ESP8266HTTPClient.cpp

/**
 * ESP8266HTTPClient.cpp
 *
 * Created on: 02.11.2015
 *
 * Copyright (c) 2015 Markus Sattler. All rights reserved.
 * This file is part of the ESP8266HTTPClient for Arduino.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */
#include <Arduino.h>
#include <coredecls.h>

#include "ESP8266HTTPClient.h"
#include <ESP8266WiFi.h>
#include <StreamDev.h>
#include <base64.h>

// per https://github.com/esp8266/Arduino/issues/8231
// make sure HTTPClient can be utilized as a movable class member
static_assert(std::is_default_constructible_v<HTTPClient>, "");
static_assert(!std::is_copy_constructible_v<HTTPClient>, "");
static_assert(std::is_move_constructible_v<HTTPClient>, "");
static_assert(std::is_move_assignable_v<HTTPClient>, "");

static const char defaultUserAgentPstr[] PROGMEM = "ESP8266HTTPClient";
const String HTTPClient::defaultUserAgent = defaultUserAgentPstr;

int HTTPClient::StreamReportToHttpClientReport (Stream::Report streamSendError)
{
    switch (streamSendError)
    {
    case Stream::Report::TimedOut: return HTTPC_ERROR_READ_TIMEOUT;
    case Stream::Report::ReadError: return HTTPC_ERROR_NO_STREAM;
    case Stream::Report::WriteError: return HTTPC_ERROR_STREAM_WRITE;
    case Stream::Report::ShortOperation: return HTTPC_ERROR_STREAM_WRITE;
    case Stream::Report::Success: return 0;
    }
    return 0; // never reached, keep gcc quiet
}

void HTTPClient::clear()
{
    _returnCode = 0;
    _size = -1;
    _headers.clear();
    _location.clear();
    _payload.reset();
}


/**
 * parsing the url for all needed parameters
 * @param client Client&
 * @param url String
 * @param https bool
 * @return success bool
 */
bool HTTPClient::begin(WiFiClient &client, const String& url) {
    // check for : (http: or https:)
    int index = url.indexOf(':');
    if(index < 0) {
        DEBUG_HTTPCLIENT("[HTTP-Client][begin] failed to parse protocol\n");
        return false;
    }

    String protocol = url.substring(0, index);
    protocol.toLowerCase();
    if(protocol != "http" && protocol != "https") {
        DEBUG_HTTPCLIENT("[HTTP-Client][begin] unknown protocol '%s'\n", protocol.c_str());
        return false;
    }

    _port = (protocol == "https" ? 443 : 80);
    _client = client.clone();

    return beginInternal(url, protocol.c_str());
}


/**
 * directly supply all needed parameters
 * @param client Client&
 * @param host String
 * @param port uint16_t
 * @param uri String
 * @param https bool
 * @return success bool
 */
bool HTTPClient::begin(WiFiClient &client, const String& host, uint16_t port, const String& uri, bool https)
{
    // Disconnect when reusing HTTPClient to talk to a different host
    if (!_host.isEmpty() && _host != host) {
        _canReuse = false;
        disconnect(true);
    }

    _client = client.clone();

    clear();

    _host = host;
    _port = port;
    _uri = uri;
    _protocol = (https ? "https" : "http");
    return true;
}


bool HTTPClient::beginInternal(const String& __url, const char* expectedProtocol)
{
    String url(__url);

    DEBUG_HTTPCLIENT("[HTTP-Client][begin] url: %s\n", url.c_str());
    clear();

    // check for : (http: or https:
    int index = url.indexOf(':');
    if(index < 0) {
        DEBUG_HTTPCLIENT("[HTTP-Client][begin] failed to parse protocol\n");
        return false;
    }

    _protocol = url.substring(0, index);
    _protocol.toLowerCase();
    url.remove(0, (index + 3)); // remove http:// or https://

    if (_protocol == "http") {
        // set default port for 'http'
        _port = 80;
    } else if (_protocol == "https") {
        // set default port for 'https'
        _port = 443;
    } else {
        DEBUG_HTTPCLIENT("[HTTP-Client][begin] unsupported protocol: %s\n", _protocol.c_str());
        return false;
    }

    index = url.indexOf('/');
    String host = url.substring(0, index);
    url.remove(0, index); // remove host part

