/*
 * Copyright (c) 2015, Peter Thorson. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the WebSocket++ Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL PETER THORSON BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef WEBSOCKETPP_PROCESSOR_HYBI13_HPP
#define WEBSOCKETPP_PROCESSOR_HYBI13_HPP

#include <websocketpp/processors/processor.hpp>

#include <websocketpp/frame.hpp>
#include <websocketpp/http/constants.hpp>

#include <websocketpp/utf8_validator.hpp>
#include <websocketpp/sha1/sha1.hpp>
#include <websocketpp/base64/base64.hpp>

#include <websocketpp/common/network.hpp>
#include <websocketpp/common/platforms.hpp>

#include <algorithm>
#include <cassert>
#include <string>
#include <vector>
#include <utility>

namespace websocketpp {
namespace processor {

/// Processor for Hybi version 13 (RFC6455)
template <typename config>
class hybi13 : public processor<config> {
public:
    typedef processor<config> base;

    typedef typename config::request_type request_type;
    typedef typename config::response_type response_type;

    typedef typename config::message_type message_type;
    typedef typename message_type::ptr message_ptr;

    typedef typename config::con_msg_manager_type msg_manager_type;
    typedef typename msg_manager_type::ptr msg_manager_ptr;
    typedef typename config::rng_type rng_type;

    typedef typename config::permessage_deflate_type permessage_deflate_type;

    typedef std::pair<lib::error_code,std::string> err_str_pair;

    explicit hybi13(bool secure, bool p_is_server, msg_manager_ptr manager, rng_type& rng)
      : processor<config>(secure, p_is_server)
      , m_msg_manager(manager)
      , m_rng(rng)
    {
        reset_headers();
    }

    int get_version() const {
        return 13;
    }

    bool has_permessage_deflate() const {
        return m_permessage_deflate.is_implemented();
    }

    err_str_pair negotiate_extensions(request_type const & request) {
        return negotiate_extensions_helper(request);
    }
    
    err_str_pair negotiate_extensions(response_type const & response) {
        return negotiate_extensions_helper(response);
    }
    
    /// Extension negotiation helper function
    /**
     * This exists mostly because the code for requests and responses is
     * identical and I can't have virtual template methods.
     */
    template <typename header_type>
    err_str_pair negotiate_extensions_helper(header_type const & header) {
        err_str_pair ret;

        // Respect blanket disabling of all extensions and don't even parse
        // the extension header
        if (!config::enable_extensions) {
            ret.first = make_error_code(error::extensions_disabled);
            return ret;
        }

        http::parameter_list p;

        bool error = header.get_header_as_plist("Sec-WebSocket-Extensions",p);

        if (error) {
            ret.first = make_error_code(error::extension_parse_error);
            return ret;
        }

        // If there are no extensions parsed then we are done!
        if (p.size() == 0) {
            return ret;
        }

        http::parameter_list::const_iterator it;

        // look through the list of extension requests to find the first
        // one that we can accept.
        if (m_permessage_deflate.is_implemented()) {
            err_str_pair neg_ret;
            for (it = p.begin(); it != p.end(); ++it) {
                // not a permessage-deflate extension request, ignore
                if (it->first != "permessage-deflate") {
                    continue;
                }

                // if we have already successfully negotiated this extension
                // then skip any other requests to negotiate the same one
                // with different parameters 
                if (m_permessage_deflate.is_enabled()) {
                    continue;
                }
                
                // attempt to negotiate this offer
                neg_ret = m_permessage_deflate.negotiate(it->second);

                if (neg_ret.first) {
                    // negotiation offer failed. Do nothing. We will continue
                    // searching for a permessage-deflate config that succeeds
                    continue;
                }

