using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;

namespace StgSharp.Graphics
{
    public unsafe partial class Form
    {
        internal GLcontext* glContext;

        private int missingAPIcount = 0;
        private int problemAPIcount = 0;


        public unsafe IntPtr LoadGLfunc([MarshalAs(UnmanagedType.LPStr)] string name)
        {

            IntPtr ret = InternalIO.glfw.GetProcAddress(name);
            if (ret == default)
            {
                InternalIO.InternalWriteLog(
                    $"Cannot load OpenGL api called {name}, this api may not exist or supported.",
                    LogType.Warning);
                missingAPIcount++;
                return ret;
            }
            return ret;
        }


        public unsafe void LoadGlapi()
        {
            GLcontext* context = (GLcontext*)InternalIO.internalCreatGLcontext(LoadGLfunc);
            if ((ulong)context == 0)
            {
                throw new Exception($"Failed to load OpenGL api for current context \"{(ulong)glContext}\"");
            }

            //check out if all api is converted correctely.
            FieldInfo[] fieldInfos = typeof(GLcontext).GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
            string problemLog = "Have problem in converting the fallowing GL API to C# delegates:\n";
            foreach (FieldInfo item in fieldInfos)
            {
                if (item.FieldType.Name.Contains("PFNG"))
                {
                    if (item.GetValue(*glContext) == null)
                    {
                        problemLog += item.Name + ",";
                        problemAPIcount++;
                    }
                }
            }
            InternalIO.InternalWriteLog(problemLog, LogType.Error);



            if (problemAPIcount > missingAPIcount)
            {
                InternalIO.InternalWriteLog("Attempt to reload GL APIs", LogType.Info);

                //use IntPtr as interface
                GLcontextIO* iopack = (GLcontextIO*)context;

                FieldInfo[] source = typeof(GLcontextIO).GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);


                foreach (FieldInfo item in source)
                {
                    if (item.FieldType.IsSubclassOf(typeof(Delegate))
                        && item.GetValue(*context) == null)
                    {
                        IntPtr funcPtr = LoadGLfunc(item.Name);
                        if (funcPtr != IntPtr.Zero)
                        {
                            try
                            {
                                Delegate dele = Marshal.GetDelegateForFunctionPointer(funcPtr, item.FieldType);
                                item.SetValue(*context, dele);
                            }
                            catch (Exception ex)
                            {
                                InternalIO.InternalWriteLog(
                                    $"{ex.Message}",
                                    LogType.Error);
                            }
                        }

                    }
                }
            }
            glContext = context;
            GL.gl = glContext;

        }



    }
}