//
// Copyright (c) 2013-2016 Vinnie Falco (vinnie dot falco at gmail dot 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)
//

#ifndef BEAST_HTTP_BASIC_HEADERS_HPP
#define BEAST_HTTP_BASIC_HEADERS_HPP

#include <beast/core/detail/ci_char_traits.hpp>
#include <beast/core/detail/empty_base_optimization.hpp>
#include <boost/intrusive/list.hpp>
#include <boost/intrusive/set.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/utility/string_ref.hpp>
#include <algorithm>
#include <cctype>
#include <memory>
#include <string>
#include <type_traits>
#include <utility>

namespace beast {
namespace http {

template<class Allocator>
class basic_headers;

namespace detail {

class basic_headers_base
{
public:
    struct value_type
    {
        std::string first;
        std::string second;

        value_type(boost::string_ref const& name_,
                boost::string_ref const& value_)
            : first(name_)
            , second(value_)
        {
        }

        boost::string_ref
        name() const
        {
            return first;
        }

        boost::string_ref
        value() const
        {
            return second;
        }
    };

protected:
    template<class Allocator>
    friend class beast::http::basic_headers;

    struct element
        : boost::intrusive::set_base_hook <
            boost::intrusive::link_mode <
                boost::intrusive::normal_link>>
        , boost::intrusive::list_base_hook <
            boost::intrusive::link_mode <
                boost::intrusive::normal_link>>
    {
        value_type data;

        element(boost::string_ref const& name,
                boost::string_ref const& value)
            : data(name, value)
        {
        }
    };

    struct less : private beast::detail::ci_less
    {
        template<class String>
        bool
        operator()(String const& lhs, element const& rhs) const
        {
            return ci_less::operator()(lhs, rhs.data.first);
        }

        template<class String>
        bool
        operator()(element const& lhs, String const& rhs) const
        {
            return ci_less::operator()(lhs.data.first, rhs);
        }

        bool
        operator()(element const& lhs, element const& rhs) const
        {
            return ci_less::operator()(
                lhs.data.first, rhs.data.first);
        }
    };

    using list_t = typename boost::intrusive::make_list<
        element, boost::intrusive::constant_time_size<false>>::type;

    using set_t = typename boost::intrusive::make_set<
        element, boost::intrusive::constant_time_size<true>,
            boost::intrusive::compare<less>>::type;

    // data
    set_t set_;
    list_t list_;

    basic_headers_base(set_t&& set, list_t&& list)
        : set_(std::move(set))
        , list_(std::move(list))
    {

    }

public:
    class const_iterator;

    using iterator = const_iterator;

    basic_headers_base() = default;

    /// Returns an iterator to the beginning of the field sequence.
    iterator
    begin() const;

    /// Returns an iterator to the end of the field sequence.
    iterator
    end() const;

    /// Returns an iterator to the beginning of the field sequence.
    iterator
    cbegin() const;

    /// Returns an iterator to the end of the field sequence.
    iterator
    cend() const;
};

//------------------------------------------------------------------------------

class basic_headers_base::const_iterator
{
    using iter_type = list_t::const_iterator;

    iter_type it_;

    template<class Allocator>
    friend class beast::http::basic_headers;

    friend class basic_headers_base;

    const_iterator(iter_type it)
        : it_(it)
    {
    }

public:
    using value_type =
        typename basic_headers_base::value_type;
    using pointer = value_type const*;
    using reference = value_type const&;
    using difference_type = std::ptrdiff_t;
    using iterator_category =
        std::bidirectional_iterator_tag;

    const_iterator() = default;
    const_iterator(const_iterator&& other) = default;
    const_iterator(const_iterator const& other) = default;
    const_iterator& operator=(const_iterator&& other) = default;
    const_iterator& operator=(const_iterator const& other) = default;

    bool
    operator==(const_iterator const& other) const
    {
        return it_ == other.it_;
    }

    bool
    operator!=(const_iterator const& other) const
    {
        return !(*this == other);
    }

    reference
    operator*() const
    {
        return it_->data;
    }

    pointer
    operator->() const
    {
        return &**this;
    }

    const_iterator&
    operator++()
    {
        ++it_;
        return *this;
    }

    const_iterator
    operator++(int)
    {
        auto temp = *this;
        ++(*this);
        return temp;
    }

    const_iterator&
    operator--()
    {
        --it_;
        return *this;
    }

    const_iterator
    operator--(int)
    {
        auto temp = *this;
        --(*this);
        return temp;
    }
};

} // detail

//------------------------------------------------------------------------------

/** A container for storing HTTP headers.

    This container is designed to store the field value pairs that make
    up the headers and trailers in a HTTP message. Objects of this type
    are iterable, which each element holding the field name and field
    value.