    // get Authorization
    index = host.indexOf('@');
    if(index >= 0) {
        // auth info
        String auth = host.substring(0, index);
        host.remove(0, index + 1); // remove auth part including @
        _base64Authorization = base64::encode(auth, false /* doNewLines */);
    }

    const String oldHost = _host;

    // get port
    index = host.indexOf(':');
    if(index >= 0) {
        _host = host.substring(0, index); // hostname
        host.remove(0, (index + 1)); // remove hostname + :
        _port = host.toInt(); // get port
    } else {
        _host = host;
    }

    // Disconnect when reusing HTTPClient to talk to a different host
    if (!oldHost.isEmpty() && _host != oldHost) {
        _canReuse = false;
        disconnect(true);
    }

    _uri = url;

    if ( expectedProtocol != nullptr && _protocol != expectedProtocol) {
        DEBUG_HTTPCLIENT("[HTTP-Client][begin] unexpected protocol: %s, expected %s\n", _protocol.c_str(), expectedProtocol);
        return false;
    }
    DEBUG_HTTPCLIENT("[HTTP-Client][begin] host: %s port: %d url: %s\n", _host.c_str(), _port, _uri.c_str());
    return true;
}


/**
 * end
 * called after the payload is handled
 */
void HTTPClient::end(void)
{
    disconnect(false);
    clear();
}

/**
 * disconnect
 * close the TCP socket
 */
void HTTPClient::disconnect(bool preserveClient)
{
    if(connected()) {
        if(_client->available() > 0) {
            DEBUG_HTTPCLIENT("[HTTP-Client][end] still data in buffer (%d), clean up.\n", _client->available());
            while(_client->available() > 0) {
                _client->read();
            }
        }

        if(_reuse && _canReuse) {
            DEBUG_HTTPCLIENT("[HTTP-Client][end] tcp kept open for reuse\n");
        } else {
            DEBUG_HTTPCLIENT("[HTTP-Client][end] tcp stop\n");
            if(_client) {
                _client->stop();
                if (!preserveClient) {
                    _client = nullptr;
                }
            }
        }
    } else {
        if (!preserveClient && _client) { // Also destroy _client if not connected()
            _client = nullptr;
        }

        DEBUG_HTTPCLIENT("[HTTP-Client][end] tcp is closed\n");
    }
}

/**
 * connected
 * @return connected status
 */
bool HTTPClient::connected()
{
    if(_client) {
        return (_client->connected() || (_client->available() > 0));
    }
    return false;
}

/**
 * try to reuse the connection to the server
 * keep-alive
 * @param reuse bool
 */
void HTTPClient::setReuse(bool reuse)
{
    _reuse = reuse;
}

/**
 * set User Agent
 * @param userAgent const char *
 */
void HTTPClient::setUserAgent(const String& userAgent)
{
    _userAgent = userAgent;
}

/**
 * set the Authorizatio for the http request
 * @param user const char *
 * @param password const char *
 */
void HTTPClient::setAuthorization(const char * user, const char * password)
{
    if(user && password) {
        String auth = user;
        auth += ':';
        auth += password;
        _base64Authorization = base64::encode(auth, false /* doNewLines */);
    }
}

/**
 * set the Authorization for the http request
 * @param auth const char * base64
 */
void HTTPClient::setAuthorization(const char * auth)
{
    if (auth) {
        setAuthorization(String(auth));
    }
}

/**
 * set the Authorization for the http request
 * @param auth String base64
 */
void HTTPClient::setAuthorization(String auth)
{
    _base64Authorization = std::move(auth);
    _base64Authorization.replace(String('\n'), emptyString);
}

/**
 * set the wall time for operations
 * @param timeout unsigned int
 */
void HTTPClient::setWallTime(unsigned long wallTime)
{
    _wallTime.reset(wallTime?: esp8266::polledTimeout::oneShotMs::neverExpires);
}

