text: /**
   * @file       TinyGsmClientESP8266.h
   * @author     Volodymyr Shymanskyy
   * @license    LGPL-3.0
   * @copyright  Copyright (c) 2016 Volodymyr Shymanskyy
   * @date       Nov 2016
   */
  
  #ifndef TinyGsmClientESP8266_h
  #define TinyGsmClientESP8266_h
  
  //#define TINY_GSM_DEBUG Serial
  
  #if !defined(TINY_GSM_RX_BUFFER)
    #define TINY_GSM_RX_BUFFER 512
  #endif
  
  #define TINY_GSM_MUX_COUNT 5
  
  #include <TinyGsmCommon.h>
  
  #define GSM_NL "\r\n"
  static const char GSM_OK[] TINY_GSM_PROGMEM = "OK" GSM_NL;
  static const char GSM_ERROR[] TINY_GSM_PROGMEM = "ERROR" GSM_NL;
  static unsigned TINY_GSM_TCP_KEEP_ALIVE = 120;
  
  class TinyGsm
  {
  
  public:
  
  class GsmClient : public Client
  {
    friend class TinyGsm;
    typedef TinyGsmFifo<uint8_t, TINY_GSM_RX_BUFFER> RxFifo;
  
  public:
    GsmClient() {}
  
    GsmClient(TinyGsm& modem, uint8_t mux = 1) {
      init(&modem, mux);
    }
  
    bool init(TinyGsm* modem, uint8_t mux = 1) {
      this->at = modem;
      this->mux = mux;
      sock_connected = false;
  
      at->sockets[mux] = this;
  
      return true;
    }
  
  public:
    virtual int connect(const char *host, uint16_t port) {
      TINY_GSM_YIELD();
      rx.clear();
      sock_connected = at->modemConnect(host, port, mux);
      return sock_connected;
    }
  
    virtual int connect(IPAddress ip, uint16_t port) {
      String host; host.reserve(16);
      host += ip[0];
      host += ".";
      host += ip[1];
      host += ".";
      host += ip[2];
      host += ".";
      host += ip[3];
      return connect(host.c_str(), port);
    }
  
    virtual void stop() {
      TINY_GSM_YIELD();
      at->sendAT(GF("+CIPCLOSE="), mux);
      sock_connected = false;
      at->waitResponse();
    }
  
    virtual size_t write(const uint8_t *buf, size_t size) {
      TINY_GSM_YIELD();
      //at->maintain();
      return at->modemSend(buf, size, mux);
    }
  
    virtual size_t write(uint8_t c) {
      return write(&c, 1);
    }
  
    virtual int available() {
      TINY_GSM_YIELD();
      if (!rx.size() && sock_connected) {
        at->maintain();
      }
      return rx.size();
    }
  
    virtual int read(uint8_t *buf, size_t size) {
      TINY_GSM_YIELD();
      size_t cnt = 0;
      while (cnt < size) {
        size_t chunk = TinyGsmMin(size-cnt, rx.size());
        if (chunk > 0) {
          rx.get(buf, chunk);
          buf += chunk;
          cnt += chunk;
          continue;
        }
        // TODO: Read directly into user buffer?
        if (!rx.size() && sock_connected) {
          at->maintain();
          //break;
        }
      }
      return cnt;
    }
  
    virtual int read() {
      uint8_t c;
      if (read(&c, 1) == 1) {
        return c;
      }
      return -1;
    }
  
    virtual int peek() { return -1; } //TODO
    virtual void flush() { at->stream.flush(); }
  
    virtual uint8_t connected() {
      if (available()) {
        return true;
      }
      return sock_connected;
    }
    virtual operator bool() { return connected(); }
  
