Created a WalletManager to manage the user's wallets.

Replace Create/Recover and Load methods to use it.

Breeze/Breeze.vs2017.sln

 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26403.0
+VisualStudioVersion = 15.0.26403.7
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{807563C4-7259-434D-B604-A14C3DCF8E30}"
 EndProject

Breeze/src/Breeze.Api.Tests/ControllersTests.cs

@@ -6,6 +6,7 @@ using Moq;
 using Breeze.Wallet.Wrappers;
 using Breeze.Wallet;
 using Breeze.Wallet.Controllers;
+using Breeze.Wallet.Errors;
 using Breeze.Wallet.Models;
 
 namespace Breeze.Api.Tests
@@ -122,7 +123,7 @@ namespace Breeze.Api.Tests
 
             // Assert
             mockWalletWrapper.VerifyAll();
-            var viewResult = Assert.IsType<ObjectResult>(result);
+            var viewResult = Assert.IsType<ErrorResult>(result);
             Assert.NotNull(viewResult);		
             Assert.Equal(404, viewResult.StatusCode);
         }

Breeze/src/Breeze.Wallet/Controllers/WalletController.cs

@@ -48,7 +48,7 @@ namespace Breeze.Wallet.Controllers
                 var mnemonic = this.walletWrapper.Create(request.Password, walletFolder.FullName, request.Name, request.Network);
                 return this.Json(mnemonic);
             }
-            catch (NotSupportedException e)
+            catch (InvalidOperationException e)
             {
 				// indicates that this wallet already exists
 				return ErrorHelpers.BuildErrorResponse(HttpStatusCode.Conflict, "This wallet already exists.", e.ToString());
@@ -119,6 +119,11 @@ namespace Breeze.Wallet.Controllers
                 var wallet = this.walletWrapper.Recover(request.Password, walletFolder.FullName, request.Name, request.Network, request.Mnemonic);
                 return this.Json(wallet);
             }
+            catch (InvalidOperationException e)
+            {
+                // indicates that this wallet already exists
+                return ErrorHelpers.BuildErrorResponse(HttpStatusCode.Conflict, "This wallet already exists.", e.ToString());
+            }
             catch (FileNotFoundException e)
             {
 				// indicates that this wallet does not exist

Breeze/src/Breeze.Wallet/IWalletManager.cs

+using System;
+using NBitcoin;
+
+namespace Breeze.Wallet
+{
+    /// <summary>
+    /// Interface for a manager providing operations on wallets.
+    /// </summary>
+    public interface IWalletManager : IDisposable
+    {
+        /// <summary>
+        /// Creates a wallet and persist it as a file on the local system.
+        /// </summary>
+        /// <param name="password">The password used to encrypt sensitive info.</param>
+        /// <param name="passphrase">The passphrase used in the seed.</param>
+        /// <param name="walletFilePath">The path where the wallet file will be created.</param>
+        /// <param name="network">The network this wallet is for.</param>
+        /// <returns>A mnemonic defining the wallet's seed used to generate addresses.</returns>
+        Mnemonic CreateWallet(string password, string walletFilePath, Network network, string passphrase = null);
+
+        /// <summary>
+        /// Loads a wallet from a file.
+        /// </summary>
+        /// <param name="password">The password used to encrypt sensitive info.</param>
+        /// <param name="walletFilePath">The location of the wallet file.</param>
+        /// <returns>The wallet.</returns>
+        Wallet LoadWallet(string password, string walletFilePath);
+
+        /// <summary>
+        /// Recovers a wallet.
+        /// </summary>
+        /// <param name="mnemonic">A mnemonic defining the wallet's seed used to generate addresses.</param>
+        /// <param name="password">The password used to encrypt sensitive info.</param>
+        /// <param name="walletFilePath">The location of the wallet file.</param>
+        /// <param name="network">The network this wallet is for.</param>
+        /// <param name="passphrase">The passphrase used in the seed.</param>
+        /// <param name="creationTime">The time this wallet was created.</param>
+        /// <returns>The recovered wallet.</returns>
+        Wallet RecoverWallet(Mnemonic mnemonic, string password, string walletFilePath, Network network, string passphrase = null, DateTimeOffset? creationTime = null);
+
+        /// <summary>
+        /// Deleted a wallet.
+        /// </summary>
+        /// <param name="walletFilePath">The location of the wallet file.</param>        
+        void DeleteWallet(string walletFilePath);
+    }
+}

