using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace SmartCoalApplication.SystemLayer
{
    public unsafe static class Memory
    {
        private static IntPtr hHeap;

        static Memory()
        {
            hHeap = SafeNativeMethods.HeapCreate(0, IntPtr.Zero, IntPtr.Zero);

            uint info = 2;

            try
            {
                SafeNativeMethods.HeapSetInformation(hHeap,
                    NativeConstants.HeapCompatibilityInformation,
                    (void*)&info,
                    sizeof(uint));
            }

            catch (Exception)
            {
                
            }

            Application.ApplicationExit += new EventHandler(Application_ApplicationExit);
        }

        private static void DestroyHeap()
        {
            IntPtr hHeap2 = hHeap;
            hHeap = IntPtr.Zero;
            SafeNativeMethods.HeapDestroy(hHeap2);
        }

        private static void Application_ApplicationExit(object sender, EventArgs e)
        {
            DestroyHeap();
        }

        public static IntPtr Allocate(ulong bytes)
        {
            if (hHeap == IntPtr.Zero)
            {
                throw new InvalidOperationException("heap has already been destroyed");
            }
            else
            {
                IntPtr block = SafeNativeMethods.HeapAlloc(hHeap, 0, new UIntPtr(bytes));

                if (block == IntPtr.Zero)
                {
                    throw new OutOfMemoryException("HeapAlloc returned a null pointer");
                }

                if (bytes > 0)
                {
                    GC.AddMemoryPressure((long)bytes);
                }

                return block;
            }
        }

        
        public static IntPtr AllocateLarge(ulong bytes)
        {
            IntPtr block = SafeNativeMethods.VirtualAlloc(IntPtr.Zero, new UIntPtr(bytes),
                NativeConstants.MEM_COMMIT, NativeConstants.PAGE_READWRITE);

            if (block == IntPtr.Zero)
            {
                throw new OutOfMemoryException("VirtualAlloc returned a null pointer");
            }

            if (bytes > 0)
            {
                GC.AddMemoryPressure((long)bytes);
            }

            return block;
        }

        
        public static IntPtr AllocateBitmap(int width, int height, out IntPtr handle)
        {
            NativeStructs.BITMAPINFO bmi = new NativeStructs.BITMAPINFO();
            bmi.bmiHeader.biSize = (uint)sizeof(NativeStructs.BITMAPINFOHEADER);
            bmi.bmiHeader.biWidth = width;
            bmi.bmiHeader.biHeight = -height;
            bmi.bmiHeader.biPlanes = 1;
            bmi.bmiHeader.biBitCount = 32;
            bmi.bmiHeader.biCompression = NativeConstants.BI_RGB;
            bmi.bmiHeader.biSizeImage = 0;
            bmi.bmiHeader.biXPelsPerMeter = 96;
            bmi.bmiHeader.biYPelsPerMeter = 96;
            bmi.bmiHeader.biClrUsed = 0;
            bmi.bmiHeader.biClrImportant = 0;

            IntPtr pvBits;
            IntPtr hBitmap = SafeNativeMethods.CreateDIBSection(
                IntPtr.Zero,
                ref bmi,
                NativeConstants.DIB_RGB_COLORS,
                out pvBits,
                IntPtr.Zero,
                0);

            if (hBitmap == IntPtr.Zero)
            {
                throw new OutOfMemoryException("CreateDIBSection returned NULL (" + Marshal.GetLastWin32Error().ToString() + ") while attempting to allocate " + width + "x" + height + " bitmap");
            }

            handle = hBitmap;
            long bytes = (long)width * (long)height * 4;

            if (bytes > 0)
            {
                GC.AddMemoryPressure(bytes);
            }

            return pvBits;
        }

        /// <summary>
        /// Frees a bitmap previously allocated with AllocateBitmap.
        /// </summary>
        /// <param name="handle">The handle that was returned from a previous call to AllocateBitmap.</param>
        /// <param name="width">The width of the bitmap, as specified in the original call to AllocateBitmap.</param>
        /// <param name="height">The height of the bitmap, as specified in the original call to AllocateBitmap.</param>
        public static void FreeBitmap(IntPtr handle, int width, int height)
        {
            long bytes = (long)width * (long)height * 4;

            bool bResult = SafeNativeMethods.DeleteObject(handle);

            if (!bResult)
            {
                throw new Win32Exception("DeleteObject returned false");
            }

            if (bytes > 0)
            {
                GC.RemoveMemoryPressure(bytes);
            }
        }

        /// <summary>
        /// Frees a block of memory previously allocated with Allocate().
        /// </summary>
        /// <param name="block">The block to free.</param>
        /// <exception cref="InvalidOperationException">There was an error freeing the block.</exception>
        public static void Free(IntPtr block)
        {
            if (Memory.hHeap != IntPtr.Zero)
            {
                long bytes = (long)SafeNativeMethods.HeapSize(hHeap, 0, block);

                bool result = SafeNativeMethods.HeapFree(hHeap, 0, block);

                if (!result)
                {
                    int error = System.Runtime.InteropServices.Marshal.GetLastWin32Error();
                    throw new InvalidOperationException("HeapFree returned an error: " + error.ToString());
                }

                if (bytes > 0)
                {
                    GC.RemoveMemoryPressure(bytes);
                }
            }
        }

        /// <summary>
        /// Frees a block of memory previous allocated with AllocateLarge().
        /// </summary>
        /// <param name="block">The block to free.</param>
        /// <param name="bytes">The size of the block.</param>
        public static void FreeLarge(IntPtr block, ulong bytes)
        {
            bool result = SafeNativeMethods.VirtualFree(block, UIntPtr.Zero, NativeConstants.MEM_RELEASE);

            if (!result)
            {
                int error = System.Runtime.InteropServices.Marshal.GetLastWin32Error();
                throw new InvalidOperationException("VirtualFree returned an error: " + error.ToString());
            }

            if (bytes > 0)
            {
                GC.RemoveMemoryPressure((long)bytes);
            }
        }

        public static void Copy(void* dst, void* src, ulong length)
        {
            SafeNativeMethods.memcpy(dst, src, new UIntPtr(length));
        }

        public static void SetToZero(void* dst, ulong length)
        {
            SafeNativeMethods.memset(dst, 0, new UIntPtr(length));
        }
    }
}