                // Negotiation tentatively succeeded

                // Actually try to initialize the extension before we
                // deem negotiation complete
                lib::error_code ec = m_permessage_deflate.init(base::m_server);

                if (ec) {
                    // Negotiation succeeded but initialization failed this is 
                    // an error that should stop negotiation of permessage 
                    // deflate. Return the reason for the init failure

                    ret.first = ec;
                    break;
                } else {
                    // Successfully initialized, push the negotiated response into
                    // the reply and stop looking for additional permessage-deflate
                    // extensions
                    ret.second += neg_ret.second;
                    break;
                }
            }
        }

        // support for future extensions would go here. Should check the value of 
        // ret.first before continuing. Might need to consider whether failure of
        // negotiation of an earlier extension should stop negotiation of subsequent
        // ones

        return ret;
    }

    lib::error_code validate_handshake(request_type const & r) const {
        if (r.get_method() != "GET") {
            return make_error_code(error::invalid_http_method);
        }

        if (r.get_version() != "HTTP/1.1") {
            return make_error_code(error::invalid_http_version);
        }

        // required headers
        // Host is required by HTTP/1.1
        // Connection is required by is_websocket_handshake
        // Upgrade is required by is_websocket_handshake
        if (r.get_header("Sec-WebSocket-Key").empty()) {
            return make_error_code(error::missing_required_header);
        }

        return lib::error_code();
    }

    /* TODO: the 'subprotocol' parameter may need to be expanded into a more
     * generic struct if other user input parameters to the processed handshake
     * are found.
     */
    lib::error_code process_handshake(request_type const & request, 
        std::string const & subprotocol, response_type & response) const
    {
        std::string server_key = request.get_header("Sec-WebSocket-Key");

        lib::error_code ec = process_handshake_key(server_key);

        if (ec) {
            return ec;
        }

        response.replace_header("Sec-WebSocket-Accept",server_key);
        response.append_header("Upgrade",constants::upgrade_token);
        response.append_header("Connection",constants::connection_token);

        if (!subprotocol.empty()) {
            response.replace_header("Sec-WebSocket-Protocol",subprotocol);
        }

        return lib::error_code();
    }

    /// Fill in a set of request headers for a client connection request
    /**
     * @param [out] req  Set of headers to fill in
     * @param [in] uri The uri being connected to
     * @param [in] subprotocols The list of subprotocols to request
     */
    lib::error_code client_handshake_request(request_type & req, uri_ptr
        uri, std::vector<std::string> const & subprotocols) const
    {
        req.set_method("GET");
        req.set_uri(uri->get_resource());
        req.set_version("HTTP/1.1");

        req.append_header("Upgrade","websocket");
        req.append_header("Connection","Upgrade");
        req.replace_header("Sec-WebSocket-Version","13");
        req.replace_header("Host",uri->get_host_port());

        if (!subprotocols.empty()) {
            std::ostringstream result;
            std::vector<std::string>::const_iterator it = subprotocols.begin();
            result << *it++;
            while (it != subprotocols.end()) {
                result << ", " << *it++;
            }

            req.replace_header("Sec-WebSocket-Protocol",result.str());
        }

        // Generate handshake key
        frame::uint32_converter conv;
        unsigned char raw_key[16];

        for (int i = 0; i < 4; i++) {
            conv.i = m_rng();
            std::copy(conv.c,conv.c+4,&raw_key[i*4]);
        }

        req.replace_header("Sec-WebSocket-Key",base64_encode(raw_key, 16));

        if (m_permessage_deflate.is_implemented()) {
            std::string offer = m_permessage_deflate.generate_offer();
            if (!offer.empty()) {
                req.replace_header("Sec-WebSocket-Extensions",offer);
            }
        }

        return lib::error_code();
    }

    /// Validate the server's response to an outgoing handshake request
    /**
     * @param req The original request sent
     * @param res The reponse to generate
     * @return An error code, 0 on success, non-zero for other errors
     */
    lib::error_code validate_server_handshake_response(request_type const & req,
        response_type& res) const
    {
        // A valid response has an HTTP 101 switching protocols code
        if (res.get_status_code() != http::status_code::switching_protocols) {
            return error::make_error_code(error::invalid_http_status);
        }

