package config

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os/user"
	"strings"

	"github.com/ditcraft/client/helpers"
	"github.com/ethereum/go-ethereum/crypto"
	"golang.org/x/crypto/ssh/terminal"
)

// DitConfig is exported since it needs to be accessed from other packages all the time
var DitConfig ditConfig

type ditConfig struct {
	DitCoordinator   string       `json:"dit_coordinator"`
	KNWVoting        string       `json:"knw_voting"`
	KNWToken         string       `json:"knw_token"`
	DitToken         string       `json:"dit_token,omitempty"`
	Currency         string       `json:"currency"`
	PassedKYC        bool         `json:"passed_kyc"`
	DemoModeActive   bool         `json:"demo_mode_active"`
	EthereumKeys     ethereumKeys `json:"ethereum_keys"`
	LiveRepositories []Repository `json:"live_repositories"`
	DemoRepositories []Repository `json:"demo_repositories"`
}

type ethereumKeys struct {
	PrivateKey string `json:"private_key"`
	Address    string `json:"address"`
}

// Repository struct, exported since its used in the ethereum package for new repositories
type Repository struct {
	Name            string       `json:"name"`
	Provider        string       `json:"provider"`
	KnowledgeLabels []string     `json:"knowledge_labels"`
	ActiveVotes     []ActiveVote `json:"active_votes"`
}

// ActiveVote struct, exported since its used in the ethereum package for new votes
type ActiveVote struct {
	ID             int    `json:"id"`
	KNWVoteID      int    `json:"knw_vote_id"`
	KnowledgeLabel string `json:"knowledge_label"`
	Choice         int    `json:"choice"`
	Salt           int    `json:"salt"`
	NumTokens      int    `json:"num_tokens"`
	NumVotes       int    `json:"num_votes"`
	NumKNW         int    `json:"num_knw"`
	CommitEnd      int    `json:"commit_end"`
	RevealEnd      int    `json:"reveal_end"`
	Resolved       bool   `json:"resolved"`
	DemoChoices    []int  `json:"demo_choices"`
	DemoSalts      []int  `json:"demo_salts"`
}

// GetPrivateKey will prompt the user for his password and return the decrypted ethereum private key
func GetPrivateKey() (string, error) {
	// Prompting the user
	helpers.PrintLine("This action requires to send a transaction to the ethereum blockchain.", 0)
	helpers.Printf("Please provide your password to unlock your ethereum account: ", 0)
	password, err := terminal.ReadPassword(0)
	fmt.Printf("\n")
	if err != nil {
		return "", errors.New("Failed to retrieve password")
	}

	// Converting the encrypted private key from hex to bytes
	encPrivateKey, err := hex.DecodeString(DitConfig.EthereumKeys.PrivateKey)
	if err != nil {
		return "", errors.New("Failed to decode private key from config")
	}

	// Decrypting the private key
	decryptedPrivateKey, err := decrypt(encPrivateKey, string(password))
	if err != nil {
		return "", errors.New("Failed to decrypt the encrypted private key - wrong password?")
	}

	return string(decryptedPrivateKey), nil
}

// Load will load the config and set it to the exported variable "DitConfig"
func Load() error {
	// Retrieve the home directory of the user
	usr, err := user.Current()
	if err != nil {
		return errors.New("Failed to retrieve home-directory of user")
	}

	// Reading the config file
	configFile, err := ioutil.ReadFile(usr.HomeDir + "/.ditconfig")
	if err != nil {
		if strings.Contains(err.Error(), "no such file or directory") {
			return errors.New("Config file not found - please use '" + helpers.ColorizeCommand("setup") + "'")
		}
		return errors.New("Failed to load config file")
	}

	// Parsing the json into a public object
	err = json.Unmarshal(configFile, &DitConfig)
	if err != nil {
		return errors.New("Failed to unmarshal JSON of config file")
	}

	// If the config is valid, it will contain an ethereum address with a length of 42
	if len(DitConfig.EthereumKeys.Address) != 42 {
		return errors.New("Invalid config file")
	}

	return nil
}

// Create will create a new config file
func Create(_demoMode bool) error {
	helpers.PrintLine("Initializing the ditClient...", 0)
	DitConfig = ditConfig{}
	DitConfig.DemoModeActive = _demoMode

	if !DitConfig.DemoModeActive {
		helpers.PrintLine("You are initializing the client in live mode, you will be staking real xDai.", 1)
		helpers.PrintLine("If you just want to play around with dit, you can also use the demo mode with '"+helpers.ColorizeCommand("setup --demo")+"'", 0)
		fmt.Println()
	} else {
		helpers.PrintLine("You are initializing the client in demo mode, feel free to play around with it!", 0)
		helpers.PrintLine("If you want to switch to the live mode later on, you can do so with '"+helpers.ColorizeCommand("mode live")+"'", 0)
		fmt.Println()
	}
	// Prompting the user for his choice on the ethereum key generation/importing
	answerPrivateKeySelection := helpers.GetUserInputChoice("You can either (a) sample a new ethereum private-key or (b) provide your own one", "a", "b")

