mapnik/include/mapnik/sql_utils.hpp

/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2021 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifndef MAPNIK_SQL_UTILS_HPP
#define MAPNIK_SQL_UTILS_HPP

// mapnik
#include <mapnik/util/trim.hpp> // for trim

// boost
#include <mapnik/warning.hpp>
MAPNIK_DISABLE_WARNING_PUSH
#include <mapnik/warning_ignore.hpp>
#include <boost/algorithm/string/replace.hpp>
MAPNIK_DISABLE_WARNING_POP

// stl
#include <iosfwd>
#include <regex>
#include <string>
#include <sstream>

namespace mapnik {
namespace sql_utils {

struct quoted_string
{
    std::string const* operator->() const { return &str; }
    std::string const& str;
    char const quot;
};

inline quoted_string identifier(std::string const& str)
{
    return {str, '"'};
}

inline quoted_string literal(std::string const& str)
{
    return {str, '\''};
}

inline std::ostream& operator<<(std::ostream& os, quoted_string qs)
{
    std::size_t pos = 0, next;

    os.put(qs.quot);
    while ((next = qs->find(qs.quot, pos)) != std::string::npos)
    {
        os.write(qs->data() + pos, next - pos + 1);
        os.put(qs.quot);
        pos = next + 1;
    }
    if ((next = qs->size()) > pos)
    {
        os.write(qs->data() + pos, next - pos);
    }
    return os.put(qs.quot);
}

// Does nothing if `str` doesn't start with `quot`.
// Otherwise erases the opening quote, collapses inner quote pairs,
// and erases everything from the closing quote to the end of the
// string. The closing quote is the first non-paired quote after the
// opening one. For a well-formed quoted string, it is also the last
// character, so nothing gets lost.
inline void unquote(char quot, std::string& str)
{
    if (!str.empty() && str.front() == quot)
    {
        std::size_t di = 0;
        for (std::size_t si = 1; si < str.size(); ++si)
        {
            char c = str[si];
            if (c == quot && (++si >= str.size() || str[si] != quot))
                break;
            str[di++] = c;
        }
        str.erase(di);
    }
}

inline std::string unquote_copy(char quot, std::string const& str)
{
    std::string tmp(str);
    sql_utils::unquote(quot, tmp);
    return tmp;
}

[[deprecated("flawed")]] inline std::string unquote_double(std::string const& sql)
{
    std::string table_name = sql;
    util::unquote_double(table_name);
    return table_name;
}

[[deprecated("flawed")]] inline std::string unquote(std::string const& sql)
{
    std::string table_name = sql;
    util::unquote(table_name);
    return table_name;
}

[[deprecated("flawed")]] inline void quote_attr(std::ostringstream& s, std::string const& field)
{
    s << ",\"" << field << "\"";
}

const std::regex re_from{"\\bFROM\\b", std::regex::icase};

const std::regex re_table_name{"\\s*(\\w+|(\"[^\"]*\")+)"   // $1 = schema
                               "(\\.(\\w+|(\"[^\"]*\")+))?" // $4 = table
                               "\\s*"};

inline bool table_from_sql(std::string const& sql, std::string& schema, std::string& table)
{
    std::smatch m;
    auto start = sql.begin();
    auto end = sql.end();
    auto flags = std::regex_constants::match_default;
    auto found = std::regex_match(start, end, m, re_table_name);
    auto extract_matched_parts = [&]() {
        if (m[4].matched)
        {
            table.assign(m[4].first, m[4].second);
            schema.assign(m[1].first, m[1].second);
        }
        else
        {
            table.assign(m[1].first, m[1].second);
            schema.clear();
        }
    };

    if (found)
    {
        // input is not subquery, just "[schema.]table"
        extract_matched_parts();
    }
    else
    {
        // search "FROM [schema.]table" in subquery
        while (std::regex_search(start, end, m, re_from, flags))
        {
            start = m[0].second;
            if (std::regex_search(start, end, m, re_table_name, std::regex_constants::match_continuous))
            {
                extract_matched_parts();
                found = true;
                start = m[0].second;
            }
            flags = std::regex_constants::match_prev_avail;
        }
    }
    if (found)
    {
        sql_utils::unquote('"', schema);
        sql_utils::unquote('"', table);
    }
    return found;
}

inline std::string table_from_sql(std::string const& sql)
{
    std::string table_name = sql;
    boost::algorithm::replace_all(table_name, "\n", " ");
    boost::algorithm::ireplace_all(table_name, " from ", " FROM ");

    std::string::size_type idx = table_name.rfind(" FROM ");
    if (idx != std::string::npos)
    {
        idx = table_name.find_first_not_of(" ", idx + 5);
        if (idx != std::string::npos)
        {
            table_name = table_name.substr(idx);
        }
        idx = table_name.find_first_of(", )");
        if (idx != std::string::npos)
        {
            table_name = table_name.substr(0, idx);
        }
    }
    return table_name;
}
} // namespace sql_utils
} // namespace mapnik

#endif // MAPNIK_SQL_UTILS_HPP