mapnik/src/value.cpp

/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2017 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
 *
 *****************************************************************************/

// mapnik
#include <mapnik/value.hpp>
#include <mapnik/value/types.hpp>
#include <mapnik/util/conversions.hpp>

// stl
#include <cmath>
#include <string>
#include <type_traits>
// icu
#include <unicode/unistr.h>
#include <unicode/ustring.h>

namespace mapnik {

namespace detail {

namespace {
template <typename T, typename U>
struct both_arithmetic : std::integral_constant<bool,
                                                std::is_arithmetic<T>::value &&
                                                std::is_arithmetic<U>::value> {};

struct equals
{
    static bool apply(value_null, value_unicode_string const& rhs)
    {
        return false;
    }

    template <typename T>
    static auto apply(T const& lhs, T const& rhs)
        -> decltype(lhs == rhs)
    {
        return lhs == rhs;
    }
};

struct not_equal
{
    // back compatibility shim to equate empty string with null for != test
    // https://github.com/mapnik/mapnik/issues/1859
    // TODO - consider removing entire specialization at Mapnik 3.1.x
    static bool apply(value_null, value_unicode_string const& rhs)
    {
        if (rhs.isEmpty()) return false;
        return true;
    }

    template <typename T>
    static auto apply(T const& lhs, T const& rhs)
        -> decltype(lhs != rhs)
    {
        return lhs != rhs;
    }
};

struct greater_than
{
    static bool apply(value_null, value_unicode_string const& rhs)
    {
        return false;
    }

    template <typename T>
    static auto apply(T const& lhs, T const& rhs)
        -> decltype(lhs > rhs)
    {
        return lhs > rhs;
    }
};

struct greater_or_equal
{
    static bool apply(value_null, value_unicode_string const& rhs)
    {
        return false;
    }

    template <typename T>
    static auto apply(T const& lhs, T const& rhs)
        -> decltype(lhs >= rhs)
    {
        return lhs >= rhs;
    }
};

struct less_than
{
    static bool apply(value_null, value_unicode_string const& rhs)
    {
        return false;
    }

    template <typename T>
    static auto apply(T const& lhs, T const& rhs)
        -> decltype(lhs < rhs)
    {
        return lhs < rhs;
    }
};

struct less_or_equal
{
    static bool apply(value_null, value_unicode_string const& rhs)
    {
        return false;
    }

    template <typename T>
    static auto apply(T const& lhs, T const& rhs)
        -> decltype(lhs <= rhs)
    {
        return lhs <= rhs;
    }
};
}

template <typename Op, bool default_result>
struct comparison
{
    // special case for unicode_strings (fixes MSVC C4800)
    bool operator()(value_unicode_string const& lhs,
                    value_unicode_string const& rhs) const
    {
        return Op::apply(lhs, rhs) ? true : false;
    }

    //////////////////////////////////////////////////////////////////////////
    // special case for unicode_string and value_null
    //////////////////////////////////////////////////////////////////////////

    bool operator()(value_null const& lhs, value_unicode_string const& rhs) const
    {
        return Op::apply(lhs, rhs);
    }
    //////////////////////////////////////////////////////////////////////////

    // same types
    template <typename T>
    bool operator()(T lhs, T rhs) const
    {
        return Op::apply(lhs, rhs);
    }

    // both types are arithmetic - promote to the common type
    template <typename T, typename U, typename std::enable_if<both_arithmetic<T, U>::value, int>::type = 0>
    bool operator()(T const& lhs, U const& rhs) const
    {
        using common_type = typename std::common_type<T, U>::type;
        return Op::apply(static_cast<common_type>(lhs), static_cast<common_type>(rhs));
    }

    //
    template <typename T, typename U, typename std::enable_if<!both_arithmetic<T, U>::value, int>::type = 0>
    bool operator()(T const& lhs, U const& rhs) const
    {
        return default_result;
    }
};

template <typename V>
struct add
{
    using value_type = V;
    value_type operator()(value_unicode_string const& lhs,
                          value_unicode_string const& rhs) const
    {
        return lhs + rhs;
    }

    value_type operator()(value_null const& lhs,
                          value_null const& rhs) const
    {
        return lhs;
    }

    value_type operator()(value_unicode_string const& lhs, value_null) const
    {
        return lhs;
    }

    value_type operator()(value_null, value_unicode_string const& rhs) const
    {
        return rhs;
    }

    template <typename L>
    value_type operator()(L const& lhs, value_null const&) const
    {
        return lhs;
    }

    template <typename R>
    value_type operator()(value_null const&, R const& rhs) const
    {
        return rhs;
    }

    template <typename L>
    value_type operator()(L const& lhs, value_unicode_string const& rhs) const
    {
        std::string val;
        if (util::to_string(val, lhs))
            return value_unicode_string(val.c_str()) + rhs;
        return rhs;
    }

