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/*******************************************************************************
* Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
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* OTHER DEALINGS IN THE SOFTWARE.
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*/

#include <vector>

#include "WebServerInterface.hpp"
#include "ESP8266.hpp"
#include "OneWire_Masters/ISha256MacCoprocessor.hpp"
#include "common.hpp"
#include "mbed.h"

const char WebServerInterface::wifiSsid[] = "WifiSsid";
const char WebServerInterface::wifiPassword[] = "WifiPassword";
const char WebServerInterface::serverAddress[] = "website.com";
const unsigned int WebServerInterface::serverPort = 80;
const char WebServerInterface::serverPostPath[] = "/post.php";
const char WebServerInterface::serverChallengePath[] = "/challenge.php";

// HTTP formatting constants
static const char keyValSeparator = '=';
static const char fieldSeparator = '&';
static const std::string newline = "\r\n";
static const char sessionIdKey[] = "SessionId";

// Authentication MAC constants
static const std::size_t challengeLen = 32;
static const std::uint8_t defaultPaddingByte = 0x00;

/// Select the Transport Secret for the web server in the Controller.
/// @returns True on success.
static bool setHttpPostSecret(ISha256MacCoprocessor & MacCoproc)
{
  ISha256MacCoprocessor::DevicePage::Buffer fillData;
  std::memset(fillData, defaultPaddingByte, ISha256MacCoprocessor::DevicePage::length);
  // static_assert(ISha256MacCoprocessor::DevicePage::length > ISha256MacCoprocessor::SlaveSecretData::length);
  return (MacCoproc.computeSlaveSecret(fillData, fillData, reinterpret_cast<const ISha256MacCoprocessor::SlaveSecretData::Buffer &>(fillData)) == ISha256MacCoprocessor::Success);
}

WebServerInterface::WebServerInterface(ESP8266 & esp8266, mbed::Serial * pc)
  : esp8266(esp8266), pc(pc)
{
  
}

bool WebServerInterface::initialize()
{
  esp8266.setPowered(true);
  esp8266.reset();
  bool result = (esp8266.performSelfTest() == ESP8266::AT_OK);
  if (!result)
  {
    return false;
  }
  result = (esp8266.setCurrentWifiMode(ESP8266::softAP_station_mode) == ESP8266::AT_OK);
  if (!result)
  {
    return false;
  }
  result = (esp8266.setMaxRFTXPower(10) == ESP8266::AT_OK);
  if (!result)
  {
    return false;
  }
  result = (esp8266.joinCurrentAccessPoint(wifiSsid, wifiPassword) == ESP8266::AT_OK);
  if (!result)
  {
    return false;
  }
  return true;
}

/// Format an HTTP GET request as a string for transmission.
/// @param host Web server address.
/// @param path Web server location to retrieve.
/// @param sessionId Session ID used to identify this controller.
/// @returns GET request string.
static std::string formatHttpGet(const std::string & host, const std::string & path, const std::string & sessionId)
{
  std::ostringstream httpGetStream;
  httpGetStream << "GET " << path;
  if (sessionId.length() > 0)
    httpGetStream << '?' << sessionIdKey << keyValSeparator << sessionId;
  httpGetStream << " HTTP/1.1" << newline;
  httpGetStream << "Host: " << host << newline;
  httpGetStream << newline;
  return httpGetStream.str();
}

/// Computes a MAC using the Transport Secret to sign HTTP POST requests.
/// @param macCoproc Coprocessor such as the DS2465 used to calculate the authentication MAC.
/// @param input Message array used for MAC calculation.
/// @param ilen Length of array input.
/// @param output Calculated MAC output.
static void calculateHttpPostMac(const ISha256MacCoprocessor & macCoproc, const std::uint8_t * input, std::size_t ilen, ISha256MacCoprocessor::Mac & output)
{
  ISha256MacCoprocessor::DeviceScratchpad block;
  std::size_t index = 0;
  ISha256MacCoprocessor::AuthMacData padding;
  std::memset(padding, defaultPaddingByte, padding.length);
  std::memset(output, defaultPaddingByte, output.length); // Set initial hash value
  while (index < ilen)
  {
    if ((index + block.length) <= ilen) // Full block
    {
      std::memcpy(block, &input[index], block.length);
      index += block.length;
    }
    else // Partial block with padding
    {
      std::memcpy(block, &input[index], ilen - index);
      std::memset(&block[ilen - index], defaultPaddingByte, block.length - (ilen - index));
      index = ilen;
    }
    // Write data to coprocessor and hash block
    macCoproc.computeAuthMac(output, block, padding, output);
  }
}

/// Format an HTTP POST request as a string for transmission.
/// @param host Web server address.
/// @param path Web server location to receive POST.
/// @param sessionId Session ID used to identify this Controller.
/// @param macCoproc Coprocessor such as the DS2465 used to calculate the authentication MAC.
/// @param event Event message type.
/// @param initialPostBody Message body as determined by the event message type.
/// @param challenge Challenge previously received from web server for use in authentication MAC.
/// @returns POST request string.
static std::string formatHttpPost(const std::string & host, const std::string & path, const std::string & sessionId,
                                  const ISha256MacCoprocessor & macCoproc, PostEvent event, const std::string & initialPostBody,
                                  const std::uint8_t (&challenge)[challengeLen])
{
  const std::size_t headerReserve = 115, bodyReserve = 200;
  
  std::string httpPost;
  httpPost.reserve(initialPostBody.length() + headerReserve + bodyReserve);
  
  // Add session ID to post body
  if (sessionId.length() > 0)
  {
    httpPost += sessionIdKey;
    httpPost += keyValSeparator;
    httpPost += sessionId;
  }
  
