using MediaBrowser.Common.Configuration;
using MediaBrowser.Controller.Entities;
using MediaBrowser.Controller.Persistence;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.Logging;
using MediaBrowser.Model.Serialization;
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SQLite;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace MediaBrowser.Server.Implementations.Persistence
{
    /// <summary>
    /// Class SQLiteItemRepository
    /// </summary>
    public class SqliteItemRepository : IItemRepository
    {
        private SQLiteConnection _connection;

        private readonly ILogger _logger;

        private readonly TypeMapper _typeMapper = new TypeMapper();
        
        /// <summary>
        /// Gets the name of the repository
        /// </summary>
        /// <value>The name.</value>
        public string Name
        {
            get
            {
                return "SQLite";
            }
        }

        /// <summary>
        /// Gets the json serializer.
        /// </summary>
        /// <value>The json serializer.</value>
        private readonly IJsonSerializer _jsonSerializer;

        /// <summary>
        /// The _app paths
        /// </summary>
        private readonly IApplicationPaths _appPaths;

        /// <summary>
        /// The _save item command
        /// </summary>
        private SQLiteCommand _saveItemCommand;

        private readonly string _criticReviewsPath;

        private SqliteChapterRepository _chapterRepository;

        private SQLiteCommand _deleteChildrenCommand;
        private SQLiteCommand _saveChildrenCommand;
        
        /// <summary>
        /// Initializes a new instance of the <see cref="SqliteItemRepository"/> class.
        /// </summary>
        /// <param name="appPaths">The app paths.</param>
        /// <param name="jsonSerializer">The json serializer.</param>
        /// <param name="logManager">The log manager.</param>
        /// <exception cref="System.ArgumentNullException">
        /// appPaths
        /// or
        /// jsonSerializer
        /// </exception>
        public SqliteItemRepository(IApplicationPaths appPaths, IJsonSerializer jsonSerializer, ILogManager logManager)
        {
            if (appPaths == null)
            {
                throw new ArgumentNullException("appPaths");
            }
            if (jsonSerializer == null)
            {
                throw new ArgumentNullException("jsonSerializer");
            }

            _appPaths = appPaths;
            _jsonSerializer = jsonSerializer;

            _criticReviewsPath = Path.Combine(_appPaths.DataPath, "critic-reviews");

            _logger = logManager.GetLogger(GetType().Name);

            var chapterDbFile = Path.Combine(_appPaths.DataPath, "chapters.db");

            var chapterConnection = SqliteExtensions.ConnectToDb(chapterDbFile).Result;

            _chapterRepository = new SqliteChapterRepository(chapterConnection, logManager);
        }

        /// <summary>
        /// Opens the connection to the database
        /// </summary>
        /// <returns>Task.</returns>
        public async Task Initialize()
        {
            var dbFile = Path.Combine(_appPaths.DataPath, "library.db");
            
            _connection = await SqliteExtensions.ConnectToDb(dbFile).ConfigureAwait(false);

            string[] queries = {

                                "create table if not exists TypedBaseItems (guid GUID primary key, type TEXT, data BLOB)",
                                "create index if not exists idx_TypedBaseItems on TypedBaseItems(guid)",

                                "create table if not exists ChildrenIds (ParentId GUID, ItemId GUID, PRIMARY KEY (ParentId, ItemId))",
                                "create index if not exists idx_ChildrenIds on ChildrenIds(ParentId,ItemId)",

                                //pragmas
                                "pragma temp_store = memory"
                               };

            _connection.RunQueries(queries, _logger);

            PrepareStatements();

            _chapterRepository.Initialize();
        }

        /// <summary>
        /// The _write lock
        /// </summary>
        private readonly SemaphoreSlim _writeLock = new SemaphoreSlim(1, 1);

        /// <summary>
        /// Prepares the statements.
        /// </summary>
        private void PrepareStatements()
        {
            _saveItemCommand = new SQLiteCommand
            {
                CommandText = "replace into TypedBaseItems (guid, type, data) values (@1, @2, @3)"
            };

            _saveItemCommand.Parameters.Add(new SQLiteParameter("@1"));
            _saveItemCommand.Parameters.Add(new SQLiteParameter("@2"));
            _saveItemCommand.Parameters.Add(new SQLiteParameter("@3"));

            _deleteChildrenCommand = new SQLiteCommand
            {
                CommandText = "delete from ChildrenIds where ParentId=@ParentId"
            };

            _deleteChildrenCommand.Parameters.Add(new SQLiteParameter("@ParentId"));

            _saveChildrenCommand = new SQLiteCommand
            {
                CommandText = "replace into ChildrenIds (ParentId, ItemId) values (@ParentId, @ItemId)"
            };

