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


        public unsafe void LoadGlapi()
        {
            InternalIO.InternalLoaderLoadGLapi(glContext, LoadGLfunc);


            //check out if all api is converted correctely.
            FieldInfo[] target = 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 target)
            {
                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
                TypedReference contextref = __makeref(*glContext);
                GLcontextIO* iopack = (GLcontextIO*)glContext;
                TypedReference iosource = __makeref(*iopack);

                foreach (FieldInfo item in target)
                {
                    if (item.FieldType.IsSubclassOf(typeof(Delegate))
                        && item.GetValueDirect(contextref) == null)
                    {
                        IntPtr proc = default;
                        proc = LoadGLfunc("gl" + item.Name);
                        if (proc != IntPtr.Zero)
                        {
                            try
                            {
                                Delegate dele = Marshal.GetDelegateForFunctionPointer(proc, item.FieldType);
                                item.SetValueDirect(contextref, dele);
                            }
                            catch (Exception ex)
                            {
                                InternalIO.InternalWriteLog(
                                    $"{ex.Message}",
                                    LogType.Error);
                            }
                        }
                    }
                }
            }
            GL.gl = glContext;
        }



    }
}