/*
  xdrv_121_gpioviewer.ino - GPIOViewer for Tasmota

  SPDX-FileCopyrightText: 2024 Theo Arends, Stephan Hadinger and Charles Giguere

  SPDX-License-Identifier: GPL-3.0-only
*/

#ifdef USE_GPIO_VIEWER
/*********************************************************************************************\
 * GPIOViewer support based on work by Charles Giguere
 * 
 * Resources:
 *       GPIO Viewer: https://github.com/thelastoutpostworkshop/gpio_viewer
 * Server Sent Event: https://github.com/esp8266/Arduino/issues/7008
 *    Tasmota hosted: https://ota.tasmota.com/tasmota/release-13.4.0/gpio_viewer_1_5/
 * 
 * Supported commands:
 *   GvViewer               - Show current viewer state
 *   GvViewer 0             - Turn viewer off
 *   GvViewer 1             - Turn viewer on
 *   GvViewer 2             - Toggle viewer state
 *   GvSampling             - Show current sampling interval in milliseconds
 *   GvSampling 1           - Select default sampling interval (GV_SAMPLING_INTERVAL)
 *   GvSampling 20 .. 1000  - Set sampling interval
 *   GvPort                 - Show current port
 *   GvPort 1               - Select default port (GV_PORT)
 *   GvPort 5557            - Set port
 *   GvUrl                  - Show current url
 *   GvUrl 1                - Select default url (GV_BASE_URL)
 *   GvUrl https://thelastoutpostworkshop.github.io/microcontroller_devkit/gpio_viewer_1_5/
 * 
 * Note 20240821
 * - GVRelease 1.5.6
 * - Add ADC pin function information
 * - Add ESP32 Touch pin function information
 * 
 * Note 20240717
 * - GVRelease 1.5.5
 * 
 * Note 20240602
 * - GVRelease 1.5.4
 * 
 * Note 20240518
 * - GVRelease 1.5.3
 * 
 * Note 20240506
 * - Tasmota v14.0.0
 * - GVRelease 1.5.2
 * - Function pinmode is not fully implemented by gpio_viewer_1_5:
 *   Only INPUT_PULLUP and INPUT_PULLDOWN are reported as INPUT
 *   Only OUTPUT and OUTPUT_OPEN_DRAIN are reported as OUTPUT
 *   All other pin modes are reported as UNKNOWN
 * - This driver is forcing INPUT_PULLUP for ANALOG and INPUT
 * - Execute once command GvUrl https://thelastoutpostworkshop.github.io/microcontroller_devkit/gpio_viewer_1_5/
 * - Clear browser cache to use new functionality
\*********************************************************************************************/

#define XDRV_121              121

#define GV_USE_ESPINFO                     // Provide ESP info
//#define GV_DEBUG

#ifndef GV_PORT
#define GV_PORT               5557         // [GvPort] SSE webserver port
#endif
#ifndef GV_SAMPLING_INTERVAL
#define GV_SAMPLING_INTERVAL  100          // [GvSampling] milliseconds - Use Tasmota Scheduler (100) or Ticker (20..99,101..1000)
#endif
#ifndef GV_BASE_URL
#define GV_BASE_URL           "https://thelastoutpostworkshop.github.io/microcontroller_devkit/gpio_viewer_1_5/"  // [GvUrl]
//#define GV_BASE_URL           "https://ota.tasmota.com/tasmota/gpioviewer/gpio_viewer_13_4_0/"  // [GvUrl]
#endif

#define GV_KEEP_ALIVE         1000         // milliseconds - If no activity after this do a heap size event anyway

const char *GVRelease = "1.5.6";

/*********************************************************************************************/

