libcruft-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.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&);
}


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 <typename Iterator>
    struct tokeniser {
    public:
        using value_type = typename std::iterator_traits<Iterator>::value_type;
        using range_type = view<Iterator>;


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

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


        struct iterator : public std::iterator<
            std::forward_iterator_tag,
            range_type,
            std::size_t
        > {
        public:
            iterator  operator++ (int)
            {
                iterator res(*this);
                ++*this;
                return res;
            }

            iterator& operator++ (void)&
            {
                auto newend = m_range.cend ();
                if (newend != m_end) {
                    CHECK_EQ (*m_range.cend (), m_separator);
                    newend++;
                }

                m_range = {
                    newend,
                    std::find (newend, m_end, m_separator)
                };

                return *this;
            }

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

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

            bool operator== (const iterator &rhs) const
            {
                return m_range == rhs.m_range && m_separator == rhs.m_separator;
            }

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

        private:
            iterator (range_type _range, value_type _separator):
                m_separator (_separator),
                m_range {
                    _range.cbegin (),
                    std::find (_range.cbegin (), _range.cend (), _separator)
                },
                m_end (_range.cend ())
            { ;  }

            value_type m_separator;
            range_type m_range;
            Iterator m_end;

            friend tokeniser;
        };


        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 range_type m_range;
        const value_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::compare {
    ///////////////////////////////////////////////////////////////////////////
    /// 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 {
        template <
            typename CharT,
            typename = std::void_t<
                typename std::char_traits<CharT>::char_type
            >
        >
        bool operator() (cruft::view<CharT const *> a, cruft::view<CharT const*> b)
        {
            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;
        }


        template <
            typename CharT,
            typename = std::void_t<
                typename std::char_traits<CharT>::char_type
            >
        >
        bool operator() (CharT const *a, CharT const *b) const noexcept
        {
            auto const *i = a;
            auto const *j = b;

            for ( ; *i && *j; ++i, ++j)
                if (TransformV (*i) != TransformV (*j))
                    return false;

            // Ensure we've reached the ends of both strings
            return !*i && !*j;
        }
    };

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