using System;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using PorygonSharp.UserData;

namespace PorygonSharp.EvalValues
{
    public static class EvalValueCreator
    {
        public static EvalValue CreateValue(object o)
        {
            if (o == null)
                return new EvalValue(CreateNilEvalValue());
            var type     = o.GetType();
            if (type.IsEnum && !type.IsGenericParameter)
            {
                var typeHash = UserDataHandler.GetTypeId(type);
                var ptr = ObjectEvalValueHandler.GetObjectPtr(o);
                return new EvalValue(CreateUserDataEvalValue(typeHash, ptr));
            }
            var typeCode = Type.GetTypeCode(type);
            switch (typeCode)
            {
                case TypeCode.Boolean:
                    return new EvalValue(CreateBoolEvalValue((bool)o));
                case TypeCode.Byte:
                case TypeCode.SByte:
                case TypeCode.Int16:
                case TypeCode.Int32:
                case TypeCode.Int64:
                case TypeCode.UInt16:
                case TypeCode.UInt32:
                case TypeCode.UInt64:
                    return new EvalValue(CreateIntegerEvalValue(Convert.ToInt64(o)));
                case TypeCode.Char:
                case TypeCode.String:
                    return new EvalValue(CreateStringEvalValue(o.ToString()));
                case TypeCode.Decimal:
                case TypeCode.Double:
                case TypeCode.Single:
                    return new EvalValue(CreateFloatEvalValue(Convert.ToDouble(o)));
                case TypeCode.Object:
                    if (typeof(IList).IsAssignableFrom(type))
                        return CreateListEvalValue((IList)o, type);
                    if (!UserDataHandler.IsTypeRegistered(type) && !UserDataHandler.TryResolveType(type))
                    {
                        throw new Exception($"Type is not registered for use: {type.FullName}");
                    }
                    var typeHash = UserDataHandler.GetTypeId(type);
                    var ptr = ObjectEvalValueHandler.GetObjectPtr(o);
                    return new EvalValue(CreateUserDataEvalValue(typeHash, ptr));
                default:
                    throw new Exception($"Type {type} is not currently available as EvalValue");
            }
        }

        public static EvalValue FunctionEvalValue(IntPtr func, IntPtr parent)
        {
            return new EvalValue(CreateFunctionEvalValue(func, parent));
        }

        private static EvalValue CreateListEvalValue(IList collection, Type type)
        {
            var helper = new ListEvalValue(collection, type);
            var ptr = CreateCollectionValue(IntPtr.Zero, helper.ParentCollection, helper.Getter, helper.Setter,
                helper.GetIterator);
            return new EvalValue(ptr);
        }
        
        [DllImport("PorygonLang", EntryPoint = "CreateNilEvalValue",CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr CreateNilEvalValue();
        [DllImport("PorygonLang", EntryPoint = "CreateIntegerEvalValue",CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr CreateIntegerEvalValue(long l);
        [DllImport("PorygonLang", EntryPoint = "CreateFloatEvalValue",CallingConvention = CallingConvention.Cdecl)]
        private static extern IntPtr CreateFloatEvalValue(double d);
        [DllImport("PorygonLang", EntryPoint = "CreateBoolEvalValue",CallingConvention = CallingConvention.Cdecl)]
        private static extern IntPtr CreateBoolEvalValue(bool b);
        [DllImport("PorygonLang", EntryPoint = "CreateStringEvalValue",CallingConvention = CallingConvention.Cdecl)]
        private static extern IntPtr CreateStringEvalValue([MarshalAs(UnmanagedType.LPWStr)]string s);
        [DllImport("PorygonLang", EntryPoint = "CreateUserDataEvalValue",CallingConvention = CallingConvention.Cdecl)]
        private static extern IntPtr CreateUserDataEvalValue(uint typeHash, IntPtr obj);

        [DllImport("PorygonLang", EntryPoint = "CreateFunctionEvalValue",CallingConvention = CallingConvention.Cdecl)]
        private static extern IntPtr CreateFunctionEvalValue(IntPtr func, IntPtr parent);

        [DllImport("PorygonLang", EntryPoint = "CreateCollectionValue", CallingConvention = CallingConvention.Cdecl)]
        private static extern IntPtr CreateCollectionValue(IntPtr type, IntPtr parent, IntPtr getter, IntPtr setter,
            IntPtr iterator);
    }
}