//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="ExpSource"
// Project: StgSharp
// AuthorGroup: Nitload Space
// Copyright (c) Nitload Space. All rights reserved.
//     
// 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.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.MemoryMappedFiles;
using System.Text;
using System.Threading;

namespace StgSharp.Script.Express
{
    public class ExpFileSource : IDisposable, IScriptSourceProvider
    {

        private bool disposedValue;
        private FileStream _expFileStream;
        private int _location;
        private MemoryMappedFile _expMemoryMappedFile;
        private MemoryMappedViewStream _expMemoryMappedStream;

        private SemaphoreSlim readLineSemaphore = new SemaphoreSlim(1, 1);
        private StreamReader _memoryReader;

        public ExpFileSource(string path)
        {
            if (!File.Exists(path)) {
                throw new FileNotFoundException();
            }
            _expFileStream = new FileStream(path, FileMode.Open, FileAccess.Read);
            _expMemoryMappedFile = MemoryMappedFile.CreateFromFile(
                _expFileStream, null, 0, MemoryMappedFileAccess.Read, HandleInheritability.None, true);
            _expMemoryMappedStream = _expMemoryMappedFile.CreateViewStream(
                offset:0, size:0, access:MemoryMappedFileAccess.Read);
            _memoryReader = new StreamReader(_expMemoryMappedStream);
        }

        public bool IsEmpty => _memoryReader.EndOfStream;

        public int Location => _location;

        // ~ExpFileSource()
        // {
        // Dispose(disposing: false);
        // }

        public void Dispose()
        {
            Dispose(disposing:true);
            GC.SuppressFinalize(this);
        }

        public void EndWriting() { }

        public string ReadLine()
        {
            readLineSemaphore.Wait();
            string line = _memoryReader.ReadLine()!;
            _location++;
            readLineSemaphore.Release();
            return line;
        }

        public string ReadLine(out int position)
        {
            throw new NotImplementedException();
        }

        public void ResetToBegin()
        {
            readLineSemaphore.Wait();
            _expMemoryMappedStream.Seek(0, SeekOrigin.Begin);
            _location = 0;
            readLineSemaphore.Release();
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                if (disposing)
                {
                    _expFileStream.Dispose();
                    _expMemoryMappedFile.Dispose();
                    _expMemoryMappedStream.Dispose();
                    _memoryReader.Dispose();
                }
                disposedValue = true;
            }
        }

        IScriptSourceProvider IScriptSourceProvider.Slice(int location, int count)
        {
            throw new NotSupportedException();
        }

    }
}