/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSim Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.Reflection;
using libsecondlife;
using log4net;
using MySql.Data.MySqlClient;
using OpenSim.Framework;

namespace OpenSim.Data.MySQL
{
    /// <summary>
    /// A MySQL interface for the inventory server
    /// </summary>
    public class MySQLInventoryData : IInventoryDataPlugin
    {
        private static readonly ILog m_log
            = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>
        /// The database manager
        /// </summary>
        private MySQLManager database;

        public void Initialise() 
        { 
            m_log.Info("[MySQLInventoryData]: " + Name + " cannot be default-initialized!");
            throw new PluginNotInitialisedException (Name);
        }

        /// <summary>
        /// <para>Initialises Inventory interface</para>
        /// <para>
        /// <list type="bullet">
        /// <item>Loads and initialises the MySQL storage plugin</item>
        /// <item>warns and uses the obsolete mysql_connection.ini if connect string is empty.</item>
        /// <item>Check for migration</item>
        /// </list>
        /// </para>
        /// </summary>
        /// <param name="connect">connect string</param>
        public void Initialise(string connect)
        {
            if (connect != String.Empty)
            {
                database = new MySQLManager(connect);
            }
            else
            {
                m_log.Warn("Reverting to deprecated mysql_connection.ini file for connection info");
                IniFile GridDataMySqlFile = new IniFile("mysql_connection.ini");
                string settingHostname = GridDataMySqlFile.ParseFileReadValue("hostname");
                string settingDatabase = GridDataMySqlFile.ParseFileReadValue("database");
                string settingUsername = GridDataMySqlFile.ParseFileReadValue("username");
                string settingPassword = GridDataMySqlFile.ParseFileReadValue("password");
                string settingPooling = GridDataMySqlFile.ParseFileReadValue("pooling");
                string settingPort = GridDataMySqlFile.ParseFileReadValue("port");
                
                database =
                    new MySQLManager(settingHostname, settingDatabase, settingUsername, settingPassword, settingPooling,
                                     settingPort);
            }

            // This actually does the roll forward assembly stuff
            Assembly assem = GetType().Assembly;
            Migration m = new Migration(database.Connection, assem, "InventoryStore");

            // TODO: After rev 6000, remove this.  People should have
            // been rolled onto the new migration code by then.
            TestTables(database.Connection, m);

            m.Update();
        }

        #region Test and initialization code

        /// <summary>
        /// <list type="bullet">
        /// <item>Execute CreateFoldersTable.sql if oldVersion == null</item>
        /// <item>do nothing if oldVersion != null</item>
        /// </list>
        /// </summary>
        /// <param name="oldVersion"></param>
        private void UpgradeFoldersTable(string oldVersion)
        {
            // null as the version, indicates that the table didn't exist
            if (oldVersion == null)
            {
                database.ExecuteResourceSql("CreateFoldersTable.sql");
                return;
            }

            //// if the table is already at the current version, then we can exit immediately
            // if (oldVersion == "Rev. 2")
            // return;
            // database.ExecuteResourceSql("UpgradeFoldersTableToVersion2.sql");
        }

        /// <summary>
        /// <list type="bullet">
        /// <item>Execute CreateItemsTable.sql if oldVersion == null</item>
        /// <item>Execute "UpgradeItemsTableToVersion3.sql" if oldVersion start with "Rev. 2;"</item>
        /// </list>
        /// </summary>
        /// <param name="oldVersion"></param>
        private void UpgradeItemsTable(string oldVersion)
        {
            // null as the version, indicates that the table didn't exist
            if (oldVersion == null)
            {
                database.ExecuteResourceSql("CreateItemsTable.sql");
                return;
            }