/**
 * set the URL to a new value. Handy for following redirects.
 * @param url
 */
bool HTTPClient::setURL(const String& url)
{
    // if the new location is only a path then only update the URI
    if (url && url[0] == '/') {
        _uri = url;
        clear();
        return true;
    }

    if (!url.startsWith(_protocol + ':')) {
        DEBUG_HTTPCLIENT("[HTTP-Client][setURL] new URL not the same protocol, expected '%s', URL: '%s'\n", _protocol.c_str(), url.c_str());
        return false;
    }
    // disconnect but preserve _client (clear _canReuse so disconnect will close the connection)
    _canReuse = false;
    disconnect(true);
    return beginInternal(url, nullptr);
}

/**
 * set redirect follow mode. See `followRedirects_t` enum for available modes.
 * @param follow
 */
void HTTPClient::setFollowRedirects(followRedirects_t follow)
{
    _followRedirects = follow;
}

void HTTPClient::setRedirectLimit(uint16_t limit)
{
    _redirectLimit = limit;
}

/**
 * use HTTP1.0
 * @param useHTTP10 bool
 */
void HTTPClient::useHTTP10(bool useHTTP10)
{
    _useHTTP10 = useHTTP10;
    _reuse = !useHTTP10;
}

/**
 * send a GET request
 * @return http code
 */
int HTTPClient::GET()
{
    return sendRequest("GET");
}
/**
 * send a DELETE request
 * @return http code
 */
int HTTPClient::DELETE()
{
    return sendRequest("DELETE");
}

/**
 * sends a post request to the server
 * @param payload const uint8_t *
 * @param size size_t
 * @return http code
 */
int HTTPClient::POST(const uint8_t* payload, size_t size)
{
    return sendRequest("POST", payload, size);
}

int HTTPClient::POST(const String& payload)
{
    return POST((uint8_t *) payload.c_str(), payload.length());
}

/**
 * sends a put request to the server
 * @param payload uint8_t *
 * @param size size_t
 * @return http code
 */
int HTTPClient::PUT(const uint8_t* payload, size_t size) {
    return sendRequest("PUT", payload, size);
}

int HTTPClient::PUT(const String& payload) {
    return PUT((const uint8_t *) payload.c_str(), payload.length());
}

/**
 * sends a patch request to the server
 * @param payload const uint8_t *
 * @param size size_t
 * @return http code
 */
int HTTPClient::PATCH(const uint8_t * payload, size_t size) {
    return sendRequest("PATCH", payload, size);
}

int HTTPClient::PATCH(const String& payload) {
    return PATCH((const uint8_t *) payload.c_str(), payload.length());
}

/**
 * sendRequest
 * @param type const char *     "GET", "POST", ....
 * @param payload String        data for the message body
 * @return
 */
int HTTPClient::sendRequest(const char * type, const String& payload)
{
    return sendRequest(type, (const uint8_t *) payload.c_str(), payload.length());
}

/**
 * sendRequest
 * @param type const char *           "GET", "POST", ....
 * @param payload const uint8_t *     data for the message body if null not send
 * @param size size_t                 size for the message body if 0 not send
 * @return -1 if no info or > 0 when Content-Length is set by server
 */
int HTTPClient::sendRequest(const char * type, const uint8_t * payload, size_t size)
{
    int code;
    bool redirect = false;
    uint16_t redirectCount = 0;
    do {
        // wipe out any existing headers from previous request
        for(size_t i = 0; i < _headerKeysCount; i++) {
            if (_currentHeaders[i].value.length() > 0) {
                _currentHeaders[i].value.clear();
            }
        }

        DEBUG_HTTPCLIENT("[HTTP-Client][sendRequest] type: '%s' redirCount: %d\n", type, redirectCount);

        // connect to server
        if(!connect()) {
            return returnError(HTTPC_ERROR_CONNECTION_FAILED);
        }

        addHeader(F("Content-Length"), String(payload && size > 0 ? size : 0));

        // send Header
        if(!sendHeader(type)) {
            return returnError(HTTPC_ERROR_SEND_HEADER_FAILED);
        }

