#region License
/* Vorbisfile# - C# Wrapper for Vorbisfile
 *
 * Copyright (c) 2013-2015 Ethan Lee.
 *
 * This software is provided 'as-is', without any express or implied warranty.
 * In no event will the authors be held liable for any damages arising from
 * the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 * claim that you wrote the original software. If you use this software in a
 * product, an acknowledgment in the product documentation would be
 * appreciated but is not required.
 *
 * 2. Altered source versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.
 *
 * 3. This notice may not be removed or altered from any source distribution.
 *
 * Ethan "flibitijibibo" Lee <flibitijibibo@flibitijibibo.com>
 *
 */
#endregion

#region Using Statements
using System;
using System.Runtime.InteropServices;
#endregion

public static class Vorbisfile
{
	#region Native Library Name

	private const string nativeLibName = "libvorbisfile";

	#endregion

	#region malloc/free Entry Points

	// Yes, we're seriously using these. -flibit

	[DllImport("msvcrt.dll", CallingConvention = CallingConvention.Cdecl)]
	private static extern IntPtr malloc(IntPtr size);

	[DllImport("msvcrt.dll", CallingConvention = CallingConvention.Cdecl)]
	private static extern void free(IntPtr memblock);

	#endregion

	#region C stdio Macros

	// Used by ov_callbacks, seek_func
	public enum SeekWhence : int
	{
		SEEK_SET = 0,
		SEEK_CUR = 1,
		SEEK_END = 2
	}

	#endregion

	#region Vorbis Delegates

	/* IntPtr refers to a size_t */
	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	public delegate IntPtr read_func(
		IntPtr ptr,		// Refers to a void*
		IntPtr size,		// Refers to a size_t
		IntPtr nmemb,		// Refers to a size_t
		IntPtr datasource	// Refers to a void*
	);

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	public delegate int seek_func(
		IntPtr datasource,	// Refers to a void*
		long offset,		// Refers to an ogg_int64_t
		SeekWhence whence
	);

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	public delegate int close_func(
		IntPtr datasource	// Refers to a void*
	);

	/* IntPtr refers to a long, ignoring Win64! */
	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	public delegate IntPtr tell_func(
		IntPtr datasource	// Refers to a void*
	);

	#endregion

	#region Vorbis Structures

	[StructLayout(LayoutKind.Sequential)]
	public struct vorbis_info
	{
		public int version;
		public int channels;
		public IntPtr rate;		// refers to a long, ignoring Win64!
		public IntPtr bitrate_upper;	// refers to a long, ignoring Win64!
		public IntPtr bitrate_nominal;	// refers to a long, ignoring Win64!
		public IntPtr bitrate_lower;	// refers to a long, ignoring Win64!
		public IntPtr bitrate_window;	// refers to a long, ignoring Win64!
		public IntPtr codec_setup;	// Refers to a void*
	}

	[StructLayout(LayoutKind.Sequential)]
	public struct vorbis_comment
	{
		public IntPtr user_comments;	// Refers to a char**
		public IntPtr comment_lengths;	// Refers to an int*
		public int comments;
		public IntPtr vendor;		// Refers to a char*
	}

	[StructLayout(LayoutKind.Sequential)]
	public struct ov_callbacks
	{
		public read_func read_func;
		public seek_func seek_func;
		public close_func close_func;
		public tell_func tell_func;
	}

	#endregion

	#region Vorbisfile Implementation

	[DllImport(nativeLibName, EntryPoint = "ov_fopen", CallingConvention = CallingConvention.Cdecl)]
	private static extern int INTERNAL_ov_fopen(
		[In()] [MarshalAs(UnmanagedType.LPStr)]
			string path,
		IntPtr vf
	);
	public static int ov_fopen(string path, out IntPtr vf)
	{
		vf = AllocVorbisFile();
		return INTERNAL_ov_fopen(path, vf);
	}

	[DllImport(nativeLibName, EntryPoint = "ov_open_callbacks", CallingConvention = CallingConvention.Cdecl)]
	private static extern int INTERNAL_ov_open_callbacks(
		IntPtr datasource,
		IntPtr vf,
		IntPtr initial,
		IntPtr ibytes,
		ov_callbacks callbacks
	);
	public static int ov_open_callbacks(
		IntPtr datasource,	// Refers to a void*
		out IntPtr vf,
		IntPtr initial,		// Refers to a char*
		IntPtr ibytes,		// Refers to a long, ignoring Win64!
		ov_callbacks callbacks
	) {
		vf = AllocVorbisFile();
		return INTERNAL_ov_open_callbacks(
			datasource,
			vf,
			initial,
			ibytes,
			callbacks
		);
	}