            // if the table is already at the current version, then we can exit immediately
            if (oldVersion.StartsWith("Rev. 2;"))
            {
                m_log.Info("[INVENTORY DB]: Upgrading inventory items table from Rev. 2 to Rev. 3");
                database.ExecuteResourceSql("UpgradeItemsTableToVersion3.sql");
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="conn">MySQL connection handler</param>
        /// <param name="m"></param>
        private void TestTables(MySqlConnection conn, Migration m)
        {
            Dictionary<string, string> tableList = new Dictionary<string, string>();

            tableList["inventoryfolders"] = null;
            tableList["inventoryitems"] = null;

            database.GetTableVersion(tableList);

            // if we've already started using migrations, get out of
            // here, we've got this under control
            if (m.Version > 0)
                return;

            // if there are no tables, get out of here and let
            // migrations do their job
            if (
               tableList["inventoryfolders"] == null &&
               tableList["inventoryitems"] == null
               )
                return;

            // otherwise, let the upgrade on legacy proceed...
            UpgradeFoldersTable(tableList["inventoryfolders"]);
            UpgradeItemsTable(tableList["inventoryitems"]);

            // ... and set the version
            if (m.Version == 0)
                m.Version = 1;
            
        }

        #endregion

        /// <summary>
        /// The name of this DB provider
        /// </summary>
        /// <returns>Name of DB provider</returns>
        public string Name
        {
            get { return "MySQL Inventory Data Interface"; }
        }

        /// <summary>
        /// Closes this DB provider
        /// </summary>
        /// <remarks>do nothing</remarks>
        public void Dispose()
        {
            // Do nothing.
        }

        /// <summary>
        /// Returns the version of this DB provider
        /// </summary>
        /// <returns>A string containing the DB provider version</returns>
        public string Version
        {
            get { return database.getVersion(); }
        }

        /// <summary>
        /// Returns a list of items in a specified folder
        /// </summary>
        /// <param name="folderID">The folder to search</param>
        /// <returns>A list containing inventory items</returns>
        public List<InventoryItemBase> getInventoryInFolder(LLUUID folderID)
        {
            try
            {
                lock (database)
                {
                    List<InventoryItemBase> items = new List<InventoryItemBase>();

                    database.CheckConnection();

                    MySqlCommand result =
                        new MySqlCommand("SELECT * FROM inventoryitems WHERE parentFolderID = ?uuid",
                                         database.Connection);
                    result.Parameters.AddWithValue("?uuid", folderID.ToString());
                    MySqlDataReader reader = result.ExecuteReader();

                    while (reader.Read())
                        items.Add(readInventoryItem(reader));

                    reader.Close();
                    result.Dispose();

                    return items;
                }
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
                return null;
            }
        }

        /// <summary>
        /// Returns a list of the root folders within a users inventory
        /// </summary>
        /// <param name="user">The user whos inventory is to be searched</param>
        /// <returns>A list of folder objects</returns>
        public List<InventoryFolderBase> getUserRootFolders(LLUUID user)
        {
            try
            {
                lock (database)
                {
                    database.CheckConnection();

                    MySqlCommand result =
                        new MySqlCommand(
                            "SELECT * FROM inventoryfolders WHERE parentFolderID = ?zero AND agentID = ?uuid",
                            database.Connection);
                    result.Parameters.AddWithValue("?uuid", user.ToString());
                    result.Parameters.AddWithValue("?zero", LLUUID.Zero.ToString());
                    MySqlDataReader reader = result.ExecuteReader();

                    List<InventoryFolderBase> items = new List<InventoryFolderBase>();
                    while (reader.Read())
                        items.Add(readInventoryFolder(reader));


                    reader.Close();
                    result.Dispose();

                    return items;
                }
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
                return null;
            }
        }

     
        /// <summary>
        /// see <see cref="InventoryItemBase.getUserRootFolder"/>
        /// </summary>
        /// <param name="user">The user UUID</param>
        /// <returns></returns>
        public InventoryFolderBase getUserRootFolder(LLUUID user)
        {
            try
            {
                lock (database)
                {
                    database.CheckConnection();