        // transfer all of it, with send-timeout
        if (size && StreamConstPtr(payload, size).sendAll(_client.get()) != size)
            return returnError(HTTPC_ERROR_SEND_PAYLOAD_FAILED);

        // handle Server Response (Header)
        code = handleHeaderResponse();

        //
        // Handle redirections as stated in RFC document:
        // https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
        //
        // Implementing HTTP_CODE_FOUND as redirection with GET method,
        // to follow most of existing user agent implementations.
        //
        redirect = false;
        if (
            _followRedirects != HTTPC_DISABLE_FOLLOW_REDIRECTS &&
            redirectCount < _redirectLimit &&
            _location.length() > 0
        ) {
            switch (code) {
                // redirecting using the same method
                case HTTP_CODE_MOVED_PERMANENTLY:
                case HTTP_CODE_TEMPORARY_REDIRECT: {
                    if (
                        // allow to force redirections on other methods
                        // (the RFC require user to accept the redirection)
                        _followRedirects == HTTPC_FORCE_FOLLOW_REDIRECTS ||
                        // allow GET and HEAD methods without force
                        !strcmp(type, "GET") ||
                        !strcmp(type, "HEAD")
                    ) {
                        redirectCount += 1;
                        DEBUG_HTTPCLIENT("[HTTP-Client][sendRequest] following redirect (the same method): '%s' redirCount: %d\n", _location.c_str(), redirectCount);
                        if (!setURL(_location)) {
                            DEBUG_HTTPCLIENT("[HTTP-Client][sendRequest] failed setting URL for redirection\n");
                            // no redirection
                            break;
                        }
                        // redirect using the same request method and payload, different URL
                        redirect = true;
                    }
                    break;
                }
                // redirecting with method dropped to GET or HEAD
                // note: it does not need `HTTPC_FORCE_FOLLOW_REDIRECTS` for any method
                case HTTP_CODE_FOUND:
                case HTTP_CODE_SEE_OTHER: {
                    redirectCount += 1;
                    DEBUG_HTTPCLIENT("[HTTP-Client][sendRequest] following redirect (dropped to GET/HEAD): '%s' redirCount: %d\n", _location.c_str(), redirectCount);
                    if (!setURL(_location)) {
                        DEBUG_HTTPCLIENT("[HTTP-Client][sendRequest] failed setting URL for redirection\n");
                        // no redirection
                        break;
                    }
                    // redirect after changing method to GET/HEAD and dropping payload
                    type = "GET";
                    payload = nullptr;
                    size = 0;
                    redirect = true;
                    break;
                }

                default:
                    break;
            }
        }
    } while (redirect);

    // handle Server Response (Header)
    return returnError(code);
}

/**
 * sendRequest
 * @param type const char *     "GET", "POST", ....
 * @param stream Stream *       data stream for the message body
 * @param size size_t           size for the message body if 0 not Content-Length is send
 * @return -1 if no info or > 0 when Content-Length is set by server
 */
int HTTPClient::sendRequest(const char * type, Stream * stream, size_t size)
{

    if(!stream) {
        return returnError(HTTPC_ERROR_NO_STREAM);
    }

    // connect to server
    if(!connect()) {
        return returnError(HTTPC_ERROR_CONNECTION_FAILED);
    }

    if(size > 0) {
        addHeader(F("Content-Length"), String(size));
    }

    // send Header
    if(!sendHeader(type)) {
        return returnError(HTTPC_ERROR_SEND_HEADER_FAILED);
    }

    // transfer all of it, with timeout
    size_t transferred = stream->sendSize(_client.get(), size);
    if (transferred != size)
    {
        DEBUG_HTTPCLIENT("[HTTP-Client][sendRequest] short write, asked for %zu but got %zu failed.\n", size, transferred);
        esp_yield();
        return returnError(HTTPC_ERROR_SEND_PAYLOAD_FAILED);
    }

    // handle Server Response (Header)
    return returnError(handleHeaderResponse());
}

