using System;
using System.Collections.Generic;
using System.Data.Common;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace LinqToDB.DataProvider.Informix
{
	using Common;
	using Data;
	using SqlProvider;

	sealed class InformixBulkCopy : BasicBulkCopy
	{
		protected override int                  MaxSqlLength  => 32767;
		private readonly   InformixDataProvider _provider;

		public InformixBulkCopy(InformixDataProvider provider)
		{
			_provider = provider;
		}

		protected override BulkCopyRowsCopied ProviderSpecificCopy<T>(
			ITable<T> table, DataOptions options, IEnumerable<T> source)
		{
			if ((_provider.Adapter.InformixBulkCopy != null || _provider.Adapter.DB2BulkCopy != null)
				&& table.TryGetDataConnection(out var dataConnection) && dataConnection.Transaction == null)
			{
				var connection = _provider.TryGetProviderConnection(dataConnection, dataConnection.Connection);

				if (connection != null)
				{
					if (_provider.Adapter.InformixBulkCopy != null)
						return IDSProviderSpecificCopy(
							table,
							options.BulkCopyOptions,
							source,
							dataConnection,
							connection,
							_provider.Adapter.InformixBulkCopy);
					else
						return DB2.DB2BulkCopyShared.ProviderSpecificCopyImpl(
							table,
							options.BulkCopyOptions,
							source,
							dataConnection,
							connection,
							_provider.Adapter.DB2BulkCopy!,
							TraceAction);
				}
			}

			return MultipleRowsCopy(table, options, source);
		}

		protected override Task<BulkCopyRowsCopied> ProviderSpecificCopyAsync<T>(
			ITable<T> table, DataOptions options, IEnumerable<T> source, CancellationToken cancellationToken)
		{
			if ((_provider.Adapter.InformixBulkCopy != null || _provider.Adapter.DB2BulkCopy != null)
				&& table.TryGetDataConnection(out var dataConnection) && dataConnection.Transaction == null)
			{
				var connection = _provider.TryGetProviderConnection(dataConnection, dataConnection.Connection);

				if (connection != null)
				{
					// call the synchronous provider-specific implementation
					if (_provider.Adapter.InformixBulkCopy != null)
						return Task.FromResult(IDSProviderSpecificCopy(
							table,
							options.BulkCopyOptions,
							source,
							dataConnection,
							connection,
							_provider.Adapter.InformixBulkCopy));
					else
						return Task.FromResult(DB2.DB2BulkCopyShared.ProviderSpecificCopyImpl(
							table,
							options.BulkCopyOptions,
							source,
							dataConnection,
							connection,
							_provider.Adapter.DB2BulkCopy!,
							TraceAction));
				}
			}

			return MultipleRowsCopyAsync(table, options, source, cancellationToken);
		}

#if NATIVE_ASYNC
		protected override async Task<BulkCopyRowsCopied> ProviderSpecificCopyAsync<T>(
			ITable<T> table, DataOptions options, IAsyncEnumerable<T> source, CancellationToken cancellationToken)
		{
			if ((_provider.Adapter.InformixBulkCopy != null || _provider.Adapter.DB2BulkCopy != null)
				&& table.TryGetDataConnection(out var dataConnection) && dataConnection.Transaction == null)
			{
				var connection = _provider.TryGetProviderConnection(dataConnection, dataConnection.Connection);

				if (connection != null)
				{
					var enumerator = source.GetAsyncEnumerator(cancellationToken);
					await using (enumerator.ConfigureAwait(Configuration.ContinueOnCapturedContext))
					{
						// call the synchronous provider-specific implementation
						var syncSource = EnumerableHelper.AsyncToSyncEnumerable(enumerator);
						if (_provider.Adapter.InformixBulkCopy != null)
							return IDSProviderSpecificCopy(
								table,
								options.BulkCopyOptions,
								syncSource,
								dataConnection,
								connection,
								_provider.Adapter.InformixBulkCopy);
						else
							return DB2.DB2BulkCopyShared.ProviderSpecificCopyImpl(
								table,
								options.BulkCopyOptions,
								syncSource,
								dataConnection,
								connection,
								_provider.Adapter.DB2BulkCopy!,
								TraceAction);
					}
				}
			}

