﻿// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF 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.

using System;
using System.Collections.Generic;
using System.Collections;
using System.Globalization;
using System.IO;
using System.Linq;
using Org.Apache.REEF.IO.FileSystem;
using Org.Apache.REEF.IO.PartitionedData.FileSystem.Parameters;
using Org.Apache.REEF.Tang.Annotations;
using Org.Apache.REEF.Tang.Formats;
using Org.Apache.REEF.Tang.Implementations.Configuration;
using Org.Apache.REEF.Tang.Implementations.Tang;
using Org.Apache.REEF.Tang.Interface;
using Org.Apache.REEF.Utilities.Logging;

namespace Org.Apache.REEF.IO.PartitionedData.FileSystem
{
    /// <summary>
    /// This class is an implementation of IPartitionedDataSet for FileSystem.
    /// It requires the client to provide configuration for FileSerializer 
    /// T is a type for data, e.g. a class like Row, or int, byte
    /// </summary>
    /// <typeparam name="T"></typeparam>
    internal sealed class FileSystemPartitionInputDataSet<T> : IPartitionedInputDataSet
    {
        private static readonly Logger Logger = Logger.GetLogger(typeof(FileSystemPartitionInputDataSet<T>));
        private readonly Dictionary<string, IPartitionDescriptor> _partitions;
        private readonly int _count;
        private const string StringSeparators = ";";
        private const string IdPrefix = "FileSystemDataSet-";
        private readonly string _id;
        
        [Inject]
        private FileSystemPartitionInputDataSet(
            [Parameter(typeof(FilePathsForInputPartitions))] ISet<string> filePaths,
            IFileSystem fileSystem,
            [Parameter(typeof(CopyToLocal))] bool copyToLocal,
            [Parameter(typeof(FileDeSerializerConfigString))] string fileSerializerConfigString,
            AvroConfigurationSerializer avroConfigurationSerializer)
        {
            _count = filePaths.Count;
            _id = FormId(filePaths);

            _partitions = new Dictionary<string, IPartitionDescriptor>(_count);

            var fileSerializerConfig = 
                avroConfigurationSerializer.FromString(fileSerializerConfigString); 

            int i = 0;
            foreach (var path in filePaths)
            {
                var paths = path.Split(new string[] { StringSeparators }, StringSplitOptions.None);
               
                var id = "FilePartition-" + i++;
                _partitions[id] = new FileInputPartitionDescriptor<T>(id, paths.ToList(), copyToLocal, fileSerializerConfig); 
            }
        }

        /// <summary>
        /// It returns the number of partions in the data set
        /// </summary>
        public int Count
        {
            get { return _count; }
        }

        /// <summary>
        /// It returns the id of the file system data set
        /// </summary>
        public string Id
        {
            get { return _id; }
        }

        /// <summary>
        /// It returns Partition Descriptor by given id
        /// If id doesn't exists, it is callers responsibility to catch and handle exception
        /// </summary>
        /// <param name="partitionId"></param>
        /// <returns></returns>
        public IPartitionDescriptor GetPartitionDescriptorForId(string partitionId)
        {
            return _partitions[partitionId];
        }

        /// <summary>
        /// Returns IEnumerator of IPartitionDescriptor
        /// </summary>
        /// <returns></returns>
        public IEnumerator<IPartitionDescriptor> GetEnumerator()
        {
            return _partitions.Values.GetEnumerator();
        }

        /// <summary>
        /// Returns IEnumerator of IPartitionDescriptor in the partitions
        /// </summary>
        /// <returns></returns>
        IEnumerator IEnumerable.GetEnumerator()
        {
            return _partitions.Values.GetEnumerator();
        }

        /// <summary>
        /// The id is derived form the a input file name. For whatever reason if it doesn't work out, default will be used.
        /// </summary>
        /// <param name="filePaths"></param>
        /// <returns></returns>
        private static string FormId(ISet<string> filePaths)
        {
            string id = string.Empty;
            try
            {
                if (filePaths != null && filePaths.Count > 0)
                {
                    var path = filePaths.First();
                    var paths = path.Split(new string[] { "/", "//", "\\" }, StringSplitOptions.None);
                    if (paths.Length > 0)
                    {
                        id = paths[paths.Length - 1];
                    }
                }
            }
            catch (Exception e)
            {
                Logger.Log(Level.Warning, string.Format(CultureInfo.CurrentCulture, "The filePaths cannot be parsed for generating dataset id", e));
            }

            return IdPrefix + id;
        }
    }
}