//
// 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_RFC2616_HPP
#define BEAST_HTTP_RFC2616_HPP

#include <boost/range/algorithm/equal.hpp>
#include <boost/range/iterator_range.hpp>
#include <boost/utility/string_ref.hpp>
#include <algorithm>
#include <cctype>
#include <string>
#include <iterator>
#include <tuple> // for std::tie, remove ASAP
#include <utility>
#include <vector>

namespace beast {

#if ! GENERATING_DOCS

/** Routines for performing RFC2616 compliance.
    RFC2616:
        Hypertext Transfer Protocol -- HTTP/1.1
        http://www.w3.org/Protocols/rfc2616/rfc2616
*/
namespace rfc2616 {

namespace detail {

struct ci_equal_pred
{
    bool operator()(char c1, char c2)
    {
        // VFALCO TODO Use a table lookup here
        return std::tolower(c1) == std::tolower(c2);
    }
};

} // detail

/** Returns `true` if `c` is linear white space.

    This excludes the CRLF sequence allowed for line continuations.
*/
inline
bool
is_lws(char c)
{
    return c == ' ' || c == '\t';
}

/** Returns `true` if `c` is any whitespace character. */
inline
bool
is_white(char c)
{
    switch (c)
    {
    case ' ':  case '\f': case '\n':
    case '\r': case '\t': case '\v':
        return true;
    };
    return false;
}

/** Returns `true` if `c` is a control character. */
inline
bool
is_control(char c)
{
    return c <= 31 || c >= 127;
}

/** Returns `true` if `c` is a separator. */
inline
bool
is_separator(char c)
{
    // VFALCO Could use a static table
    switch (c)
    {
    case '(': case ')': case '<': case '>':  case '@':
    case ',': case ';': case ':': case '\\': case '"':
    case '{': case '}': case ' ': case '\t':
        return true;
    };
    return false;
}

/** Returns `true` if `c` is a character. */
inline
bool
is_char(char c)
{
    return c >= 0 && c <= 127;
}

template <class FwdIter>
FwdIter
trim_left (FwdIter first, FwdIter last)
{
    return std::find_if_not (first, last,
        is_white);
}

template <class FwdIter>
FwdIter
trim_right (FwdIter first, FwdIter last)
{
    if (first == last)
        return last;
    do
    {
        --last;
        if (! is_white (*last))
            return ++last;
    }
    while (last != first);
    return first;
}

template <class CharT, class Traits, class Allocator>
void
trim_right_in_place (std::basic_string <
    CharT, Traits, Allocator>& s)
{
    s.resize (std::distance (s.begin(),
        trim_right (s.begin(), s.end())));
}

template <class FwdIter>
std::pair <FwdIter, FwdIter>
trim (FwdIter first, FwdIter last)
{
    first = trim_left (first, last);
    last = trim_right (first, last);
    return std::make_pair (first, last);
}

template <class String>
String
trim (String const& s)
{
    using std::begin;
    using std::end;
    auto first = begin(s);
    auto last = end(s);
    std::tie (first, last) = trim (first, last);
    return { first, last };
}

template <class String>
String
trim_right (String const& s)
{
    using std::begin;
    using std::end;
    auto first (begin(s));
    auto last (end(s));
    last = trim_right (first, last);
    return { first, last };
}

inline
std::string
trim (std::string const& s)
{
    return trim <std::string> (s);
}

/** Parse a character sequence of values separated by commas.
    Double quotes and escape sequences will be converted.  Excess white
    space, commas, double quotes, and empty elements are not copied.
    Format:
       #(token|quoted-string)
    Reference:
        http://www.w3.org/Protocols/rfc2616/rfc2616-sec2.html#sec2
*/
template <class FwdIt,
    class Result = std::vector<
        std::basic_string<typename
            std::iterator_traits<FwdIt>::value_type>>,
                class Char>
Result
split(FwdIt first, FwdIt last, Char delim)
{
    Result result;
    using string = typename Result::value_type;
    FwdIt iter = first;
    string e;
    while (iter != last)
    {
        if (*iter == '"')
        {
            // quoted-string
            ++iter;
            while (iter != last)
            {
                if (*iter == '"')
                {
                    ++iter;
                    break;
                }

