// Copyright (c) 2004, 2021, Oracle and/or its affiliates.
//
// 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 MySql.Data.Common;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Text;
using Sog.Properties;

namespace MySql.Data.MySqlClient
{
    internal abstract class Statement
    {
        protected MySqlCommand command;
        private readonly List<MySqlPacket> _buffers;
        protected string commandText;
        protected int paramsPosition;

        private Statement(MySqlCommand cmd)
        {
            this.command = cmd;
            this._buffers = new List<MySqlPacket>();
        }

        protected Statement(MySqlCommand cmd, string text)
          : this(cmd)
        {
            this.commandText = text;
        }

        #region Properties

        public virtual string ResolvedCommandText
        {
            get { return this.commandText; }
        }

        protected Driver Driver => this.command.Connection.driver;

        protected MySqlConnection Connection => this.command.Connection;

        protected MySqlParameterCollection Parameters => this.command.Parameters;

        protected MySqlAttributeCollection Attributes => this.command.Attributes;

        #endregion

        public virtual void Close(MySqlDataReader reader)
        {
        }

        public virtual void Resolve(bool preparing)
        {
        }

        public virtual void Execute()
        {
            // we keep a reference to this until we are done
            this.BindParameters();
            this.ExecuteNext();
        }

        public virtual bool ExecuteNext()
        {
            if (this._buffers.Count == 0)
            {
                return false;
            }

            MySqlPacket packet = this._buffers[0];
            this.Driver.SendQuery(packet, this.paramsPosition);
            this._buffers.RemoveAt(0);
            return true;
        }

        protected virtual void BindParameters()
        {
            MySqlParameterCollection parameters = this.command.Parameters;
            MySqlAttributeCollection attributes = this.command.Attributes;
            int index = 0;

            while (true)
            {
                MySqlPacket packet = this.BuildInitialPartQueryPacket(parameters, attributes);
                this.InternalBindParameters(this.ResolvedCommandText, parameters, packet);

                // if we are not batching, then we are done.  This is only really relevant the
                // first time through
                if (this.command.Batch == null)
                {
                    return;
                }

                while (index < this.command.Batch.Count)
                {
                    MySqlCommand batchedCmd = this.command.Batch[index++];
                    packet = (MySqlPacket)this._buffers[this._buffers.Count - 1];

                    // now we make a guess if this statement will fit in our current stream
                    long estimatedCmdSize = batchedCmd.EstimatedSize();
                    if (((packet.Length - 4) + estimatedCmdSize) > this.Connection.driver.MaxPacketSize)
                    {
                        // it won't, so we setup to start a new run from here
                        parameters = batchedCmd.Parameters;
                        break;
                    }

                    // looks like we might have room for it so we remember the current end of the stream
                    this._buffers.RemoveAt(this._buffers.Count - 1);

                    // long originalLength = packet.Length - 4;

                    // and attempt to stream the next command
                    string text = this.ResolvedCommandText;
                    if (text.StartsWith("(", StringComparison.Ordinal))
                    {
                        packet.WriteStringNoNull(", ");
                    }
                    else
                    {
                        packet.WriteStringNoNull("; ");
                    }

                    this.InternalBindParameters(text, batchedCmd.Parameters, packet);
                    if ((packet.Length - 4) > this.Connection.driver.MaxPacketSize)
                    {
                        // TODO
                        // stream.InternalBuffer.SetLength(originalLength);
                        parameters = batchedCmd.Parameters;
                        break;
                    }
                }

                if (index == this.command.Batch.Count)
                {
                    return;
                }
            }
        }

        /// <summary>
        /// Builds the initial part of the COM_QUERY packet
        /// </summary>
        /// <param name="parameters">Collection of parameters</param>
        /// <param name="attributes">Collection of attributes</param>
        /// <returns>A <see cref="MySqlPacket"/></returns>
        private MySqlPacket BuildInitialPartQueryPacket(MySqlParameterCollection parameters, MySqlAttributeCollection attributes)
        {
            MySqlPacket packet;
            packet = new MySqlPacket(this.Driver.Encoding) { Version = this.Driver.Version };
            packet.WriteByte(0);

            if (attributes.Count > 0 && !this.Driver.SupportsQueryAttributes)
            {
                MySqlTrace.LogWarning(this.Connection.ServerThread, string.Format(Resources.QueryAttributesNotSupported, this.Driver.Version));
            }
            else if (this.Driver.SupportsQueryAttributes)
            {
                int paramCount = parameters.Count + attributes.Count;
                packet.WriteLength(paramCount); // int<lenenc> parameter_count - Number of parameters
                packet.WriteByte(1); // int<lenenc> parameter_set_count - Number of parameter sets. Currently always 1

                if (paramCount > 0)
                {
                    // now prepare our null map
                    BitArray _nullMap = new BitArray(paramCount);
                    int numNullBytes = (_nullMap.Length + 7) / 8;
                    int _nullMapPosition = packet.Position;
                    packet.Position += numNullBytes;  // leave room for our null map
                    packet.WriteByte((byte)1); // new_params_bind_flag - Always 1. Malformed packet error if not 1