        // And the upgrade token in an upgrade header
        std::string const & upgrade_header = res.get_header("Upgrade");
        if (utility::ci_find_substr(upgrade_header, constants::upgrade_token,
            sizeof(constants::upgrade_token)-1) == upgrade_header.end())
        {
            return error::make_error_code(error::missing_required_header);
        }

        // And the websocket token in the connection header
        std::string const & con_header = res.get_header("Connection");
        if (utility::ci_find_substr(con_header, constants::connection_token,
            sizeof(constants::connection_token)-1) == con_header.end())
        {
            return error::make_error_code(error::missing_required_header);
        }

        // And has a valid Sec-WebSocket-Accept value
        std::string key = req.get_header("Sec-WebSocket-Key");
        lib::error_code ec = process_handshake_key(key);

        if (ec || key != res.get_header("Sec-WebSocket-Accept")) {
            return error::make_error_code(error::missing_required_header);
        }

        // check extensions

        return lib::error_code();
    }

    std::string get_raw(response_type const & res) const {
        return res.raw();
    }

    std::string const & get_origin(request_type const & r) const {
        return r.get_header("Origin");
    }

    lib::error_code extract_subprotocols(request_type const & req,
        std::vector<std::string> & subprotocol_list)
    {
        if (!req.get_header("Sec-WebSocket-Protocol").empty()) {
            http::parameter_list p;

             if (!req.get_header_as_plist("Sec-WebSocket-Protocol",p)) {
                 http::parameter_list::const_iterator it;

                 for (it = p.begin(); it != p.end(); ++it) {
                     subprotocol_list.push_back(it->first);
                 }
             } else {
                 return error::make_error_code(error::subprotocol_parse_error);
             }
        }
        return lib::error_code();
    }

    uri_ptr get_uri(request_type const & request) const {
        return get_uri_from_host(request,(base::m_secure ? "wss" : "ws"));
    }

    /// Process new websocket connection bytes
    /**
     *
     * Hybi 13 data streams represent a series of variable length frames. Each
     * frame is made up of a series of fixed length fields. The lengths of later
     * fields are contained in earlier fields. The first field length is fixed
     * by the spec.
     *
     * This processor represents a state machine that keeps track of what field
     * is presently being read and how many more bytes are needed to complete it
     *
     *
     *
     *
     * Read two header bytes
     *   Extract full frame length.
     *   Read extra header bytes
     * Validate frame header (including extension validate)
     * Read extension data into extension message state object
     * Read payload data into payload
     *
     * @param buf Input buffer
     *
     * @param len Length of input buffer
     *
     * @return Number of bytes processed or zero on error
     */
    size_t consume(uint8_t * buf, size_t len, lib::error_code & ec) {
        size_t p = 0;

        ec = lib::error_code();

        //std::cout << "consume: " << utility::to_hex(buf,len) << std::endl;

        // Loop while we don't have a message ready and we still have bytes
        // left to process.
        while (m_state != READY && m_state != FATAL_ERROR &&
               (p < len || m_bytes_needed == 0))
        {
            if (m_state == HEADER_BASIC) {
                p += this->copy_basic_header_bytes(buf+p,len-p);

                if (m_bytes_needed > 0) {
                    continue;
                }

                ec = this->validate_incoming_basic_header(
                    m_basic_header, base::m_server, !m_data_msg.msg_ptr
                );
                if (ec) {break;}

                // extract full header size and adjust consume state accordingly
                m_state = HEADER_EXTENDED;
                m_cursor = 0;
                m_bytes_needed = frame::get_header_len(m_basic_header) -
                    frame::BASIC_HEADER_LENGTH;
            } else if (m_state == HEADER_EXTENDED) {
                p += this->copy_extended_header_bytes(buf+p,len-p);

                if (m_bytes_needed > 0) {
                    continue;
                }

                ec = validate_incoming_extended_header(m_basic_header,m_extended_header);
                if (ec){break;}

                m_state = APPLICATION;
                m_bytes_needed = static_cast<size_t>(get_payload_size(m_basic_header,m_extended_header));