                    MySqlCommand result =
                        new MySqlCommand(
                            "SELECT * FROM inventoryfolders WHERE parentFolderID = ?zero AND agentID = ?uuid",
                            database.Connection);
                    result.Parameters.AddWithValue("?uuid", user.ToString());
                    result.Parameters.AddWithValue("?zero", LLUUID.Zero.ToString());

                    MySqlDataReader reader = result.ExecuteReader();

                    List<InventoryFolderBase> items = new List<InventoryFolderBase>();
                    while (reader.Read())
                        items.Add(readInventoryFolder(reader));

                    InventoryFolderBase rootFolder = null;

                    // There should only ever be one root folder for a user.  However, if there's more
                    // than one we'll simply use the first one rather than failing.  It would be even
                    // nicer to print some message to this effect, but this feels like it's too low a
                    // to put such a message out, and it's too minor right now to spare the time to
                    // suitably refactor.
                    if (items.Count > 0)
                    {
                        rootFolder = items[0];
                    }

                    reader.Close();
                    result.Dispose();

                    return rootFolder;
                }
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
                return null;
            }
        }

        /// <summary>
        /// Return a list of folders in a users inventory contained within the specified folder.
        /// This method is only used in tests - in normal operation the user always have one,
        /// and only one, root folder.
        /// </summary>
        /// <param name="parentID">The folder to search</param>
        /// <returns>A list of inventory folders</returns>
        public List<InventoryFolderBase> getInventoryFolders(LLUUID parentID)
        {
            try
            {
                lock (database)
                {
                    database.CheckConnection();

                    MySqlCommand result =
                        new MySqlCommand("SELECT * FROM inventoryfolders WHERE parentFolderID = ?uuid",
                                         database.Connection);
                    result.Parameters.AddWithValue("?uuid", parentID.ToString());
                    MySqlDataReader reader = result.ExecuteReader();

                    List<InventoryFolderBase> items = new List<InventoryFolderBase>();

                    while (reader.Read())
                        items.Add(readInventoryFolder(reader));

                    reader.Close();
                    result.Dispose();

                    return items;
                }
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
                return null;
            }
        }

        /// <summary>
        /// Reads a one item from an SQL result
        /// </summary>
        /// <param name="reader">The SQL Result</param>
        /// <returns>the item read</returns>
        private static InventoryItemBase readInventoryItem(MySqlDataReader reader)
        {
            try
            {
                InventoryItemBase item = new InventoryItemBase();

                item.ID = new LLUUID((string) reader["inventoryID"]);
                item.AssetID = new LLUUID((string) reader["assetID"]);
                item.AssetType = (int) reader["assetType"];
                item.Folder = new LLUUID((string) reader["parentFolderID"]);
                item.Owner = new LLUUID((string) reader["avatarID"]);
                item.Name = (string) reader["inventoryName"];
                item.Description = (string) reader["inventoryDescription"];
                item.NextPermissions = (uint) reader["inventoryNextPermissions"];
                item.CurrentPermissions = (uint) reader["inventoryCurrentPermissions"];
                item.InvType = (int) reader["invType"];
                item.Creator = new LLUUID((string) reader["creatorID"]);
                item.BasePermissions = (uint) reader["inventoryBasePermissions"];
                item.EveryOnePermissions = (uint) reader["inventoryEveryOnePermissions"];
                item.SalePrice = (int) reader["salePrice"];
                item.SaleType = Convert.ToByte(reader["saleType"]);
                item.CreationDate = (int) reader["creationDate"];
                item.GroupID = new LLUUID(reader["groupID"].ToString());
                item.GroupOwned = Convert.ToBoolean(reader["groupOwned"]);
                item.Flags = (uint) reader["flags"];

                return item;
            }
            catch (MySqlException e)
            {
                m_log.Error(e.ToString());
            }

            return null;
        }

        /// <summary>
        /// Returns a specified inventory item
        /// </summary>
        /// <param name="item">The item to return</param>
        /// <returns>An inventory item</returns>
        public InventoryItemBase getInventoryItem(LLUUID itemID)
        {
            try
            {
                lock (database)
                {
                    database.CheckConnection();