                    // set type and name for each parameter
                    foreach (MySqlParameter parameter in parameters)
                    {
                        packet.WriteInteger(parameter.GetPSType(), 2);
                        packet.WriteLenString(parameter.ParameterName);
                    }

                    // set type and name for each attribute
                    foreach (MySqlAttribute attribute in attributes)
                    {
                        packet.WriteInteger(attribute.GetPSType(), 2);
                        packet.WriteLenString(attribute.AttributeName);
                    }

                    // set value for each parameter
                    for (int i = 0; i < parameters.Count; i++)
                    {
                        MySqlParameter param = parameters[i];
                        _nullMap[i] = (param.Value == DBNull.Value || param.Value == null) || param.Direction == ParameterDirection.Output;
                        if (_nullMap[i])
                        {
                            continue;
                        }

                        param.Serialize(packet, true, this.Connection.Settings);
                    }

                    // set value for each attribute
                    for (int i = 0; i < attributes.Count; i++)
                    {
                        MySqlAttribute attr = attributes[i];
                        _nullMap[i] = (attr.Value == DBNull.Value || attr.Value == null);
                        if (_nullMap[i])
                        {
                            continue;
                        }

                        attr.Serialize(packet, true, this.Connection.Settings);
                    }

                    byte[] tempByteArray = new byte[(_nullMap.Length + 7) >> 3];
                    _nullMap.CopyTo(tempByteArray, 0);

                    Array.Copy(tempByteArray, 0, packet.Buffer, _nullMapPosition, tempByteArray.Length);
                }
            }

            this.paramsPosition = packet.Position;
            return packet;
        }

        private void InternalBindParameters(string sql, MySqlParameterCollection parameters, MySqlPacket packet)
        {
            bool sqlServerMode = this.command.Connection.Settings.SqlServerMode;

            MySqlTokenizer tokenizer = new MySqlTokenizer(sql)
            {
                ReturnComments = true,
                SqlServerMode = sqlServerMode
            };

            int pos = 0;
            string token = tokenizer.NextToken();
            int parameterCount = 0;
            while (token != null)
            {
                // serialize everything that came before the token (i.e. whitespace)
                packet.WriteStringNoNull(sql.Substring(pos, tokenizer.StartIndex - pos));
                pos = tokenizer.StopIndex;

                if (MySqlTokenizer.IsParameter(token))
                {
                    if ((!parameters.containsUnnamedParameters && token.Length == 1 && parameterCount > 0) || parameters.containsUnnamedParameters && token.Length > 1)
                    {
                        throw new MySqlException(Resources.MixedParameterNamingNotAllowed);
                    }

                    parameters.containsUnnamedParameters = token.Length == 1;
                    if (this.SerializeParameter(parameters, packet, token, parameterCount))
                    {
                        token = null;
                    }

                    parameterCount++;
                }

                if (token != null)
                {
                    if (sqlServerMode && tokenizer.Quoted && token.StartsWith("[", StringComparison.Ordinal))
                    {
                        token = String.Format("`{0}`", token.Substring(1, token.Length - 2));
                    }

                    packet.WriteStringNoNull(token);
                }

                token = tokenizer.NextToken();
            }

            this._buffers.Add(packet);
        }

        protected virtual bool ShouldIgnoreMissingParameter(string parameterName)
        {
            if (this.Connection.Settings.AllowUserVariables)
            {
                return true;
            }

            if (parameterName.StartsWith("@" + StoredProcedure.ParameterPrefix, StringComparison.OrdinalIgnoreCase))
            {
                return true;
            }

            if (parameterName.Length > 1 &&
                (parameterName[1] == '`' || parameterName[1] == '\''))
            {
                return true;
            }

            return false;
        }

        /// <summary>
        /// Serializes the given parameter to the given memory stream
        /// </summary>
        /// <remarks>
        /// <para>This method is called by PrepareSqlBuffers to convert the given
        /// parameter to bytes and write those bytes to the given memory stream.
        /// </para>
        /// </remarks>
        /// <returns>True if the parameter was successfully serialized, false otherwise.</returns>
        private bool SerializeParameter(
            MySqlParameterCollection parameters,
                                        MySqlPacket packet, string parmName, int parameterIndex)
        {
            MySqlParameter parameter = null;

            if (!parameters.containsUnnamedParameters)
            {
                parameter = parameters.GetParameterFlexible(parmName, false);
            }
            else
            {
                if (parameterIndex <= parameters.Count)
                {
                    parameter = parameters[parameterIndex];
                }
                else
                {
                    throw new MySqlException(Resources.ParameterIndexNotFound);
                }
            }

            if (parameter == null)
            {
                // if we are allowing user variables and the parameter name starts with @
                // then we can't throw an exception
                if (parmName.StartsWith("@", StringComparison.Ordinal) && this.ShouldIgnoreMissingParameter(parmName))
                {
                    return false;
                }

                throw new MySqlException(
                    String.Format(Resources.ParameterMustBeDefined, parmName));
            }

            parameter.Serialize(packet, false, this.Connection.Settings);
            return true;
        }
    }
}