    /*
     * Extended API
     */
  
    String remoteIP() TINY_GSM_ATTR_NOT_IMPLEMENTED;
  
  private:
    TinyGsm*      at;
    uint8_t       mux;
    bool          sock_connected;
    RxFifo        rx;
  };
  
  class GsmClientSecure : public GsmClient
  {
  public:
    GsmClientSecure() {}
  
    GsmClientSecure(TinyGsm& modem, uint8_t mux = 1)
      : GsmClient(modem, mux)
    {}
  
  public:
    virtual int connect(const char *host, uint16_t port) {
      TINY_GSM_YIELD();
      rx.clear();
      sock_connected = at->modemConnect(host, port, mux, true);
      return sock_connected;
    }
  };
  
  public:
  
    TinyGsm(Stream& stream)
      : stream(stream)
    {
      memset(sockets, 0, sizeof(sockets));
    }
  
    /*
     * Basic functions
     */
    bool begin() {
      return init();
    }
  
    bool init() {
      if (!testAT()) {
        return false;
      }
      sendAT(GF("E0"));   // Echo Off
      if (waitResponse() != 1) {
        return false;
      }
      return true;
    }
  
    void setBaud(unsigned long baud) {
      sendAT(GF("+IPR="), baud);
    }
  
    bool testAT(unsigned long timeout = 10000L) {
      for (unsigned long start = millis(); millis() - start < timeout; ) {
        sendAT(GF(""));
        if (waitResponse(200) == 1) {
            delay(100);
            return true;
        }
        delay(100);
      }
      return false;
    }
  
    void maintain() {
        waitResponse(10, NULL, NULL);
    }
  
    bool factoryDefault() {
      sendAT(GF("+RESTORE"));
      return waitResponse() == 1;
    }
  
    String getModemInfo() {
      sendAT(GF("+GMR"));
      String res;
      if (waitResponse(1000L, res) != 1) {
        return "";
      }
      res.replace(GSM_NL "OK" GSM_NL, "");
      res.replace(GSM_NL, " ");
      res.trim();
      return res;
    }
  
    bool hasSSL() {
      return true;
    }
  
    /*
     * Power functions
     */
  
    bool restart() {
      if (!testAT()) {
        return false;
      }
      sendAT(GF("+RST"));
      if (waitResponse(10000L) != 1) {
        return false;
      }
      if (waitResponse(10000L, GF(GSM_NL "ready" GSM_NL)) != 1) {
        return false;
      }
      delay(500);
      return init();
    }
  
  
    /*
     * Generic network functions
     */
  
    int getSignalQuality() {
      sendAT(GF("+CWJAP_CUR?"));
      int res1 = waitResponse(GF("No AP"), GF("+CWJAP_CUR:"));
      if (res1 != 2) {
        waitResponse();
        return 0;
      }
      streamSkipUntil(',');  // Skip SSID
      streamSkipUntil(',');  // Skip BSSID/MAC address
      streamSkipUntil(',');  // Skip Chanel number
      int res2 = stream.parseInt();  // Read RSSI
      waitResponse();  // Returns an OK after the value
      return res2;
    }
  
    bool isNetworkConnected() {
      sendAT(GF("+CIPSTATUS"));
      int res1 = waitResponse(3000, GF("STATUS:"));
      int res2 = 0;
      if (res1 == 1) {
        res2 = waitResponse(GFP(GSM_ERROR), GF("2"), GF("3"), GF("4"), GF("5"));
      }
      // <stat> status of ESP8266 station interface
      // 2 : ESP8266 station connected to an AP and has obtained IP
      // 3 : ESP8266 station created a TCP or UDP transmission
      // 4 : the TCP or UDP transmission of ESP8266 station disconnected (but AP is connected)
      // 5 : ESP8266 station did NOT connect to an AP
      waitResponse();  // Returns an OK after the status
      if (res2 == 2 || res2 == 3 || res2 == 4) return true;
      else return false;
    }
  
    bool waitForNetwork(unsigned long timeout = 60000L) {
      for (unsigned long start = millis(); millis() - start < timeout; ) {
        sendAT(GF("+CIPSTATUS"));
        int res1 = waitResponse(3000, GF("busy p..."), GF("STATUS:"));
        if (res1 == 2) {
          int res2 = waitResponse(GFP(GSM_ERROR), GF("2"), GF("3"), GF("4"), GF("5"));
          if (res2 == 2 || res2 == 3 || res2 == 4) {
              waitResponse();
              return true;
           }
          }
        delay(250);
      }
      return false;
    }
  