                // check if this frame is the start of a new message and set up
                // the appropriate message metadata.
                frame::opcode::value op = frame::get_opcode(m_basic_header);

                // TODO: get_message failure conditions

                if (frame::opcode::is_control(op)) {
                    m_control_msg = msg_metadata(
                        m_msg_manager->get_message(op,m_bytes_needed),
                        frame::get_masking_key(m_basic_header,m_extended_header)
                    );

                    m_current_msg = &m_control_msg;
                } else {
                    if (!m_data_msg.msg_ptr) {
                        if (m_bytes_needed > base::m_max_message_size) {
                            ec = make_error_code(error::message_too_big);
                            break;
                        }
                        
                        m_data_msg = msg_metadata(
                            m_msg_manager->get_message(op,m_bytes_needed),
                            frame::get_masking_key(m_basic_header,m_extended_header)
                        );
                        
                        if (m_permessage_deflate.is_enabled()) {
                            m_data_msg.msg_ptr->set_compressed(frame::get_rsv1(m_basic_header));
                        }
                    } else {
                        // Fetch the underlying payload buffer from the data message we
                        // are writing into.
                        std::string & out = m_data_msg.msg_ptr->get_raw_payload();
                        
                        if (out.size() + m_bytes_needed > base::m_max_message_size) {
                            ec = make_error_code(error::message_too_big);
                            break;
                        }
                        
                        // Each frame starts a new masking key. All other state
                        // remains between frames.
                        m_data_msg.prepared_key = prepare_masking_key(
                            frame::get_masking_key(
                                m_basic_header,
                                m_extended_header
                            )
                        );
                        
                        out.reserve(out.size() + m_bytes_needed);
                    }
                    m_current_msg = &m_data_msg;
                }
            } else if (m_state == EXTENSION) {
                m_state = APPLICATION;
            } else if (m_state == APPLICATION) {
                size_t bytes_to_process = (std::min)(m_bytes_needed,len-p);

                if (bytes_to_process > 0) {
                    p += this->process_payload_bytes(buf+p,bytes_to_process,ec);

                    if (ec) {break;}
                }

                if (m_bytes_needed > 0) {
                    continue;
                }

                // If this was the last frame in the message set the ready flag.
                // Otherwise, reset processor state to read additional frames.
                if (frame::get_fin(m_basic_header)) {
                    ec = finalize_message();
                    if (ec) {
                        break;
                    }
                } else {
                    this->reset_headers();
                }
            } else {
                // shouldn't be here
                ec = make_error_code(error::general);
                return 0;
            }
        }

        return p;
    }

    /// Perform any finalization actions on an incoming message
    /**
     * Called after the full message is received. Provides the opportunity for
     * extensions to complete any data post processing as well as final UTF8
     * validation checks for text messages.
     *
     * @return A code indicating errors, if any
     */
    lib::error_code finalize_message() {
        std::string & out = m_current_msg->msg_ptr->get_raw_payload();

        // if the frame is compressed, append the compression
        // trailer and flush the compression buffer.
        if (m_permessage_deflate.is_enabled()
            && m_current_msg->msg_ptr->get_compressed())
        {
            uint8_t trailer[4] = {0x00, 0x00, 0xff, 0xff};

            // Decompress current buffer into the message buffer
            lib::error_code ec;
            ec = m_permessage_deflate.decompress(trailer,4,out);
            if (ec) {
                return ec;
            }
        }