/**
 * size of message body / payload
 * @return -1 if no info or > 0 when Content-Length is set by server
 */
int HTTPClient::getSize(void)
{
    return _size;
}

/**
 * Location if redirect
 */
const String& HTTPClient::getLocation(void)
{
    return _location;
}

/**
 * returns the stream of the tcp connection
 * @return WiFiClient
 */
WiFiClient& HTTPClient::getStream(void)
{
    if(connected()) {
        return *_client;
    }

    DEBUG_HTTPCLIENT("[HTTP-Client] getStream: not connected\n");
    static WiFiClient empty;
    return empty;
}

/**
 * returns the stream of the tcp connection
 * @return WiFiClient *
 */
WiFiClient* HTTPClient::getStreamPtr(void)
{
    if(connected()) {
        return _client.get();
    }

    DEBUG_HTTPCLIENT("[HTTP-Client] getStreamPtr: not connected\n");
    return nullptr;
}

/**
 * return all payload as String (may need lot of ram or trigger out of memory!)
 * @return String
 */
const String& HTTPClient::getString(int reserve)
{
    if (_payload) {
        return *_payload;
    }

    _payload.reset(new StreamString());

    if (_size > 0 && _size > reserve)
        reserve = _size;

    if (reserve > 0 && !_payload->reserve(reserve)) {
        DEBUG_HTTPCLIENT("[HTTP-Client][getString] not enough memory to reserve a string! need: %d\n", reserve);
        return *_payload;
    }

    writeToStream(_payload.get());
    return *_payload;
}

/**
 * converts error code to String
 * @param error int
 * @return String
 */
String HTTPClient::errorToString(int error)
{
    switch(error) {
    case HTTPC_ERROR_CONNECTION_FAILED:
        return F("connection failed");
    case HTTPC_ERROR_SEND_HEADER_FAILED:
        return F("send header failed");
    case HTTPC_ERROR_SEND_PAYLOAD_FAILED:
        return F("send payload failed");
    case HTTPC_ERROR_NOT_CONNECTED:
        return F("not connected");
    case HTTPC_ERROR_CONNECTION_LOST:
        return F("connection lost");
    case HTTPC_ERROR_NO_STREAM:
        return F("no stream");
    case HTTPC_ERROR_NO_HTTP_SERVER:
        return F("no HTTP server");
    case HTTPC_ERROR_TOO_LESS_RAM:
        return F("not enough ram");
    case HTTPC_ERROR_ENCODING:
        return F("Transfer-Encoding not supported");
    case HTTPC_ERROR_STREAM_WRITE:
        return F("Stream write error");
    case HTTPC_ERROR_READ_TIMEOUT:
        return F("read Timeout");
    default:
        return String();
    }
}

/**
 * adds Header to the request
 * @param name
 * @param value
 * @param first
 */
void HTTPClient::addHeader(const String& name, const String& value, bool first, bool replace)
{
    // not allow set of Header handled by code
    if (!name.equalsIgnoreCase(F("Connection")) &&
        !name.equalsIgnoreCase(F("User-Agent")) &&
        !name.equalsIgnoreCase(F("Host")) &&
        !(name.equalsIgnoreCase(F("Authorization")) && _base64Authorization.length())) {

        String headerLine;
        headerLine.reserve(name.length() + value.length() + 4);
        headerLine += name;
        headerLine += ": ";

        if (replace) {
            int headerStart = _headers.indexOf(headerLine);
            if (headerStart != -1) {
                int headerEnd = _headers.indexOf('\n', headerStart);
                _headers = _headers.substring(0, headerStart) + _headers.substring(headerEnd + 1);
            }
        }

        headerLine += value;
        headerLine += "\r\n";
        if (first) {
            _headers = headerLine + _headers;
        } else {
            _headers += headerLine;
        }
    }
}

void HTTPClient::collectHeaders(const char* headerKeys[], const size_t headerKeysCount)
{
    _headerKeysCount = headerKeysCount;
    _currentHeaders = std::make_unique<RequestArgument[]>(_headerKeysCount);
    for(size_t i = 0; i < _headerKeysCount; i++) {
        _currentHeaders[i].key = headerKeys[i];
    }
}

