libcruft-util/cruft/util/string.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2011-2018 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "ascii.hpp"
#include "debug/assert.hpp"
#include "view.hpp"

#include <string>
#include <type_traits>


namespace cruft {
    std::string to_utf8 (const wchar_t*);
    std::string to_utf8 (const std::wstring&);


    /// Apply a functor to each character of a string and return the result.
    template <typename FunctionT>
    std::string
    transform (std::string &&val, FunctionT &&func)
    {
        std::transform (
            std::begin (val),
            std::end   (val),
            std::begin (val),
            std::forward<FunctionT> (func)
        );

        return std::move (val);
    }


    /// Apply a functor to each character of a string and return the result.
    template <typename FunctionT>
    std::string
    transform (std::string_view val, FunctionT &&func)
    {
        std::string res;
        res.reserve (val.size ());

        std::transform (
            std::begin (val),
            std::end   (val),
            std::back_inserter (res),
            std::forward<FunctionT> (func)
        );

        return res;
    }


    inline std::string
    to_upper (std::string_view const &val)
    {
        return transform (val, ::toupper);
    }


    template <std::size_t N>
    inline std::string
    to_upper (char const (&val)[N])
    {
        return to_upper (std::string_view (val));
    }


    /// Convert the provided string to all upper case
    inline std::string
    to_upper (std::string &&val)
    {
        return transform (std::move (val), ::toupper);
    }


    /// Convert the provided string to all upper case
    inline std::string
    to_upper (std::string const &val)
    {
        return transform (val, ::toupper);
    }


    /// Convert the provided string to all upper case
    inline std::string
    to_lower (std::string &&val)
    {
        return transform (std::move (val), ::tolower);
    }


    /// Convert the provided string to all upper case
    inline std::string
    to_lower (std::string const &val)
    {
        return transform (val, ::tolower);
    }


    inline std::string_view
    lstrip (std::string_view str)
    {
        auto const pos = std::find_if_not (std::begin (str), std::end (str), ascii::is_space);
        return { pos, std::end (str) };
    }


    inline std::string_view
    rstrip (std::string_view str)
    {
        auto const pos = std::find_if_not (std::rbegin (str), std::rend (str), ascii::is_space);
        return { str.begin (), pos.base () };
    }


    inline std::string_view
    strip (std::string_view str)
    {
        return lstrip (rstrip (str));
    }
}


bool
strbegins(const char *restrict str,
          const char *restrict prefix);


namespace cruft {
    /// Provides an iterator interface over a string, breaking at each
    /// occurence of a specific character.
    ///
    /// It is up to the constructor to ensure the lifetime of the string.
    /// This class simply provides an interface for iteration and doesn't
    /// concern itself with lifetimes.
    template <std::forward_iterator Iterator>
    struct tokeniser {
    public:
        using value_type = view<Iterator>;
        using element_type = typename std::iterator_traits<Iterator>::value_type;

        tokeniser (cruft::view<Iterator,Iterator> _range, element_type _separator):
            m_range (_range),
            m_separator (_separator)
        { ; }

        tokeniser (const char *_range, char _separator):
            m_range (_range),
            m_separator (_separator)
        { ; }

        struct iterator {
        public:
            using iterator_category = std::forward_iterator_tag;
            using value_type = tokeniser::value_type;
            using difference_type = std::iter_difference_t<Iterator>;
            using pointer = value_type*;
            using reference = value_type&;

            iterator
            operator++ (int)
            {
                iterator res(*this);
                ++*this;
                return res;
            }

            iterator& operator++ (void)&
            {
                if (m_data.end () == m_end) {
                    m_data = { m_data.end (), m_data.end () };
                    m_base = m_end;
                    return *this;
                }

                m_base = m_data.end ();
                m_data = { m_data.end () + 1, std::find (m_data.end () + 1, m_end, m_separator) };
                return *this;
            }

            iterator operator+ (int count)
            {
                return std::next (*this, count);
            }

            auto const&
            operator* (void) const&
            {
                return m_data;
            }

            auto
            operator-> (void) const&
            {
                return &m_data;
            }

            bool operator== (const iterator &rhs) const
            {
                CHECK_EQ (m_separator, rhs.m_separator);
                return m_base == rhs.m_base;
            }

            bool operator!= (iterator const &rhs) const
            {
                return !(*this == rhs);
            }

            iterator (value_type _range, element_type _separator)
                : m_separator (_separator)
                , m_base (_range.begin ())
                , m_data (_range.begin (), std::find (_range.begin (), _range.end (), _separator))
                , m_end  (_range.end ())
            { ; }

        private:
            element_type m_separator;

