// Copyright © 2009, 2018, 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.Diagnostics;
using MySql.Data.Types;
using Sog.Properties;

namespace MySql.Data.MySqlClient
{
    internal class ResultSet
    {
        private Driver _driver;
        private bool[] _uaFieldsUsed;
        private Dictionary<string, int> _fieldHashCi;
        private int _rowIndex;
        private bool _readDone;
        private bool _isSequential;
        private int _seqIndex;
        private readonly int _statementId;
        private bool _cached;
        private List<IMySqlValue[]> _cachedValues;

        public ResultSet(int affectedRows, long insertedId)
        {
            this.AffectedRows = affectedRows;
            this.InsertedId = insertedId;
            this._readDone = true;
        }

        public ResultSet(Driver d, int statementId, int numCols)
        {
            this.AffectedRows = -1;
            this.InsertedId = -1;
            this._driver = d;
            this._statementId = statementId;
            this._rowIndex = -1;
            this.LoadColumns(numCols);
            this.IsOutputParameters = this.IsOutputParameterResultSet();
            this.HasRows = this.GetNextRow();
            this._readDone = !this.HasRows;
        }

        #region Properties

        public bool HasRows { get; }

        public int Size => this.Fields?.Length ?? 0;

        public MySqlField[] Fields { get; private set; }

        public IMySqlValue[] Values { get; private set; }

        public bool IsOutputParameters { get; set; }

        public int AffectedRows { get; private set; }

        public long InsertedId { get; private set; }

        public int TotalRows { get; private set; }

        public int SkippedRows { get; private set; }

        public bool Cached
        {
            get { return this._cached; }
            set
            {
                this._cached = value;
                if (this._cached && this._cachedValues == null)
                {
                    this._cachedValues = new List<IMySqlValue[]>();
                }
            }
        }

        #endregion

        /// <summary>
        /// return the ordinal for the given column name
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public int GetOrdinal(string name)
        {
            int ordinal;

            // quick hash lookup using CI hash
            if (this._fieldHashCi.TryGetValue(name, out ordinal))
            {
                return ordinal;
            }

            // Throw an exception if the ordinal cannot be found.
            throw new IndexOutOfRangeException(
                String.Format(Resources.CouldNotFindColumnName, name));
        }

        /// <summary>
        /// Retrieve the value as the given column index
        /// </summary>
        /// <param name="index">The column value to retrieve</param>
        /// <returns>The value as the given column</returns>
        public IMySqlValue this[int index]
        {
            get
            {
                if (this._rowIndex < 0)
                {
                    throw new MySqlException(Resources.AttemptToAccessBeforeRead);
                }

                // keep count of how many columns we have left to access
                this._uaFieldsUsed[index] = true;

                if (this._isSequential && index != this._seqIndex)
                {
                    if (index < this._seqIndex)
                    {
                        throw new MySqlException(Resources.ReadingPriorColumnUsingSeqAccess);
                    }

                    while (this._seqIndex < (index - 1))
                    {
                        this._driver.SkipColumnValue(this.Values[++this._seqIndex]);
                    }

                    this.Values[index] = this._driver.ReadColumnValue(index, this.Fields[index], this.Values[index]);
                    this._seqIndex = index;
                }

                return this.Values[index];
            }
        }

        private bool GetNextRow()
        {
            bool fetched = this._driver.FetchDataRow(this._statementId, this.Size);
            if (fetched)
            {
                this.TotalRows++;
            }

            return fetched;
        }


        public bool NextRow(CommandBehavior behavior)
        {
            if (this._readDone)
            {
                if (this.Cached)
                {
                    return this.CachedNextRow(behavior);
                }

                return false;
            }

            if ((behavior & CommandBehavior.SingleRow) != 0 && this._rowIndex == 0)
            {
                return false;
            }

            this._isSequential = (behavior & CommandBehavior.SequentialAccess) != 0;
            this._seqIndex = -1;

