using System;
using System.Runtime.InteropServices;

namespace Python.Runtime
{
 /* buffer interface */
 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
 internal struct Py_buffer {
 public IntPtr buf;
 public IntPtr obj; /* owned reference */
 /// <summary>Buffer size in bytes</summary>
 [MarshalAs(UnmanagedType.SysInt)]
 public nint len;
 [MarshalAs(UnmanagedType.SysInt)]
 public nint itemsize; /* This is Py_ssize_t so it can be
 pointed to by strides in simple case.*/
 [MarshalAs(UnmanagedType.Bool)]
 public bool _readonly;
 public int ndim;
 [MarshalAs(UnmanagedType.LPStr)]
 public string? format;
 public IntPtr shape;
 public IntPtr strides;
 public IntPtr suboffsets;
 public IntPtr _internal;
 }

 public enum BufferOrderStyle
 {
 C,
 Fortran,
 EitherOne,
 }

 /* Flags for getting buffers */
 public enum PyBUF
 {
 /// <summary>
 /// Simple buffer without shape strides and suboffsets
 /// </summary>
 SIMPLE = 0,
 /// <summary>
 /// Controls the <see cref="PyBuffer.ReadOnly"/> field. If set, the exporter MUST provide a writable buffer or else report failure. Otherwise, the exporter MAY provide either a read-only or writable buffer, but the choice MUST be consistent for all consumers.
 /// </summary>
 WRITABLE = 0x0001,
 /// <summary>
 /// Controls the <see cref="PyBuffer.Format"/> field. If set, this field MUST be filled in correctly. Otherwise, this field MUST be NULL.
 /// </summary>
 FORMATS = 0x0004,
 /// <summary>
 /// N-Dimensional buffer with shape
 /// </summary>
 ND = 0x0008,
 /// <summary>
 /// Buffer with strides and shape
 /// </summary>
 STRIDES = (0x0010 | ND),
 /// <summary>
 /// C-Contigous buffer with strides and shape
 /// </summary>
 C_CONTIGUOUS = (0x0020 | STRIDES),
 /// <summary>
 /// F-Contigous buffer with strides and shape
 /// </summary>
 F_CONTIGUOUS = (0x0040 | STRIDES),
 /// <summary>
 /// C or Fortran contigous buffer with strides and shape
 /// </summary>
 ANY_CONTIGUOUS = (0x0080 | STRIDES),
 /// <summary>
 /// Buffer with suboffsets (if needed)
 /// </summary>
 INDIRECT = (0x0100 | STRIDES),
 /// <summary>
 /// Writable C-Contigous buffer with shape
 /// </summary>
 CONTIG = (ND | WRITABLE),
 /// <summary>
 /// Readonly C-Contigous buffer with shape
 /// </summary>
 CONTIG_RO = (ND),
 /// <summary>
 /// Writable buffer with shape and strides
 /// </summary>
 STRIDED = (STRIDES | WRITABLE),
 /// <summary>
 /// Readonly buffer with shape and strides
 /// </summary>
 STRIDED_RO = (STRIDES),
 /// <summary>
 /// Writable buffer with shape, strides and format
 /// </summary>
 RECORDS = (STRIDES | WRITABLE | FORMATS),
 /// <summary>
 /// Readonly buffer with shape, strides and format
 /// </summary>
 RECORDS_RO = (STRIDES | FORMATS),
 /// <summary>
 /// Writable indirect buffer with shape, strides, format and suboffsets (if needed)
 /// </summary>
 FULL = (INDIRECT | WRITABLE | FORMATS),
 /// <summary>
 /// Readonly indirect buffer with shape, strides, format and suboffsets (if needed)
 /// </summary>
 FULL_RO = (INDIRECT | FORMATS),
 }

 internal struct PyBufferProcs
 {
 public IntPtr Get;
 public IntPtr Release;
 }

 [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 delegate int GetBufferProc(BorrowedReference obj, out Py_buffer buffer, PyBUF flags);
 [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
 delegate void ReleaseBufferProc(BorrowedReference obj, ref Py_buffer buffer);
}