const String& HTTPClient::header(const char* name)
{
    for(size_t i = 0; i < _headerKeysCount; ++i) {
        if(_currentHeaders[i].key == name) {
            return _currentHeaders[i].value;
        }
    }
    return emptyString;
}

const String& HTTPClient::header(size_t i)
{
    if(i < _headerKeysCount) {
        return _currentHeaders[i].value;
    }
    return emptyString;
}

const String& HTTPClient::headerName(size_t i)
{
    if(i < _headerKeysCount) {
        return _currentHeaders[i].key;
    }
    return emptyString;
}

int HTTPClient::headers()
{
    return _headerKeysCount;
}

bool HTTPClient::hasHeader(const char* name)
{
    for(size_t i = 0; i < _headerKeysCount; ++i) {
        if((_currentHeaders[i].key == name) && (_currentHeaders[i].value.length() > 0)) {
            return true;
        }
    }
    return false;
}

/**
 * init TCP connection and handle ssl verify if needed
 * @return true if connection is ok
 */
bool HTTPClient::connect(void)
{
    if(_reuse && _canReuse && connected()) {
        DEBUG_HTTPCLIENT("[HTTP-Client] connect: already connected, reusing connection\n");

#if defined(NO_GLOBAL_INSTANCES) || defined(NO_GLOBAL_STREAMDEV)
        StreamNull devnull;
#endif
        _client->sendAvailable(devnull); // clear _client's output (all of it, no timeout)
        return true;
    }

    if(!_client) {
        DEBUG_HTTPCLIENT("[HTTP-Client] connect: HTTPClient::begin was not called or returned error\n");
        return false;
    }

    if(!_client->connect(_host.c_str(), _port)) {
        DEBUG_HTTPCLIENT("[HTTP-Client] failed connect to %s:%u\n", _host.c_str(), _port);
        return false;
    }

    DEBUG_HTTPCLIENT("[HTTP-Client] connected to %s:%u\n", _host.c_str(), _port);

#ifdef ESP8266
    _client->setNoDelay(true);
#endif
    return connected();
}

/**
 * sends HTTP request header
 * @param type (GET, POST, ...)
 * @return status
 */
bool HTTPClient::sendHeader(const char * type)
{
    if(!connected()) {
        return false;
    }

    String header;
    // 128: Arbitrarily chosen to have enough buffer space for avoiding internal reallocations
    header.reserve(_headers.length() + _uri.length() +
            _base64Authorization.length() + _host.length() + _userAgent.length() + 128);
    header += type;
    header += ' ';
    if (_uri.length()) {
        header += _uri;
    } else {
        header += '/';
    }
    header += F(" HTTP/1.");

    if(_useHTTP10) {
        header += '0';
    } else {
        header += '1';
    }

    header += F("\r\nHost: ");
    header += _host;
    if (_port != 80 && _port != 443)
    {
        header += ':';
        header += String(_port);
    }
    if (_userAgent.length()) {
        header += F("\r\nUser-Agent: ");
        header += _userAgent;
    }

    if (!_useHTTP10) {
        header += F("\r\nAccept-Encoding: identity;q=1,chunked;q=0.1,*;q=0");
    }

    if (_base64Authorization.length()) {
        header += F("\r\nAuthorization: Basic ");
        header += _base64Authorization;
    }

    header += F("\r\nConnection: ");
    header += _reuse ? F("keep-alive") : F("close");
    header += "\r\n";

    header += _headers;
    header += "\r\n";

    DEBUG_HTTPCLIENT("[HTTP-Client] sending request header\n-----\n%s-----\n", header.c_str());

    // transfer all of it, with timeout
    return StreamConstPtr(header).sendAll(_client.get()) == header.length();
}

/**
 * reads the response from the server
 * @return int http code
 */
int HTTPClient::handleHeaderResponse()
{
    if(!connected()) {
        return HTTPC_ERROR_NOT_CONNECTED;
    }

    clear();

    _canReuse = _reuse;

    String transferEncoding;

