MQTT Wire Encoding / Decoding (#7)

* add MQTT protocol version

* optimized enums to `byte` data storage

* make the compiler happy

* added some basic tests for packet types

* more fixes

* added MQTT 3.1.1 ConnectPacket size estimation specs

* fixed some failing specs

* adjusted namespaces

* added MQTT5 size estimation specs

* fixed the ASCII indicator for MQTT 3.1.1

* working on ConnAckSpecs

* added ConnAck specs

* finished all packet size estimators

* fixed compilation errors

* enabled treat warnings as errors

Directory.Build.props

@@ -2,6 +2,7 @@
     <PropertyGroup>
         <Copyright>Copyright © 2023 Your Company</Copyright>
         <NoWarn>$(NoWarn);CS1591</NoWarn>
+        <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
         <VersionPrefix>1.0.0</VersionPrefix>
     </PropertyGroup>
 
@@ -17,10 +18,6 @@
         <PackageReadmeFile>README.md</PackageReadmeFile>
     </PropertyGroup>
 
-    <PropertyGroup Label="Dependencies">
-        <PbmVersion>1.4.0</PbmVersion>
-    </PropertyGroup>
-
     <ItemGroup>
         <None Include="$(MSBuildThisFileDirectory)\README.md" Pack="true" Visible="false" PackagePath="\"/>
         <None Include="$(MSBuildThisFileDirectory)\LICENSE.md" Pack="true" Visible="false" PackagePath="\"/>

src/TurboMqtt.Core/ControlPacketHeaders.cs

@@ -14,7 +14,7 @@ namespace TurboMqtt.Core;
 ///
 /// Also supports MQTT 5.0.
 /// </remarks>
-public enum MqttPacketType
+public enum MqttPacketType : byte
 {
     Connect = 0x10,
     ConnAck = 0x20,

src/TurboMqtt.Core/PacketTypes/AuthPacket.cs

@@ -54,7 +54,7 @@ public override string ToString()
 /// <summary>
 /// Enumerates the reason codes applicable to the AUTH packet in MQTT 5.0.
 /// </summary>
-public enum AuthReasonCode
+public enum AuthReasonCode : byte
 {
     Success = 0x00,
     ContinueAuthentication = 0x18,

src/TurboMqtt.Core/PacketTypes/ConnAckPacket.cs

@@ -17,15 +17,15 @@ public sealed class ConnAckPacket : MqttPacket
     public ConnAckReasonCode ReasonCode { get; set; } // Enum defined below
 
     // MQTT 5.0 - Optional Properties
-    public IReadOnlyDictionary<string, string>? Properties { get; set; }
+    public IReadOnlyDictionary<string, string>? UserProperties { get; set; }
 
     public override string ToString()
     {
         return $"ConnAck: [SessionPresent={SessionPresent}] [ReasonCode={ReasonCode}]";
     }
 }
 
-public enum ConnAckReasonCode
+public enum ConnAckReasonCode : byte
 {
     Success = 0x00,
     UnspecifiedError = 0x80,

src/TurboMqtt.Core/PacketTypes/ConnectPacket.cs

@@ -4,34 +4,114 @@
 // </copyright>
 // -----------------------------------------------------------------------
 
+using TurboMqtt.Core.Protocol;
+
 namespace TurboMqtt.Core.PacketTypes;
 
 /// <summary>
 /// Used to initiate a connection to the MQTT broker.
 /// </summary>
-public class ConnectPacket(string clientId) : MqttPacket
+public class ConnectPacket(string clientId, MqttProtocolVersion protocolVersion) : MqttPacket
 {
     public override MqttPacketType PacketType => MqttPacketType.Connect;
 