        // ensure that text messages end on a valid UTF8 code point
        if (frame::get_opcode(m_basic_header) == frame::opcode::TEXT) {
            if (!m_current_msg->validator.complete()) {
                return make_error_code(error::invalid_utf8);
            }
        }

        m_state = READY;

        return lib::error_code();
    }

    void reset_headers() {
        m_state = HEADER_BASIC;
        m_bytes_needed = frame::BASIC_HEADER_LENGTH;

        m_basic_header.b0 = 0x00;
        m_basic_header.b1 = 0x00;

        std::fill_n(
            m_extended_header.bytes,
            frame::MAX_EXTENDED_HEADER_LENGTH,
            0x00
        );
    }

    /// Test whether or not the processor has a message ready
    bool ready() const {
        return (m_state == READY);
    }

    message_ptr get_message() {
        if (!ready()) {
            return message_ptr();
        }
        message_ptr ret = m_current_msg->msg_ptr;
        m_current_msg->msg_ptr.reset();

        if (frame::opcode::is_control(ret->get_opcode())) {
            m_control_msg.msg_ptr.reset();
        } else {
            m_data_msg.msg_ptr.reset();
        }

        this->reset_headers();

        return ret;
    }

    /// Test whether or not the processor is in a fatal error state.
    bool get_error() const {
        return m_state == FATAL_ERROR;
    }

    size_t get_bytes_needed() const {
        return m_bytes_needed;
    }

    /// Prepare a user data message for writing
    /**
     * Performs validation, masking, compression, etc. will return an error if
     * there was an error, otherwise msg will be ready to be written
     *
     * TODO: tests
     *
     * @param in An unprepared message to prepare
     * @param out A message to be overwritten with the prepared message
     * @return error code
     */
    virtual lib::error_code prepare_data_frame(message_ptr in, message_ptr out)
    {
        if (!in || !out) {
            return make_error_code(error::invalid_arguments);
        }

        frame::opcode::value op = in->get_opcode();

        // validate opcode: only regular data frames
        if (frame::opcode::is_control(op)) {
            return make_error_code(error::invalid_opcode);
        }

        std::string& i = in->get_raw_payload();
        std::string& o = out->get_raw_payload();

        // validate payload utf8
        if (op == frame::opcode::TEXT && !utf8_validator::validate(i)) {
            return make_error_code(error::invalid_payload);
        }

        frame::masking_key_type key;
        bool masked = !base::m_server;
        bool compressed = m_permessage_deflate.is_enabled()
                          && in->get_compressed();
        bool fin = in->get_fin();

        if (masked) {
            // Generate masking key.
            key.i = m_rng();
        } else {
            key.i = 0;
        }

        // prepare payload
        if (compressed) {
            // compress and store in o after header.
            m_permessage_deflate.compress(i,o);

            if (o.size() < 4) {
                return make_error_code(error::general);
            }

            // Strip trailing 4 0x00 0x00 0xff 0xff bytes before writing to the
            // wire
            o.resize(o.size()-4);

            // mask in place if necessary
            if (masked) {
                this->masked_copy(o,o,key);
            }
        } else {
            // no compression, just copy data into the output buffer
            o.resize(i.size());

            // if we are masked, have the masking function write to the output
            // buffer directly to avoid another copy. If not masked, copy
            // directly without masking.
            if (masked) {
                this->masked_copy(i,o,key);
            } else {
                std::copy(i.begin(),i.end(),o.begin());
            }
        }

        // generate header
        frame::basic_header h(op,o.size(),fin,masked,compressed);

        if (masked) {
            frame::extended_header e(o.size(),key.i);
            out->set_header(frame::prepare_header(h,e));
        } else {
            frame::extended_header e(o.size());
            out->set_header(frame::prepare_header(h,e));
        }

        out->set_prepared(true);
        out->set_opcode(op);

        return lib::error_code();
    }

    /// Get URI
    lib::error_code prepare_ping(std::string const & in, message_ptr out) const {
        return this->prepare_control(frame::opcode::PING,in,out);
    }