    _transferEncoding = HTTPC_TE_IDENTITY;
    _wallTime.reset();

    while(connected()) {
        size_t len = _client->available();
        if(len > 0) {
            int headerSeparator = -1;
            String headerLine = _client->readStringUntil('\n');

            DEBUG_HTTPCLIENT("[HTTP-Client][handleHeaderResponse] RX: '%s'\n", headerLine.c_str());

            if (headerLine.startsWith(F("HTTP/1."))) {

                constexpr auto httpVersionIdx = sizeof "HTTP/1." - 1;
                _canReuse = _canReuse && (headerLine[httpVersionIdx] != '0');
                _returnCode = headerLine.substring(httpVersionIdx + 2, headerLine.indexOf(' ', httpVersionIdx + 2)).toInt();
                _canReuse = _canReuse && (_returnCode > 0) && (_returnCode < 500);

            } else if ((headerSeparator = headerLine.indexOf(':')) > 0) {
                String headerName = headerLine.substring(0, headerSeparator);
                String headerValue = headerLine.substring(headerSeparator + 1);
                headerValue.trim();

                if(headerName.equalsIgnoreCase(F("Content-Length"))) {
                    _size = headerValue.toInt();
                }

                if(_canReuse && headerName.equalsIgnoreCase(F("Connection"))) {
                    if (headerValue.indexOf(F("close")) >= 0 &&
                            headerValue.indexOf(F("keep-alive")) < 0) {
                        _canReuse = false;
                    }
                }

                if(headerName.equalsIgnoreCase(F("Transfer-Encoding"))) {
                    transferEncoding = headerValue;
                }

                if(headerName.equalsIgnoreCase(F("Location"))) {
                    _location = headerValue;
                }

                for (size_t i = 0; i < _headerKeysCount; i++) {
                    if (_currentHeaders[i].key.equalsIgnoreCase(headerName)) {
                        if (!_currentHeaders[i].value.isEmpty()) {
                            // Existing value, append this one with a comma
                            _currentHeaders[i].value += ',';
                            _currentHeaders[i].value += headerValue;
                        } else {
                            _currentHeaders[i].value = headerValue;
                        }
                        break; // We found a match, stop looking
                    }
                }
                continue;
            }

            headerLine.trim(); // remove \r

            if (headerLine.isEmpty()) {
                DEBUG_HTTPCLIENT("[HTTP-Client][handleHeaderResponse] code: %d\n", _returnCode);

                if(_size > 0) {
                    DEBUG_HTTPCLIENT("[HTTP-Client][handleHeaderResponse] size: %d\n", _size);
                }

                if(transferEncoding.length() > 0) {
                    DEBUG_HTTPCLIENT("[HTTP-Client][handleHeaderResponse] Transfer-Encoding: %s\n", transferEncoding.c_str());
                    if(transferEncoding.equalsIgnoreCase(F("chunked"))) {
                        _transferEncoding = HTTPC_TE_CHUNKED;
                    } else {
                        _returnCode = HTTPC_ERROR_ENCODING;
                        return _returnCode;
                    }
                } else {
                    _transferEncoding = HTTPC_TE_IDENTITY;
                }

                if(_returnCode <= 0) {
                    DEBUG_HTTPCLIENT("[HTTP-Client][handleHeaderResponse] Remote host is not an HTTP Server!");
                    _returnCode = HTTPC_ERROR_NO_HTTP_SERVER;
                }
                return _returnCode;
            }

        } else {
            if(_wallTime) {
                return HTTPC_ERROR_READ_TIMEOUT;
            }
            esp_yield();
        }
    }

    return HTTPC_ERROR_CONNECTION_LOST;
}

/**
 * called to handle error return, may disconnect the connection if still exists
 * @param error
 * @return error
 */
int HTTPClient::returnError(int error)
{
    if(error < 0) {
        DEBUG_HTTPCLIENT("[HTTP-Client][returnError] error(%d): %s\n", error, errorToString(error).c_str());
        if(connected()) {
            DEBUG_HTTPCLIENT("[HTTP-Client][returnError] tcp stop\n");
            _client->stop();
        }
    }
    return error;
}