package direct

import (
	"context"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"sync"

	"github.com/google/uuid"
	"github.com/logrusorgru/aurora"
	"github.com/pkg/errors"
	"github.com/prysmaticlabs/go-ssz"
	validatorpb "github.com/prysmaticlabs/prysm/proto/validator/accounts/v2"
	"github.com/prysmaticlabs/prysm/shared/bls"
	"github.com/prysmaticlabs/prysm/shared/bytesutil"
	"github.com/prysmaticlabs/prysm/shared/depositutil"
	"github.com/prysmaticlabs/prysm/shared/petnames"
	"github.com/prysmaticlabs/prysm/shared/roughtime"
	"github.com/prysmaticlabs/prysm/validator/accounts/v2/iface"
	"github.com/prysmaticlabs/prysm/validator/flags"
	v2keymanager "github.com/prysmaticlabs/prysm/validator/keymanager/v2"
	"github.com/sirupsen/logrus"
	keystorev4 "github.com/wealdtech/go-eth2-wallet-encryptor-keystorev4"
)

var log = logrus.WithField("prefix", "direct-keymanager-v2")

const (
	// DepositTransactionFileName for the encoded, eth1 raw deposit tx data
	// for a validator account.
	DepositTransactionFileName = "deposit_transaction.rlp"
	// TimestampFileName stores a timestamp for account creation as a
	// file for a direct keymanager account.
	TimestampFileName = "created_at.txt"
	// KeystoreFileName exposes the expected filename for the keystore file for an account.
	KeystoreFileName = "keystore-*.json"
	// KeystoreFileNameFormat exposes the filename the keystore should be formatted in.
	KeystoreFileNameFormat = "keystore-%d.json"
	// PasswordFileSuffix for passwords persisted as text to disk.
	PasswordFileSuffix  = ".pass"
	depositDataFileName = "deposit_data.ssz"
	eipVersion          = "EIP-2335"
)

// Config for a direct keymanager.
type Config struct {
	EIPVersion                string `json:"direct_eip_version"`
	AccountPasswordsDirectory string `json:"direct_accounts_passwords_directory"`
}

// Keymanager implementation for direct keystores utilizing EIP-2335.
type Keymanager struct {
	wallet    iface.Wallet
	cfg       *Config
	keysCache map[[48]byte]bls.SecretKey
	lock      sync.RWMutex
}

// DefaultConfig for a direct keymanager implementation.
func DefaultConfig() *Config {
	return &Config{
		EIPVersion:                eipVersion,
		AccountPasswordsDirectory: flags.WalletPasswordsDirFlag.Value,
	}
}

// NewKeymanager instantiates a new direct keymanager from configuration options.
func NewKeymanager(ctx context.Context, wallet iface.Wallet, cfg *Config) (*Keymanager, error) {
	k := &Keymanager{
		wallet:    wallet,
		cfg:       cfg,
		keysCache: make(map[[48]byte]bls.SecretKey),
	}
	// If the wallet has the capability of unlocking accounts using
	// passphrases, then we initialize a cache of public key -> secret keys
	// used to retrieve secrets keys for the accounts via password unlock.
	// This cache is needed to process Sign requests using a public key.
	if err := k.initializeSecretKeysCache(ctx); err != nil {
		return nil, errors.Wrap(err, "could not initialize keys cache")
	}
	return k, nil
}

// UnmarshalConfigFile attempts to JSON unmarshal a direct keymanager
// configuration file into the *Config{} struct.
func UnmarshalConfigFile(r io.ReadCloser) (*Config, error) {
	enc, err := ioutil.ReadAll(r)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err := r.Close(); err != nil {
			log.Errorf("Could not close keymanager config file: %v", err)
		}
	}()
	cfg := &Config{}
	if err := json.Unmarshal(enc, cfg); err != nil {
		return nil, err
	}
	return cfg, nil
}

// MarshalConfigFile returns a marshaled configuration file for a keymanager.
func MarshalConfigFile(ctx context.Context, cfg *Config) ([]byte, error) {
	return json.MarshalIndent(cfg, "", "\t")
}

// Config for the direct keymanager.
func (dr *Keymanager) Config() *Config {
	return dr.cfg
}

// String pretty-print of a direct keymanager configuration.
func (c *Config) String() string {
	au := aurora.NewAurora(true)
	var b strings.Builder
	strAddr := fmt.Sprintf("%s: %s\n", au.BrightMagenta("EIP Version"), c.EIPVersion)
	if _, err := b.WriteString(strAddr); err != nil {
		log.Error(err)
		return ""
	}
	strCrt := fmt.Sprintf(
		"%s: %s\n", au.BrightMagenta("Accounts Passwords Directory"), c.AccountPasswordsDirectory,
	)
	if _, err := b.WriteString(strCrt); err != nil {
		log.Error(err)
		return ""
	}
	return b.String()
}

// ValidatingAccountNames for a direct keymanager.
func (dr *Keymanager) ValidatingAccountNames() ([]string, error) {
	return dr.wallet.ListDirs()
}

