// RichTextKit
// Copyright © 2019-2020 Topten Software. All Rights Reserved.
// 
// Licensed under the Apache License, Version 2.0 (the "License"); you may 
// not use this product except in compliance with the License. You may obtain 
// a copy of the License at
// 
// http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 
// License for the specific language governing permissions and limitations 
// under the License.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Topten.RichTextKit.Utils;

namespace Topten.RichTextKit.Utils
{
	/// <summary>
	/// Miscellaneous utility functions for working with UTF-32 data.
	/// </summary>
	public static class Utf32Utils
	{
		/// <summary>
		/// Convert a slice of UTF-32 integer code points to a string
		/// </summary>
		/// <param name="buffer">The code points to convert</param>
		/// <returns>A string</returns>
		public static string FromUtf32( Slice<int> buffer )
		{
			unsafe
			{
				fixed ( int* p = buffer.Underlying )
				{
					var pBuf = p + buffer.Start;
					return new string( (sbyte*)pBuf, 0, buffer.Length * sizeof( int ), Encoding.UTF32 );
				}
			}
		}

		/// <summary>
		/// Converts a string to an integer array of UTF-32 code points
		/// </summary>
		/// <param name="str">The string to convert</param>
		/// <returns>The converted code points</returns>
		public static int[] ToUtf32( string str )
		{
			unsafe
			{
				fixed ( char* pstr = str )
				{
					// Get required byte count
					int byteCount = Encoding.UTF32.GetByteCount( pstr, str.Length );
					System.Diagnostics.Debug.Assert( (byteCount % 4) == 0 );

					// Allocate buffer
					int[] utf32 = new int[byteCount / sizeof( int )];
					fixed ( int* putf32 = utf32 )
					{
						// Convert
						Encoding.UTF32.GetBytes( pstr, str.Length, (byte*)putf32, byteCount );

						// Done
						return utf32;
					}
				}
			}
		}
	}
}
