//
// Copyright (c) 2013-2017 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_MESSAGE_HPP
#define BEAST_HTTP_MESSAGE_HPP

#include <beast/config.hpp>
#include <beast/http/fields.hpp>
#include <beast/http/verb.hpp>
#include <beast/http/status.hpp>
#include <beast/http/type_traits.hpp>
#include <beast/core/string.hpp>
#include <beast/core/detail/integer_sequence.hpp>
#include <boost/optional.hpp>
#include <boost/throw_exception.hpp>
#include <memory>
#include <stdexcept>
#include <string>
#include <tuple>
#include <utility>

namespace beast {
namespace http {

/** A container for an HTTP request or response header.

    This container is derived from the `Fields` template type.
    To understand all of the members of this class it is necessary
    to view the declaration for the `Fields` type. When using
    the default fields container, those declarations are in
    @ref fields.

    A `header` includes the start-line and header-fields.
*/
#if BEAST_DOXYGEN
template<bool isRequest, class Fields = fields>
struct header : Fields

#else
template<bool isRequest, class Fields = fields>
struct header;

template<class Fields>
struct header<true, Fields> : Fields
#endif
{
    static_assert(is_fields<Fields>::value,
        "Fields requirements not met");

    /// Indicates if the header is a request or response.
#if BEAST_DOXYGEN
    using is_request = std::integral_constant<bool, isRequest>;
#else
    using is_request = std::true_type;
#endif

    /// The type representing the fields.
    using fields_type = Fields;

    /** The HTTP-version.

        This holds both the major and minor version numbers,
        using these formulas:
        @code
            unsigned major = version / 10;
            unsigned minor = version % 10;
        @endcode

        Newly constructed headers will use HTTP/1.1 by default.
    */
    unsigned version = 11;

    /// Default constructor
    header() = default;

    /// Move constructor
    header(header&&) = default;

    /// Copy constructor
    header(header const&) = default;

    /// Move assignment
    header& operator=(header&&) = default;

    /// Copy assignment
    header& operator=(header const&) = default;

    /** Return the request-method verb.

        If the request-method is not one of the recognized verbs,
        @ref verb::unknown is returned. Callers may use @ref method_string
        to retrieve the exact text.

        @note This function is only available when `isRequest == true`.

        @see @ref method_string
    */
    verb
    method() const;

    /** Set the request-method.

        This function will set the method for requests to a known verb.

        @param v The request method verb to set.
        This may not be @ref verb::unknown.

        @throws std::invalid_argument when `v == verb::unknown`.

        @note This function is only available when `isRequest == true`.
    */
    void
    method(verb v);

    /** Return the request-method as a string.

        @note This function is only available when `isRequest == true`.

        @see @ref method
    */
    string_view
    method_string() const;

    /** Set the request-method.

        This function will set the request-method a known verb
        if the string matches, otherwise it will store a copy of
        the passed string.

        @param s A string representing the request-method.

        @note This function is only available when `isRequest == true`.
    */
    void
    method_string(string_view s);

    /** Returns the request-target string.

        @note This function is only available when `isRequest == true`.
    */
    string_view
    target() const;

    /** Set the request-target string.

        @param s A string representing the request-target.

        @note This function is only available when `isRequest == true`.
    */
    void
    target(string_view s);

    // VFALCO Don't move these declarations around,
    //        otherwise the documentation will be wrong.

    /** Constructor

        @param args Arguments forwarded to the `Fields`
        base class constructor.

        @note This constructor participates in overload
        resolution if and only if the first parameter is
        not convertible to @ref header.
    */
#if BEAST_DOXYGEN
    template<class... Args>
    explicit
    header(Args&&... args);

#else
    template<class Arg1, class... ArgN,
        class = typename std::enable_if<
            (sizeof...(ArgN) > 0) || ! std::is_convertible<
                typename std::decay<Arg1>::type,
                    header>::value>::type>
    explicit
    header(Arg1&& arg1, ArgN&&... argn);

private:
    template<bool, class, class>
    friend struct message;

    template<class T>
    friend
    void
    swap(header<true, T>& m1, header<true, T>& m2);

    verb method_ = verb::unknown;
};

/** A container for an HTTP request or response header.

    A `header` includes the start-line and header-fields.
*/
template<class Fields>
struct header<false, Fields> : Fields
{
    static_assert(is_fields<Fields>::value,
        "Fields requirements not met");

    /// Indicates if the header is a request or response.
#if BEAST_DOXYGEN
    using is_request = std::integral_constant<bool, isRequest>;
#else
    using is_request = std::false_type;
#endif

    /// The type representing the fields.
    using fields_type = Fields;

    /** The HTTP version.