Breeze/src/Breeze.Wallet/JsonConverters/ByteArrayConverter.cs

+using System;
+using System.Collections.Generic;
+using System.Text;
+using Newtonsoft.Json;
+
+namespace Breeze.Wallet.JsonConverters
+{
+    /// <summary>
+    /// Converter used to convert <see cref="byte"/> arrays to and from JSON.
+    /// </summary>
+    /// <seealso cref="Newtonsoft.Json.JsonConverter" />
+    public class ByteArrayConverter : JsonConverter
+    {
+        /// <inheritdoc />
+        public override bool CanConvert(Type objectType)
+        {
+            return objectType == typeof(byte[]);
+        }
+
+        /// <inheritdoc />
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            return Convert.FromBase64String((string)reader.Value);
+        }
+
+        /// <inheritdoc />
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            writer.WriteValue(Convert.ToBase64String((byte[])value));
+        }
+    }
+}

Breeze/src/Breeze.Wallet/JsonConverters/DateTimeOffsetConverter.cs

+using Newtonsoft.Json;
+using System;
+
+namespace Breeze.Wallet.JsonConverters
+{
+    /// <summary>
+    /// Converter used to convert <see cref="DateTimeOffset"/> to and from Unix time.
+    /// </summary>
+    /// <seealso cref="Newtonsoft.Json.JsonConverter" />
+    public class DateTimeOffsetConverter : JsonConverter
+    {
+        /// <inheritdoc />
+        public override bool CanConvert(Type objectType)
+        {
+            return objectType == typeof(DateTimeOffset);
+        }
+
+        /// <inheritdoc />
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            return DateTimeOffset.FromUnixTimeMilliseconds(long.Parse((string)reader.Value));            
+        }
+
+        /// <inheritdoc />
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {            
+            writer.WriteValue(((DateTimeOffset)value).ToUnixTimeMilliseconds().ToString());
+        }
+    }
+}

Breeze/src/Breeze.Wallet/JsonConverters/NetworkConverter.cs

+using System;
+using Breeze.Wallet.Helpers;
+using NBitcoin;
+using Newtonsoft.Json;
+
+namespace Breeze.Wallet.JsonConverters
+{
+    /// <summary>
+    /// Converter used to convert <see cref="Network"/> to and from JSON.
+    /// </summary>
+    /// <seealso cref="Newtonsoft.Json.JsonConverter" />
+    public class NetworkConverter : JsonConverter
+    {
+        /// <inheritdoc />
+        public override bool CanConvert(Type objectType)
+        {
+            return objectType == typeof(Network);
+        }
+
+        /// <inheritdoc />
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            return WalletHelpers.GetNetwork((string)reader.Value);
+        }
+
+        /// <inheritdoc />
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            writer.WriteValue(((Network)value).ToString());
+        }
+    }
+}

Breeze/src/Breeze.Wallet/Wallet.cs

+using System;
+using NBitcoin;
+
+namespace Breeze.Wallet
+{
+    /// <summary>
+    /// A wallet
+    /// </summary>
+    public class Wallet
+    {
+        /// <summary>
+        /// The chain code. 
+        /// </summary>
+        public byte[] ChainCode { get; set; }
+
+        /// <summary>
+        /// The network this wallet is for.
+        /// </summary>
+        public Network Network { get; set; }
+
+        /// <summary>
+        /// The time this wallet was created.
+        /// </summary>
+        public DateTimeOffset CreationTime { get; set; }
+
+        /// <summary>
+        /// The location of the wallet file on the local system.
+        /// </summary>
+        public string WalletFilePath { get; set; }
+
+        /// <summary>
+        /// The key used to generate keys.
+        /// </summary>
+        public ExtKey ExtendedKey { get; set; }
+    }
+}
\ No newline at end of file

Breeze/src/Breeze.Wallet/WalletFeature.cs

@@ -41,6 +41,7 @@ namespace Breeze.Wallet
 				{
 					services.AddTransient<IWalletWrapper, WalletWrapper>();
 					services.AddTransient<ITrackerWrapper, TrackerWrapper>();
+				    services.AddSingleton<IWalletManager, WalletManager>();
 					services.AddSingleton<WalletController>();
 				});
 			});

