using System;
using System.IO;
using System.Runtime.InteropServices;

namespace SvdCli.Storage
{
    internal static class NativeIoSupport
    {
        public static bool SetSparse(this FileStream fileStream)
        {
            if (fileStream == null) throw new ArgumentNullException(nameof(fileStream));
            if (fileStream.SafeFileHandle == null) throw new ArgumentException($"{nameof(fileStream.SafeFileHandle)} is null", nameof(fileStream));

            FILE_SET_SPARSE_BUFFER sparse;
            sparse.SetSparse = true;
            uint bytesTransferred;

            return DeviceIoControl(fileStream.SafeFileHandle.DangerousGetHandle(),
                0x900c4/*FSCTL_SET_SPARSE*/,
                ref sparse, (uint)Marshal.SizeOf(sparse),
                IntPtr.Zero, 0, out bytesTransferred, IntPtr.Zero);
        }

        public static bool Trim(this FileStream fileStream, long offset, long length)
        {
            if (fileStream == null) throw new ArgumentNullException(nameof(fileStream));
            if (fileStream.SafeFileHandle == null) throw new ArgumentException($"{nameof(fileStream.SafeFileHandle)} is null", nameof(fileStream));

            FILE_ZERO_DATA_INFORMATION zero;
            uint bytesTransferred;

            zero.FileOffset = offset;
            zero.BeyondFinalZero = offset + length;

            return DeviceIoControl(fileStream.SafeFileHandle.DangerousGetHandle(),
                0x980c8 /* FSCTL_SET_ZERO_DATA */,
                ref zero, (uint)Marshal.SizeOf(zero),
                IntPtr.Zero, 0, out bytesTransferred, IntPtr.Zero);
        }

        /* interop */

        [StructLayout(LayoutKind.Sequential)]
        private struct FILE_SET_SPARSE_BUFFER
        {
            public bool SetSparse;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct FILE_ZERO_DATA_INFORMATION
        {
            public long FileOffset;
            public long BeyondFinalZero;
        }

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.U1)]
        private static extern bool DeviceIoControl(
            IntPtr hDevice,
            uint dwIoControlCode,
            ref FILE_SET_SPARSE_BUFFER lpInBuffer,
            uint nInBufferSize,
            IntPtr lpOutBuffer,
            uint nOutBufferSize,
            out uint lpBytesReturned,
            IntPtr overlapped);

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.U1)]
        private static extern bool DeviceIoControl(
            IntPtr hDevice,
            uint dwIoControlCode,
            ref FILE_ZERO_DATA_INFORMATION lpInBuffer,
            uint nInBufferSize,
            IntPtr lpOutBuffer,
            uint nOutBufferSize,
            out uint lpBytesReturned,
            IntPtr overlapped);
    }
}