                    MySqlCommand result =
                        new MySqlCommand("SELECT * FROM inventoryitems WHERE inventoryID = ?uuid", database.Connection);
                    result.Parameters.AddWithValue("?uuid", itemID.ToString());
                    MySqlDataReader reader = result.ExecuteReader();

                    InventoryItemBase item = null;
                    if (reader.Read())
                        item = readInventoryItem(reader);

                    reader.Close();
                    result.Dispose();

                    return item;
                }
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
            }
            return null;
        }

        /// <summary>
        /// Reads a list of inventory folders returned by a query.
        /// </summary>
        /// <param name="reader">A MySQL Data Reader</param>
        /// <returns>A List containing inventory folders</returns>
        protected static InventoryFolderBase readInventoryFolder(MySqlDataReader reader)
        {
            try
            {
                InventoryFolderBase folder = new InventoryFolderBase();
                folder.Owner = new LLUUID((string) reader["agentID"]);
                folder.ParentID = new LLUUID((string) reader["parentFolderID"]);
                folder.ID = new LLUUID((string) reader["folderID"]);
                folder.Name = (string) reader["folderName"];
                folder.Type = (short) reader["type"];
                folder.Version = (ushort) ((int) reader["version"]);
                return folder;
            }
            catch (Exception e)
            {
                m_log.Error(e.ToString());
            }

            return null;
        }


        /// <summary>
        /// Returns a specified inventory folder
        /// </summary>
        /// <param name="folder">The folder to return</param>
        /// <returns>A folder class</returns>
        public InventoryFolderBase getInventoryFolder(LLUUID folderID)
        {
            try
            {
                lock (database)
                {
                    database.CheckConnection();

                    MySqlCommand result =
                        new MySqlCommand("SELECT * FROM inventoryfolders WHERE folderID = ?uuid", database.Connection);
                    result.Parameters.AddWithValue("?uuid", folderID.ToString());
                    MySqlDataReader reader = result.ExecuteReader();

                    reader.Read();
                    InventoryFolderBase folder = readInventoryFolder(reader);
                    reader.Close();
                    result.Dispose();

                    return folder;
                }
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
                return null;
            }
        }

        /// <summary>
        /// Adds a specified item to the database
        /// </summary>
        /// <param name="item">The inventory item</param>
        public void addInventoryItem(InventoryItemBase item)
        {
            string sql =
                "REPLACE INTO inventoryitems (inventoryID, assetID, assetType, parentFolderID, avatarID, inventoryName"
                    + ", inventoryDescription, inventoryNextPermissions, inventoryCurrentPermissions, invType"
                    + ", creatorID, inventoryBasePermissions, inventoryEveryOnePermissions, salePrice, saleType"
                    + ", creationDate, groupID, groupOwned, flags) VALUES ";
            sql +=
                "(?inventoryID, ?assetID, ?assetType, ?parentFolderID, ?avatarID, ?inventoryName, ?inventoryDescription"
                    + ", ?inventoryNextPermissions, ?inventoryCurrentPermissions, ?invType, ?creatorID"
                    + ", ?inventoryBasePermissions, ?inventoryEveryOnePermissions, ?salePrice, ?saleType, ?creationDate"
                    + ", ?groupID, ?groupOwned, ?flags)";

            try
            {
                database.CheckConnection();