  // Add event to post body
  std::string eventString;
  switch (event)
  {
  case SensorDataEvent:
    eventString = "SensorData";
    break;
    
  case InvalidSensorEvent:
    eventString = "InvalidSensor";
    break;
  }
  if (eventString.length() > 0)
  {
    if (httpPost.length() > 0)
      httpPost += fieldSeparator;
    httpPost += "Event";
    httpPost += keyValSeparator;
    httpPost += eventString;
  }
  
  // Add initial post body
  if (initialPostBody.length() > 0)
  {
    if (httpPost.length() > 0)
      httpPost += fieldSeparator;
    httpPost += initialPostBody;
  }
  
  // Combine initial post body with initial secret and hash
  std::vector<std::uint8_t> hashInput;
  hashInput.reserve(challengeLen + httpPost.length());
  hashInput.insert(hashInput.end(), challenge, challenge + challengeLen);
  hashInput.insert(hashInput.end(), httpPost.begin(), httpPost.end());
  ISha256MacCoprocessor::Mac mac;
  calculateHttpPostMac(macCoproc, &hashInput[0], hashInput.size(), mac);
  
  char contentLen[5];
  std::snprintf(contentLen, sizeof(contentLen) / sizeof(char), "%u", (hashInput.size() - challengeLen) + (mac.length * charsPerByte) + 5 /* &MAC= */);
  
  // Construct full post request
  httpPost = "";
  httpPost += "POST ";
  httpPost += path;
  httpPost += " HTTP/1.1";
  httpPost += newline;
  httpPost += "Host: ";
  httpPost += host;
  httpPost += newline;
  httpPost += "Accept: */*";
  httpPost += newline;
  httpPost += "Content-Length: ";
  httpPost += contentLen;
  httpPost += newline;
  httpPost += "Content-Type: application/x-www-form-urlencoded";
  httpPost += newline;
  httpPost += newline;
  // Add post body
  httpPost.append(reinterpret_cast<char *>(&hashInput[challengeLen]), hashInput.size() - challengeLen);
  // Convert hash to hex string and add to post body
  httpPost += fieldSeparator;
  httpPost += "MAC";
  httpPost += keyValSeparator;
  byteArrayToHexString(mac, mac.length, httpPost);
  httpPost += newline;
  
  return httpPost;
}

bool WebServerInterface::authPostHttpEvent(ISha256MacCoprocessor & macCoproc, PostEvent event, const std::string & postData, bool setSecret)
{
  const std::string challengeSearch(newline + newline);
  bool result;
  std::uint8_t challenge[challengeLen];
  std::string response;
  
  std::memset(challenge, defaultPaddingByte, challengeLen);
  response.reserve(300);
  
  if (setSecret)
  {
    result = setHttpPostSecret(macCoproc);
    if (!result)
      return result;
  }
  
  // Open connection
  esp8266.clearRecvData(); // Clear received data buffer
  result = (esp8266.openConnection(ESP8266::TCP, serverAddress, 80) == ESP8266::AT_OK);
  if (result)
  {
    // Request challenge
    result = (esp8266.sendData(formatHttpGet(serverAddress, serverChallengePath, sessionId)) == ESP8266::AT_OK);
    if (result)
    {
      // Receive server response
      for (int i = 0; i < 10; i++)
      {
        while (esp8266.recvIpDataReadable())
        {
          char read = esp8266.getcRecvIpData();
          if (pc != NULL)
            pc->putc(read);
          if (response.length() < response.capacity())
          {
            response += read;
          }
          else
          {
            wait_ms(ESP8266::sendDataRecoveryTimeMs); // Wait for ESP8266 specified recovery time
            goto close_get_connection;
          }
        }
        wait_ms(100);
      }
      // Close connection
    close_get_connection:
      esp8266.closeConnection();
      
      // Parse challenge from response
      std::size_t challengePos = response.find(challengeSearch);
      if ((challengePos != std::string::npos) && ((challengePos + challengeSearch.length() + (challengeLen * charsPerByte)) <= response.length()))
      {
        challengePos += challengeSearch.length();
        for (std::size_t i = 0; i < challengeLen; i++)
        {
          std::sscanf(response.substr(challengePos + (i * charsPerByte), charsPerByte).c_str(), "%2hhx", &challenge[i]);
        }
      }
      
      // Post sensor data
      result = (esp8266.openConnection(ESP8266::TCP, serverAddress, serverPort) == ESP8266::AT_OK);
      if (result)
      {
        result = (esp8266.sendData(formatHttpPost(serverAddress, serverPostPath, sessionId, macCoproc, event, postData, challenge)) == ESP8266::AT_OK);
        wait_ms(ESP8266::sendDataRecoveryTimeMs); // Wait for ESP8266 specified recovery time
      }
    }
    
    // Close connection
    esp8266.closeConnection();
  }
  
  return result;
}

std::string WebServerInterface::formatSensorDataPostBody(const SensorData & sensorData)
{
  // Create initial post body string from input data
  std::ostringstream postBodyStream;
  postBodyStream << "Temp" << keyValSeparator << static_cast<int>(sensorData.temp);
  postBodyStream << fieldSeparator;
  postBodyStream << "FilterLife" << keyValSeparator << static_cast<unsigned>(sensorData.filterLife);
  postBodyStream << fieldSeparator;
  postBodyStream << "TempAlarm" << keyValSeparator << (sensorData.tempAlarm() ? "true" : "false");
  postBodyStream << fieldSeparator;
  postBodyStream << "FilterLifeAlarm" << keyValSeparator << (sensorData.filterLifeAlarm() ? "true" : "false");
  return postBodyStream.str();
}