using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using PorygonSharp.EvalValues;
using PorygonSharp.Utilities;

namespace PorygonSharp.UserData
{
    internal class UserDataFunctionField : UserDataField
    {
        public readonly IntPtr MethodPtr;
        private readonly List<CallerDelegate> _callers;
        public UserDataFunctionField(MethodInfo method, IntPtr methodPtr)
        {
            _getter = ptr =>
            {
                var funcPtr = Marshal.GetFunctionPointerForDelegate(_callers[0]);
                var val = EvalValueCreator.FunctionEvalValue(funcPtr, ptr);
                for (var i = 1; i < _callers.Count; i++)
                {
                    funcPtr = Marshal.GetFunctionPointerForDelegate(_callers[i]);
                    RegisterFunctionEvalValueOption(val.GetPointer(), funcPtr, ptr);
                }
                return val.GetPointer();
            };
            MethodPtr = methodPtr;
            _callers = new List<CallerDelegate>(){CreateCaller(method)};
        }

        private CallerDelegate CreateCaller(MethodInfo method)
        {
            var parameterTypes = method.GetParameters().Select(x => x.ParameterType).ToArray();
            return (parent, scriptOptions, parameters, size) =>
            {
                var evaluatedParameters = new object[size];
                for (var i = 0; i < size; i++)
                {
                    var eval = new EvalValue(parameters[i]);
                    evaluatedParameters[i] = Caster.Cast(eval, parameterTypes[i]);
                }

                var parentObj = GCHandle.FromIntPtr(parent).Target;
                var result = method.Invoke(parentObj, evaluatedParameters);
                return EvalValueCreator.CreateValue(result).GetPointer();
            };
        }

        internal void RegisterOption(MethodInfo method)
        {
            _callers.Add(CreateCaller(method));
        }
        
        [DllImport("PorygonLang", EntryPoint = "RegisterFunctionEvalValueOption",CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr RegisterFunctionEvalValueOption(IntPtr val, IntPtr func, IntPtr obj);
    }
}