                MySqlCommand result = new MySqlCommand(sql, database.Connection);
                result.Parameters.AddWithValue("?inventoryID", item.ID.ToString());
                result.Parameters.AddWithValue("?assetID", item.AssetID.ToString());
                result.Parameters.AddWithValue("?assetType", item.AssetType.ToString());
                result.Parameters.AddWithValue("?parentFolderID", item.Folder.ToString());
                result.Parameters.AddWithValue("?avatarID", item.Owner.ToString());
                result.Parameters.AddWithValue("?inventoryName", item.Name);
                result.Parameters.AddWithValue("?inventoryDescription", item.Description);
                result.Parameters.AddWithValue("?inventoryNextPermissions", item.NextPermissions.ToString());
                result.Parameters.AddWithValue("?inventoryCurrentPermissions",
                                               item.CurrentPermissions.ToString());
                result.Parameters.AddWithValue("?invType", item.InvType);
                result.Parameters.AddWithValue("?creatorID", item.Creator.ToString());
                result.Parameters.AddWithValue("?inventoryBasePermissions", item.BasePermissions);
                result.Parameters.AddWithValue("?inventoryEveryOnePermissions", item.EveryOnePermissions);
                result.Parameters.AddWithValue("?salePrice", item.SalePrice);
                result.Parameters.AddWithValue("?saleType", item.SaleType);
                result.Parameters.AddWithValue("?creationDate", item.CreationDate);
                result.Parameters.AddWithValue("?groupID", item.GroupID);
                result.Parameters.AddWithValue("?groupOwned", item.GroupOwned);
                result.Parameters.AddWithValue("?flags", item.Flags);

                lock (database)
                {
                    result.ExecuteNonQuery();
                }

                result.Dispose();
            }
            catch (MySqlException e)
            {
                m_log.Error(e.ToString());
            }
        }

        /// <summary>
        /// Updates the specified inventory item
        /// </summary>
        /// <param name="item">Inventory item to update</param>
        public void updateInventoryItem(InventoryItemBase item)
        {
            addInventoryItem(item);
        }

        /// <summary>
        /// Detele the specified inventory item
        /// </summary>
        /// <param name="item">The inventory item UUID to delete</param>
        public void deleteInventoryItem(LLUUID itemID)
        {
            try
            {
                database.CheckConnection();

                MySqlCommand cmd =
                    new MySqlCommand("DELETE FROM inventoryitems WHERE inventoryID=?uuid", database.Connection);
                cmd.Parameters.AddWithValue("?uuid", itemID.ToString());

                lock (database)
                {
                    cmd.ExecuteNonQuery();
                }
            }
            catch (MySqlException e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
            }
        }

        /// <summary>
        /// Creates a new inventory folder
        /// </summary>
        /// <param name="folder">Folder to create</param>
        public void addInventoryFolder(InventoryFolderBase folder)
        {
            string sql =
                "REPLACE INTO inventoryfolders (folderID, agentID, parentFolderID, folderName, type, version) VALUES ";
            sql += "(?folderID, ?agentID, ?parentFolderID, ?folderName, ?type, ?version)";

            database.CheckConnection();

            MySqlCommand cmd = new MySqlCommand(sql, database.Connection);
            cmd.Parameters.AddWithValue("?folderID", folder.ID.ToString());
            cmd.Parameters.AddWithValue("?agentID", folder.Owner.ToString());
            cmd.Parameters.AddWithValue("?parentFolderID", folder.ParentID.ToString());
            cmd.Parameters.AddWithValue("?folderName", folder.Name);
            cmd.Parameters.AddWithValue("?type", (short) folder.Type);
            cmd.Parameters.AddWithValue("?version", folder.Version);

            try
            {
                lock (database)
                {
                    cmd.ExecuteNonQuery();
                }
            }
            catch (Exception e)
            {
                m_log.Error(e.ToString());
            }
        }

        /// <summary>
        /// Updates an inventory folder
        /// </summary>
        /// <param name="folder">Folder to update</param>
        public void updateInventoryFolder(InventoryFolderBase folder)
        {
            addInventoryFolder(folder);
        }

        /// <summary>
        /// Move an inventory folder
        /// </summary>
        /// <param name="folder">Folder to move</param>
        /// <remarks>UPDATE inventoryfolders SET parentFolderID=?parentFolderID WHERE folderID=?folderID</remarks>
        public void moveInventoryFolder(InventoryFolderBase folder)
        {
            string sql =
                "UPDATE inventoryfolders SET parentFolderID=?parentFolderID WHERE folderID=?folderID";

            database.CheckConnection();

