/* This file is part of the KDE project
   Copyright (C) 2003 Lucijan Busch <lucijan@kde.org>
   Copyright (C) 2004 Jaroslaw Staniek <js@iidea.pl>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
*/

#ifndef KEXIDBPARSER_H
#define KEXIDBPARSER_H

#include <tqobject.h>
#include <tqptrlist.h>
#include <tqvariant.h>

#include <kexidb/field.h>
#include <kexidb/expression.h>

namespace KexiDB
{

class Connection;
class QuerySchema;
class TableSchema;
class Field;

/**
 * Provides detailed i18n'ed error description about the \a Parser .
 */
class KEXI_DB_EXPORT ParserError
{
	public:

		/**
		 * Empty constructor.
		 */
		ParserError();

		/**
		 * Constructor.
		 *
		 * \param type The errortype.
		 * \param error A description of the error.
		 * \param hint Token where the error happend.
		 * \param at The position where the error happend.
		 */
		ParserError(const TQString &type, const TQString &error, const TQString &hint, int at);

		/**
		 * Destructor.
		 */
		~ParserError();

		/**
		 * \return the errortype.
		 */
		TQString	type() { return m_type; }

		/**
		 * \return a descriping error message.
		 */
		TQString	error() { return m_error; }

		/**
		 * \return position where the error happend.
		 */
		int	at() { return m_at; }

	private:
		TQString m_type;
		TQString m_error;
		TQString m_hint;
		int m_at;
//		bool	m_isNull;
};

class ParserPrivate;

/**
 * Parser for SQL statements.
 *
 * The best and prefeerred way to run queries is using the KexiDB::Parser functionality
 * and use the resulting QuerySchema object since this offers a database-backend-independent 
 * way to deal with SQL statements on the one hand and offers high level 
 * functionality on the other. Also BLOBs like images are handled that way.
 *
 * For example if we like to use the SELECT statement
 * "SELECT dir.path, media.filename FROM dir, media WHERE dir.id=media.dirId AND media.id=%s"
 * we are able to use the \a Connection::prepareStatement method which takes the type of
 * the statement (in our case \a PreparedStatement::SelectStatement ), a list of fields (in
 * our case dir.path and media.filename) and returns a \a PreparedStatement::Ptr instance.
 * By using the \a QuerySchema::addRelationship and \a QuerySchema::addToWhereExpression methods
 * the SQL statement could be extended with relationships and WHERE expressions.
 *
 * For more, see \a KexiDB::PreparedStatement and \a Connection::selectStatement() . A more
 * complex example that looks at what the user has defined and carefully builds 
 * \a KexiDB::QuerySchema object, including the WHERE expression can be found in 
 * the Query Designer's source code in the method \a KexiQueryDesignerGuiEditor::buildSchema().
 */
class KEXI_DB_EXPORT Parser
{
	public:

		/**
		 * The operation-code of the statement.
		 */
		enum OPCode
		{
			OP_None = 0, /// No statement parsed or reseted.
			OP_Error, /// Error while parsing.
			OP_CreateTable, /// Create a table.
			OP_AlterTable, /// Alter an existing table
			OP_Select, /// Query-statement.
			OP_Insert, /// Insert new content.
			OP_Update, /// Update existing content.
			OP_Delete  /// Delete existing content.
		};

		/**
		 * constructs an empty object of the parser
		 * \param connection is used for things like wildcard resolution. If 0 parser works in "pure mode"
		 */
		Parser(Connection *connection);
		~Parser();

		/**
		 * clears previous results and runs the parser
		 */
		bool parse(const TQString &statement);

		/**
		 * rests results
		 */
		void clear();

		/**
		 * \return the resulting operation or OP_Error if failed
		 */
		OPCode operation() const;

		/**
		 * \return the resulting operation as string.
		 */
		TQString operationString() const;

		/**
		 * \return a pointer to a KexiDBTable on CREATE TABLE
		 * or 0 on any other operation or error. Returned object is owned by you.
		 * You can call this method only once every time after doing parse().
		 * Next time, the call will return 0.
		 */
		TableSchema *table();

		/**
		 * \return a pointer to KexiDBSelect if 'SELECT ...' was called
		 * or 0 on any other operation or error. Returned object is owned by you.
		 * You can call this method only once every time after doing parse().
		 * Next time, the call will return 0.
		 */
		QuerySchema *query();

		/**
		 * \return a pointer to the used database connection or 0 if not set
		 * You can call this method only once every time after doing parse().
		 * Next time, the call will return 0.
		 */
		Connection	*db() const;

		/**
		 * \return detailed information about last error.
		 * If no error occurred ParserError isNull()
		 */
		ParserError error() const;

		/**
		 * \return the statement passed on the last \a parse method-call.
		 */
		TQString statement() const;

		/**
		 * \internal
		 * sets the operation (only parser will need to call this)
		 */
		void setOperation(OPCode op);

		/**
		 * \internal
		 * creates a new table (only parser will need to call this)
		 */
		void createTable(const char *t);

		/**
		 * \internal
		 * sets \a query schema object (only parser will need to call this)
		 */
//todo: other query types
		void setQuerySchema(QuerySchema *query);

		/**
		 * \internal
		 * \return query schema
		 */
		QuerySchema *select() const;

		/**
		 * \internal
		 * INTERNAL use only: sets a error
		 */
		void setError(const ParserError &err);

		/**
		 * \return true if the \param str is an reserved
		 * keyword (see tokens.cpp for a list of reserved
		 * keywords).
		 */
		bool isReservedKeyword(const char *str);

	protected:
		void init();

		ParserError m_error; //!< detailed information about last error.
		ParserPrivate *d; //!< \internal d-pointer class.
};

}

#endif

