package keys

import (
	"fmt"
	"strings"

	"github.com/pkg/errors"
	crypto "github.com/tendermint/go-crypto"
	dbm "github.com/tendermint/tmlibs/db"

	"github.com/tendermint/go-crypto/nano"
)

// XXX Lets use go-crypto/bcrypt and ascii encoding directly in here without
// further wrappers around a store or DB.
// Copy functions from: https://github.com/tendermint/mintkey/blob/master/cmd/mintkey/common.go
//
// dbKeybase combines encyption and storage implementation to provide
// a full-featured key manager
type dbKeybase struct {
	db    dbm.DB
	codec Codec
}

func New(db dbm.DB, codec Codec) dbKeybase {
	return dbKeybase{
		db:    db,
		codec: codec,
	}
}

var _ Keybase = dbKeybase{}

// Create adds a new key to the storage engine, returning error if
// another key already stored under this name
//
// algo must be a supported go-crypto algorithm: ed25519, secp256k1
func (kb dbKeybase) Create(name, passphrase, algo string) (Info, string, error) {
	// 128-bits are the all the randomness we can make use of
	secret := crypto.CRandBytes(16)
	key, err := generate(algo, secret)
	if err != nil {
		return Info{}, "", err
	}

	public := kb.writeKey(key, name, passphrase)

	// we append the type byte to the serialized secret to help with recovery
	// ie [secret] = [secret] + [type]
	typ := key.Bytes()[0]
	secret = append(secret, typ)

	seed, err := kb.codec.BytesToWords(secret)
	phrase := strings.Join(seed, " ")
	return public, phrase, err
}

// Recover takes a seed phrase and tries to recover the private key.
//
// If the seed phrase is valid, it will create the private key and store
// it under name, protected by passphrase.
//
// Result similar to New(), except it doesn't return the seed again...
func (kb dbKeybase) Recover(name, passphrase, seedphrase string) (Info, error) {
	words := strings.Split(strings.TrimSpace(seedphrase), " ")
	secret, err := kb.codec.WordsToBytes(words)
	if err != nil {
		return Info{}, err
	}

	// secret is comprised of the actual secret with the type appended
	// ie [secret] = [secret] + [type]
	l := len(secret)
	secret, typ := secret[:l-1], secret[l-1]

	key, err := generateByType(typ, secret)
	if err != nil {
		return Info{}, err
	}

	// d00d, it worked!  create the bugger....
	public := kb.writeKey(key, name, passphrase)
	return public, err
}

// List loads the keys from the storage and enforces alphabetical order
func (kb dbKeybase) List() ([]Info, error) {
	var res []Info
	for iter := kb.db.Iterator(); iter.Valid(); iter.Next() {
		key := iter.Key()
		if isPub(key) {
			info, err := readInfo(iter.Value())
			if err != nil {
				return nil, err
			}
			res = append(res, info)
		}
	}
	return res, nil
}

// Get returns the public information about one key
func (kb dbKeybase) Get(name string) (Info, error) {
	bs := kb.db.Get(pubName(name))
	return readInfo(bs)
}

// Sign will modify the Signable in order to attach a valid signature with
// this public key
//
// If no key for this name, or the passphrase doesn't match, returns an error
func (kb dbKeybase) Sign(name, passphrase string, msg []byte) (sig crypto.Signature, pk crypto.PubKey, err error) {
	var key crypto.PrivKey
	bs := kb.db.Get(privName(name))
	key, err = unarmorDecryptPrivKey(string(bs), passphrase)
	if err != nil {
		return
	}

	sig = key.Sign(msg)
	pk = key.PubKey()
	return
}

// Export decodes the private key with the current password, encodes
// it with a secure one-time password and generates a sequence that can be
// Imported by another dbKeybase
//
// This is designed to copy from one device to another, or provide backups
// during version updates.
func (kb dbKeybase) Export(name, oldpass, transferpass string) ([]byte, error) {
	bs := kb.db.Get(privName(name))
	key, err := unarmorDecryptPrivKey(string(bs), oldpass)
	if err != nil {
		return nil, err
	}

	if transferpass == "" {
		return key.Bytes(), nil
	}
	res := encryptArmorPrivKey(key, transferpass)
	return []byte(res), nil
}

// Import accepts bytes generated by Export along with the same transferpass
// If they are valid, it stores the password under the given name with the
// new passphrase.
func (kb dbKeybase) Import(name, newpass, transferpass string, data []byte) (err error) {
	var key crypto.PrivKey
	if transferpass == "" {
		key, err = crypto.PrivKeyFromBytes(data)
	} else {
		key, err = unarmorDecryptPrivKey(string(data), transferpass)
	}
	if err != nil {
		return err
	}

	kb.writeKey(key, name, newpass)
	return nil
}

// Delete removes key forever, but we must present the
// proper passphrase before deleting it (for security)
func (kb dbKeybase) Delete(name, passphrase string) error {
	// verify we have the proper password before deleting
	bs := kb.db.Get(privName(name))
	_, err := unarmorDecryptPrivKey(string(bs), passphrase)
	if err != nil {
		return err
	}
	kb.db.DeleteSync(pubName(name))
	kb.db.DeleteSync(privName(name))
	return nil
}

// Update changes the passphrase with which a already stored key is encoded.
//
// oldpass must be the current passphrase used for encoding, newpass will be
// the only valid passphrase from this time forward
func (kb dbKeybase) Update(name, oldpass, newpass string) error {
	bs := kb.db.Get(privName(name))
	key, err := unarmorDecryptPrivKey(string(bs), oldpass)
	if err != nil {
		return err
	}

	// we must delete first, as Putting over an existing name returns an error
	kb.db.DeleteSync(pubName(name))
	kb.db.DeleteSync(privName(name))
	kb.writeKey(key, name, newpass)
	return nil
}

func (kb dbKeybase) writeKey(priv crypto.PrivKey, name, passphrase string) Info {
	// generate the public bytes
	public := info(name, priv)
	// generate the encrypted privkey
	private := encryptArmorPrivKey(priv, passphrase)

	// write them both
	kb.db.SetSync(pubName(name), public.bytes())
	kb.db.SetSync(privName(name), []byte(private))

	return public
}

func generate(algo string, secret []byte) (crypto.PrivKey, error) {
	switch algo {
	case crypto.NameEd25519:
		return crypto.GenPrivKeyEd25519FromSecret(secret).Wrap(), nil
	case crypto.NameSecp256k1:
		return crypto.GenPrivKeySecp256k1FromSecret(secret).Wrap(), nil
	case nano.NameLedgerEd25519:
		return nano.NewPrivKeyLedgerEd25519Ed25519()
	default:
		err := errors.Errorf("Cannot generate keys for algorithm: %s", algo)
		return crypto.PrivKey{}, err
	}
}

func generateByType(typ byte, secret []byte) (crypto.PrivKey, error) {
	switch typ {
	case crypto.TypeEd25519:
		return generate(crypto.NameEd25519, secret)
	case crypto.TypeSecp256k1:
		return generate(crypto.NameSecp256k1, secret)
	case nano.TypeLedgerEd25519:
		return generate(nano.NameLedgerEd25519, secret)
	default:
		err := errors.Errorf("Cannot generate keys for algorithm: %X", typ)
		return crypto.PrivKey{}, err
	}
}

func pubName(name string) []byte {
	return []byte(fmt.Sprintf("%s.pub", name))
}

func privName(name string) []byte {
	return []byte(fmt.Sprintf("%s.priv", name))
}

func isPub(name []byte) bool {
	return strings.HasSuffix(string(name), ".pub")
}