            MySqlCommand cmd = new MySqlCommand(sql, database.Connection);
            cmd.Parameters.AddWithValue("?folderID", folder.ID.ToString());
            cmd.Parameters.AddWithValue("?parentFolderID", folder.ParentID.ToString());

            try
            {
                lock (database)
                {
                    cmd.ExecuteNonQuery();
                }
            }
            catch (Exception e)
            {
                m_log.Error(e.ToString());
            }
        }

        /// <summary>
        /// Append a list of all the child folders of a parent folder
        /// </summary>
        /// <param name="folders">list where folders will be appended</param>
        /// <param name="parentID">ID of parent</param>
        protected void getInventoryFolders(ref List<InventoryFolderBase> folders, LLUUID parentID)
        {
            List<InventoryFolderBase> subfolderList = getInventoryFolders(parentID);

            foreach (InventoryFolderBase f in subfolderList)
                folders.Add(f);
        }


        /// <summary>
        /// See IInventoryDataPlugin
        /// </summary>
        /// <param name="parentID"></param>
        /// <returns></returns>
        public List<InventoryFolderBase> getFolderHierarchy(LLUUID parentID)
        {
            /* Note: There are subtle changes between this implementation of getFolderHierarchy and the previous one
                 * - We will only need to hit the database twice instead of n times.
                 * - We assume the database is well-formed - no stranded/dangling folders, all folders in heirarchy owned
                 *   by the same person, each user only has 1 inventory heirarchy
                 * - The returned list is not ordered, instead of breadth-first ordered   
               There are basically 2 usage cases for getFolderHeirarchy:
                 1) Getting the user's entire inventory heirarchy when they log in
                 2) Finding a subfolder heirarchy to delete when emptying the trash.                 
               This implementation will pull all inventory folders from the database, and then prune away any folder that
               is not part of the requested sub-heirarchy. The theory is that it is cheaper to make 1 request from the
               database than to make n requests. This pays off only if requested heirarchy is large.
               By making this choice, we are making the worst case better at the cost of making the best case worse.
               This way is generally better because we don't have to rebuild the connection/sql query per subfolder,
               even if we end up getting more data from the SQL server than we need.
                 - Francis
             */
            try
            {
                List<InventoryFolderBase> folders = new List<InventoryFolderBase>();
                Dictionary<LLUUID, List<InventoryFolderBase>> hashtable
                    = new Dictionary<LLUUID, List<InventoryFolderBase>>(); ;
                List<InventoryFolderBase> parentFolder = new List<InventoryFolderBase>();
                lock (database)
                {
                    MySqlCommand result;
                    MySqlDataReader reader;
                    bool buildResultsFromHashTable = false;

                    database.CheckConnection();

                    /* Fetch the parent folder from the database to determine the agent ID, and if
                     * we're querying the root of the inventory folder tree */
                    result = new MySqlCommand("SELECT * FROM inventoryfolders WHERE folderID = ?uuid",
                                              database.Connection);
                    result.Parameters.AddWithValue("?uuid", parentID.ToString());
                    reader = result.ExecuteReader();
                    while (reader.Read())          // Should be at most 1 result
                        parentFolder.Add(readInventoryFolder(reader));
                    reader.Close();
                    result.Dispose();

