Backend,Frontend: import wallet using BIP39 seed

Added option to import wallet using BIP39 seed phrase
(mnemonic). All funds from imported wallet (currently only
first receiving address is used) are sent to BTC account of
choice. After that, imported account is converted to archived
account so geewallet will warn the user if more funds arrive
to it in the future.

src/GWallet.Backend/Account.fs

@@ -7,6 +7,8 @@ open System.Threading.Tasks
 
 open GWallet.Backend.FSharpUtil.UwpHacks
 
+open NBitcoin
+
 // this exception, if it happens, it would cause a crash because we don't handle it yet
 type UnhandledCurrencyServerException(currency: Currency,
                                       innerException: Exception) =
@@ -394,6 +396,43 @@ module Account =
         |> ignore<ArchivedAccount>
         Config.RemoveNormalAccount account
 
+    let CreateEphemeralAccountFromSeedMenmonic (mnemonic: string) : UtxoCoin.EphemeralUtxoAccount =
+        let standardBip84DerivationPath = KeyPath("m/84'/0'/0'")
+        let rootKey = Mnemonic(mnemonic).DeriveExtKey().Derive(standardBip84DerivationPath)
+        let firstReceivingAddressKey = rootKey.Derive(0u).Derive(0u)
+
+        let currency = Currency.BTC
+        let network = UtxoCoin.Account.GetNetwork currency
+        let privateKeyString =
+            firstReceivingAddressKey.PrivateKey.GetWif(network).ToWif()
+
+        let fromPublicKeyToPublicAddress (publicKey: PubKey) =
+            publicKey.GetAddress(ScriptPubKeyType.Segwit, network).ToString()
+
+        let fromAccountFileToPrivateKey (accountConfigFile: FileRepresentation) =
+            Key.Parse(accountConfigFile.Content(), network)
+
+        let fromAccountFileToPublicAddress (accountConfigFile: FileRepresentation) =
+            fromPublicKeyToPublicAddress(fromAccountFileToPrivateKey(accountConfigFile).PubKey)
+
+        let fromAccountFileToPublicKey (accountConfigFile: FileRepresentation) =
+            fromAccountFileToPrivateKey(accountConfigFile).PubKey
+
+        let fileName = fromPublicKeyToPublicAddress(firstReceivingAddressKey.GetPublicKey())
+        let accountFileRepresentation = { Name = fileName; Content = fun _ -> privateKeyString }
+
+        UtxoCoin.EphemeralUtxoAccount(
+            currency, 
+            accountFileRepresentation,
+            fromAccountFileToPublicAddress,
+            fromAccountFileToPublicKey
+        )
+
+    let ConvertEphemeralAccountToArchivedAccount (ephemeralAccount: EphemeralAccount) (currency: Currency) : unit  =
+        // no need for removing account since we don't create any file to begin with (see CreateEphemeralAccountFromSeedMenmonic)
+        let privateKeyAsString = ephemeralAccount.GetUnencryptedPrivateKey()
+        CreateArchivedAccount currency privateKeyAsString |> ignore<ArchivedAccount>
+
     let SweepArchivedFunds (account: ArchivedAccount)
                            (balance: decimal)
                            (destination: IAccount)

src/GWallet.Backend/AccountTypes.fs

@@ -2,9 +2,11 @@ namespace GWallet.Backend
 
 open System.IO
 
+type UtxoPublicKey = string
+
 type WatchWalletInfo =
     {
-        UtxoCoinPublicKey: string
+        UtxoCoinPublicKey: UtxoPublicKey
         EtherPublicAddress: string
     }
 