     public string ClientId { get; } = clientId;
-    public bool CleanSession { get; set; }
     public ushort KeepAlive { get; set; }
-
-    // MQTT 5.0 - Optional Properties
+    public ConnectFlags Flags { get; set; }
+
+    public MqttLastWill? Will { get; set; }
+
     public string? Username { get; set; }
-    public string? Password { get; set; }
+    public ReadOnlyMemory<byte>? Password { get; set; }
+
+    public MqttProtocolVersion ProtocolVersion { get; } = protocolVersion;
+
+    // MQTT 5.0 - Optional Properties
+    public ushort ReceiveMaximum { get; set; } // MQTT 5.0 only
+    public uint MaximumPacketSize { get; set; } // MQTT 5.0 only
+    public ushort TopicAliasMaximum { get; set; } // MQTT 5.0 only
+    public uint SessionExpiryInterval { get; set; } // MQTT 5.0 only
+    public bool RequestProblemInformation { get; set; } // MQTT 5.0 only
+    public bool RequestResponseInformation { get; set; } // MQTT 5.0 only
+    public string? AuthenticationMethod { get; set; } // MQTT 5.0 only
+    public ReadOnlyMemory<byte>? AuthenticationData { get; set; } // MQTT 5.0 only
+    public IReadOnlyDictionary<string, string>? UserProperties { get; set; } // MQTT 5.0 custom properties
+
+
+}
+
+/// <summary>
+/// Payload for the Last Will and Testament message.
+/// </summary>
+public sealed class MqttLastWill
+{
+    public MqttLastWill(string topic, ReadOnlyMemory<byte> message)
+    {
+        Topic = topic;
+        Message = message;
+
+        // throw if topic is invalid
+        if (string.IsNullOrEmpty(topic))
+            throw new ArgumentException("Topic cannot be null or empty.", nameof(topic));
+    }
 
-    public bool? WillFlag { get; set; }
-    public string? WillTopic { get; set; }
-    public ReadOnlyMemory<byte>? WillMessage { get; set; }
-    public QualityOfService? WillQos { get; set; }
-    public bool? WillRetain { get; set; }
+    public string Topic { get; }
+    public ReadOnlyMemory<byte> Message { get; }
+
+    // MQTT 5.0 - Optional Properties for Last Will and Testament
+    public string? ResponseTopic { get; set; } // MQTT 5.0 only
+    public ReadOnlyMemory<byte>? WillCorrelationData { get; set; } // MQTT 5.0 only
+    public string? ContentType { get; set; } // MQTT 5.0 only
+    public PayloadFormatIndicator PayloadFormatIndicator { get; set; } // MQTT 5.0 only
+    public NonZeroUInt32 DelayInterval { get; set; } // MQTT 5.0 only
+    public uint MessageExpiryInterval { get; set; } // MQTT 5.0 only
+    public IReadOnlyDictionary<string, string>? WillProperties { get; set; } // MQTT 5.0 custom properties
+
+    // QoS and Retain are determined by ConnectFlags
+}
 
-    public IReadOnlyDictionary<string, string>?
-        Properties { get; set; } // Custom properties like Session Expiry Interval, Maximum Packet Size, etc.
+public struct ConnectFlags
+{
+    public bool UsernameFlag { get; set; }
+    public bool PasswordFlag { get; set; }
+    public bool WillRetain { get; set; }
+    public QualityOfService WillQoS { get; set; }
+    public bool WillFlag { get; set; }
+    public bool CleanSession { get; set; }  // Renamed from CleanStart for 3.1.1 compatibility
 