// CreateAccount for a direct keymanager implementation. This utilizes
// the EIP-2335 keystore standard for BLS12-381 keystores. It
// stores the generated keystore.json file in the wallet and additionally
// generates withdrawal credentials. At the end, it logs
// the raw deposit data hex string for users to copy.
func (dr *Keymanager) CreateAccount(ctx context.Context, password string) (string, error) {
	// Create a petname for an account from its public key and write its password to disk.
	validatingKey := bls.RandKey()
	accountName, err := dr.generateAccountName(validatingKey.PublicKey().Marshal())
	if err != nil {
		return "", errors.Wrap(err, "could not generate unique account name")
	}
	if err := dr.wallet.WritePasswordToDisk(ctx, accountName+".pass", password); err != nil {
		return "", errors.Wrap(err, "could not write password to disk")
	}
	// Generates a new EIP-2335 compliant keystore file
	// from a BLS private key and marshals it as JSON.
	encoded, err := dr.generateKeystoreFile(validatingKey, password)
	if err != nil {
		return "", err
	}

	// Generate a withdrawal key and confirm user
	// acknowledgement of a 256-bit entropy mnemonic phrase.
	withdrawalKey := bls.RandKey()
	log.Info(
		"Write down the private key, as it is your unique " +
			"withdrawal private key for eth2",
	)
	fmt.Printf(`
==========================Withdrawal Key===========================

%#x

===================================================================
	`, withdrawalKey.Marshal())
	fmt.Println(" ")

	// Upon confirmation of the withdrawal key, proceed to display
	// and write associated deposit data to disk.
	tx, depositData, err := depositutil.GenerateDepositTransaction(validatingKey, withdrawalKey)
	if err != nil {
		return "", errors.Wrap(err, "could not generate deposit transaction data")
	}

	// Log the deposit transaction data to the user.
	depositutil.LogDepositTransaction(log, tx)

	// We write the raw deposit transaction as an .rlp encoded file.
	if err := dr.wallet.WriteFileAtPath(ctx, accountName, DepositTransactionFileName, tx.Data()); err != nil {
		return "", errors.Wrapf(err, "could not write for account %s: %s", accountName, DepositTransactionFileName)
	}

	// We write the ssz-encoded deposit data to disk as a .ssz file.
	encodedDepositData, err := ssz.Marshal(depositData)
	if err != nil {
		return "", errors.Wrap(err, "could not marshal deposit data")
	}
	if err := dr.wallet.WriteFileAtPath(ctx, accountName, depositDataFileName, encodedDepositData); err != nil {
		return "", errors.Wrapf(err, "could not write for account %s: %s", accountName, encodedDepositData)
	}

	// Write the encoded keystore to disk with the timestamp appended
	createdAt := roughtime.Now().Unix()
	if err := dr.wallet.WriteFileAtPath(ctx, accountName, fmt.Sprintf(KeystoreFileNameFormat, createdAt), encoded); err != nil {
		return "", errors.Wrapf(err, "could not write keystore file for account %s", accountName)
	}

	log.WithFields(logrus.Fields{
		"name": accountName,
		"path": dr.wallet.AccountsDir(),
	}).Info("Successfully created new validator account")
	return accountName, nil
}

// FetchValidatingPublicKeys fetches the list of public keys from the direct account keystores.
func (dr *Keymanager) FetchValidatingPublicKeys(ctx context.Context) ([][48]byte, error) {
	accountNames, err := dr.ValidatingAccountNames()
	if err != nil {
		return nil, err
	}

	// Return the public keys from the cache if they match the
	// number of accounts from the wallet.
	publicKeys := make([][48]byte, len(accountNames))
	dr.lock.Lock()
	defer dr.lock.Unlock()
	if dr.keysCache != nil && len(dr.keysCache) == len(accountNames) {
		var i int
		for k := range dr.keysCache {
			publicKeys[i] = k
			i++
		}
		return publicKeys, nil
	}

	for i, name := range accountNames {
		encoded, err := dr.wallet.ReadFileAtPath(ctx, name, KeystoreFileName)
		if err != nil {
			return nil, errors.Wrapf(err, "could not read keystore file for account %s", name)
		}
		keystoreFile := &v2keymanager.Keystore{}
		if err := json.Unmarshal(encoded, keystoreFile); err != nil {
			return nil, errors.Wrapf(err, "could not decode keystore json for account: %s", name)
		}
		pubKeyBytes, err := hex.DecodeString(keystoreFile.Pubkey)
		if err != nil {
			return nil, errors.Wrapf(err, "could not decode pubkey bytes: %#x", keystoreFile.Pubkey)
		}
		publicKeys[i] = bytesutil.ToBytes48(pubKeyBytes)
	}
	return publicKeys, nil
}

// Sign signs a message using a validator key.
func (dr *Keymanager) Sign(ctx context.Context, req *validatorpb.SignRequest) (bls.Signature, error) {
	rawPubKey := req.PublicKey
	if rawPubKey == nil {
		return nil, errors.New("nil public key in request")
	}
	dr.lock.RLock()
	defer dr.lock.RUnlock()
	secretKey, ok := dr.keysCache[bytesutil.ToBytes48(rawPubKey)]
	if !ok {
		return nil, errors.New("no signing key found in keys cache")
	}
	return secretKey.Sign(req.SigningRoot), nil
}