        This holds both the major and minor version numbers,
        using these formulas:
        @code
            unsigned major = version / 10;
            unsigned minor = version % 10;
        @endcode

        Newly constructed headers will use HTTP/1.1 by default.
    */
    unsigned version = 11;

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

    /// Move constructor
    header(header&&) = default;

    /// Copy constructor
    header(header const&) = default;

    /// Move assignment
    header& operator=(header&&) = default;

    /// Copy assignment
    header& operator=(header const&) = default;

    /** Constructor

        @param args Arguments forwarded to the `Fields`
        base class constructor.

        @note This constructor participates in overload
        resolution if and only if the first parameter is
        not convertible to @ref header.
    */
    template<class Arg1, class... ArgN,
        class = typename std::enable_if<
            (sizeof...(ArgN) > 0) || ! std::is_convertible<
                typename std::decay<Arg1>::type,
                    header>::value>::type>
    explicit
    header(Arg1&& arg1, ArgN&&... argn);
#endif

    /** The response status-code result.

        If the actual status code is not a known code, this
        function returns @ref status::unknown. Use @ref result_int
        to return the raw status code as a number.

        @note This member is only available when `isRequest == false`.
    */
    status
    result() const;

    /** Set the response status-code.

        @param v The code to set.

        @note This member is only available when `isRequest == false`.
    */
    void
    result(status v);

    /** Set the response status-code as an integer.

        This sets the status code to the exact number passed in.
        If the number does not correspond to one of the known
        status codes, the function @ref result will return
        @ref status::unknown. Use @ref result_int to obtain the
        original raw status-code.

        @param v The status-code integer to set.

        @throws std::invalid_argument if `v > 999`.
    */
    void
    result(unsigned v);

    /** The response status-code expressed as an integer.

        This returns the raw status code as an integer, even
        when that code is not in the list of known status codes.

        @note This member is only available when `isRequest == false`.
    */
    unsigned
    result_int() const;

    /** Return the response reason-phrase.

        The reason-phrase is obsolete as of rfc7230.

        @note This function is only available when `isRequest == false`.
    */
    string_view
    reason() const;

    /** Set the response reason-phrase (deprecated)

        This function sets a custom reason-phrase to a copy of
        the string passed in. Normally it is not necessary to set
        the reason phrase on an outgoing response object; the
        implementation will automatically use the standard reason
        text for the corresponding status code.

        To clear a previously set custom phrase, pass an empty
        string. This will restore the default standard reason text
        based on the status code used when serializing.

        The reason-phrase is obsolete as of rfc7230.

        @param s The string to use for the reason-phrase.

        @note This function is only available when `isRequest == false`.
    */
    void
    reason(string_view s);

private:
#if ! BEAST_DOXYGEN
    template<bool, class, class>
    friend struct message;

    template<class T>
    friend
    void
    swap(header<false, T>& m1, header<false, T>& m2);

    status result_;
#endif
};

/** A container for a complete HTTP message.

    This container is derived from the `Fields` template type.
    To understand all of the members of this class it is necessary
    to view the declaration for the `Fields` type. When using
    the default fields container, those declarations are in
    @ref fields.

    A message can be a request or response, depending on the
    `isRequest` template argument value. Requests and responses
    have different types; functions may be overloaded based on
    the type if desired.

    The `Body` template argument type determines the model used
    to read or write the content body of the message.

    @tparam isRequest `true` if this represents a request,
    or `false` if this represents a response. Some class data
    members are conditionally present depending on this value.

    @tparam Body A type meeting the requirements of Body.

    @tparam Fields The type of container used to hold the
    field value pairs.
*/
template<bool isRequest, class Body, class Fields = fields>
struct message : header<isRequest, Fields>
{
    /// The base class used to hold the header portion of the message.
    using header_type = header<isRequest, Fields>;

    /** The type providing the body traits.

        The @ref message::body member will be of type `body_type::value_type`.
    */
    using body_type = Body;

    /// A value representing the body.
    typename Body::value_type body;

    /// Default constructor
    message() = default;

    /// Move constructor
    message(message&&) = default;

    /// Copy constructor
    message(message const&) = default;

    /// Move assignment
    message& operator=(message&&) = default;

    /// Copy assignment
    message& operator=(message const&) = default;

    /** Constructor.

        @param h The header to move construct from.

        @param args Optional arguments forwarded
        to the body constructor.
    */
    template<class... Args>
    explicit
    message(header_type&& h, Args&&... args);

    /** Constructor.

        @param h The header to copy construct from.

        @param args Optional arguments forwarded
        to the body constructor.
    */
    template<class... Args>
    explicit
    message(header_type const& h, Args&&... args);

    /** Construct a message.

        @param body_arg An argument forwarded to the body constructor.

        @note This constructor participates in overload resolution
        only if `body_arg` is not convertible to `header_type`.
    */
    template<class BodyArg
#if ! BEAST_DOXYGEN
        , class = typename std::enable_if<
            ! std::is_convertible<typename
                std::decay<BodyArg>::type, header_type>::value>::type
#endif
    >
    explicit
    message(BodyArg&& body_arg);

    /** Construct a message.

