// Copyright ?2006, 2019, Oracle and/or its affiliates. All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License, version 2.0, for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System;
using System.Collections.Generic;
using System.Data;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.IO;
using Sog.Properties;

namespace MySql.Data.MySqlClient
{
    /// <summary>
    /// Allows importing large amounts of data into a database with bulk loading.
    /// </summary>
    public class MySqlBulkLoader
    {
        // constant values
        private const string defaultFieldTerminator = "\t";
        private const string defaultLineTerminator = "\n";
        private const char defaultEscapeCharacter = '\\';

        // fields

        public MySqlBulkLoader(MySqlConnection connection)
        {
            this.Connection = connection;
            this.Local = false;
            this.FieldTerminator = defaultFieldTerminator;
            this.LineTerminator = defaultLineTerminator;
            this.FieldQuotationCharacter = Char.MinValue;
            this.ConflictOption = MySqlBulkLoaderConflictOption.None;
            this.Columns = new List<string>();
            this.Expressions = new List<string>();
        }

        #region Properties

        /// <summary>
        /// Gets or sets the connection.
        /// </summary>
        /// <value>The connection.</value>
        public MySqlConnection Connection { get; set; }

        /// <summary>
        /// Gets or sets the field terminator.
        /// </summary>
        /// <value>The field terminator.</value>
        public string FieldTerminator { get; set; }

        /// <summary>
        /// Gets or sets the line terminator.
        /// </summary>
        /// <value>The line terminator.</value>
        public string LineTerminator { get; set; }

        /// <summary>
        /// Gets or sets the name of the table.
        /// </summary>
        /// <value>The name of the table.</value>
        public string TableName { get; set; }

        /// <summary>
        /// Gets or sets the character set.
        /// </summary>
        /// <value>The character set.</value>
        public string CharacterSet { get; set; }

        /// <summary>
        /// Gets or sets the name of the file.
        /// </summary>
        /// <value>The name of the file.</value>
        public string FileName { get; set; }

        /// <summary>
        /// Gets or sets the timeout.
        /// </summary>
        /// <value>The timeout.</value>
        public int Timeout { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether the file name that is to be loaded
        /// is local to the client or not. The default value is false.
        /// </summary>
        /// <value><c>true</c> if local; otherwise, <c>false</c>.</value>
        public bool Local { get; set; }

        /// <summary>
        /// Gets or sets the number of lines to skip.
        /// </summary>
        /// <value>The number of lines to skip.</value>
        public int NumberOfLinesToSkip { get; set; }

        /// <summary>
        /// Gets or sets the line prefix.
        /// </summary>
        /// <value>The line prefix.</value>
        public string LinePrefix { get; set; }

        /// <summary>
        /// Gets or sets the field quotation character.
        /// </summary>
        /// <value>The field quotation character.</value>
        public char FieldQuotationCharacter { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether [field quotation optional].
        /// </summary>
        /// <value>
        /// 	<c>true</c> if [field quotation optional]; otherwise, <c>false</c>.
        /// </value>
        public bool FieldQuotationOptional { get; set; }

        /// <summary>
        /// Gets or sets the escape character.
        /// </summary>
        /// <value>The escape character.</value>
        public char EscapeCharacter { get; set; }

        /// <summary>
        /// Gets or sets the conflict option.
        /// </summary>
        /// <value>The conflict option.</value>
        public MySqlBulkLoaderConflictOption ConflictOption { get; set; }

        /// <summary>
        /// Gets or sets the priority.
        /// </summary>
        /// <value>The priority.</value>
        public MySqlBulkLoaderPriority Priority { get; set; }

        /// <summary>
        /// Gets the columns.
        /// </summary>
        /// <value>The columns.</value>
        public List<string> Columns { get; }

        /// <summary>
        /// Gets the expressions.
        /// </summary>
        /// <value>The expressions.</value>
        public List<string> Expressions { get; }

        #endregion

        /// <summary>
        /// Executes the load operation.
        /// </summary>
        /// <returns>The number of rows inserted.</returns>
        public int Load()
        {
            bool openedConnection = false;

            if (this.Connection == null)
            {
                throw new InvalidOperationException(Resources.ConnectionNotSet);
            }

            // next we open up the connetion if it is not already open
            if (this.Connection.State != ConnectionState.Open)
            {
                openedConnection = true;
                this.Connection.Open();
            }

            try
            {
                string sql = this.BuildSqlCommand();
                MySqlCommand cmd = new MySqlCommand(sql, this.Connection) { CommandTimeout = this.Timeout };
                return cmd.ExecuteNonQuery();
            }
            finally
            {
                if (openedConnection)
                {
                    this.Connection.Close();
                }
            }
        }

        #region Async

        /// <summary>
        /// Asynchronous version of the load operation.
        /// </summary>
        /// <returns>The number of rows inserted.</returns>
        public Task<int> LoadAsync()
        {
            return this.LoadAsync(CancellationToken.None);
        }