    /*
     * WiFi functions
     */
    bool networkConnect(const char* ssid, const char* pwd) {
  
      sendAT(GF("+CIPMUX=1"));
      if (waitResponse() != 1) {
        return false;
      }
  
      sendAT(GF("+CWMODE_CUR=1"));
      if (waitResponse() != 1) {
        return false;
      }
  
      sendAT(GF("+CWJAP_CUR=\""), ssid, GF("\",\""), pwd, GF("\""));
      if (waitResponse(30000L, GFP(GSM_OK), GF(GSM_NL "FAIL" GSM_NL)) != 1) {
        return false;
      }
  
      return true;
    }
  
    bool networkDisconnect() {
      sendAT(GF("+CWQAP"));
      bool retVal = waitResponse(10000L) == 1;
      waitResponse(GF("WIFI DISCONNECT"));
      return retVal;
    }
  
    String getLocalIP() {
      sendAT(GF("+CIPSTA_CUR??"));
      int res1 = waitResponse(GF("ERROR"), GF("+CWJAP_CUR:"));
      if (res1 != 2) {
        return "";
      }
      String res2 = stream.readStringUntil('"');
      waitResponse();
      return res2;
    }
  
    IPAddress localIP() {
      return TinyGsmIpFromString(getLocalIP());
    }
  
  protected:
  
    bool modemConnect(const char* host, uint16_t port, uint8_t mux, bool ssl = false) {
      if (ssl) {
        sendAT(GF("+CIPSSLSIZE=4096"));
        waitResponse();
      }
      sendAT(GF("+CIPSTART="), mux, ',', ssl ? GF("\"SSL") : GF("\"TCP"), GF("\",\""), host, GF("\","), port, GF(","), TINY_GSM_TCP_KEEP_ALIVE);
      // TODO: Check mux
      int rsp = waitResponse(75000L,
                             GFP(GSM_OK),
                             GFP(GSM_ERROR),
                             GF("ALREADY CONNECT"));
      // if (rsp == 3) waitResponse();  // May return "ERROR" after the "ALREADY CONNECT"
      return (1 == rsp);
    }
  
    int modemSend(const void* buff, size_t len, uint8_t mux) {
      sendAT(GF("+CIPSEND="), mux, ',', len);
      if (waitResponse(GF(">")) != 1) {
        return -1;
      }
      stream.write((uint8_t*)buff, len);
      stream.flush();
      if (waitResponse(10000L, GF(GSM_NL "SEND OK" GSM_NL)) != 1) {
        return -1;
      }
      return len;
    }
  
    bool modemGetConnected(uint8_t mux) {
      sendAT(GF("+CIPSTATUS="), mux);
      int res1 = waitResponse(3000, GF("STATUS:"));
      int res2;
      if (res1 == 1) {
        res2 = waitResponse(GFP(GSM_ERROR), GF("2"), GF("3"), GF("4"), GF("5"));
      }
      // <stat> status of ESP8266 station interface
      // 2 : ESP8266 station connected to an AP and has obtained IP
      // 3 : ESP8266 station created a TCP or UDP transmission
      // 4 : the TCP or UDP transmission of ESP8266 station disconnected (but AP is connected)
      // 5 : ESP8266 station did NOT connect to an AP
      waitResponse();  // Returns an OK after the status
      if (res2 == 2 || res2 == 3 || res2 == 4) return true;
      else return false;
    }
  
  public:
  
    /* Utilities */
  
    template<typename T>
    void streamWrite(T last) {
      stream.print(last);
    }
  
    template<typename T, typename... Args>
    void streamWrite(T head, Args... tail) {
      stream.print(head);
      streamWrite(tail...);
    }
  
    bool streamSkipUntil(char c) { //TODO: timeout
      while (true) {
        while (!stream.available()) { TINY_GSM_YIELD(); }
        if (stream.read() == c)
          return true;
      }
      return false;
    }
  
    template<typename... Args>
    void sendAT(Args... cmd) {
      streamWrite("AT", cmd..., GSM_NL);
      stream.flush();
      TINY_GSM_YIELD();
      //DBG("### AT:", cmd...);
    }
  
