/**
 *    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.
 */

#include <string>

#include "mongo/db/fts/fts_query_parser.h"
#include "mongo/util/str.h"

namespace mongo {

namespace fts {

FTSQueryParser::FTSQueryParser(StringData str) : _pos(0), _raw(str) {
    skipWhitespace();
    _previousWhiteSpace = true;
}

bool FTSQueryParser::more() const {
    return _pos < _raw.size();
}

QueryToken FTSQueryParser::next() {
    if (_pos >= _raw.size())
        return QueryToken(QueryToken::INVALID, "", 0, false);

    unsigned start = _pos++;
    QueryToken::Type type = getType(_raw[start]);

    // Query Parser should never land on whitespace
    if (type == QueryToken::WHITESPACE) {
        MONGO_UNREACHABLE;
    }

    if (type == QueryToken::TEXT) {
        while (_pos < _raw.size() && getType(_raw[_pos]) == type) {
            _pos++;
        }
    }

    StringData ret = _raw.substr(start, _pos - start);
    bool old = _previousWhiteSpace;
    _previousWhiteSpace = skipWhitespace();

    return QueryToken(type, ret, start, old);
}

bool FTSQueryParser::skipWhitespace() {
    unsigned start = _pos;

    while (_pos < _raw.size() && getType(_raw[_pos]) == QueryToken::WHITESPACE) {
        _pos++;
    }

    return _pos > start;
}


QueryToken::Type FTSQueryParser::getType(char c) const {
    switch (c) {
        // Unicode TR29 defines these as Word Boundaries
        case '\n':  // U+000A - LF
        case '\v':  // U+000B - Veritical Tab
        case '\f':  // U+000C - Form Feed
        case '\r':  // U+000D - CR
        // Unicode TR29 remarks this could be used MidNum for Word Boundaries
        // but we treat this as a token separator
        case ' ':  // U+0020 - Space
            return QueryToken::WHITESPACE;
        // Unicode TR29 has a particular note about the complexity of hyphens.
        // Since we use them for negation, we are sensitive to them, and we simply drop
        // them otherwise from words
        case '-':
        case '"':
            return QueryToken::DELIMITER;
        default:
            return QueryToken::TEXT;
    }
}
}  // namespace fts
}  // namespace mongo