            _saveChildrenCommand.Parameters.Add(new SQLiteParameter("@ParentId"));
            _saveChildrenCommand.Parameters.Add(new SQLiteParameter("@ItemId"));
        }

        /// <summary>
        /// Save a standard item in the repo
        /// </summary>
        /// <param name="item">The item.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>Task.</returns>
        /// <exception cref="System.ArgumentNullException">item</exception>
        public Task SaveItem(BaseItem item, CancellationToken cancellationToken)
        {
            if (item == null)
            {
                throw new ArgumentNullException("item");
            }

            return SaveItems(new[] { item }, cancellationToken);
        }

        /// <summary>
        /// Saves the items.
        /// </summary>
        /// <param name="items">The items.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>Task.</returns>
        /// <exception cref="System.ArgumentNullException">
        /// items
        /// or
        /// cancellationToken
        /// </exception>
        public async Task SaveItems(IEnumerable<BaseItem> items, CancellationToken cancellationToken)
        {
            if (items == null)
            {
                throw new ArgumentNullException("items");
            }

            if (cancellationToken == null)
            {
                throw new ArgumentNullException("cancellationToken");
            }

            cancellationToken.ThrowIfCancellationRequested();

            await _writeLock.WaitAsync(cancellationToken).ConfigureAwait(false);

            SQLiteTransaction transaction = null;

            try
            {
                transaction = _connection.BeginTransaction();

                foreach (var item in items)
                {
                    cancellationToken.ThrowIfCancellationRequested();

                    _saveItemCommand.Parameters[0].Value = item.Id;
                    _saveItemCommand.Parameters[1].Value = item.GetType().FullName;
                    _saveItemCommand.Parameters[2].Value = _jsonSerializer.SerializeToBytes(item);

                    _saveItemCommand.Transaction = transaction;

                    await _saveItemCommand.ExecuteNonQueryAsync(cancellationToken);
                }

                transaction.Commit();
            }
            catch (OperationCanceledException)
            {
                if (transaction != null)
                {
                    transaction.Rollback();
                }

                throw;
            }
            catch (Exception e)
            {
                _logger.ErrorException("Failed to save items:", e);

                if (transaction != null)
                {
                    transaction.Rollback();
                }

                throw;
            }
            finally
            {
                if (transaction != null)
                {
                    transaction.Dispose();
                }

                _writeLock.Release();
            }
        }

        /// <summary>
        /// Internal retrieve from items or users table
        /// </summary>
        /// <param name="id">The id.</param>
        /// <returns>BaseItem.</returns>
        /// <exception cref="System.ArgumentNullException">id</exception>
        /// <exception cref="System.ArgumentException"></exception>
        public BaseItem RetrieveItem(Guid id)
        {
            if (id == Guid.Empty)
            {
                throw new ArgumentNullException("id");
            }

            using (var cmd = _connection.CreateCommand())
            {
                cmd.CommandText = "select type,data from TypedBaseItems where guid = @guid";
                var guidParam = cmd.Parameters.Add("@guid", DbType.Guid);
                guidParam.Value = id;

                using (var reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess | CommandBehavior.SingleResult | CommandBehavior.SingleRow))
                {
                    if (reader.Read())
                    {
                        var typeString = reader.GetString(0);

                        var type = _typeMapper.GetType(typeString);

                        if (type == null)
                        {
                            _logger.Debug("Unknown type {0}", typeString);

                            return null;
                        }

                        using (var stream = reader.GetMemoryStream(1))
                        {
                            return _jsonSerializer.DeserializeFromStream(stream, type) as BaseItem;
                        }
                    }
                }
                return null;
            }
        }

        /// <summary>
        /// Gets the critic reviews.
        /// </summary>
        /// <param name="itemId">The item id.</param>
        /// <returns>Task{IEnumerable{ItemReview}}.</returns>
        public IEnumerable<ItemReview> GetCriticReviews(Guid itemId)
        {
            try
            {
                var path = Path.Combine(_criticReviewsPath, itemId + ".json");

                return _jsonSerializer.DeserializeFromFile<List<ItemReview>>(path);
            }
            catch (DirectoryNotFoundException)
            {
                return new List<ItemReview>();
            }
            catch (FileNotFoundException)
            {
                return new List<ItemReview>();
            }
        }

        /// <summary>
        /// Saves the critic reviews.
        /// </summary>
        /// <param name="itemId">The item id.</param>
        /// <param name="criticReviews">The critic reviews.</param>
        /// <returns>Task.</returns>
        public Task SaveCriticReviews(Guid itemId, IEnumerable<ItemReview> criticReviews)
        {
            return Task.Run(() =>
            {
                if (!Directory.Exists(_criticReviewsPath))
                {
                    Directory.CreateDirectory(_criticReviewsPath);
                }

                var path = Path.Combine(_criticReviewsPath, itemId + ".json");

