using System;
using System.Runtime.InteropServices;

namespace WinDll.Utils
{

    ///***************************************
    /// The Maybe datatype
    ///***************************************
    public enum ListMaybe { cMaybeNothing, cMaybeJust };

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct Nothing
    {
    };

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public unsafe struct Just
    {
        public void* maybe_just_var1;
    };

    [StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
    public struct MaybeUnion
    {
        [FieldOffset(0)]
        public Nothing nothing;
        [FieldOffset(0)]
        public Just just;
    };

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public unsafe struct Maybe
    {
        public ListMaybe tag;
        public MaybeUnion* elt;
    };

    public unsafe partial class FFI
    {

        [DllImport("msvcrt.dll",CallingConvention=CallingConvention.Cdecl,EntryPoint="_msize")]
        public unsafe static extern uint _msize(void* obj);

        [DllImport("msvcrt.dll",CallingConvention=CallingConvention.Cdecl,EntryPoint="free", SetLastError =true)]
        private unsafe static extern void freeNative(void* obj);

        public unsafe static void free(void* obj)
        {
            if (obj == null) return;
            freeNative(obj);
            obj = null;
        }

        public static void free(IntPtr ptr)
        {
            if (ptr != IntPtr.Zero)
                free(ptr.ToPointer());
        }

        public static unsafe void freeTuple(Tuples.Tuple3* tuple3)
        {
            if (tuple3 == null) return;

            FFI.free(tuple3->tuple3_var1);
            FFI.free(tuple3->tuple3_var2);
            FFI.free(tuple3->tuple3_var3);
            FFI.free(tuple3);
            tuple3 = null;
        }

        public static unsafe void freeTuple(Tuples.Tuple2* tuple2)
        {
            if (tuple2 == null) return;

            FFI.free(tuple2->tuple2_var1);
            FFI.free(tuple2->tuple2_var2);
            FFI.free(tuple2);
            tuple2 = null;
        }

        public static unsafe void* readMaybe(Maybe* value)
        {
            void* val = null;
            switch (value->tag)
            {
                case ListMaybe.cMaybeNothing:
                    break;
                case ListMaybe.cMaybeJust:
                    val = value->elt->just.maybe_just_var1;
                    break;
                default:
                    break;
            }

            free(value->elt);
            free(value);

            return val;
        }

        /// <summary>
        /// In an indexed tuple the first element is a normal integer and not a pointer, so we shouldn't try to free it.
        /// </summary>
        /// <param name="tuple2"></param>
        public static unsafe void freeIndexTuple(Tuples.Tuple2* tuple2)
        {
            if (tuple2 == null) return;

            FFI.free(tuple2->tuple2_var2);
            FFI.free(tuple2);
            tuple2 = null;
        }

    }

    public unsafe class Tuples
    {
        ///***************************************
        /// The Tuple datatypes
        ///***************************************

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple2 {
            public void* tuple2_var1;
            public void* tuple2_var2;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple3 {
            public void* tuple3_var1;
            public void* tuple3_var2;
            public void* tuple3_var3;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple4 {
            public void* tuple4_var1;
            public void* tuple4_var2;
            public void* tuple4_var3;
            public void* tuple4_var4;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple5 {
            public void* tuple5_var1;
            public void* tuple5_var2;
            public void* tuple5_var3;
            public void* tuple5_var4;
            public void* tuple5_var5;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple6 {
            public void* tuple6_var1;
            public void* tuple6_var2;
            public void* tuple6_var3;
            public void* tuple6_var4;
            public void* tuple6_var5;
            public void* tuple6_var6;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple7 {
            public void* tuple7_var1;
            public void* tuple7_var2;
            public void* tuple7_var3;
            public void* tuple7_var4;
            public void* tuple7_var5;
            public void* tuple7_var6;
            public void* tuple7_var7;
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct Tuple8 {
            public void* tuple8_var1;
            public void* tuple8_var2;
            public void* tuple8_var3;
            public void* tuple8_var4;
            public void* tuple8_var5;
            public void* tuple8_var6;
            public void* tuple8_var7;
            public void* tuple8_var8;
        };

    }
}