/* SPDX-License-Identifier: Apache-2.0
*
* The OpenSearch Contributors require contributions made to
* this file be licensed under the Apache-2.0 license or a
* compatible open source license.
*/
/*
* Modifications Copyright OpenSearch Contributors. See
* GitHub history for details.
*
*  Licensed to Elasticsearch B.V. under one or more contributor
*  license agreements. See the NOTICE file distributed with
*  this work for additional information regarding copyright
*  ownership. Elasticsearch B.V. licenses this file to you under
*  the Apache License, Version 2.0 (the "License"); you may
*  not use this file 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.
*/

#region Utf8Json License https://github.com/neuecc/Utf8Json/blob/master/LICENSE
// MIT License
//
// Copyright (c) 2017 Yoshifumi Kawai
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
#endregion

using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using System.Reflection.Emit;
using System.Text.RegularExpressions;

namespace OpenSearch.Net.Utf8Json.Internal.Emit
{
	internal class ILStreamReader : BinaryReader
	{
		private static readonly OpCode[] OneByteOpCodes = new OpCode[0x100];
		private static readonly OpCode[] TwoByteOpCodes = new OpCode[0x100];

		private readonly int _endPosition;

		public int CurrentPosition => (int)BaseStream.Position;

		public bool EndOfStream => !((int)BaseStream.Position < _endPosition);

		static ILStreamReader()
		{
			foreach (var fi in typeof(OpCodes).GetFields(BindingFlags.Public | BindingFlags.Static))
			{
				var opCode = (OpCode)fi.GetValue(null);
				var value =  unchecked((ushort)opCode.Value);

				if (value < 0x100)
					OneByteOpCodes[value] = opCode;
				else if ((value & 0xff00) == 0xfe00)
					TwoByteOpCodes[value & 0xff] = opCode;
			}
		}

		public ILStreamReader(byte[] ilByteArray)
			: base(RecyclableMemoryStreamFactory.Default.Create(ilByteArray)) =>
			_endPosition = ilByteArray.Length;

		public OpCode ReadOpCode()
		{
			var code = ReadByte();
			if (code != 0xFE)
				return OneByteOpCodes[code];

			code = ReadByte();
			return TwoByteOpCodes[code];
		}

		public int ReadMetadataToken() => ReadInt32();
	}
}