// GPIO FUNCTIONS as defined by esp32-hal-gpio.h to be used by ESP8266 too, which uses different numbers
// Also defined in gpio_viewer_1_5 const.ts
#define GV_UNAVAILABLE        -2           // Addition by gpio_viewer_1_5
#define GV_NOT_SET            -1           // Addition by gpio_viewer_1_5
#define GV_NOT_USED           0            // Addition by this driver
#define GV_INPUT              0x01         // Not defined in gpio_viewer_1_5 !?!
#define GV_OUTPUT             0x03
#define GV_PULLUP             0x04
#define GV_INPUT_PULLUP       0x05
#define GV_PULLDOWN           0x08
#define GV_INPUT_PULLDOWN     0x09
#define GV_OPEN_DRAIN         0x10
#define GV_OUTPUT_OPEN_DRAIN  0x13
#define GV_ANALOG             0xC0

#ifdef USE_UNISHOX_COMPRESSION
  #include "./html_compressed/HTTP_GV_PAGE.h"
#else
  #include "./html_uncompressed/HTTP_GV_PAGE.h"
#endif  // USE_UNISHOX_COMPRESSION

const char HTTP_GV_EVENT[] PROGMEM =
  "HTTP/1.1 200 OK\n"
  "Content-Type: text/event-stream;\n"     // Server Sent Event protocol
  "Connection: keep-alive\n"               // Permanent connection
  "Cache-Control: no-cache\n"              // Do not store data into local cache
  "Access-Control-Allow-Origin: *\n\n";    // Enable CORS

enum GVPinTypes {
  GV_DigitalPin = 0,
  GV_PWMPin = 1,
  GV_AnalogPin = 2
};

typedef struct {
  ESP8266WebServer *WebServer;
  Ticker ticker;
  String baseUrl;
  int lastPinStates[MAX_GPIO_PIN];
  int pinmode[MAX_GPIO_PIN];
  uint32_t lastSentWithNoActivity;
  uint32_t freeHeap;
  uint32_t freePSRAM;
  uint16_t sampling;
  uint16_t init_done;
  uint16_t port;
  uint8_t ADCPinsCount;
#ifdef ESP8266
  uint8_t ADCPins[1];
#else  // ESP32
  uint8_t ADCPins[MAX_GPIO_PIN];
  uint8_t TouchPins[MAX_GPIO_PIN];
  uint8_t TouchPinsCount;
#endif  // ESP32
  bool mutex;
  bool sse_ready;
} tGV;
tGV* GV = nullptr;
WiFiClient GVWebClient;

/*********************************************************************************************/

int GetPinMode(uint32_t pin) {
#ifdef ESP8266  
//  if (17 == pin) { return GV_ANALOG; }    
  if (17 == pin) { return GV_INPUT_PULLUP; }  // See Note 20240506
  if (16 == pin) { return GV_NOT_USED; }      // Skip GPIO16
#endif  // ESP8266

  uint32_t bit = digitalPinToBitMask(pin);
  uint32_t port = digitalPinToPort(pin);
  volatile uint32_t *reg = portModeRegister(port);
  if (*reg & bit) { return GV_OUTPUT; }       // ESP8266 = 0x01, ESP32 = 0x03
  // Detecting INPUT_PULLUP doesn't function consistently
//  volatile uint32_t *out = portOutputRegister(port);
//  return ((*out & bit) ? GV_INPUT_PULLUP : GV_INPUT);  // ESP8266 = 0x02 : 0x00, ESP32 = 0x05 : x01
  return GV_INPUT_PULLUP;                     // ESP8266 = 0x02 : 0x00, ESP32 = 0x05 : x01
}

/*-------------------------------------------------------------------------------------------*/

#ifdef ESP32
#ifdef SOC_ADC_SUPPORTED
#include "soc/adc_periph.h"

int8_t GVDigitalPinToAnalogChannel(uint8_t pin) {
  uint8_t channel = 0;
  if (pin < SOC_GPIO_PIN_COUNT) {
    for (uint8_t j = 0; j < SOC_ADC_MAX_CHANNEL_NUM; j++) {
      if (adc_channel_io_map[0][j] == pin) {  // Tasmota supports ADC1 only
        return channel;
      }
      channel++;
    }
  }
  return -1;
}
#endif  // SOC_ADC_SUPPORTED
#endif  // ESP32