                    if (parentFolder.Count >= 1)   // No result means parent folder does not exist
                    {
                        if (parentFolder[0].ParentID == LLUUID.Zero) // We are querying the root folder
                        {
                            /* Get all of the agent's folders from the database, put them in a list and return it */
                            result = new MySqlCommand("SELECT * FROM inventoryfolders WHERE agentID = ?uuid",
                                                      database.Connection);
                            result.Parameters.AddWithValue("?uuid", parentFolder[0].Owner.ToString());
                            reader = result.ExecuteReader();
                            while (reader.Read())
                            {
                                InventoryFolderBase curFolder = readInventoryFolder(reader);
                                if (curFolder.ID != parentID) // Do not need to add the root node of the tree to the list
                                    folders.Add(curFolder);
                            }
                            reader.Close();
                            result.Dispose();
                        } // if we are querying the root folder
                        else // else we are querying a subtree of the inventory folder tree
                        {
                            /* Get all of the agent's folders from the database, put them all in a hash table
                             * indexed by their parent ID */
                            result = new MySqlCommand("SELECT * FROM inventoryfolders WHERE agentID = ?uuid",
                                                      database.Connection);
                            result.Parameters.AddWithValue("?uuid", parentFolder[0].Owner.ToString());
                            reader = result.ExecuteReader();
                            while (reader.Read())
                            {
                                InventoryFolderBase curFolder = readInventoryFolder(reader);
                                if (hashtable.ContainsKey(curFolder.ParentID))      // Current folder already has a sibling 
                                    hashtable[curFolder.ParentID].Add(curFolder);   // append to sibling list
                                else // else current folder has no known (yet) siblings
                                {
                                    List<InventoryFolderBase> siblingList = new List<InventoryFolderBase>();
                                    siblingList.Add(curFolder);
                                    // Current folder has no known (yet) siblings
                                    hashtable.Add(curFolder.ParentID, siblingList);
                                }
                            } // while more items to read from the database
                            reader.Close();
                            result.Dispose();

                            // Set flag so we know we need to build the results from the hash table after
                            // we unlock the database
                            buildResultsFromHashTable = true;

                        } // else we are querying a subtree of the inventory folder tree
                    } // if folder parentID exists

                    if (buildResultsFromHashTable)
                    {
                        /* We have all of the user's folders stored in a hash table indexed by their parent ID
                         * and we need to return the requested subtree. We will build the requested subtree
                         * by performing a breadth-first-search on the hash table */
                        if (hashtable.ContainsKey(parentID))
                            folders.AddRange(hashtable[parentID]);
                        for (int i = 0; i < folders.Count; i++) // **Note: folders.Count is *not* static
                            if (hashtable.ContainsKey(folders[i].ID))
                                folders.AddRange(hashtable[folders[i].ID]);
                    }
                } // lock(database)
                return folders;
            }
            catch (Exception e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
                return null;
            }
        }

        /// <summary>
        /// Delete a folder from database
        /// </summary>
        /// <param name="folderID">the folder UUID</param>
        protected void deleteOneFolder(LLUUID folderID)
        {
            try
            {
                database.CheckConnection();

                MySqlCommand cmd =
                    new MySqlCommand("DELETE FROM inventoryfolders WHERE folderID=?uuid", database.Connection);
                cmd.Parameters.AddWithValue("?uuid", folderID.ToString());

                lock (database)
                {
                    cmd.ExecuteNonQuery();
                }
            }
            catch (MySqlException e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
            }
        }

        /// <summary>
        /// Delete all item in a folder
        /// </summary>
        /// <param name="folderID">the folder UUID</param>
        protected void deleteItemsInFolder(LLUUID folderID)
        {
            try
            {
                database.CheckConnection();

                MySqlCommand cmd =
                    new MySqlCommand("DELETE FROM inventoryitems WHERE parentFolderID=?uuid", database.Connection);
                cmd.Parameters.AddWithValue("?uuid", folderID.ToString());

                lock (database)
                {
                    cmd.ExecuteNonQuery();
                }
            }
            catch (MySqlException e)
            {
                database.Reconnect();
                m_log.Error(e.ToString());
            }
        }

        /// <summary>
        /// Deletes an inventory folder
        /// </summary>
        /// <param name="folderId">Id of folder to delete</param>
        public void deleteInventoryFolder(LLUUID folderID)
        {
            List<InventoryFolderBase> subFolders = getFolderHierarchy(folderID);

            //Delete all sub-folders
            foreach (InventoryFolderBase f in subFolders)
            {
                deleteOneFolder(f.ID);
                deleteItemsInFolder(f.ID);
            }

            //Delete the actual row
            deleteOneFolder(folderID);
            deleteItemsInFolder(folderID);
        }
    }
}