    // TODO: Optimize this!
    uint8_t waitResponse(uint32_t timeout, String& data,
                         GsmConstStr r1=GFP(GSM_OK), GsmConstStr r2=GFP(GSM_ERROR),
                         GsmConstStr r3=NULL, GsmConstStr r4=NULL, GsmConstStr r5=NULL)
    {
      /*String r1s(r1); r1s.trim();
      String r2s(r2); r2s.trim();
      String r3s(r3); r3s.trim();
      String r4s(r4); r4s.trim();
      String r5s(r5); r5s.trim();
      DBG("### ..:", r1s, ",", r2s, ",", r3s, ",", r4s, ",", r5s);*/
      data.reserve(64);
      int index = 0;
      unsigned long startMillis = millis();
      do {
        TINY_GSM_YIELD();
        while (stream.available() > 0) {
          int a = stream.read();
          if (a <= 0) continue; // Skip 0x00 bytes, just in case
          data += (char)a;
          if (r1 && data.endsWith(r1)) {
            index = 1;
            goto finish;
          } else if (r2 && data.endsWith(r2)) {
            index = 2;
            goto finish;
          } else if (r3 && data.endsWith(r3)) {
            index = 3;
            goto finish;
          } else if (r4 && data.endsWith(r4)) {
            index = 4;
            goto finish;
          } else if (r5 && data.endsWith(r5)) {
            index = 5;
            goto finish;
          } else if (data.endsWith(GF(GSM_NL "+IPD,"))) {
            int mux = stream.readStringUntil(',').toInt();
            int len = stream.readStringUntil(':').toInt();
            int len_orig = len;
            if (len > sockets[mux]->rx.free()) {
              DBG("### Buffer overflow: ", len, "->", sockets[mux]->rx.free());
            } else {
              DBG("### Got: ", len, "->", sockets[mux]->rx.free());
            }
            while (len--) {
              while (!stream.available()) { TINY_GSM_YIELD(); }
              sockets[mux]->rx.put(stream.read());
            }
            if (len_orig > sockets[mux]->available()) { // TODO
              DBG("### Fewer characters received than expected: ", sockets[mux]->available(), " vs ", len_orig);
            }
            data = "";
          } else if (data.endsWith(GF("CLOSED"))) {
            int muxStart = max(0,data.lastIndexOf(GSM_NL, data.length()-8));
            int coma = data.indexOf(',', muxStart);
            int mux = data.substring(muxStart, coma).toInt();
            if (mux >= 0 && mux < TINY_GSM_MUX_COUNT && sockets[mux]) {
              sockets[mux]->sock_connected = false;
            }
            data = "";
            DBG("### Closed: ", mux);
          }
        }
      } while (millis() - startMillis < timeout);
  finish:
      if (!index) {
        data.trim();
        if (data.length()) {
          DBG("### Unhandled:", data);
        }
        data = "";
      }
      return index;
    }
  
    uint8_t waitResponse(uint32_t timeout,
                         GsmConstStr r1=GFP(GSM_OK), GsmConstStr r2=GFP(GSM_ERROR),
                         GsmConstStr r3=NULL, GsmConstStr r4=NULL, GsmConstStr r5=NULL)
    {
      String data;
      return waitResponse(timeout, data, r1, r2, r3, r4, r5);
    }
  
    uint8_t waitResponse(GsmConstStr r1=GFP(GSM_OK), GsmConstStr r2=GFP(GSM_ERROR),
                         GsmConstStr r3=NULL, GsmConstStr r4=NULL, GsmConstStr r5=NULL)
    {
      return waitResponse(1000, r1, r2, r3, r4, r5);
    }
  
  protected:
    Stream&       stream;
    GsmClient*    sockets[TINY_GSM_MUX_COUNT];
  };
  
  #endif
  