                _jsonSerializer.SerializeToFile(criticReviews.ToList(), path);
            });
        }

        /// <summary>
        /// Gets chapters for an item
        /// </summary>
        /// <param name="id">The id.</param>
        /// <returns>IEnumerable{ChapterInfo}.</returns>
        /// <exception cref="System.ArgumentNullException">id</exception>
        public IEnumerable<ChapterInfo> GetChapters(Guid id)
        {
            return _chapterRepository.GetChapters(id);
        }

        /// <summary>
        /// Gets a single chapter for an item
        /// </summary>
        /// <param name="id">The id.</param>
        /// <param name="index">The index.</param>
        /// <returns>ChapterInfo.</returns>
        /// <exception cref="System.ArgumentNullException">id</exception>
        public ChapterInfo GetChapter(Guid id, int index)
        {
            return _chapterRepository.GetChapter(id, index);
        }

        /// <summary>
        /// Saves the chapters.
        /// </summary>
        /// <param name="id">The id.</param>
        /// <param name="chapters">The chapters.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>Task.</returns>
        /// <exception cref="System.ArgumentNullException">
        /// id
        /// or
        /// chapters
        /// or
        /// cancellationToken
        /// </exception>
        public Task SaveChapters(Guid id, IEnumerable<ChapterInfo> chapters, CancellationToken cancellationToken)
        {
            return _chapterRepository.SaveChapters(id, chapters, cancellationToken);
        }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private readonly object _disposeLock = new object();

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        /// <param name="dispose"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected virtual void Dispose(bool dispose)
        {
            if (dispose)
            {
                try
                {
                    lock (_disposeLock)
                    {
                        if (_connection != null)
                        {
                            if (_connection.IsOpen())
                            {
                                _connection.Close();
                            }

                            _connection.Dispose();
                            _connection = null;
                        }
                    }
                }
                catch (Exception ex)
                {
                    _logger.ErrorException("Error disposing database", ex);
                }

                if (_chapterRepository != null)
                {
                    _chapterRepository.Dispose();
                    _chapterRepository = null;
                }
            }
        }

        public IEnumerable<Guid> GetChildren(Guid parentId)
        {
            if (parentId == Guid.Empty)
            {
                throw new ArgumentNullException("parentId");
            }

            using (var cmd = _connection.CreateCommand())
            {
                cmd.CommandText = "select ItemId from ChildrenIds where ParentId = @ParentId";

                cmd.Parameters.Add("@ParentId", DbType.Guid).Value = parentId;

                using (var reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess | CommandBehavior.SingleResult))
                {
                    while (reader.Read())
                    {
                        yield return reader.GetGuid(0);
                    }
                }
            }
        }

        public async Task SaveChildren(Guid parentId, IEnumerable<Guid> children, CancellationToken cancellationToken)
        {
            if (parentId == Guid.Empty)
            {
                throw new ArgumentNullException("parentId");
            }

            if (children == null)
            {
                throw new ArgumentNullException("children");
            }

            if (cancellationToken == null)
            {
                throw new ArgumentNullException("cancellationToken");
            }

            cancellationToken.ThrowIfCancellationRequested();

            await _writeLock.WaitAsync(cancellationToken).ConfigureAwait(false);

            SQLiteTransaction transaction = null;

            try
            {
                transaction = _connection.BeginTransaction();

                // First delete 
                _deleteChildrenCommand.Parameters[0].Value = parentId;
                _deleteChildrenCommand.Transaction = transaction;
                await _deleteChildrenCommand.ExecuteNonQueryAsync(cancellationToken);

                foreach (var id in children)
                {
                    cancellationToken.ThrowIfCancellationRequested();

                    _saveChildrenCommand.Parameters[0].Value = parentId;
                    _saveChildrenCommand.Parameters[1].Value = id;

                    _saveChildrenCommand.Transaction = transaction;

                    await _saveChildrenCommand.ExecuteNonQueryAsync(cancellationToken);
                }

                transaction.Commit();
            }
            catch (OperationCanceledException)
            {
                if (transaction != null)
                {
                    transaction.Rollback();
                }

                throw;
            }
            catch (Exception e)
            {
                _logger.ErrorException("Failed to save children:", e);

                if (transaction != null)
                {
                    transaction.Rollback();
                }

                throw;
            }
            finally
            {
                if (transaction != null)
                {
                    transaction.Dispose();
                }

                _writeLock.Release();
            }
        }
    }
}