			return await MultipleRowsCopyAsync(table, options, source, cancellationToken)
				.ConfigureAwait(Configuration.ContinueOnCapturedContext);
		}
#endif

		private BulkCopyRowsCopied IDSProviderSpecificCopy<T>(
			ITable<T>                               table,
			BulkCopyOptions                         options,
			IEnumerable<T>                          source,
			DataConnection                          dataConnection,
			DbConnection                            connection,
			InformixProviderAdapter.BulkCopyAdapter bulkCopy)
			where T: notnull
		{
			var ed      = table.DataContext.MappingSchema.GetEntityDescriptor(typeof(T), dataConnection.Options.ConnectionOptions.OnEntityDescriptorCreated);
			var columns = ed.Columns.Where(c => !c.SkipOnInsert || options.KeepIdentity == true && c.IsIdentity).ToList();
			var sb      = _provider.CreateSqlBuilder(table.DataContext.MappingSchema, dataConnection.Options);
			var rd      = new BulkCopyReader<T>(dataConnection, columns, source);
			var sqlopt  = InformixProviderAdapter.IfxBulkCopyOptions.Default;
			var rc      = new BulkCopyRowsCopied();

			if (options.KeepIdentity == true) sqlopt |= InformixProviderAdapter.IfxBulkCopyOptions.KeepIdentity;
			if (options.TableLock    == true) sqlopt |= InformixProviderAdapter.IfxBulkCopyOptions.TableLock;

			using (var bc = bulkCopy.Create(connection, sqlopt))
			{
				if (options.NotifyAfter != 0 && options.RowsCopiedCallback != null)
				{
					bc.NotifyAfter = options.NotifyAfter;

					bc.IfxRowsCopied += (sender, args) =>
					{
						rc.RowsCopied = args.RowsCopied;
						options.RowsCopiedCallback(rc);
						if (rc.Abort)
							args.Abort = true;
					};
				}

				if (options.BulkCopyTimeout.HasValue)
					bc.BulkCopyTimeout = options.BulkCopyTimeout.Value;
				else if (Configuration.Data.BulkCopyUseConnectionCommandTimeout)
					bc.BulkCopyTimeout = connection.ConnectionTimeout;

				var tableName = GetTableName(sb, options, table);

				bc.DestinationTableName = tableName;

				for (var i = 0; i < columns.Count; i++)
					bc.ColumnMappings.Add(bulkCopy.CreateColumnMapping(i, sb.ConvertInline(columns[i].ColumnName, ConvertType.NameToQueryField)));

				TraceAction(
					dataConnection,
					() => "INSERT BULK " + tableName + "(" + string.Join(", ", columns.Select(x => x.ColumnName)) + ")" + Environment.NewLine,
					() => { bc.WriteToServer(rd); return rd.Count; });
			}

			if (rc.RowsCopied != rd.Count)
			{
				rc.RowsCopied = rd.Count;

				if (options.NotifyAfter != 0 && options.RowsCopiedCallback != null)
					options.RowsCopiedCallback(rc);
			}

			return rc;
		}

		protected override BulkCopyRowsCopied MultipleRowsCopy<T>(
			ITable<T> table, DataOptions options, IEnumerable<T> source)
		{
			using ((IDisposable)new InvariantCultureRegion(null))
				return base.MultipleRowsCopy(table, options, source);
		}

		protected override async Task<BulkCopyRowsCopied> MultipleRowsCopyAsync<T>(
			ITable<T> table, DataOptions options, IEnumerable<T> source, CancellationToken cancellationToken)
		{
#if NATIVE_ASYNC
			await using (new InvariantCultureRegion(null))
#else
			using ((IDisposable)new InvariantCultureRegion(null))
#endif
				return await base.MultipleRowsCopyAsync(table, options, source, cancellationToken).ConfigureAwait(Configuration.ContinueOnCapturedContext);
		}

#if NATIVE_ASYNC
		protected override async Task<BulkCopyRowsCopied> MultipleRowsCopyAsync<T>(
			ITable<T> table, DataOptions options, IAsyncEnumerable<T> source, CancellationToken cancellationToken)
		{
			await using (new InvariantCultureRegion(null))
				return await base.MultipleRowsCopyAsync(table, options, source, cancellationToken).ConfigureAwait(Configuration.ContinueOnCapturedContext);
		}
#endif
	}
}
