Imports System.IO
Imports System.Runtime.CompilerServices
Imports System.Text
Imports Microsoft.VisualBasic.ValueTypes

Module EmitHandler

    Public Delegate Function toBuffer(obj As Object) As Stream
    Public Delegate Function loadBuffer(buf As Stream) As Object

    Public Iterator Function PopulatePrimitiveHandles() As IEnumerable(Of (target As Type, emit As toBuffer))
        Yield (GetType(Integer), Function(i) New MemoryStream(BitConverter.GetBytes(DirectCast(i, Integer))))
        Yield (GetType(UInteger), Function(i) New MemoryStream(BitConverter.GetBytes(DirectCast(i, UInteger))))

        Yield (GetType(Long), Function(l) New MemoryStream(BitConverter.GetBytes(DirectCast(l, Long))))
        Yield (GetType(ULong), Function(l) New MemoryStream(BitConverter.GetBytes(DirectCast(l, ULong))))

        Yield (GetType(Single), Function(f) New MemoryStream(BitConverter.GetBytes(DirectCast(f, Single))))
        Yield (GetType(Double), Function(d) New MemoryStream(BitConverter.GetBytes(DirectCast(d, Double))))

        Yield (GetType(UShort), Function(s) New MemoryStream(BitConverter.GetBytes(DirectCast(s, UShort))))
        Yield (GetType(Boolean), Function(b) New MemoryStream(New Byte() {If(DirectCast(b, Boolean), 1, 0)}))
        Yield (GetType(String), Function(s) New MemoryStream(Encoding.UTF8.GetBytes(DirectCast(s, String))))
        Yield (GetType(Char), Function(c) New MemoryStream(BitConverter.GetBytes(AscW(DirectCast(c, Char)))))

        Yield (GetType(Byte), Function(b) New MemoryStream({DirectCast(b, Byte)}))
        Yield (GetType(Date), Function(d) New MemoryStream(BitConverter.GetBytes(DirectCast(d, Date).UnixTimeStamp)))
    End Function

    Public Iterator Function PopulatePrimitiveParsers() As IEnumerable(Of (target As Type, emit As loadBuffer))
        Yield (GetType(Integer), Function(i) BitConverter.ToInt32(i.readAllBytes, Scan0))
        Yield (GetType(UInteger), Function(i) BitConverter.ToUInt32(i.readAllBytes, Scan0))

        Yield (GetType(Long), Function(l) BitConverter.ToInt64(l.readAllBytes, Scan0))
        Yield (GetType(ULong), Function(l) BitConverter.ToUInt64(l.readAllBytes, Scan0))

        Yield (GetType(Single), Function(f) BitConverter.ToSingle(f.readAllBytes, Scan0))
        Yield (GetType(Double), Function(d) BitConverter.ToDouble(d.readAllBytes, Scan0))

        Yield (GetType(Short), Function(s) BitConverter.ToInt16(s.readAllBytes, Scan0))
        Yield (GetType(UShort), Function(s) BitConverter.ToUInt16(s.readAllBytes, Scan0))

        Yield (GetType(Boolean), Function(b) b.readAllBytes()(Scan0) <> 0)
        Yield (GetType(String), Function(s) Encoding.UTF8.GetString(s.readAllBytes))
        Yield (GetType(Char), Function(c) ChrW(BitConverter.ToInt32(c.readAllBytes, Scan0)))

        Yield (GetType(Byte), Function(b) b.readAllBytes()(Scan0))
        Yield (GetType(Date), Function(d) FromUnixTimeStamp(BitConverter.ToDouble(d.readAllBytes, Scan0)))
    End Function

    <Extension>
    Private Function readAllBytes(buf As Stream) As Byte()
        Dim bytes As Byte() = New Byte(buf.Length - 1) {}
        Call buf.Read(bytes, Scan0, bytes.Length - 1)
        Return bytes
    End Function
End Module