            // if we are at row index >= 0 then we need to fetch the data row and load it
            if (this._rowIndex >= 0)
            {
                bool fetched = false;
                try
                {
                    fetched = this.GetNextRow();
                }
                catch (MySqlException ex)
                {
                    if (ex.IsQueryAborted)
                    {
                        // avoid hanging on Close()
                        this._readDone = true;
                    }

                    throw;
                }

                if (!fetched)
                {
                    this._readDone = true;
                    return false;
                }
            }

            if (!this._isSequential)
            {
                this.ReadColumnData(false);
            }

            this._rowIndex++;
            return true;
        }

        private bool CachedNextRow(CommandBehavior behavior)
        {
            if ((behavior & CommandBehavior.SingleRow) != 0 && this._rowIndex == 0)
            {
                return false;
            }

            if (this._rowIndex == (this.TotalRows - 1))
            {
                return false;
            }

            this._rowIndex++;
            this.Values = this._cachedValues[this._rowIndex];
            return true;
        }

        /// <summary>
        /// Closes the current resultset, dumping any data still on the wire
        /// </summary>
        public void Close()
        {
            if (!this._readDone)
            {

                // if we have rows but the user didn't read the first one then mark it as skipped
                if (this.HasRows && this._rowIndex == -1)
                {
                    this.SkippedRows++;
                }

                try
                {
                    while (this._driver.IsOpen && this._driver.SkipDataRow())
                    {
                        this.TotalRows++;
                        this.SkippedRows++;
                    }
                }
                catch (System.IO.IOException)
                {
                    // it is ok to eat IO exceptions here, we just want to 
                    // close the result set
                }

                this._readDone = true;
            }
            else if (this._driver == null)
            {
                this.CacheClose();
            }

            this._driver = null;
            if (this.Cached)
            {
                this.CacheReset();
            }
        }

        private void CacheClose()
        {
            this.SkippedRows = this.TotalRows - this._rowIndex - 1;
        }

        private void CacheReset()
        {
            if (!this.Cached)
            {
                return;
            }

            this._rowIndex = -1;
            this.AffectedRows = -1;
            this.InsertedId = -1;
            this.SkippedRows = 0;
        }

        public bool FieldRead(int index)
        {
            Debug.Assert(this.Size > index);
            return this._uaFieldsUsed[index];
        }

        public void SetValueObject(int i, IMySqlValue valueObject)
        {
            Debug.Assert(this.Values != null);
            Debug.Assert(i < this.Values.Length);
            this.Values[i] = valueObject;
        }

        private bool IsOutputParameterResultSet()
        {
            if (this._driver.HasStatus(ServerStatusFlags.OutputParameters))
            {
                return true;
            }

            if (this.Fields.Length == 0)
            {
                return false;
            }

            for (int x = 0; x < this.Fields.Length; x++)
            {
                if (!this.Fields[x].ColumnName.StartsWith("@" + StoredProcedure.ParameterPrefix, StringComparison.OrdinalIgnoreCase))
                {
                    return false;
                }
            }

            return true;
        }

        /// <summary>
        /// Loads the column metadata for the current resultset
        /// </summary>
        private void LoadColumns(int numCols)
        {
            this.Fields = this._driver.GetColumns(numCols);

            this.Values = new IMySqlValue[numCols];
            this._uaFieldsUsed = new bool[numCols];
            this._fieldHashCi = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);

            for (int i = 0; i < this.Fields.Length; i++)
            {
                string columnName = this.Fields[i].ColumnName;
                if (!this._fieldHashCi.ContainsKey(columnName))
                {
                    this._fieldHashCi.Add(columnName, i);
                }

                this.Values[i] = this.Fields[i].GetValueObject();
            }
        }

        private void ReadColumnData(bool outputParms)
        {
            for (int i = 0; i < this.Size; i++)
            {
                this.Values[i] = this._driver.ReadColumnValue(i, this.Fields[i], this.Values[i]);
            }

            // if we are caching then we need to save a copy of this row of data values
            if (this.Cached)
            {
                this._cachedValues.Add((IMySqlValue[])this.Values.Clone());
            }

            // we don't need to worry about caching the following since you won't have output
            // params with TableDirect commands
            if (!outputParms)
            {
                return;
            }

            bool rowExists = this._driver.FetchDataRow(this._statementId, this.Fields.Length);
            this._rowIndex = 0;
            if (rowExists)
            {
                throw new MySqlException(Resources.MoreThanOneOPRow);
            }
        }
    }
}