-    public override string ToString()
+    public byte Encode(MqttProtocolVersion version)
     {
-        return $"Connect: [ClientId={ClientId}] [CleanSession={CleanSession}] [KeepAlive={KeepAlive}]";
+        byte result = 0;
+        if (UsernameFlag)
+            result |= 0b1000_0000;
+        if (PasswordFlag)
+            result |= 0b0100_0000;
+        if (version == MqttProtocolVersion.V5_0 && WillRetain)
+            result |= 0b0010_0000;
+        if (WillFlag)
+            result |= 0b0000_0100;
+        if (CleanSession)
+            result |= 0b0000_0010;
+        if (WillFlag) // Only encode Will QoS if Will is set
+            result |= (byte)(((int)WillQoS & 0x03) << 3);
+
+        return result;
+    }
+
+    public static ConnectFlags Decode(byte flags)
+    {
+        var result = new ConnectFlags
+        {
+            UsernameFlag = (flags & 0b1000_0000) != 0,
+            PasswordFlag = (flags & 0b0100_0000) != 0,
+            WillRetain = (flags & 0b0010_0000) != 0,
+            WillFlag = (flags & 0b0000_0100) != 0,
+            CleanSession = (flags & 0b0000_0010) != 0
+        };
+
+        if (result.WillFlag)
+            result.WillQoS = (QualityOfService)((flags & 0b0001_1000) >> 3);
+
+        return result;
     }
-}
+}

src/TurboMqtt.Core/PacketTypes/DisconnectPacket.cs

@@ -40,7 +40,7 @@ public override string ToString()
     }
 }
 
-public enum DisconnectReasonCode
+public enum DisconnectReasonCode : byte
 {
     NormalDisconnection = 0x00,
     DisconnectWithWillMessage = 0x04,

src/TurboMqtt.Core/PacketTypes/PubCompPacket.cs

@@ -40,7 +40,7 @@ public override string ToString()
 /// <summary>
 /// Enum for PUBCOMP reason codes, using the same as PUBREC for simplicity and because MQTT 5.0 reuses these
 /// </summary>
-public enum PubCompReasonCode
+public enum PubCompReasonCode : byte
 {
     Success = 0x00,
     PacketIdentifierNotFound = 0x92

src/TurboMqtt.Core/PacketTypes/PubRecPacket.cs

@@ -40,7 +40,7 @@ public override string ToString()
 /// <summary>
 ///  Enum for PUBREC and PUBCOMP reason codes (as they share the same codes)
 /// </summary>
-public enum PubRecReasonCode
+public enum PubRecReasonCode : byte
 {
     Success = 0x00,
     NoMatchingSubscribers = 0x10,

src/TurboMqtt.Core/PacketTypes/PubRelPacket.cs

@@ -40,7 +40,7 @@ public override string ToString()
 /// <summary>
 /// Enum for PUBREL reason codes (typically these would be simpler as successful flow is usually assumed)
 /// </summary>
-public enum PubRelReasonCode
+public enum PubRelReasonCode : byte
 {
     Success = 0x00,
     PacketIdentifierNotFound = 0x92

src/TurboMqtt.Core/PacketTypes/PublishAckPacket.cs

@@ -6,7 +6,42 @@
 
 namespace TurboMqtt.Core.PacketTypes;
 
-using static MqttPubAckHelpers;
+/// <summary>
+/// All possible reason codes for the PubAck packet.
+/// </summary>
+public enum MqttPubAckReasonCode : byte
+{
+    Success = 0x00,
+    NoMatchingSubscribers = 0x10,
+    UnspecifiedError = 0x80,
+    ImplementationSpecificError = 0x83,
+    NotAuthorized = 0x87,
+    TopicNameInvalid = 0x90,
+    PacketIdentifierInUse = 0x91,
+    QuotaExceeded = 0x97,
+    PayloadFormatInvalid = 0x99
+}
+
+// add a static helper method that can turn a MqttPubAckReason code into a hard-coded string representation
+internal static class MqttPubAckHelpers
+{
+    public static string ReasonCodeToString(MqttPubAckReasonCode reasonCode)
+    {
+        return reasonCode switch
+        {
+            MqttPubAckReasonCode.Success => "Success",
+            MqttPubAckReasonCode.NoMatchingSubscribers => "NoMatchingSubscribers",
+            MqttPubAckReasonCode.UnspecifiedError => "UnspecifiedError",
+            MqttPubAckReasonCode.ImplementationSpecificError => "ImplementationSpecificError",
+            MqttPubAckReasonCode.NotAuthorized => "NotAuthorized",
+            MqttPubAckReasonCode.TopicNameInvalid => "TopicNameInvalid",
+            MqttPubAckReasonCode.PacketIdentifierInUse => "PacketIdentifierInUse",
+            MqttPubAckReasonCode.QuotaExceeded => "QuotaExceeded",
+            MqttPubAckReasonCode.PayloadFormatInvalid => "PayloadFormatInvalid",
+            _ => throw new ArgumentOutOfRangeException(nameof(reasonCode), reasonCode, null)
+        };
+    }
+}
 
