// 
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//

using System;
using System.Collections.Generic;
using System.IO;
using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts;

namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.DataStorage
{
    /// <summary>
    /// Abstract class for implementing writers that save results to file. Stores some basic info
    /// that all save as writer would need.
    /// </summary>
    public abstract class SaveAsStreamWriter : IFileStreamWriter
    {
        /// <summary>
        /// Stores the internal state for the writer that will be necessary for any writer.
        /// </summary>
        /// <param name="stream">The stream that will be written to</param>
        /// <param name="requestParams">The SaveAs request parameters</param>
        protected SaveAsStreamWriter(Stream stream, SaveResultsRequestParams requestParams)
        {
            FileStream = stream;
            var saveParams = requestParams;
            if (requestParams.IsSaveSelection)
            {
                // ReSharper disable PossibleInvalidOperationException  IsSaveSelection verifies these values exist
                ColumnStartIndex = saveParams.ColumnStartIndex.Value;
                ColumnEndIndex = saveParams.ColumnEndIndex.Value;
                ColumnCount = saveParams.ColumnEndIndex.Value - saveParams.ColumnStartIndex.Value + 1;
                // ReSharper restore PossibleInvalidOperationException
            }
        }

        #region Properties

        /// <summary>
        /// Index of the first column to write to the output file
        /// </summary>
        protected int? ColumnStartIndex { get; private set; }

        /// <summary>
        /// Number of columns to write to the output file
        /// </summary>
        protected int? ColumnCount { get; private set; }

        /// <summary>
        /// Index of the last column to write to the output file
        /// </summary>
        protected int? ColumnEndIndex { get; private set; }

        /// <summary>
        /// The file stream to use to write the output file
        /// </summary>
        protected Stream FileStream { get; private set; }

        #endregion

        /// <summary>
        /// Not implemented, do not use.
        /// </summary>
        [Obsolete]
        public int WriteRow(StorageDataReader dataReader)
        {
            throw new InvalidOperationException("This type of writer is meant to write values from a list of cell values only.");
        }

        /// <summary>
        /// Writes a row of data to the output file using the format provided by the implementing class.
        /// </summary>
        /// <param name="row">The row of data to output</param>
        /// <param name="columns">The list of columns to output</param>
        public abstract void WriteRow(IList<DbCellValue> row, IList<DbColumnWrapper> columns);

        /// <summary>
        /// Not implemented, do not use.
        /// </summary>
        [Obsolete]
        public void Seek(long offset)
        {
            throw new InvalidOperationException("SaveAs writers are meant to be written once contiguously.");
        }

        /// <summary>
        /// Flushes the file stream buffer
        /// </summary>
        public void FlushBuffer()
        {
            FileStream.Flush();
        }

        #region IDisposable Implementation

        private bool disposed;

        /// <summary>
        /// Disposes the instance by flushing and closing the file stream
        /// </summary>
        /// <param name="disposing"></param>
        protected virtual void Dispose(bool disposing)
        {
            if (disposed)
                return;

            if (disposing)
            {
                FileStream.Dispose();
            }
            disposed = true;
        }

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

        #endregion
    }
}