        @param body_arg An argument forwarded to the body constructor.

        @param header_arg An argument forwarded to the header constructor.

        @note This constructor participates in overload resolution
        only if `body_arg` is not convertible to `header_type`.
    */
    template<class BodyArg, class HeaderArg
#if ! BEAST_DOXYGEN
        ,class = typename std::enable_if<
            ! std::is_convertible<
                typename std::decay<BodyArg>::type,
                    header_type>::value>::type
#endif
    >
    message(BodyArg&& body_arg, HeaderArg&& header_arg);

    /** Construct a message.

        @param body_args A tuple forwarded as a parameter pack to the body constructor.
    */
    template<class... BodyArgs>
    message(std::piecewise_construct_t,
        std::tuple<BodyArgs...> body_args);

    /** Construct a message.

        @param body_args A tuple forwarded as a parameter pack to the body constructor.

        @param header_args A tuple forwarded as a parameter pack to the fields constructor.
    */
    template<class... BodyArgs, class... HeaderArgs>
    message(std::piecewise_construct_t,
        std::tuple<BodyArgs...>&& body_args,
            std::tuple<HeaderArgs...>&& header_args);

    /// Returns the header portion of the message
    header_type const&
    header_part() const
    {
        return *this;
    }

    /// Returns the header portion of the message
    header_type&
    header_part()
    {
        return *this;
    }

    /** Returns the payload size of the body in octets if possible.

        This function invokes the @b Body algorithm to measure
        the number of octets in the serialized body container. If
        there is no body, this will return zero. Otherwise, if the
        body exists but is not known ahead of time, `boost::none`
        is returned (usually indicating that a chunked Transfer-Encoding
        will be used).

        @note The value of the Content-Length field in the message
        is not inspected.
    */
    boost::optional<std::uint64_t>
    payload_size() const;


    /** Prepare the message payload fields for the body.

        This function will adjust the Content-Length and
        Transfer-Encoding field values based on the properties
        of the body.

        @par Example
        @code
        request<string_body> req;
        req.version = 11;
        req.method(verb::upgrade);
        req.target("/");
        req.set(field::user_agent, "Beast");
        req.body = "Hello, world!";
        req.prepare_payload();
        @endcode
    */
    void
    prepare_payload()
    {
        prepare_payload(typename header_type::is_request{});
    }

private:
    static_assert(is_body<Body>::value,
        "Body requirements not met");

    template<
        class... BodyArgs,
        std::size_t... IBodyArgs>
    message(
        std::piecewise_construct_t,
        std::tuple<BodyArgs...>& body_args,
        beast::detail::index_sequence<IBodyArgs...>)
        : body(std::forward<BodyArgs>(
            std::get<IBodyArgs>(body_args))...)
    {
        boost::ignore_unused(body_args);
    }

    template<
        class... BodyArgs,
        class... FieldsArgs,
        std::size_t... IBodyArgs,
        std::size_t... IFieldsArgs>
    message(
        std::piecewise_construct_t,
        std::tuple<BodyArgs...>& body_args,
        std::tuple<FieldsArgs...>& fields_args,
        beast::detail::index_sequence<IBodyArgs...>,
        beast::detail::index_sequence<IFieldsArgs...>)
        : header_type(std::forward<FieldsArgs>(
            std::get<IFieldsArgs>(fields_args))...)
        , body(std::forward<BodyArgs>(
            std::get<IBodyArgs>(body_args))...)
    {
        boost::ignore_unused(body_args);
        boost::ignore_unused(fields_args);
    }

    boost::optional<std::uint64_t>
    payload_size(std::true_type) const
    {
        return Body::size(body);
    }

    boost::optional<std::uint64_t>
    payload_size(std::false_type) const
    {
        return boost::none;
    }

    void
    prepare_payload(std::true_type);

    void
    prepare_payload(std::false_type);
};

/// A typical HTTP request
template<class Body, class Fields = fields>
using request = message<true, Body, Fields>;

/// A typical HTTP response
template<class Body, class Fields = fields>
using response = message<false, Body, Fields>;

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

#if BEAST_DOXYGEN
/** Swap two header objects.

    @par Requirements
    `Fields` is @b Swappable.
*/
template<bool isRequest, class Fields>
void
swap(
    header<isRequest, Fields>& m1,
    header<isRequest, Fields>& m2);
#endif

/** Swap two message objects.

    @par Requirements:
    `Body::value_type` and `Fields` are @b Swappable.
*/
template<bool isRequest, class Body, class Fields>
void
swap(
    message<isRequest, Body, Fields>& m1,
    message<isRequest, Body, Fields>& m2);

} // http
} // beast

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

#endif