// PublicKeyForAccount returns the associated public key for an account name.
func (dr *Keymanager) PublicKeyForAccount(accountName string) ([48]byte, error) {
	accountKeystore, err := dr.keystoreForAccount(accountName)
	if err != nil {
		return [48]byte{}, errors.Wrap(err, "could not get keystore")
	}
	pubKey, err := hex.DecodeString(accountKeystore.Pubkey)
	if err != nil {
		return [48]byte{}, errors.Wrap(err, "could decode pubkey string")
	}
	return bytesutil.ToBytes48(pubKey), nil
}

func (dr *Keymanager) keystoreForAccount(accountName string) (*v2keymanager.Keystore, error) {
	encoded, err := dr.wallet.ReadFileAtPath(context.Background(), accountName, KeystoreFileName)
	if err != nil {
		return nil, errors.Wrap(err, "could not read keystore file")
	}
	keystoreJSON := &v2keymanager.Keystore{}
	if err := json.Unmarshal(encoded, &keystoreJSON); err != nil {
		return nil, errors.Wrap(err, "could not decode json")
	}
	return keystoreJSON, nil
}

func (dr *Keymanager) initializeSecretKeysCache(ctx context.Context) error {
	accountNames, err := dr.ValidatingAccountNames()
	if err != nil {
		return err
	}

	for _, name := range accountNames {
		password, err := dr.wallet.ReadPasswordFromDisk(ctx, name+PasswordFileSuffix)
		if err != nil {
			return errors.Wrapf(err, "could not read password for account %s", name)
		}
		encoded, err := dr.wallet.ReadFileAtPath(ctx, name, KeystoreFileName)
		if err != nil {
			return errors.Wrapf(err, "could not read keystore file for account %s", name)
		}
		keystoreFile := &v2keymanager.Keystore{}
		if err := json.Unmarshal(encoded, keystoreFile); err != nil {
			return errors.Wrapf(err, "could not decode keystore json for account: %s", name)
		}
		// We extract the validator signing private key from the keystore
		// by utilizing the password and initialize a new BLS secret key from
		// its raw bytes.
		decryptor := keystorev4.New()
		rawSigningKey, err := decryptor.Decrypt(keystoreFile.Crypto, []byte(password))
		if err != nil {
			return errors.Wrapf(err, "could not decrypt validator signing key for account: %s", name)
		}
		validatorSigningKey, err := bls.SecretKeyFromBytes(rawSigningKey)
		if err != nil {
			return errors.Wrapf(err, "could not instantiate bls secret key from bytes for account: %s", name)
		}

		// Update a simple cache of public key -> secret key utilized
		// for fast signing access in the direct keymanager.
		dr.keysCache[bytesutil.ToBytes48(validatorSigningKey.PublicKey().Marshal())] = validatorSigningKey
	}
	return nil
}

func (dr *Keymanager) generateKeystoreFile(validatingKey bls.SecretKey, password string) ([]byte, error) {
	encryptor := keystorev4.New()
	cryptoFields, err := encryptor.Encrypt(validatingKey.Marshal(), []byte(password))
	if err != nil {
		return nil, errors.Wrap(err, "could not encrypt validating key into keystore")
	}
	id, err := uuid.NewRandom()
	if err != nil {
		return nil, err
	}
	keystoreFile := &v2keymanager.Keystore{
		Crypto:  cryptoFields,
		ID:      id.String(),
		Pubkey:  fmt.Sprintf("%x", validatingKey.PublicKey().Marshal()),
		Version: encryptor.Version(),
		Name:    encryptor.Name(),
	}
	return json.MarshalIndent(keystoreFile, "", "\t")
}

func (dr *Keymanager) generateAccountName(pubKey []byte) (string, error) {
	var accountExists bool
	var accountName string
	for !accountExists {
		accountName = petnames.DeterministicName(pubKey, "-")
		exists, err := hasDir(filepath.Join(dr.wallet.AccountsDir(), accountName))
		if err != nil {
			return "", errors.Wrapf(err, "could not check if account exists in dir: %s", dr.wallet.AccountsDir())
		}
		if !exists {
			break
		}
	}
	return accountName, nil
}

func (dr *Keymanager) checkPasswordForAccount(accountName string, password string) error {
	accountKeystore, err := dr.keystoreForAccount(accountName)
	if err != nil {
		return errors.Wrap(err, "could not get keystore")
	}
	decryptor := keystorev4.New()
	_, err = decryptor.Decrypt(accountKeystore.Crypto, []byte(password))
	if err != nil {
		return errors.Wrap(err, "could not decrypt keystore")
	}
	return nil
}

// Checks if a directory indeed exists at the specified path.
func hasDir(dirPath string) (bool, error) {
	info, err := os.Stat(dirPath)
	if os.IsNotExist(err) {
		return false, nil
	}
	return info.IsDir(), err
}