    template <typename R>
    value_type operator()(value_unicode_string const& lhs, R const& rhs) const
    {
        std::string val;
        if (util::to_string(val, rhs))
            return lhs + value_unicode_string(val.c_str());
        return lhs;
    }

    template <typename T1, typename T2>
    value_type operator()(T1 const& lhs, T2 const& rhs) const
    {
        return typename std::common_type<T1, T2>::type{lhs + rhs};
    }

    value_type operator()(value_bool lhs, value_bool rhs) const
    {
        return value_integer(lhs + rhs);
    }
};

template <typename V>
struct sub
{
    using value_type = V;

    value_type operator()(value_null const& lhs,
                          value_null const& rhs) const
    {
        return lhs;
    }

    value_type operator()(value_null, value_unicode_string const& rhs) const
    {
        return rhs;
    }
    value_type operator()(value_unicode_string const& lhs, value_null) const
    {
        return lhs;
    }

    template <typename R>
    value_type operator()(value_unicode_string const& lhs, R const&) const
    {
        return lhs;
    }

    template <typename L>
    value_type operator()(L const&, value_unicode_string const& rhs) const
    {
        return rhs;
    }

    template <typename L>
    value_type operator()(L const& lhs, value_null const&) const
    {
        return lhs;
    }

    template <typename R>
    value_type operator()(value_null const&, R const& rhs) const
    {
        return rhs;
    }

    template <typename T>
    value_type operator()(T lhs, T rhs) const
    {
        return lhs - rhs;
    }

    value_type operator()(value_unicode_string const&,
                          value_unicode_string const&) const
    {
        return value_type();
    }

    template <typename T1, typename T2>
    value_type operator()(T1 const& lhs, T2 const& rhs) const
    {
        return typename std::common_type<T1, T2>::type{lhs - rhs};
    }

    value_type operator()(value_bool lhs, value_bool rhs) const
    {
        return value_integer(lhs - rhs);
    }
};

template <typename V>
struct mult
{
    using value_type = V;

    value_type operator()(value_null const& lhs,
                          value_null const& rhs) const
    {
        return lhs;
    }

    value_type operator()(value_unicode_string const& lhs, value_null) const
    {
        return lhs;
    }

    value_type operator()(value_null, value_unicode_string const& rhs) const
    {
        return rhs;
    }

    template <typename L>
    value_type operator()(L const& lhs, value_null const&) const
    {
        return lhs;
    }

    template <typename R>
    value_type operator()(value_null const&, R const& rhs) const
    {
        return rhs;
    }

    template <typename R>
    value_type operator()(value_unicode_string const& lhs, R const&) const
    {
        return lhs;
    }

    template <typename L>
    value_type operator()(L const&, value_unicode_string const& rhs) const
    {
        return rhs;
    }

    template <typename T>
    value_type operator()(T lhs, T rhs) const
    {
        return lhs * rhs;
    }

    value_type operator()(value_unicode_string const&,
                          value_unicode_string const&) const
    {
        return value_type();
    }

    template <typename T1, typename T2>
    value_type operator()(T1 const& lhs, T2 const& rhs) const
    {
        return typename std::common_type<T1, T2>::type{lhs * rhs};
    }

    value_type operator()(value_bool lhs, value_bool rhs) const
    {
        return value_integer(lhs * rhs);
    }
};

template <typename V>
struct div
{
    using value_type = V;

    value_type operator()(value_null const& lhs,
                          value_null const& rhs) const
    {
        return lhs;
    }

    value_type operator()(value_unicode_string const& lhs, value_null) const
    {
        return lhs;
    }

    value_type operator()(value_null, value_unicode_string const& rhs) const
    {
        return rhs;
    }

    template <typename L>
    value_type operator()(L const& lhs, value_null const&) const
    {
        return lhs;
    }

    template <typename R>
    value_type operator()(value_null const&, R const& rhs) const
    {
        return rhs;
    }

    template <typename T>
    value_type operator()(T lhs, T rhs) const
    {
        if (rhs == 0) return value_type();
        return lhs / rhs;
    }

    value_type operator()(value_bool lhs, value_bool rhs) const
    {
        if (rhs == 0) return lhs;
        return value_integer(lhs) / value_integer(rhs);
    }

    value_type operator()(value_unicode_string const&,
                          value_unicode_string const&) const
    {
        return value_type();
    }

    template <typename R>
    value_type operator()(value_unicode_string const& lhs, R const&) const
    {
        return lhs;
    }

    template <typename L>
    value_type operator()(L const&, value_unicode_string const& rhs) const
    {
        return rhs;
    }

    template <typename T1, typename T2>
    value_type operator()(T1 const& lhs, T2 const& rhs) const
    {
        if (rhs == 0) return value_type();
        using common_type = typename std::common_type<T1, T2>::type;
        return common_type(lhs) / common_type(rhs);
    }
};