    lib::error_code prepare_pong(std::string const & in, message_ptr out) const {
        return this->prepare_control(frame::opcode::PONG,in,out);
    }

    virtual lib::error_code prepare_close(close::status::value code,
        std::string const & reason, message_ptr out) const
    {
        if (close::status::reserved(code)) {
            return make_error_code(error::reserved_close_code);
        }

        if (close::status::invalid(code) && code != close::status::no_status) {
            return make_error_code(error::invalid_close_code);
        }

        if (code == close::status::no_status && reason.size() > 0) {
            return make_error_code(error::reason_requires_code);
        }

        if (reason.size() > frame:: limits::payload_size_basic-2) {
            return make_error_code(error::control_too_big);
        }

        std::string payload;

        if (code != close::status::no_status) {
            close::code_converter val;
            val.i = htons(code);

            payload.resize(reason.size()+2);

            payload[0] = val.c[0];
            payload[1] = val.c[1];

            std::copy(reason.begin(),reason.end(),payload.begin()+2);
        }

        return this->prepare_control(frame::opcode::CLOSE,payload,out);
    }
protected:
    /// Convert a client handshake key into a server response key in place
    lib::error_code process_handshake_key(std::string & key) const {
        key.append(constants::handshake_guid);

        unsigned char message_digest[20];
        sha1::calc(key.c_str(),key.length(),message_digest);
        key = base64_encode(message_digest,20);

        return lib::error_code();
    }

    /// Reads bytes from buf into m_basic_header
    size_t copy_basic_header_bytes(uint8_t const * buf, size_t len) {
        if (len == 0 || m_bytes_needed == 0) {
            return 0;
        }

        if (len > 1) {
            // have at least two bytes
            if (m_bytes_needed == 2) {
                m_basic_header.b0 = buf[0];
                m_basic_header.b1 = buf[1];
                m_bytes_needed -= 2;
                return 2;
            } else {
                m_basic_header.b1 = buf[0];
                m_bytes_needed--;
                return 1;
            }
        } else {
            // have exactly one byte
            if (m_bytes_needed == 2) {
                m_basic_header.b0 = buf[0];
                m_bytes_needed--;
                return 1;
            } else {
                m_basic_header.b1 = buf[0];
                m_bytes_needed--;
                return 1;
            }
        }
    }

    /// Reads bytes from buf into m_extended_header
    size_t copy_extended_header_bytes(uint8_t const * buf, size_t len) {
        size_t bytes_to_read = (std::min)(m_bytes_needed,len);

        std::copy(buf,buf+bytes_to_read,m_extended_header.bytes+m_cursor);
        m_cursor += bytes_to_read;
        m_bytes_needed -= bytes_to_read;

        return bytes_to_read;
    }

    /// Reads bytes from buf into message payload
    /**
     * This function performs unmasking and uncompression, validates the
     * decoded bytes, and writes them to the appropriate message buffer.
     *
     * This member function will use the input buffer as stratch space for its
     * work. The raw input bytes will not be preserved. This applies only to the
     * bytes actually needed. At most min(m_bytes_needed,len) will be processed.
     *
     * @param buf Input/working buffer
     * @param len Length of buf
     * @return Number of bytes processed or zero in case of an error
     */
    size_t process_payload_bytes(uint8_t * buf, size_t len, lib::error_code& ec)
    {
        // unmask if masked
        if (frame::get_masked(m_basic_header)) {
            m_current_msg->prepared_key = frame::byte_mask_circ(
                buf, len, m_current_msg->prepared_key);
            // TODO: SIMD masking
        }

        std::string & out = m_current_msg->msg_ptr->get_raw_payload();
        size_t offset = out.size();

        // decompress message if needed.
        if (m_permessage_deflate.is_enabled()
            && m_current_msg->msg_ptr->get_compressed())
        {
            // Decompress current buffer into the message buffer
            ec = m_permessage_deflate.decompress(buf,len,out);
            if (ec) {
                return 0;
            }
        } else {
            // No compression, straight copy
            out.append(reinterpret_cast<char *>(buf),len);
        }

