KeySize)
	assert.Len(t, keypair.PrivateKeyBytes(), cbk.KeySize)
	assert.Equal(t, keypair.PublicKey.Hex(), keypair.PublicKeyHex())
	assert.Equal(t, keypair.PrivateKey.Hex(), keypair.PrivateKeyHex())
	assert.Len(t, keypair.PublicKeyHex(), 2*cbk.KeySize)
}

// specMasterKeyFromMnemonic builds the BIP32 master key from specMnemonic
// the same way the package does, independently of it.
func specMasterKeyFromMnemonic(t *testing.T) *hdkeychain.ExtendedKey {
	t.Helper()

	seed := bip39.NewSeed(specMnemonic, "")

	masterKey, err := hdkeychain.NewMaster(seed, &chaincfg.MainNetParams)
	require.NoError(t, err)

	return masterKey
}