// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using Microsoft.CodeAnalysis;
using System;
using System.Diagnostics;
using System.IO;
using System.Text;
 
namespace Microsoft.CodeAnalysis
{
    internal static partial class EncodingExtensions
    {
        /// <summary>
        /// Get maximum char count needed to decode the entire stream.
        /// </summary>
        /// <exception cref="IOException">Stream is so big that max char count can't fit in <see cref="int"/>.</exception> 
        internal static int GetMaxCharCountOrThrowIfHuge(this Encoding encoding, Stream stream)
        {
            Debug.Assert(stream.CanSeek);
            long length = stream.Length;
 
            if (encoding.TryGetMaxCharCount(length, out int maxCharCount))
            {
                return maxCharCount;
            }
 
#if CODE_STYLE
            throw new IOException(CodeStyleResources.Stream_is_too_long);
#elif WORKSPACE
            throw new IOException(WorkspacesResources.Stream_is_too_long);
#else
            throw new IOException(CodeAnalysisResources.StreamIsTooLong);
#endif
        }
 
        internal static bool TryGetMaxCharCount(this Encoding encoding, long length, out int maxCharCount)
        {
            maxCharCount = 0;
 
            if (length <= int.MaxValue)
            {
                try
                {
                    maxCharCount = encoding.GetMaxCharCount((int)length);
                    return true;
                }
                catch (ArgumentOutOfRangeException)
                {
                    // Encoding does not provide a way to predict that max byte count would not
                    // fit in Int32 and we must therefore catch ArgumentOutOfRange to handle that
                    // case.
                }
            }
 
            return false;
        }
    }
}