/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */


#pragma once

#include "mongo/base/string_data.h"

namespace mongo {

namespace fts {

struct QueryToken {
    enum Type { WHITESPACE, DELIMITER, TEXT, INVALID };
    QueryToken(Type type, StringData data, unsigned offset, bool previousWhiteSpace)
        : type(type), data(data), offset(offset), previousWhiteSpace(previousWhiteSpace) {}

    bool ok() const {
        return type != INVALID;
    }

    Type type;
    StringData data;
    unsigned offset;
    bool previousWhiteSpace;
};

/**
 * The pseudo EXBNF for the query parsing language is:
 *
 * SEARCH STRING = TOKEN_LIST ( ' ' TOKEN_LIST )*
 *
 * TOKEN_LIST = SEARCH_TOKEN
 *          |'-' SEARCH_TOKEN
 *          | QUOTED_SEARCH_TOKEN
 *          |'-' QUOTED_SEARCH_TOKEN
 *
 * QUOTED_SEARCH_TOKEN = '“' SEARCH_TOKEN+ '"'
 *
 * SEARCH_TOKEN = CHARACTER_EXCLUDING_SPECIAL_CHARS
 *
 * SPECIAL_CHARS = '-' | ' ' | '"'
 */
class FTSQueryParser {
    FTSQueryParser(const FTSQueryParser&) = delete;
    FTSQueryParser& operator=(const FTSQueryParser&) = delete;

public:
    FTSQueryParser(StringData str);
    bool more() const;
    QueryToken next();

private:
    QueryToken::Type getType(char c) const;
    bool skipWhitespace();

    unsigned _pos;
    bool _previousWhiteSpace;
    const StringData _raw;
};
}  // namespace fts
}  // namespace mongo