Breeze/src/Breeze.Wallet/WalletFile.cs

+using System;
+using NBitcoin;
+using Newtonsoft.Json;
+using Breeze.Wallet.JsonConverters;
+
+namespace Breeze.Wallet
+{
+    /// <summary>
+    /// An object representing a wallet on a local file system.
+    /// </summary>
+    public class WalletFile
+    {
+        /// <summary>
+        /// The seed for this wallet, password encrypted.
+        /// </summary>
+        [JsonProperty(PropertyName = "encryptedSeed")]
+        public string EncryptedSeed { get; set; }
+
+        /// <summary>
+        /// The chain code. 
+        /// </summary>
+        [JsonProperty(PropertyName = "chainCode")]
+        [JsonConverter(typeof(ByteArrayConverter))]
+        public byte[] ChainCode { get; set; }
+
+        /// <summary>
+        /// The network this wallet is for.
+        /// </summary>
+        [JsonProperty(PropertyName = "network")]
+        [JsonConverter(typeof(NetworkConverter))]
+        public Network Network { get; set; }
+
+        /// <summary>
+        /// The time this wallet was created.
+        /// </summary>
+        [JsonProperty(PropertyName = "creationTime")]
+        [JsonConverter(typeof(DateTimeOffsetConverter))]
+        public DateTimeOffset CreationTime { get; set; }
+    }
+}

Breeze/src/Breeze.Wallet/WalletManager.cs

+using System;
+using System.IO;
+using NBitcoin;
+using Newtonsoft.Json;
+
+namespace Breeze.Wallet
+{
+    /// <summary>
+    /// A manager providing operations on wallets.
+    /// </summary>
+    public class WalletManager : IWalletManager
+    {        
+        /// <inheritdoc />
+        public Mnemonic CreateWallet(string password, string walletFilePath, Network network, string passphrase = null)
+        {
+            // generate the root seed used to generate keys from a mnemonic picked at random 
+            // and a passphrase optionally provided by the user
+            Mnemonic mnemonic = new Mnemonic(Wordlist.English, WordCount.Twelve);
+            ExtKey extendedKey = mnemonic.DeriveExtKey(passphrase);
+
+            // create a wallet file 
+            this.GenerateWalletFile(password, walletFilePath, network, extendedKey);
+            
+            return mnemonic;
+        }
+
+        /// <inheritdoc />
+        public Wallet LoadWallet(string password, string walletFilePath)
+        {
+            if (!File.Exists(walletFilePath))
+                throw new FileNotFoundException($"No wallet file found at {walletFilePath}");
+
+            // load the file from the local system
+            WalletFile walletFile = JsonConvert.DeserializeObject<WalletFile>(File.ReadAllText(walletFilePath));
+
+            // decrypt the private key and use it to regenerate the seed
+            var privateKey = Key.Parse(walletFile.EncryptedSeed, password, walletFile.Network);
+            var seedExtKey = new ExtKey(privateKey, walletFile.ChainCode);
+
+            Wallet wallet = new Wallet
+            {
+                ChainCode = walletFile.ChainCode,
+                CreationTime = walletFile.CreationTime,
+                Network = walletFile.Network,
+                WalletFilePath = walletFilePath,
+                ExtendedKey = seedExtKey
+            };
+            
+            return wallet;
+        }
+
+        /// <inheritdoc />
+        public Wallet RecoverWallet(Mnemonic mnemonic, string password, string walletFilePath, Network network, string passphrase = null, DateTimeOffset? creationTime = null)
+        {
+            // generate the root seed used to generate keys
+            ExtKey extendedKey = mnemonic.DeriveExtKey(passphrase);
+
+            // create a wallet file 
+            WalletFile walletFile = this.GenerateWalletFile(password, walletFilePath, network, extendedKey, creationTime);
+            
+            Wallet wallet = new Wallet
+            {
+                ChainCode = walletFile.ChainCode,
+                CreationTime = walletFile.CreationTime,
+                Network = walletFile.Network,
+                WalletFilePath = walletFilePath,
+                ExtendedKey = extendedKey
+            };
+
+            return wallet;
+        }
+        
+        /// <inheritdoc />
+        public void DeleteWallet(string walletFilePath)
+        {
+            File.Delete(walletFilePath);
+        }
+        
+        /// <inheritdoc />
+        public void Dispose()
+        {
+            // TODO Safely persist the wallet before disposing
+        }
+
+        /// <summary>
+        /// Generates the wallet file.
+        /// </summary>
+        /// <param name="password">The password used to encrypt sensitive info.</param>
+        /// <param name="walletFilePath">The location of the wallet file.</param>
+        /// <param name="network">The network this wallet is for.</param>
+        /// <param name="extendedKey">The root key used to generate keys.</param>
+        /// <param name="creationTime">The time this wallet was created.</param>
+        /// <returns></returns>
+        /// <exception cref="System.NotSupportedException"></exception>
+        private WalletFile GenerateWalletFile(string password, string walletFilePath, Network network, ExtKey extendedKey, DateTimeOffset? creationTime = null)
+        {
+            if (File.Exists(walletFilePath))
+                throw new InvalidOperationException($"Wallet already exists at {walletFilePath}");
+
+            WalletFile walletFile = new WalletFile
+            {
+                EncryptedSeed = extendedKey.PrivateKey.GetEncryptedBitcoinSecret(password, network).ToWif(),
+                ChainCode = extendedKey.ChainCode,
+                CreationTime = creationTime ?? DateTimeOffset.Now,
+                Network = network
+            };
+
+            // create a folder if none exists and persist the file
+            Directory.CreateDirectory(Path.GetDirectoryName(Path.GetFullPath(walletFilePath)));
+            File.WriteAllText(walletFilePath, JsonConvert.SerializeObject(walletFile, Formatting.Indented));
+
+            return walletFile;
+        }
+    }
+}