template <typename V>
struct mod
{
    using value_type = V;

    template <typename T1, typename T2>
    value_type operator()(T1 const& lhs, T2 const&) const
    {
        return lhs;
    }

    template <typename T>
    value_type operator()(T lhs, T rhs) const
    {
        return lhs % rhs;
    }

    value_type operator()(value_unicode_string const&,
                          value_unicode_string const&) const
    {
        return value_type();
    }

    value_type operator()(value_bool,
                          value_bool) const
    {
        return false;
    }

    value_type operator()(value_double lhs, value_integer rhs) const
    {
        return std::fmod(lhs, static_cast<value_double>(rhs));
    }

    value_type operator()(value_integer lhs, value_double rhs) const
    {
        return std::fmod(static_cast<value_double>(lhs), rhs);
    }

    value_type operator()(value_double lhs, value_double rhs) const
    {
        return std::fmod(lhs, rhs);
    }
};

template <typename V>
struct negate
{
    using value_type = V;

    template <typename T>
    value_type operator()(T val) const
    {
        return -val;
    }

    value_type operator()(value_null val) const
    {
        return val;
    }

    value_type operator()(value_bool val) const
    {
        return val ? value_integer(-1) : value_integer(0);
    }

    value_type operator()(value_unicode_string const&) const
    {
        return value_type();
    }
};

// converters
template <typename T>
struct convert
{
};

template <>
struct convert<value_bool>
{
    value_bool operator()(value_bool val) const
    {
        return val;
    }

    value_bool operator()(value_unicode_string const& ustr) const
    {
        return !ustr.isEmpty();
    }

    value_bool operator()(value_null const&) const
    {
        return false;
    }

    template <typename T>
    value_bool operator()(T val) const
    {
        return val > 0 ? true : false;
    }
};

template <>
struct convert<value_double>
{
    value_double operator()(value_double val) const
    {
        return val;
    }

    value_double operator()(value_integer val) const
    {
        return static_cast<value_double>(val);
    }

    value_double operator()(value_bool val) const
    {
        return static_cast<value_double>(val);
    }

    value_double operator()(std::string const& val) const
    {
        value_double result;
        if (util::string2double(val, result))
            return result;
        return 0;
    }

    value_double operator()(value_unicode_string const& val) const
    {
        std::string utf8;
        val.toUTF8String(utf8);
        return operator()(utf8);
    }

    value_double operator()(value_null const&) const
    {
        return 0.0;
    }
};

template <>
struct convert<value_integer>
{
    value_integer operator()(value_integer val) const
    {
        return val;
    }

    value_integer operator()(value_double val) const
    {
        return static_cast<value_integer>(std::floor(val) + .5);
    }

    value_integer operator()(value_bool val) const
    {
        return static_cast<value_integer>(val);
    }

    value_integer operator()(std::string const& val) const
    {
        value_integer result;
        if (util::string2int(val, result))
            return result;
        return value_integer(0);
    }

    value_integer operator()(value_unicode_string const& val) const
    {
        std::string utf8;
        val.toUTF8String(utf8);
        return operator()(utf8);
    }

    value_integer operator()(value_null const&) const
    {
        return value_integer(0);
    }
};

template <>
struct convert<std::string>
{
    template <typename T>
    std::string operator()(T val) const
    {
        std::string str;
        util::to_string(str, val);
        return str;
    }

    // specializations
    std::string operator()(value_unicode_string const& val) const
    {
        std::string utf8;
        val.toUTF8String(utf8);
        return utf8;
    }

    std::string operator()(value_double val) const
    {
        std::string str;
        util::to_string(str, val); // TODO set precision(16)
        return str;
    }

    std::string operator()(value_bool val) const
    {
        return val ? "true" : "false";
    }

    std::string operator()(value_null const&) const
    {
        return std::string("");
    }
};

struct to_unicode_impl
{

    template <typename T>
    value_unicode_string operator()(T val) const
    {
        std::string str;
        util::to_string(str, val);
        return value_unicode_string(str.c_str());
    }

