segments_view.hpp

//
// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
// Copyright (c) 2022 Alan de Freitas (alandefreitas@gmail.com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/url
//

#ifndef BOOST_URL_SEGMENTS_VIEW_HPP
#define BOOST_URL_SEGMENTS_VIEW_HPP

#include <boost/url/detail/config.hpp>
#include <boost/url/segments_base.hpp>
#include <boost/core/detail/string_view.hpp>

namespace boost {
namespace urls {

/** Non-owning decoded path segment view

    Presents the path of a URL as a read-only
    bidirectional range of percent-decoded
    segments. The range references the original
    buffer, so callers must keep that storage
    alive for as long as the view is accessed.

    @par Example
    @code
    url_view u( "/path/to/file.txt" );

    segments_view ps = u.segments();

    assert( ps.buffer().data() == u.buffer().data() );
    @endcode

    Any percent-escapes are decoded on demand
    when iterators are dereferenced.

    @par Iterator Invalidation
    Changes to the underlying character buffer
    can invalidate iterators which reference it.

    @see
        @ref segments_encoded_view,
        @ref segments_encoded_ref,
        @ref segments_ref.
*/
class BOOST_SYMBOL_VISIBLE segments_view
    : public segments_base
{
    friend class url_view_base;
    friend class segments_encoded_view;
    friend class segments_ref;

    segments_view(
        detail::path_ref const& ref) noexcept;

public:
    /** Constructor

        Default-constructed segments have
        zero elements.

        @par Example
        @code
        segments_view ps;
        @endcode

        @par Effects
        @code
        return segments_view( "" );
        @endcode

        @par Complexity
        Constant.

        @par Exception Safety
        Throws nothing.
    */
    segments_view() noexcept;

    /** Constructor

        After construction, viewss
        reference the same underlying character
        buffer.

        Ownership is not transferred; the caller
        is responsible for ensuring the lifetime
        of the buffer extends until it is no
        longer referenced.

        @par Postconditions
        @code
        this->buffer().data() == other.buffer().data()
        @endcode

        @par Complexity
        Constant

        @par Exception Safety
        Throws nothing

        @param other The other view.
    */
    segments_view(
        segments_view const& other) = default;

    /** Constructor

        This function constructs segments from
        a valid path string, which can contain
        percent escapes.
        Upon construction, the view references
        the character buffer pointed to by `s`.
        caller is responsible for ensuring
        that the lifetime of the buffer
        extends until the view is destroyed.

        @par Example
        @code
        segments_view ps( "/path/to/file.txt" );
        @endcode

        @par Effects
        @code
        return parse_path( s ).value();
        @endcode

        @par Postconditions
        @code
        this->buffer().data() == s.data()
        @endcode

        @par Complexity
        Linear in `s`.

        @par Exception Safety
        Exceptions thrown on invalid input.

        @throw system_error
        `s` contains an invalid path.

        @param s The string to parse.

        @par BNF
        @code
        path = [ "/" ] [ segment *( "/" segment ) ]

        segment = *pchar
        @endcode

        @par Specification
        @li <a href="https://datatracker.ietf.org/doc/html/rfc3986#section-3.3"
            >3.3.  Path</a>
    */
    segments_view(
        core::string_view s);

    /** Constructor

        This function creates a new @ref segments_view
        from a pair of iterators referring to
        elements of another segments view. The
        resulting view references the same
        underlying character buffer as the
        original.

        The constructed view preserves the
        original absolute flag when `first`
        selects the first segment and otherwise
        produces an absolute subview: if the
        source path is relative and `first ==
        ps.begin()` the new view is relative,
        and in every other case the subview is
        absolute with the separator immediately
        preceding `*first` retained at the front.
        This ensures the underlying text can be
        reconstructed by concatenating the buffers
        of adjacent subviews.

        The caller is responsible for ensuring
        that the lifetime of the original buffer
        extends until the constructed view is no
        longer referenced.

        @par Example
        @code
        segments_view ps( "/path/to/file.txt" );

        segments_view sub(
            std::next(ps.begin()),
            ps.end());

        segments_view first_half(
            ps.begin(),
            std::next(ps.begin()));

        // sub represents "/to/file.txt"
        std::string combined(first_half.buffer());
        combined.append(sub.buffer());
        BOOST_ASSERT(combined == ps.buffer());
        @endcode

        @par Preconditions
        The iterators must be valid and belong to
        the same @ref segments_view.

        @par Postconditions
        `sub.buffer()` references characters in the
        original `ps.buffer()`.

        @par Complexity
        Constant

        @par Exception Safety
        Throws nothing.

        @param first The beginning iterator.
        @param last The ending iterator.
    */
    segments_view(
        iterator first,
        iterator last) noexcept;

    /** Assignment

        After assignment, both views
        reference the same underlying character
        buffer.

        Ownership is not transferred; the caller
        is responsible for ensuring the lifetime
        of the buffer extends until it is no
        longer referenced.

        @par Postconditions
        @code
        this->buffer().data() == other.buffer().data()
        @endcode

        @par Complexity
        Constant

        @par Exception Safety
        Throws nothing

        @param other The other view.
        @return A reference to this object.
    */
    segments_view&
    operator=(segments_view const& other) = default;
};

} // urls
} // boost

//------------------------------------------------
//
// std::ranges::enable_borrowed_range
//
//------------------------------------------------

#ifdef BOOST_URL_HAS_CONCEPTS
#include <ranges>
namespace std::ranges {
    template<>
    inline constexpr bool
        enable_borrowed_range<
            boost::urls::segments_view> = true;
} // std::ranges
#endif

#endif