        /// <summary>
        /// Executes the load operation asynchronously while the cancellation isn't requested.
        /// </summary>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>The number of rows inserted.</returns>
        public Task<int> LoadAsync(CancellationToken cancellationToken)
        {
            var result = new TaskCompletionSource<int>();
            if (cancellationToken == CancellationToken.None || !cancellationToken.IsCancellationRequested)
            {
                try
                {
                    int loadResult = this.Load();
                    result.SetResult(loadResult);
                }
                catch (Exception ex)
                {
                    result.SetException(ex);
                }
            }
            else
            {
                result.SetCanceled();
            }

            return result.Task;
        }
        #endregion

        private string BuildSqlCommand()
        {
            StringBuilder sql = new StringBuilder("LOAD DATA ");
            if (this.Priority == MySqlBulkLoaderPriority.Low)
            {
                sql.Append("LOW_PRIORITY ");
            }
            else if (this.Priority == MySqlBulkLoaderPriority.Concurrent)
            {
                sql.Append("CONCURRENT ");
            }

            if (this.Local)
            {
                sql.Append("LOCAL ");
            }

            sql.Append("INFILE ");
            if (Path.DirectorySeparatorChar == '\\')
            {
                sql.AppendFormat("'{0}' ", this.FileName.Replace(@"\", @"\\"));
            }
            else
            {
                sql.AppendFormat("'{0}' ", this.FileName);
            }

            if (this.ConflictOption == MySqlBulkLoaderConflictOption.Ignore)
            {
                sql.Append("IGNORE ");
            }
            else if (this.ConflictOption == MySqlBulkLoaderConflictOption.Replace)
            {
                sql.Append("REPLACE ");
            }

            sql.AppendFormat("INTO TABLE {0} ", this.TableName);

            if (this.CharacterSet != null)
            {
                sql.AppendFormat("CHARACTER SET {0} ", this.CharacterSet);
            }

            StringBuilder optionSql = new StringBuilder(String.Empty);
            if (this.FieldTerminator != defaultFieldTerminator)
            {
                optionSql.AppendFormat("TERMINATED BY '{0}' ", this.FieldTerminator);
            }

            if (this.FieldQuotationCharacter != Char.MinValue)
            {
                optionSql.AppendFormat(
                    "{0} ENCLOSED BY '{1}' ",
            this.FieldQuotationOptional ? "OPTIONALLY" : "", this.FieldQuotationCharacter);
            }

            if (this.EscapeCharacter != defaultEscapeCharacter &&
                this.EscapeCharacter != Char.MinValue)
            {
                optionSql.AppendFormat("ESCAPED BY '{0}' ", this.EscapeCharacter);
            }

            if (optionSql.Length > 0)
            {
                sql.AppendFormat("FIELDS {0}", optionSql.ToString());
            }

            optionSql = new StringBuilder(String.Empty);
            if (!string.IsNullOrEmpty(this.LinePrefix))
            {
                optionSql.AppendFormat("STARTING BY '{0}' ", this.LinePrefix);
            }

            if (this.LineTerminator != defaultLineTerminator)
            {
                optionSql.AppendFormat("TERMINATED BY '{0}' ", this.LineTerminator);
            }

            if (optionSql.Length > 0)
            {
                sql.AppendFormat("LINES {0}", optionSql.ToString());
            }

            if (this.NumberOfLinesToSkip > 0)
            {
                sql.AppendFormat("IGNORE {0} LINES ", this.NumberOfLinesToSkip);
            }

            if (this.Columns.Count > 0)
            {
                sql.Append("(");
                sql.Append(this.Columns[0]);
                for (int i = 1; i < this.Columns.Count; i++)
                {
                    sql.AppendFormat(",{0}", this.Columns[i]);
                }

                sql.Append(") ");
            }

            if (this.Expressions.Count > 0)
            {
                sql.Append("SET ");
                sql.Append(this.Expressions[0]);
                for (int i = 1; i < this.Expressions.Count; i++)
                {
                    sql.AppendFormat(",{0}", this.Expressions[i]);
                }
            }

            return sql.ToString();
        }
    }

    /// <summary>
    /// Represents the priority set for bulk loading operations.
    /// </summary>
    public enum MySqlBulkLoaderPriority
    {
        /// <summary>
        /// This is the default and indicates normal priority
        /// </summary>
        None,

        /// <summary>
        /// Low priority will cause the load operation to wait until all readers of the table
        /// have finished.  This only affects storage engines that use only table-level locking
        /// such as MyISAM, Memory, and Merge.
        /// </summary>
        Low,

        /// <summary>
        /// Concurrent priority is only relevant for MyISAM tables and signals that if the table
        /// has no free blocks in the middle that other readers can retrieve data from the table
        /// while the load operation is happening.
        /// </summary>
        Concurrent
    }

    /// <summary>
    /// Represents the behavior when conflicts arise during bulk loading operations.
    /// </summary>
    public enum MySqlBulkLoaderConflictOption
    {
        /// <summary>
        /// This is the default and indicates normal operation.  In the event of a LOCAL load, this
        /// is the same as ignore.  When the data file is on the server, then a key conflict will
        /// cause an error to be thrown and the rest of the data file ignored.
        /// </summary>
        None,

        /// <summary>
        /// Replace column values when a key conflict occurs.
        /// </summary>
        Replace,

        /// <summary>
        /// Ignore any rows where the primary key conflicts.
        /// </summary>
        Ignore
    }

}