	// Sample new ethereum Keys
	if answerPrivateKeySelection == "a" {
		address, privateKey, err := sampleEthereumKeys()
		if err != nil {
			return err
		}
		DitConfig.EthereumKeys.PrivateKey = privateKey
		DitConfig.EthereumKeys.Address = address
	} else {
		// Import existing ones, prompting the user for input
		answerPrivateKeyInput := helpers.GetUserInput("Please provide a hex-formatted ethereum private-key")
		if len(answerPrivateKeyInput) == 64 || len(answerPrivateKeyInput) == 66 {
			// Remove possible "0x" at the beginning
			if strings.Contains(answerPrivateKeyInput, "0x") && len(answerPrivateKeyInput) == 66 {
				answerPrivateKeyInput = answerPrivateKeyInput[2:]
			}
			// Import the ethereum private key
			address, privateKey, err := importEthereumKey(answerPrivateKeyInput)
			if err != nil {
				return err
			}

			DitConfig.EthereumKeys.PrivateKey = privateKey
			DitConfig.EthereumKeys.Address = address
		} else {
			return errors.New("Invalid ethereum private-key")
		}
	}

	// Prompting the user to set a password for the private keys encryption
	var password []byte
	keepAsking := true
	for keepAsking {
		helpers.Printf("Please provide a password to encrypt your private key: ", 0)
		var err error
		password, err = terminal.ReadPassword(0)
		fmt.Printf("\n")
		if err != nil {
			return errors.New("Failed to retrieve password")
		}

		// Repeating the password to make sure that there are no typos
		helpers.Printf("Please repeat your password: ", 0)
		passwordAgain, err := terminal.ReadPassword(0)
		fmt.Printf("\n")
		if err != nil {
			return errors.New("Failed to retrieve password")
		}

		// If passwords don't match or are empty
		if string(passwordAgain) != string(password) {
			helpers.PrintLine("Passwords didn't match - try again!", 1)
		} else if len(password) == 0 {
			helpers.PrintLine("Password can't be empty - try again!", 1)
		} else {
			// Stop if nothing of the above is true
			keepAsking = false
		}
	}

	// Encrypt the private keys with the password
	encryptedPrivateKey, err := encrypt([]byte(DitConfig.EthereumKeys.PrivateKey), string(password))
	if err != nil {
		return errors.New("Failed to encrypt ethereum private-key")
	}

	DitConfig.EthereumKeys.PrivateKey = hex.EncodeToString(encryptedPrivateKey)
	DitConfig.LiveRepositories = make([]Repository, 0)
	DitConfig.DemoRepositories = make([]Repository, 0)

	// Write the config to the file
	err = Save()
	if err != nil {
		return err
	}

	helpers.PrintLine("Initialization successfull", 0)
	helpers.PrintLine("Your Ethereum Address is: "+DitConfig.EthereumKeys.Address, 0)

	return nil
}

// Save will write the current config object to the file
func Save() error {
	// Convert the config object to JSON
	jsonBytes, err := json.Marshal(DitConfig)
	if err != nil {
		return errors.New("Failed to marshal JSON of config file")
	}

	// Retrieve the home directory of the user
	usr, err := user.Current()
	if err != nil {
		return errors.New("Failed to retrieve home-directory of user")
	}

	// Write the above into the config file
	err = ioutil.WriteFile(usr.HomeDir+"/.ditconfig", jsonBytes, 0644)
	if err != nil {
		return errors.New("Failed to write config file")
	}

	return nil
}

// importEthereumKey will return the private key and the address of an imported private key
func importEthereumKey(privateKey string) (string, string, error) {
	helpers.PrintLine("Importing ethereum key...", 0)

	// Converting the private key string into a private key object
	key, err := crypto.HexToECDSA(privateKey)
	if err != nil {
		return "", "", errors.New("Failed to import ethereum keys")
	}

	// Calculating the address based on the privat key object
	address := crypto.PubkeyToAddress(key.PublicKey).Hex()

	// Converting the private key to string
	privateKey = hex.EncodeToString(key.D.Bytes())

	return address, privateKey, err
}

func sampleEthereumKeys() (string, string, error) {
	helpers.PrintLine("Sampling ethereum key...", 0)

	// Sampling a new private key
	key, err := crypto.GenerateKey()
	if err != nil {
		return "", "", errors.New("Failed to generate ethereum keys")
	}

	// Calculating the address based on the privat key object
	address := crypto.PubkeyToAddress(key.PublicKey).Hex()

	// Converting the private key to string
	privateKey := hex.EncodeToString(key.D.Bytes())

	return address, privateKey, err
}

// from: https://www.thepolyglotdeveloper.com/2018/02/encrypt-decrypt-data-golang-application-crypto-packages/
func encrypt(data []byte, passphrase string) ([]byte, error) {
	block, _ := aes.NewCipher([]byte(createHash(passphrase)))
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, err
	}
	ciphertext := gcm.Seal(nonce, nonce, data, nil)
	return ciphertext, nil
}

// from: https://www.thepolyglotdeveloper.com/2018/02/encrypt-decrypt-data-golang-application-crypto-packages/
func decrypt(data []byte, passphrase string) ([]byte, error) {
	key := []byte(createHash(passphrase))
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	nonceSize := gcm.NonceSize()
	nonce, ciphertext := data[:nonceSize], data[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return nil, err
	}
	return plaintext, err
}

func createHash(key string) string {
	hasher := sha256.New()
	hasher.Write([]byte(key))
	return hex.EncodeToString(hasher.Sum(nil))[0:32]
}