                if (*iter == '\\')
                {
                    // quoted-pair
                    ++iter;
                    if (iter != last)
                        e.append (1, *iter++);
                }
                else
                {
                    // qdtext
                    e.append (1, *iter++);
                }
            }
            if (! e.empty())
            {
                result.emplace_back(std::move(e));
                e.clear();
            }
        }
        else if (*iter == delim)
        {
            e = trim_right (e);
            if (! e.empty())
            {
                result.emplace_back(std::move(e));
                e.clear();
            }
            ++iter;
        }
        else if (is_lws (*iter))
        {
            ++iter;
        }
        else
        {
            e.append (1, *iter++);
        }
    }

    if (! e.empty())
    {
        e = trim_right (e);
        if (! e.empty())
            result.emplace_back(std::move(e));
    }
    return result;
}

template <class FwdIt,
    class Result = std::vector<
        std::basic_string<typename std::iterator_traits<
            FwdIt>::value_type>>>
Result
split_commas(FwdIt first, FwdIt last)
{
    return split(first, last, ',');
}

template <class Result = std::vector<std::string>>
Result
split_commas(boost::string_ref const& s)
{
    return split_commas(s.begin(), s.end());
}

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

/** Iterates through a comma separated list.

    Meets the requirements of ForwardIterator.

    List defined in rfc2616 2.1.

    @note Values returned may contain backslash escapes.
*/
class list_iterator
{
    using iter_type = boost::string_ref::const_iterator;

    iter_type it_;
    iter_type end_;
    boost::string_ref value_;

public:
    using value_type = boost::string_ref;
    using pointer = value_type const*;
    using reference = value_type const&;
    using difference_type = std::ptrdiff_t;
    using iterator_category =
        std::forward_iterator_tag;

    list_iterator(iter_type begin, iter_type end)
        : it_(begin)
        , end_(end)
    {
        if(it_ != end_)
            increment();
    }

    bool
    operator==(list_iterator const& other) const
    {
        return other.it_ == it_ && other.end_ == end_
            && other.value_.size() == value_.size();
    }

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

    reference
    operator*() const
    {
        return value_;
    }

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

    list_iterator&
    operator++()
    {
        increment();
        return *this;
    }

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

private:
    template<class = void>
    void
    increment();
};

template<class>
void
list_iterator::increment()
{
    value_.clear();
    while(it_ != end_)
    {
        if(*it_ == '"')
        {
            // quoted-string
            ++it_;
            if(it_ == end_)
                return;
            if(*it_ != '"')
            {
                auto start = it_;
                for(;;)
                {
                    ++it_;
                    if(it_ == end_)
                    {
                        value_ = boost::string_ref(
                            &*start, std::distance(start, it_));
                        return;
                    }
                    if(*it_ == '"')
                    {
                        value_ = boost::string_ref(
                            &*start, std::distance(start, it_));
                        ++it_;
                        return;
                    }
                }
            }
            ++it_;
        }
        else if(*it_ == ',')
        {
            it_++;
            continue;
        }
        else if(is_lws(*it_))
        {
            ++it_;
            continue;
        }
        else
        {
            auto start = it_;
            for(;;)
            {
                ++it_;
                if(it_ == end_ ||
                    *it_ == ',' ||
                        is_lws(*it_))
                {
                    value_ = boost::string_ref(
                        &*start, std::distance(start, it_));
                    return;
                }
            }
        }
    }
}

/** Returns true if two strings are equal.

    A case-insensitive comparison is used.
*/
inline
bool
ci_equal(boost::string_ref s1, boost::string_ref s2)
{
    return boost::range::equal(s1, s2,
        detail::ci_equal_pred{});
}

/** Returns a range representing the list. */
inline
boost::iterator_range<list_iterator>
make_list(boost::string_ref const& field)
{
    return boost::iterator_range<list_iterator>{
        list_iterator{field.begin(), field.end()},
            list_iterator{field.end(), field.end()}};
}

/** Returns true if the specified token exists in the list.

    A case-insensitive comparison is used.
*/
template<class = void>
bool
token_in_list(boost::string_ref const& value,
    boost::string_ref const& token)
{
    for(auto const& item : make_list(value))
        if(ci_equal(item, token))
            return true;
    return false;
}

} // rfc2616

#endif

} // beast

#endif