Breeze/src/Breeze.Wallet/Wrappers/WalletWrapper.cs

@@ -13,7 +13,14 @@ namespace Breeze.Wallet.Wrappers
 	/// </summary>
 	public class WalletWrapper : IWalletWrapper
 	{
-		/// <summary>
+	    private readonly IWalletManager walletManager;
+
+	    public WalletWrapper(IWalletManager walletManager)
+	    {
+	        this.walletManager = walletManager;
+	    }
+
+	    /// <summary>
 		/// Creates a wallet on the local device.
 		/// </summary>
 		/// <param name="password">The user's password.</param>
@@ -22,9 +29,8 @@ namespace Breeze.Wallet.Wrappers
 		/// <param name="network">The network for which to create a wallet.</param>
 		/// <returns>A mnemonic allowing recovery of the wallet.</returns>
 		public string Create(string password, string folderPath, string name, string network)
-		{			
-			Mnemonic mnemonic;
-			Safe wallet = Safe.Create(out mnemonic, password, Path.Combine(folderPath, $"{name}.json"), WalletHelpers.GetNetwork(network));
+		{						
+            Mnemonic mnemonic = this.walletManager.CreateWallet(password, Path.Combine(folderPath, $"{name}.json"), WalletHelpers.GetNetwork(network), password);
 			return mnemonic.ToString();
 		}
 
@@ -36,14 +42,14 @@ namespace Breeze.Wallet.Wrappers
 		/// <param name="name">The name of the wallet.</param>
 		/// <returns>The wallet loaded from the local device</returns>
 		public WalletModel Load(string password, string folderPath, string name)
-		{
-			Safe wallet = Safe.Load(password, Path.Combine(folderPath, $"{name}.json"));
-
-			//TODO review here which data should be returned
+		{		    
+		    Wallet wallet = this.walletManager.LoadWallet(password, Path.Combine(folderPath, $"{name}.json"));
+			
+            //TODO review here which data should be returned
 			return new WalletModel
 			{
 				Network = wallet.Network.Name,
-				Addresses = wallet.GetFirstNAddresses(10).Select(a => a.ToWif()),
+			//	Addresses = wallet.GetFirstNAddresses(10).Select(a => a.ToWif()),
 				FileName = wallet.WalletFilePath
 			};
 		}
@@ -59,13 +65,13 @@ namespace Breeze.Wallet.Wrappers
 		/// <returns></returns>
 		public WalletModel Recover(string password, string folderPath, string name, string network, string mnemonic)
 		{
-			Safe wallet = Safe.Recover(new Mnemonic(mnemonic), password, Path.Combine(folderPath, $"{name}.json"), WalletHelpers.GetNetwork(network));
-
+		    Wallet wallet = this.walletManager.RecoverWallet(new Mnemonic(mnemonic), password, Path.Combine(folderPath, $"{name}.json"), WalletHelpers.GetNetwork(network), password);
+			
 			//TODO review here which data should be returned
 			return new WalletModel
 			{
 				Network = wallet.Network.Name,
-				Addresses = wallet.GetFirstNAddresses(10).Select(a => a.ToWif()),
+			//	Addresses = wallet.GetFirstNAddresses(10).Select(a => a.ToWif()),
 				FileName = wallet.WalletFilePath
 			};
 		}