            Iterator m_base;
            view<Iterator> m_data;
            Iterator m_end;
        };


        iterator cbegin (void) const { return { m_range, m_separator }; }
        iterator  begin (void) const { return { m_range, m_separator }; }

        iterator cend (void) const { return { { m_range.cend (), m_range.cend () }, m_separator }; }
        iterator  end (void) const { return { { m_range.cend (), m_range.cend () }, m_separator }; }

        std::size_t
        size (void) const
        {
            return std::count (
                m_range.begin (),
                m_range.end (),
                m_separator
            ) + 1u;
        }

        bool contains (std::string_view key) const noexcept
        {
            for (auto const &i: *this)
                if (equal (i, key))
                    return true;

            return false;
        }

    private:
        const value_type m_range;
        const element_type m_separator;
    };


    template <typename ContainerT>
    tokeniser (ContainerT&, typename ContainerT::value_type) -> tokeniser<typename ContainerT::iterator>;

    tokeniser (const char*,char) -> tokeniser<const char*>;

    ///////////////////////////////////////////////////////////////////////////
    template <typename CharT, std::size_t LengthV>
    auto
    make_tokeniser (CharT (&data)[LengthV], CharT separator)
    {
        return tokeniser { std::begin (data), std::end (data), separator };
    }


    ///////////////////////////////////////////////////////////////////////////
    /// Calculate the line and column of an iterator within a view.
    ///
    /// Returns an anonymous struct containing the line and column number.
    ///
    /// The column number for newline is undefined. However it should never
    /// return the value {0,-1} and so it should not result in underruns when
    /// offsetting a pointer using the column index.
    template <typename IteratorT>
    auto
    character_position (
        cruft::view<IteratorT> data,
        IteratorT const cursor
    ) {
        using difference_type = typename std::iterator_traits<IteratorT>::difference_type;
        difference_type line_count = 0;
        auto current_line = data.begin ();

        do {
            auto next_line = std::find (current_line, data.end (), '\n');
            if (next_line == data.end () || next_line > cursor)
                break;

            ++line_count;
            current_line = next_line + 1;
        } while (1);

        struct {
            difference_type line;
            difference_type column;
        } val = {
            .line = line_count,
            .column = cursor - current_line,
        };

        return val;
    }


    ///////////////////////////////////////////////////////////////////////////
    /// A comparator for string-like objects that uses strcmp rather than
    /// pointer comparison.
    ///
    /// TODO: handle string and string_view objects
    struct string_less {
        template <
            typename CharT,
            typename = std::void_t<typename std::char_traits<CharT>::char_type>
        >
        bool operator() (CharT const *a, CharT const *b) const noexcept
        {
            return strcmp (a, b) < 0;
        }
    };
}


namespace cruft::string {
    template <char (*TransformV)(char) noexcept>
    struct less {
        bool operator() (char const *a, char const *b) const noexcept
        {
            for (; *a && *b; ++a, ++b) {
                auto const &a_val = TransformV (*a);
                auto const &b_val = TransformV (*b);

                if (a_val < b_val)
                    return true;
                if (a_val > b_val)
                    return false;
            }

            return *a == '\0' && *b != '\0';
        }

        bool operator() (std::string const &a, std::string const & b) const noexcept
        {
            return (*this) (std::string_view (a), std::string_view (b));
        }

        bool operator() (std::string_view a, std::string_view b) const noexcept
        {
            auto a_cursor = a.begin ();
            auto b_cursor = b.begin ();

            for ( ; a_cursor != a.end () && b_cursor != b.end (); ++a_cursor, ++b_cursor) {
                auto const &a_val = TransformV (*a_cursor);
                auto const &b_val = TransformV (*b_cursor);
                if (a_val < b_val)
                    return true;
                if (a_val > b_val)
                    return false;
            }

            if (a_cursor == a.end () && b_cursor != b.end ())
                return true;

            return false;
        }

        using is_transparent = void;

        template <typename A, typename B>
        requires (!std::is_same_v<A,B>)
        bool operator() (A &&a, B &&b) const noexcept
        {
            return (*this) (
                std::string_view (a),
                std::string_view (b)
            );
        }
    };


    using less_lower = less<ascii::try_lower>;
}


namespace cruft::string::equality {
    ///////////////////////////////////////////////////////////////////////////
    /// A case comparator that tests equality on a string after a
    /// per-character transform is applied.
    ///
    /// Neither string will be modified.
    ///
    /// \tparam TransformV   A character transform function
    template <char (*TransformV)(char) noexcept>
    struct transform {
        static bool operator() (
            std::string_view const &a,
            std::string_view const &b
        ) noexcept {
            if (a.size () != b.size ())
                return false;

            for (auto i = a.begin (), j = b.begin (); i != a.end (); ++i, ++j)
                if (TransformV (*i) != TransformV (*j))
                    return false;

            return true;
        }
    };

    using lower = transform<ascii::try_lower>;
    using upper = transform<ascii::try_upper>;
}