	[DllImport(nativeLibName, EntryPoint = "ov_info", CallingConvention = CallingConvention.Cdecl)]
	private static extern IntPtr INTERNAL_ov_info(
		IntPtr vf,
		int link
	);
	public static vorbis_info ov_info(
		IntPtr vf,
		int link
	) {
		IntPtr result = INTERNAL_ov_info(vf, link);
		if (result == IntPtr.Zero) throw new InvalidOperationException("Specified bitstream does not exist or the file has been initialized improperly.");
		vorbis_info info = (vorbis_info) Marshal.PtrToStructure(
			result,
			typeof(vorbis_info)
		);
		return info;
	}

	[DllImport(nativeLibName, EntryPoint = "ov_comment", CallingConvention = CallingConvention.Cdecl)]
	private static extern IntPtr INTERNAL_ov_comment(
		IntPtr vf,
		int link
	);
	public static vorbis_comment ov_comment(
		IntPtr vf,
		int link
	) {
		IntPtr result = INTERNAL_ov_comment(vf, link);
		if (result == IntPtr.Zero) throw new InvalidOperationException("Specified bitstream does not exist or the file has been initialized improperly.");
		vorbis_comment comment = (vorbis_comment) Marshal.PtrToStructure(
			result,
			typeof(vorbis_comment)
		);
		return comment;
	}

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern double ov_time_total(IntPtr vf, int i);

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern long ov_pcm_total(IntPtr vf, int i);

	/* IntPtr refers to a long, ignoring Win64! */
	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern IntPtr ov_read(
		IntPtr vf,
		byte[] buffer,
		int length,
		int bigendianp,
		int word,
		int sgned,
		out int current_section
	);

	/* IntPtr refers to a long, ignoring Win64! */
	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern IntPtr ov_read(
		IntPtr vf,
		IntPtr buffer,
		int length,
		int bigendianp,
		int word,
		int sgned,
		out int current_section
	);

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern int ov_time_seek(IntPtr vf, double s);

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern int ov_pcm_seek(IntPtr vf, long s);

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern double ov_time_tell(IntPtr vf);

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern long ov_pcm_tell(IntPtr vf);

	[DllImport(nativeLibName, EntryPoint = "ov_clear", CallingConvention = CallingConvention.Cdecl)]
	private static extern int INTERNAL_ov_clear(IntPtr vf);
	public static int ov_clear(ref IntPtr vf)
	{
		int result = INTERNAL_ov_clear(vf);
		free(vf);
		vf = IntPtr.Zero;
		return result;
	}

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern IntPtr ov_streams(IntPtr vf);

	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern IntPtr ov_seekable(IntPtr vf);

	/* IntPtr refers to a long, ignoring Win64! */
	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern int ov_raw_seek(IntPtr vf, IntPtr pos);

	/* IntPtr refers to a long, ignoring Win64! */
	[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
	public static extern IntPtr ov_raw_tell(IntPtr vf);
	
	#endregion

	#region OggVorbis_File Allocator

	/* Notice that we did not implement an OggVorbis_File struct, but are
	 * instead using a pointer natively malloc'd.
	 *
	 * C# Interop for Vorbisfile structs is basically impossible to do, so
	 * we just alloc what _should_ be the full size of the structure for
	 * the OS and architecture, then pass that around as if that's a real
	 * struct. The size is just what you get from sizeof(OggVorbis_File).
	 *
	 * Don't get mad at me, get mad at C#.
	 *
	 * -flibit
	 */

	private static IntPtr AllocVorbisFile()
	{
		// Do not attempt to understand these numbers at all costs!
		const int size32 = 720;
		const int size64Unix = 944;
		const int size64Windows = 840;

		PlatformID platform = Environment.OSVersion.Platform;
		if (IntPtr.Size == 4)
		{
			/* Technically this could be as low as 704 bytes, but
			 * some 32-bit architectures may be higher even on Unix
			 * targets (like ARMv7).
			 * -flibit
			 */
			return malloc((IntPtr) size32);
		}
		if (IntPtr.Size == 8)
		{
			if (platform == PlatformID.Unix)
			{
				return malloc((IntPtr) size64Unix);
			}
			else if (platform == PlatformID.Win32NT)
			{
				return malloc((IntPtr) size64Windows);
			}
			throw new NotSupportedException("Unhandled platform!");
		}
		throw new NotSupportedException("Unhandled architecture!");
	}

	#endregion
}