 /// <summary>
 /// Used to acknowledge the receipt of a Publish packet.
@@ -27,7 +62,7 @@ public sealed class PublishAckPacket : MqttPacketWithId
     /// User Properties, available in MQTT 5.0.
     /// These are key-value pairs that can be sent to provide additional information in the acknowledgment.
     /// </summary>
-    public string ReasonString => ReasonCodeToString(ReasonCode);
+    public string ReasonString => MqttPubAckHelpers.ReasonCodeToString(ReasonCode);
 
     public override string ToString()
     {

src/TurboMqtt.Core/PacketTypes/PublishPacket.cs

@@ -9,28 +9,33 @@ namespace TurboMqtt.Core.PacketTypes;
 /// <summary>
 /// Used to send data to the server or client.
 /// </summary>
-/// <param name="Qos">The delivery guarantee for this packet.</param>
-/// <param name="Duplicate">Is this packet a duplicate?</param>
-/// <param name="RetainRequested">Indicates whether or not this value has been retained by the MQTT broker.</param>
-public sealed class PublishPacket(QualityOfService Qos, bool Duplicate, bool RetainRequested) : MqttPacketWithId
+/// <param name="qos">The delivery guarantee for this packet.</param>
+/// <param name="duplicate">Is this packet a duplicate?</param>
+/// <param name="retainRequested">Indicates whether or not this value has been retained by the MQTT broker.</param>
+public sealed class PublishPacket(QualityOfService qos, bool duplicate, bool retainRequested, string topicName) : MqttPacketWithId
 {
     public override MqttPacketType PacketType => MqttPacketType.Publish;
 
-    public override bool Duplicate { get; } = Duplicate;
+    public override bool Duplicate { get; } = duplicate;
 
-    public override QualityOfService QualityOfService { get; } = Qos;
+    public override QualityOfService QualityOfService { get; } = qos;
 
-    public override bool RetainRequested { get; } = RetainRequested;
+    public override bool RetainRequested { get; } = retainRequested;
+
+    public ushort TopicAlias { get; set; } // MQTT 5.0 only
 
     /// <summary>
     /// Optional for <see cref="QualityOfService.AtMostOnce"/>
     /// </summary>
-    public string? TopicName { get; set; }
+    public string TopicName { get; } = topicName;
+
+    public uint MessageExpiryInterval { get; set; } // MQTT 5.0 only
 
     // Payload
     public ReadOnlyMemory<byte> Payload { get; set; } = ReadOnlyMemory<byte>.Empty;
 
     // MQTT 3.1.1 and 5.0 - Optional Properties
+    public PayloadFormatIndicator PayloadFormatIndicator { get; set; } // MQTT 5.0 only
 
     /// <summary>
     /// The Content Type property, available in MQTT 5.0.
@@ -68,4 +73,17 @@ public override string ToString()
         return
             $"Publish: [Topic={TopicName}] [PayloadLength={Payload.Length}] [QoSLevel={QualityOfService}] [Dup={Duplicate}] [Retain={RetainRequested}] [PacketIdentifier={PacketId}]";
     }
+}
+
+public enum PayloadFormatIndicator : byte
+{
+    /// <summary>
+    /// The payload is unspecified bytes, which should not be interpreted as UTF-8 encoded character data.
+    /// </summary>
+    Unspecified = 0,
+
+    /// <summary>
+    /// The payload is UTF-8 encoded character data.
+    /// </summary>
+    Utf8Encoded = 1
 }