    Field names are stored as-is, but comparison are case-insensitive.
    The container preserves the order of insertion of fields with
    different names. For fields with the same name, the implementation
    concatenates values inserted with duplicate names as per the
    rules in rfc2616 section 4.2.

    @note Meets the requirements of @b `FieldSequence`.
*/
template<class Allocator>
class basic_headers
#if ! GENERATING_DOCS
    : private beast::detail::empty_base_optimization<
        typename std::allocator_traits<Allocator>::
            template rebind_alloc<
                detail::basic_headers_base::element>>
    , public detail::basic_headers_base
#endif
{
    using alloc_type = typename
        std::allocator_traits<Allocator>::
            template rebind_alloc<
                detail::basic_headers_base::element>;

    using alloc_traits =
        std::allocator_traits<alloc_type>;

    using size_type =
        typename std::allocator_traits<Allocator>::size_type;

    void
    delete_all();

    void
    move_assign(basic_headers&, std::false_type);

    void
    move_assign(basic_headers&, std::true_type);

    void
    copy_assign(basic_headers const&, std::false_type);

    void
    copy_assign(basic_headers const&, std::true_type);

    template<class FieldSequence>
    void
    copy_from(FieldSequence const& fs)
    {
        for(auto const& e : fs)
            insert(e.first, e.second);
    }

public:
    /// The type of allocator used.
    using allocator_type = Allocator;

    /// Default constructor.
    basic_headers() = default;

    /// Destructor
    ~basic_headers();

    /** Construct the headers.

        @param alloc The allocator to use.
    */
    explicit
    basic_headers(Allocator const& alloc);

    /** Move constructor.

        The moved-from object becomes an empty field sequence.

        @param other The object to move from.
    */
    basic_headers(basic_headers&& other);

    /** Move assignment.

        The moved-from object becomes an empty field sequence.

        @param other The object to move from.
    */
    basic_headers& operator=(basic_headers&& other);

    /// Copy constructor.
    basic_headers(basic_headers const&);

    /// Copy assignment.
    basic_headers& operator=(basic_headers const&);

    /// Copy constructor.
    template<class OtherAlloc>
    basic_headers(basic_headers<OtherAlloc> const&);

    /// Copy assignment.
    template<class OtherAlloc>
    basic_headers& operator=(basic_headers<OtherAlloc> const&);

    /// Construct from a field sequence.
    template<class FwdIt>
    basic_headers(FwdIt first, FwdIt last);

    /// Returns `true` if the field sequence contains no elements.
    bool
    empty() const
    {
        return set_.empty();
    }

    /// Returns the number of elements in the field sequence.
    std::size_t
    size() const
    {
        return set_.size();
    }

    /** Returns `true` if the specified field exists. */
    bool
    exists(boost::string_ref const& name) const
    {
        return set_.find(name, less{}) != set_.end();
    }

    /** Returns an iterator to the case-insensitive matching header. */
    iterator
    find(boost::string_ref const& name) const;

    /** Returns the value for a case-insensitive matching header, or "" */
    boost::string_ref
    operator[](boost::string_ref const& name) const;

    /** Clear the contents of the basic_headers. */
    void
    clear() noexcept;

    /** Remove a field.

        @return The number of fields removed.
    */
    std::size_t
    erase(boost::string_ref const& name);

    /** Insert a field value.

        If a field value already exists the new value will be
        extended as per RFC2616 Section 4.2.
    */
    // VFALCO TODO Consider allowing rvalue references for std::move?
    void
    insert(boost::string_ref const& name,
        boost::string_ref const& value);

    /** Insert a field value.

        If a field value already exists the new value will be
        extended as per RFC2616 Section 4.2.
    */
    template<class T,
        class = typename std::enable_if<
            ! std::is_constructible<boost::string_ref, T>::value>::type>
    void
    insert(boost::string_ref name, T const& value)
    {
        insert(name,
            boost::lexical_cast<std::string>(value));
    }

    /** Replace a field value.

        The current field value, if any, is removed. Then the
        specified value is inserted as if by insert(field, value).
    */
    void
    replace(boost::string_ref const& name,
        boost::string_ref const& value);

    /** Replace a field value.

        The current field value, if any, is removed. Then the
        specified value is inserted as if by insert(field, value).
    */
    template<class T,
        class = typename std::enable_if<
            ! std::is_constructible<boost::string_ref, T>::value>::type>
    void
    replace(boost::string_ref const& name, T const& value)
    {
        replace(name,
            boost::lexical_cast<std::string>(value));
    }
};

} // http
} // beast

#include <beast/http/impl/basic_headers.ipp>

#endif