@@ -30,6 +32,7 @@ type AccountKind =
     | Normal
     | ReadOnly
     | Archived
+    | Ephemeral
     static member All() =
         seq {
             yield Normal
@@ -77,3 +80,11 @@ type ArchivedAccount(currency: Currency, accountFile: FileRepresentation,
         accountFile.Content()
 
     override __.Kind = AccountKind.Archived
+
+/// Inherits from ArchivedAccount because SweepArchivedFunds expects ArchivedAccount instance
+/// and sweep funds functionality is needed for this kind of account.
+type EphemeralAccount(currency: Currency, accountFile: FileRepresentation,
+                      fromAccountFileToPublicAddress: FileRepresentation -> string) =
+    inherit ArchivedAccount(currency, accountFile, fromAccountFileToPublicAddress)
+
+    override __.Kind = AccountKind.Ephemeral

src/GWallet.Backend/Config.fs

@@ -110,6 +110,8 @@ module Config =
                 Path.Combine(accountConfigDir, "readonly")
             | AccountKind.Archived ->
                 Path.Combine(accountConfigDir, "archived")
+            | AccountKind.Ephemeral ->
+                failwith "Ephemeral accounts are not supposed to be stored in file"
 
         let configDir = Path.Combine(baseConfigDir, currency.ToString()) |> DirectoryInfo
         if not configDir.Exists then

src/GWallet.Backend/UtxoCoin/UtxoCoinAccount.fs

@@ -52,6 +52,14 @@ type ArchivedUtxoAccount(currency: Currency, accountFile: FileRepresentation,
     interface IUtxoAccount with
         member val PublicKey = fromAccountFileToPublicKey accountFile with get
 
+type EphemeralUtxoAccount(currency: Currency, accountFile: FileRepresentation,
+                          fromAccountFileToPublicAddress: FileRepresentation -> string,
+                          fromAccountFileToPublicKey: FileRepresentation -> PubKey) =
+    inherit GWallet.Backend.EphemeralAccount(currency, accountFile, fromAccountFileToPublicAddress)
+
+    interface IUtxoAccount with
+        member val PublicKey = fromAccountFileToPublicKey accountFile with get
+
 module Account =
 
     let internal GetNetwork (currency: Currency) =

src/GWallet.Frontend.Console/Program.fs

@@ -326,6 +326,7 @@ module Program =
         | TestPaymentPassword
         | TestSeedPassphrase
         | WipeWallet
+        | TransferFundsFromWalletUsingMenmonic
 
     let rec TestPaymentPassword () =
         let password = UserInteraction.AskPassword false
@@ -348,13 +349,107 @@ module Program =
             Account.WipeAll()
         else
             ()
+
+    let TransferFundsFromWalletUsingMenmonic() =
+        let rec askForMnemonic() : UtxoCoin.EphemeralUtxoAccount =
+            Console.WriteLine "Enter mnemonic seed phrase (12, 15, 18, 21 or 24 words):"
+            let mnemonic = Console.ReadLine()
+            try
+                Account.CreateEphemeralAccountFromSeedMenmonic mnemonic
+            with
+            | :? FormatException as exn ->
+                printfn "Error reading mnemonic seed phrase: %s" exn.Message
+                askForMnemonic()
+
+        let importedAccount = askForMnemonic()
+        let currency = BTC
+
+        let maybeTotalBalance, maybeUsdValue = UserInteraction.GetAccountBalance importedAccount |> Async.RunSynchronously
+        match maybeTotalBalance with
+        | NotFresh _ ->
+            Console.WriteLine "Could not retrieve balance."
+            UserInteraction.PressAnyKeyToContinue()
+        | Fresh 0.0m ->
+            Console.WriteLine "Balance on imported account is zero. No funds to transfer."
+            UserInteraction.PressAnyKeyToContinue()
+        | Fresh balance ->
+            printfn
+                "Balance on imported account: %s BTC (%s)"
+                    (balance.ToString())
+                    (UserInteraction.BalanceInUsdString balance maybeUsdValue)
+
+            let rec chooseAccount() =
+                Console.WriteLine "Choose account to send funds to:"
+                Console.WriteLine()
+                let allAccounts = Account.GetAllActiveAccounts() |> Seq.toList
+                let btcAccounts = allAccounts |> List.filter (fun acc -> acc.Currency = currency)
+
+                match btcAccounts with
+                | [ singleAccount ] -> Some singleAccount
+                | [] -> 
+                    printfn "No BTC accounts found."
+                    None
+                | _ ->
+                    allAccounts |> Seq.iteri (fun i account ->
+                        if account.Currency = currency then
+                            let balance, maybeUsdValue = 
+                                UserInteraction.GetAccountBalance account
+                                |> Async.RunSynchronously
+                            UserInteraction.DisplayAccountStatus (i + 1) account balance maybeUsdValue
+                                |> Seq.iter Console.WriteLine
+                    )
+
+                    Console.Write "Write the account number (or 0 to cancel): "
+                    let accountNumber = Console.ReadLine()
+                    match Int32.TryParse accountNumber with
+                    | false, _ -> chooseAccount()
+                    | true, 0 -> None
+                    | true, accountParsed ->
+                        let theAccountChosen =
+                            try
+                                let selectedAccount = allAccounts.[accountParsed - 1]
+                                if selectedAccount.Currency = BTC then
+                                    Some selectedAccount
+                                else
+                                    chooseAccount()
+                            with
+                            | _ -> chooseAccount()
+                        theAccountChosen
+
+            match chooseAccount() with
+            | Some targetAccount ->
+                let destination = targetAccount.PublicAddress
+                let transferAmount = TransferAmount(balance, balance, currency) // send all funds
+                let maybeFee = UserInteraction.AskFee importedAccount transferAmount destination
+                match maybeFee with
+                | None -> ()
+                | Some fee ->
+                    let txId = 
+                        Account.SweepArchivedFunds 
+                            importedAccount
+                            balance
+                            targetAccount
+                            fee
+                            false
+                        |>  Async.RunSynchronously
+                    let uri = BlockExplorer.GetTransaction currency txId
+                    printfn "Transaction successful:"
+                    printfn "%s" (uri.ToString())
+                    Console.WriteLine()
+                    printf "Archiving imported account..."
+                    Account.ConvertEphemeralAccountToArchivedAccount importedAccount currency
+                    printfn " done."
+                    UserInteraction.PressAnyKeyToContinue()
+            | None ->
+                UserInteraction.PressAnyKeyToContinue()
 
