// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package accounts

import (
	"bytes"
	"crypto/ecdsa"
	"encoding/hex"
	"encoding/json"
	"io"
	"strings"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/crypto/secp256k1"
	"github.com/pborman/uuid"
)

const (
	version = 3
)

type Key struct {
	Id uuid.UUID // Version 4 "random" for unique id not derived from key data
	// to simplify lookups we also store the address
	Address common.Address
	// we only store privkey as pubkey/address can be derived from it
	// privkey in this struct is always in plaintext
	PrivateKey *ecdsa.PrivateKey
}

type keyStore interface {
	// create new key using io.Reader entropy source and optionally using auth string
	GenerateNewKey(io.Reader, string) (*Key, error)
	GetKey(common.Address, string) (*Key, error) // get key from addr and auth string
	GetKeyAddresses() ([]common.Address, error)  // get all addresses
	StoreKey(*Key, string) error                 // store key optionally using auth string
	DeleteKey(common.Address, string) error      // delete key by addr and auth string
	Cleanup(keyAddr common.Address) (err error)
}

type plainKeyJSON struct {
	Address    string `json:"address"`
	PrivateKey string `json:"privatekey"`
	Id         string `json:"id"`
	Version    int    `json:"version"`
}

type encryptedKeyJSONV3 struct {
	Address string     `json:"address"`
	Crypto  cryptoJSON `json:"crypto"`
	Id      string     `json:"id"`
	Version int        `json:"version"`
}

type encryptedKeyJSONV1 struct {
	Address string     `json:"address"`
	Crypto  cryptoJSON `json:"crypto"`
	Id      string     `json:"id"`
	Version string     `json:"version"`
}

type cryptoJSON struct {
	Cipher       string                 `json:"cipher"`
	CipherText   string                 `json:"ciphertext"`
	CipherParams cipherparamsJSON       `json:"cipherparams"`
	KDF          string                 `json:"kdf"`
	KDFParams    map[string]interface{} `json:"kdfparams"`
	MAC          string                 `json:"mac"`
}

type cipherparamsJSON struct {
	IV string `json:"iv"`
}

type scryptParamsJSON struct {
	N     int    `json:"n"`
	R     int    `json:"r"`
	P     int    `json:"p"`
	DkLen int    `json:"dklen"`
	Salt  string `json:"salt"`
}

func (k *Key) MarshalJSON() (j []byte, err error) {
	jStruct := plainKeyJSON{
		hex.EncodeToString(k.Address[:]),
		hex.EncodeToString(crypto.FromECDSA(k.PrivateKey)),
		k.Id.String(),
		version,
	}
	j, err = json.Marshal(jStruct)
	return j, err
}

func (k *Key) UnmarshalJSON(j []byte) (err error) {
	keyJSON := new(plainKeyJSON)
	err = json.Unmarshal(j, &keyJSON)
	if err != nil {
		return err
	}

	u := new(uuid.UUID)
	*u = uuid.Parse(keyJSON.Id)
	k.Id = *u
	addr, err := hex.DecodeString(keyJSON.Address)
	if err != nil {
		return err
	}

	privkey, err := hex.DecodeString(keyJSON.PrivateKey)
	if err != nil {
		return err
	}

	k.Address = common.BytesToAddress(addr)
	k.PrivateKey = crypto.ToECDSA(privkey)

	return nil
}

func newKeyFromECDSA(privateKeyECDSA *ecdsa.PrivateKey) *Key {
	id := uuid.NewRandom()
	key := &Key{
		Id:         id,
		Address:    crypto.PubkeyToAddress(privateKeyECDSA.PublicKey),
		PrivateKey: privateKeyECDSA,
	}
	return key
}

func NewKey(rand io.Reader) *Key {
	randBytes := make([]byte, 64)
	_, err := rand.Read(randBytes)
	if err != nil {
		panic("key generation: could not read from random source: " + err.Error())
	}
	reader := bytes.NewReader(randBytes)
	privateKeyECDSA, err := ecdsa.GenerateKey(secp256k1.S256(), reader)
	if err != nil {
		panic("key generation: ecdsa.GenerateKey failed: " + err.Error())
	}

	return newKeyFromECDSA(privateKeyECDSA)
}

// generate key whose address fits into < 155 bits so it can fit into
// the Direct ICAP spec. for simplicity and easier compatibility with
// other libs, we retry until the first byte is 0.
func NewKeyForDirectICAP(rand io.Reader) *Key {
	randBytes := make([]byte, 64)
	_, err := rand.Read(randBytes)
	if err != nil {
		panic("key generation: could not read from random source: " + err.Error())
	}
	reader := bytes.NewReader(randBytes)
	privateKeyECDSA, err := ecdsa.GenerateKey(secp256k1.S256(), reader)
	if err != nil {
		panic("key generation: ecdsa.GenerateKey failed: " + err.Error())
	}
	key := newKeyFromECDSA(privateKeyECDSA)
	if !strings.HasPrefix(key.Address.Hex(), "0x00") {
		return NewKeyForDirectICAP(rand)
	}
	return key
}