        // validate unmasked, decompressed values
        if (m_current_msg->msg_ptr->get_opcode() == frame::opcode::TEXT) {
            if (!m_current_msg->validator.decode(out.begin()+offset,out.end())) {
                ec = make_error_code(error::invalid_utf8);
                return 0;
            }
        }

        m_bytes_needed -= len;

        return len;
    }

    /// Validate an incoming basic header
    /**
     * Validates an incoming hybi13 basic header.
     *
     * @param h The basic header to validate
     * @param is_server Whether or not the endpoint that received this frame
     * is a server.
     * @param new_msg Whether or not this is the first frame of the message
     * @return 0 on success or a non-zero error code on failure
     */
    lib::error_code validate_incoming_basic_header(frame::basic_header const & h,
        bool is_server, bool new_msg) const
    {
        frame::opcode::value op = frame::get_opcode(h);

        // Check control frame size limit
        if (frame::opcode::is_control(op) &&
            frame::get_basic_size(h) > frame::limits::payload_size_basic)
        {
            return make_error_code(error::control_too_big);
        }

        // Check that RSV bits are clear
        // The only RSV bits allowed are rsv1 if the permessage_compress
        // extension is enabled for this connection and the message is not
        // a control message.
        //
        // TODO: unit tests for this
        if (frame::get_rsv1(h) && (!m_permessage_deflate.is_enabled()
                || frame::opcode::is_control(op)))
        {
            return make_error_code(error::invalid_rsv_bit);
        }

        if (frame::get_rsv2(h) || frame::get_rsv3(h)) {
            return make_error_code(error::invalid_rsv_bit);
        }

        // Check for reserved opcodes
        if (frame::opcode::reserved(op)) {
            return make_error_code(error::invalid_opcode);
        }

        // Check for invalid opcodes
        // TODO: unit tests for this?
        if (frame::opcode::invalid(op)) {
            return make_error_code(error::invalid_opcode);
        }

        // Check for fragmented control message
        if (frame::opcode::is_control(op) && !frame::get_fin(h)) {
            return make_error_code(error::fragmented_control);
        }

        // Check for continuation without an active message
        if (new_msg && op == frame::opcode::CONTINUATION) {
            return make_error_code(error::invalid_continuation);
        }

        // Check for new data frame when expecting continuation
        if (!new_msg && !frame::opcode::is_control(op) &&
            op != frame::opcode::CONTINUATION)
        {
            return make_error_code(error::invalid_continuation);
        }

        // Servers should reject any unmasked frames from clients.
        // Clients should reject any masked frames from servers.
        if (is_server && !frame::get_masked(h)) {
            return make_error_code(error::masking_required);
        } else if (!is_server && frame::get_masked(h)) {
            return make_error_code(error::masking_forbidden);
        }

        return lib::error_code();
    }

    /// Validate an incoming extended header
    /**
     * Validates an incoming hybi13 full header.
     *
     * @todo unit test for the >32 bit frames on 32 bit systems case
     *
     * @param h The basic header to validate
     * @param e The extended header to validate
     * @return An error_code, non-zero values indicate why the validation
     * failed
     */
    lib::error_code validate_incoming_extended_header(frame::basic_header h,
        frame::extended_header e) const
    {
        uint8_t basic_size = frame::get_basic_size(h);
        uint64_t payload_size = frame::get_payload_size(h,e);

        // Check for non-minimally encoded payloads
        if (basic_size == frame::payload_size_code_16bit &&
            payload_size <= frame::limits::payload_size_basic)
        {
            return make_error_code(error::non_minimal_encoding);
        }

        if (basic_size == frame::payload_size_code_64bit &&
            payload_size <= frame::limits::payload_size_extended)
        {
            return make_error_code(error::non_minimal_encoding);
        }