     let WalletOptions(): unit =
         let rec AskWalletOption(): GenericWalletOption =
             Console.WriteLine "0. Cancel, go back"
             Console.WriteLine "1. Check you still remember your payment password"
             Console.WriteLine "2. Check you still remember your secret recovery phrase"
             Console.WriteLine "3. Wipe your current wallet, in order to start from scratch"
+            Console.WriteLine "4. Transfer all funds from another wallet (given mnemonic code)"
             Console.Write "Choose an option from the ones above: "
             let optIntroduced = Console.ReadLine ()
             match UInt32.TryParse optIntroduced with
@@ -365,6 +460,7 @@ module Program =
                 | 1u -> GenericWalletOption.TestPaymentPassword
                 | 2u -> GenericWalletOption.TestSeedPassphrase
                 | 3u -> GenericWalletOption.WipeWallet
+                | 4u -> GenericWalletOption.TransferFundsFromWalletUsingMenmonic
                 | _ -> AskWalletOption()
 
         let walletOption = AskWalletOption()
@@ -377,6 +473,8 @@ module Program =
             Console.WriteLine "Success!"
         | GenericWalletOption.WipeWallet ->
             WipeWallet()
+        | GenericWalletOption.TransferFundsFromWalletUsingMenmonic ->
+            TransferFundsFromWalletUsingMenmonic()
         | _ -> ()
 
     let rec PerformOperation (numActiveAccounts: uint32) (numHotAccounts: uint32) =

src/GWallet.Frontend.Console/UserInteraction.fs

@@ -178,7 +178,7 @@ module UserInteraction =
                 password
 
     // FIXME: share code between Frontend.Console and Frontend.XF
-    let private BalanceInUsdString balance maybeUsdValue =
+    let internal BalanceInUsdString balance maybeUsdValue =
         match maybeUsdValue with
         | NotFresh(NotAvailable) -> Presentation.ExchangeRateUnreachableMsg
         | Fresh(usdValue) ->
@@ -260,7 +260,7 @@ module UserInteraction =
             return (account,balance,usdValue)
         }
 
-    let private GetAccountBalance (account: IAccount): Async<MaybeCached<decimal>*MaybeCached<decimal>> =
+    let internal GetAccountBalance (account: IAccount): Async<MaybeCached<decimal>*MaybeCached<decimal>> =
         async {
             let! (_, balance, maybeUsdValue) = GetAccountBalanceInner account false
             return (balance, maybeUsdValue)