using System.Diagnostics.CodeAnalysis;
using InnovEnergy.Lib.Protocols.DBus.Protocol.DataTypes;
using InnovEnergy.Lib.Protocols.DBus.Protocol.DataTypes.Convert;
using InnovEnergy.Lib.Protocols.DBus.Protocol.DataTypes.Signatures;
using InnovEnergy.Lib.Protocols.DBus.Protocol.Header;
using InnovEnergy.Lib.Protocols.DBus.Transport;
using InnovEnergy.Lib.Protocols.DBus.WireFormat;

namespace InnovEnergy.Lib.Protocols.DBus.Protocol;

using HeaderType      = ValueTuple<Byte, Byte, Byte, Byte, UInt32, UInt32, IReadOnlyList<(Byte, Variant)>>;
using HeaderFieldType = ValueTuple<Byte, Variant>;


[SuppressMessage("ReSharper", "UnusedMember.Global")]
public readonly struct Message
{
    public const Byte ProtocolVersion = 1;

    private static Signature HeaderSignature { get; } = Signature.FromType<HeaderType>();

    private HeaderType Header { get; }
    
    public Object? Payload      { get; }
    public Boolean ParsingError { get; }

    public MessageType  Type          => Header.MessageType();
    public UInt32       Serial        => Header.Serial();
    public Signature?   Signature     => Header.Signature();
    public String?      Interface     => Header.Interface();
    public String?      Member        => Header.Member();
    public String?      Destination   => Header.Destination();
    public String?      Sender        => Header.Sender();
    public String?      ErrorName     => Header.ErrorName();
    public UInt32?      ReplySerial   => Header.ReplySerial();
    public UInt32?      PayloadLength => Header.PayloadLength();
    public ObjectPath?  ObjectPath    => Header.ObjectPath();
    public Endian       Endian        => Header.Endian();

    public Boolean ReplyExpected                 => Header.ReplyExpected();
    public Boolean AutoStart                     => Header.AutoStart();
    public Boolean AllowInteractiveAuthorization => Header.AllowInteractiveAuthorization();

    public Boolean HasPayload => Payload is not null;
    public Boolean IsError    => Type == MessageType.Error;

    public Message(HeaderType header, Object? payload) : this(header, payload, false)
    {
    }


    private Message(HeaderType header, Object? payload, Boolean parsingError)
    {
        Header = header;
        Payload = payload;
        ParsingError = parsingError;

        CheckProtocolVersion();
    }


    private void CheckProtocolVersion()
    {
        if (Header.ProtocolVersion() != ProtocolVersion)
            throw new Exception($"Unsupported protocol version: expecting {ProtocolVersion}, got {Header.ProtocolVersion()}");
    }



    public static Message Signal(ObjectPath? objectPath,
                                     String? member,
                                     String? @interface = null,
                                     Object? payload = null)
    {
        var signature = payload.GetSignature().AsRootSignature();

        var fields = new List<HeaderFieldType>();
        AddField(FieldCode.Path, objectPath);
        AddField(FieldCode.Interface, @interface);
        AddField(FieldCode.Member, member);

        if (!signature.IsEmpty)
            AddField(FieldCode.Signature, signature);

        var bodyLength = (UInt32)signature.MeasureSize(payload);
        var serial = SerialSource.Next();


        HeaderType header =
        (
            (Byte)Env.Endianness,
            (Byte)MessageType.Signal,
            (Byte)HeaderFlags.NoReplyExpected,
            ProtocolVersion,
            bodyLength,
            serial,
            fields
        );

        return new Message(header, payload);

        void AddField(FieldCode fieldCode, Object? value)
        {
            if (value is not null)
                fields.Add(((Byte)fieldCode, value.Variant()));
        }
    }



    public static Message MethodCall(String? destination,
                                 ObjectPath? objectPath,
                                     String? member,
                                     String? @interface = null,
                                     Object? payload = null,
                                     Boolean replyExpected = true)
    {
        var signature = payload.GetSignature().AsRootSignature();

        var fields = new List<HeaderFieldType>();
        AddField(FieldCode.Path, objectPath);
        AddField(FieldCode.Destination, destination);
        AddField(FieldCode.Interface, @interface);
        AddField(FieldCode.Member, member);

        if (!signature.IsEmpty)
            AddField(FieldCode.Signature, signature);

        var flags = replyExpected ? HeaderFlags.None : HeaderFlags.NoReplyExpected;
        var bodyLength = (UInt32)signature.MeasureSize(payload);
        var serial = SerialSource.Next();


        HeaderType header =
        (
            (Byte)Env.Endianness,
            (Byte)MessageType.MethodCall,
            (Byte)flags,
            ProtocolVersion,
            bodyLength,
            serial,
            fields
        );

        return new Message(header, payload);

        void AddField(FieldCode fieldCode, Object? value)
        {
            if (value is not null)
                fields.Add(((Byte)fieldCode, value.Variant()));
        }
    }

    internal static Message Read(DBusReader reader)
    {
        var header           = ReadHeader(reader);
        var (payload, error) = ReadPayload(reader, header);

        return new Message(header, payload, error);
    }

    private static HeaderType ReadHeader(DBusReader reader)
    {
        return (HeaderType) HeaderSignature.Read(reader);
    }

    private static (Object? payload, Boolean parsingError) ReadPayload(DBusReader reader, HeaderType header)
    {
        var payloadLength = header.PayloadLength();
        var signature     = header.Signature();

        if (payloadLength == 0 || signature is null)
            return (null, false);

        reader.AlignForComposite();

        var raw = reader.ReadSegment((Int32)payloadLength);

        if (signature.IsEmpty)
            return (raw.ToArray(), true);   // no signature, but data available. should probably not happen.

        var br = new DBusBufferReader(raw, reader.SwapEndian);

        // try
        // {
            return (signature.Read(br), false);
        // }
        // catch
        // {
        //     Console.WriteLine("failed to parse payload");
        // }

        //return (raw.ToArray(), true);  // parsing error
    }

    internal void Write(DBusWriter writer)
    {
        HeaderSignature.Write(Header, writer);
        writer.AlignForComposite();

        if (Payload is null) return;
        Signature!.Write(Payload, writer);


        // TODO: on debug reread written message with reader, Roundtrip
        
        //
        // var w = new DBusBufferWriter();
        // HeaderSignature.Write(Header, w);
        // writer.AlignForComposite();
        //
        // if (Payload is null) return;
        // Signature!.Write(Payload, w);
        //
        // Console.WriteLine(w.Data.ToHexView());
        //
        // var r = new DBusBufferReader(w.Data, false);
        // var m = Message.Read(r);
    }

}