    // specializations
    value_unicode_string const& operator()(value_unicode_string const& val) const
    {
        return val;
    }

    value_unicode_string operator()(value_double val) const
    {
        std::string str;
        util::to_string(str, val);
        return value_unicode_string(str.c_str());
    }

    value_unicode_string operator()(value_bool val) const
    {
        return value_unicode_string(val ? "true" : "false");
    }

    value_unicode_string operator()(value_null const&) const
    {
        return value_unicode_string("");
    }
};

struct to_expression_string_impl
{
    struct EscapingByteSink : U_NAMESPACE_QUALIFIER ByteSink
    {
        std::string dest_;
        char quote_;

        explicit EscapingByteSink(char quote)
            : quote_(quote)
        {
        }

        virtual void Append(const char* data, int32_t n)
        {
            // reserve enough room to hold the appended chunk and quotes;
            // if another chunk follows, or any character needs escaping,
            // the string will grow naturally
            if (dest_.empty())
            {
                dest_.reserve(2 + static_cast<std::size_t>(n));
                dest_.append(1, quote_);
            }
            else
            {
                dest_.reserve(dest_.size() + n + 1);
            }

            for (auto end = data + n; data < end; ++data)
            {
                if (*data == '\\' || *data == quote_)
                    dest_.append(1, '\\');
                dest_.append(1, *data);
            }
        }

        virtual void Flush()
        {
            if (dest_.empty())
                dest_.append(2, quote_);
            else
                dest_.append(1, quote_);
        }
    };

    explicit to_expression_string_impl(char quote = '\'')
        : quote_(quote) {}

    std::string operator()(value_unicode_string const& val) const
    {
        // toUTF8(sink) doesn't Flush() the sink if the source string
        // is empty -- we must return a pair of quotes in that case
        //  https://github.com/mapnik/mapnik/issues/3362
        if (val.isEmpty())
        {
            return std::string(2, quote_);
        }
        EscapingByteSink sink(quote_);
        val.toUTF8(sink);
        return sink.dest_;
    }

    std::string operator()(value_integer val) const
    {
        std::string output;
        util::to_string(output, val);
        return output;
    }

    std::string operator()(value_double val) const
    {
        std::string output;
        util::to_string(output, val); // TODO precision(16)
        return output;
    }

    std::string operator()(value_bool val) const
    {
        return val ? "true" : "false";
    }

    std::string operator()(value_null const&) const
    {
        return "null";
    }

    const char quote_;
};

} // ns detail

namespace value_adl_barrier {

bool value::operator==(value const& other) const
{
    return util::apply_visitor(detail::comparison<detail::equals, false>(), *this, other);
}

bool value::operator!=(value const& other) const
{
    return util::apply_visitor(detail::comparison<detail::not_equal, true>(), *this, other);
}

bool value::operator>(value const& other) const
{
    return util::apply_visitor(detail::comparison<detail::greater_than, false>(), *this, other);
}

bool value::operator>=(value const& other) const
{
    return util::apply_visitor(detail::comparison<detail::greater_or_equal, false>(), *this, other);
}

bool value::operator<(value const& other) const
{
    return util::apply_visitor(detail::comparison<detail::less_than, false>(), *this, other);
}

bool value::operator<=(value const& other) const
{
    return util::apply_visitor(detail::comparison<detail::less_or_equal, false>(), *this, other);
}

value value::operator-() const
{
    return util::apply_visitor(detail::negate<value>(), *this);
}

value_bool value::to_bool() const
{
    return util::apply_visitor(detail::convert<value_bool>(), *this);
}

std::string value::to_expression_string(char quote) const
{
    return util::apply_visitor(detail::to_expression_string_impl(quote), *this);
}

std::string value::to_string() const
{
    return util::apply_visitor(detail::convert<std::string>(), *this);
}

value_unicode_string value::to_unicode() const
{
    return util::apply_visitor(detail::to_unicode_impl(), *this);
}

value_double value::to_double() const
{
    return util::apply_visitor(detail::convert<value_double>(), *this);
}

value_integer value::to_int() const
{
    return util::apply_visitor(detail::convert<value_integer>(), *this);
}

bool value::is_null() const
{
    return util::apply_visitor(mapnik::detail::is_null_visitor(), *this);
}

template <>
value_double value::convert() const
{
    return util::apply_visitor(detail::convert<value_double>(), *this);
}

template <>
value_integer value::convert() const
{
    return util::apply_visitor(detail::convert<value_integer>(), *this);
}

template <>
value_bool value::convert() const
{
    return util::apply_visitor(detail::convert<value_bool>(), *this);
}

template <>
std::string value::convert() const
{
    return util::apply_visitor(detail::convert<std::string>(), *this);
}

//
value operator+(value const& p1, value const& p2)
{
    return value(util::apply_visitor(detail::add<value>(), p1, p2));
}

value operator-(value const& p1, value const& p2)
{
    return value(util::apply_visitor(detail::sub<value>(), p1, p2));
}

value operator*(value const& p1, value const& p2)
{
    return value(util::apply_visitor(detail::mult<value>(), p1, p2));
}

value operator/(value const& p1, value const& p2)
{
    return value(util::apply_visitor(detail::div<value>(), p1, p2));
}

value operator%(value const& p1, value const& p2)
{
    return value(util::apply_visitor(detail::mod<value>(), p1, p2));
}

} // namespace value_adl_barrier
} // namespace mapnik