        // Check for >32bit frames on 32 bit systems
        if (sizeof(size_t) == 4 && (payload_size >> 32)) {
            return make_error_code(error::requires_64bit);
        }

        return lib::error_code();
    }

    /// Copy and mask/unmask in one operation
    /**
     * Reads input from one string and writes unmasked output to another.
     *
     * @param [in] i The input string.
     * @param [out] o The output string.
     * @param [in] key The masking key to use for masking/unmasking
     */
    void masked_copy (std::string const & i, std::string & o,
        frame::masking_key_type key) const
    {
        frame::byte_mask(i.begin(),i.end(),o.begin(),key);
        // TODO: SIMD masking
    }

    /// Generic prepare control frame with opcode and payload.
    /**
     * Internal control frame building method. Handles validation, masking, etc
     *
     * @param op The control opcode to use
     * @param payload The payload to use
     * @param out The message buffer to store the prepared frame in
     * @return Status code, zero on success, non-zero on error
     */
    lib::error_code prepare_control(frame::opcode::value op,
        std::string const & payload, message_ptr out) const
    {
        if (!out) {
            return make_error_code(error::invalid_arguments);
        }

        if (!frame::opcode::is_control(op)) {
            return make_error_code(error::invalid_opcode);
        }

        if (payload.size() > frame::limits::payload_size_basic) {
            return make_error_code(error::control_too_big);
        }

        frame::masking_key_type key;
        bool masked = !base::m_server;

        frame::basic_header h(op,payload.size(),true,masked);

        std::string & o = out->get_raw_payload();
        o.resize(payload.size());

        if (masked) {
            // Generate masking key.
            key.i = m_rng();

            frame::extended_header e(payload.size(),key.i);
            out->set_header(frame::prepare_header(h,e));
            this->masked_copy(payload,o,key);
        } else {
            frame::extended_header e(payload.size());
            out->set_header(frame::prepare_header(h,e));
            std::copy(payload.begin(),payload.end(),o.begin());
        }
    
        out->set_opcode(op);
        out->set_prepared(true);

        return lib::error_code();
    }

    enum state {
        HEADER_BASIC = 0,
        HEADER_EXTENDED = 1,
        EXTENSION = 2,
        APPLICATION = 3,
        READY = 4,
        FATAL_ERROR = 5
    };

    /// This data structure holds data related to processing a message, such as
    /// the buffer it is being written to, its masking key, its UTF8 validation
    /// state, and sometimes its compression state.
    struct msg_metadata {
        msg_metadata() {}
        msg_metadata(message_ptr m, size_t p) : msg_ptr(m),prepared_key(p) {}
        msg_metadata(message_ptr m, frame::masking_key_type p)
          : msg_ptr(m)
          , prepared_key(prepare_masking_key(p)) {}

        message_ptr msg_ptr;        // pointer to the message data buffer
        size_t      prepared_key;   // prepared masking key
        utf8_validator::validator validator; // utf8 validation state
    };

    // Basic header of the frame being read
    frame::basic_header m_basic_header;

    // Pointer to a manager that can create message buffers for us.
    msg_manager_ptr m_msg_manager;

    // Number of bytes needed to complete the current operation
    size_t m_bytes_needed;

    // Number of extended header bytes read
    size_t m_cursor;

    // Metadata for the current data msg
    msg_metadata m_data_msg;
    // Metadata for the current control msg
    msg_metadata m_control_msg;

    // Pointer to the metadata associated with the frame being read
    msg_metadata * m_current_msg;

    // Extended header of current frame
    frame::extended_header m_extended_header;

    rng_type & m_rng;

    // Overall state of the processor
    state m_state;

    // Extensions
    permessage_deflate_type m_permessage_deflate;
};

} // namespace processor
} // namespace websocketpp

#endif //WEBSOCKETPP_PROCESSOR_HYBI13_HPP