/*********************************************************************************************/

bool GVInit(void) {
  if (!GV) {
    // Executed once
    GV = (tGV*)calloc(1, sizeof(tGV));
    if (GV) {
      GV->sampling = (GV_SAMPLING_INTERVAL < 20) ? 20 : GV_SAMPLING_INTERVAL;
      GV->baseUrl = GV_BASE_URL;
      GV->port = GV_PORT;
#ifdef ESP8266
      GV->ADCPins[0] = 17;
      GV->ADCPinsCount = 1;
#else  // ESP32
      int8_t channel;
      for (int i = 0; i < MAX_GPIO_PIN; i++) {
#ifdef SOC_ADC_SUPPORTED
        channel = GVDigitalPinToAnalogChannel(i);
        if (channel != -1) {
          GV->ADCPins[GV->ADCPinsCount++] = i;
        }
#endif  // SOC_ADC_SUPPORTED
        channel = digitalPinToTouchChannel(i);
        if (channel != -1) {
          GV->TouchPins[GV->TouchPinsCount++] = i;
        }
      }
#endif  // ESP32
      return true;
    }
    return false;
  }
  return true;
}

/*-------------------------------------------------------------------------------------------*/

void GVBegin(void) {
  if (GV->WebServer == nullptr) {
    GV->WebServer = new ESP8266WebServer(GV->port);
    // Set CORS headers for global responses
  //  GV->WebServer->sendHeader(F("Access-Control-Allow-Origin"), F("*"));
  //  GV->WebServer->sendHeader(F("Access-Control-Allow-Methods"), F("GET, POST, OPTIONS"));
  //  GV->WebServer->sendHeader(F("Access-Control-Allow-Headers"), F("Content-Type"));
    GV->WebServer->on("/", GVHandleRoot);
    GV->WebServer->on("/events", GVHandleEvents);
    GV->WebServer->on("/release", GVHandleRelease);
    GV->WebServer->on("/free_psram", GVHandleFreePSRam);
    GV->WebServer->on("/sampling", GVHandleSampling);
    GV->WebServer->on("/espinfo", GVHandleEspInfo);
    GV->WebServer->on("/partition", GVHandlePartition);
    GV->WebServer->on("/pinmodes", GVHandlePinModes);
    GV->WebServer->on("/pinfunctions", GVHandlePinFunctions);
    GV->WebServer->begin();
  }
}

/*-------------------------------------------------------------------------------------------*/

void GVStop(void) {
  GV->sse_ready = false;
  GV->ticker.detach();

  GV->WebServer->stop();
  GV->WebServer = nullptr;
}

/*********************************************************************************************/

void GVHandleRoot(void) {
  GVCloseEvent();

  GV->init_done = 2000 / GV->sampling;     // Allow 2 seconds to stabilize on GPIO usage fixing slow browsers
  GV->mutex = false;

  char* content = ext_snprintf_malloc_P(HTTP_GV_PAGE, 
                                        SettingsTextEscaped(SET_DEVICENAME).c_str(),
                                        GV->baseUrl.c_str(),
                                        NetworkAddress().toString().c_str(),
                                        GV->port,
                                        ESP_getFreeSketchSpace() / 1024);
  if (content == nullptr) { return; }      // Avoid crash
  GV->WebServer->send_P(200, "text/html", content);
  free(content);
}

void GVWebserverSendJson(String &jsonResponse) {
#ifdef GV_DEBUG
  AddLog(LOG_LEVEL_DEBUG, PSTR("IOV: GVWebserverSendJson '%s'"), jsonResponse.c_str());
#endif  // GV_DEBUG
  GV->WebServer->send(200, "application/json", jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVHandleEvents(void) {
  GVWebClient = GV->WebServer->client();
  GVWebClient.setNoDelay(true);
//  GVWebClient.setSync(true);

  GV->WebServer->setContentLength(CONTENT_LENGTH_UNKNOWN);  // The payload can go on forever
  GV->WebServer->sendContent_P(HTTP_GV_EVENT);
#ifdef ESP32
  GVWebClient.setSSE(true);
#endif
  GV->sse_ready = true;                                     // Ready for async updates
  if (GV->sampling != 100) {
    GV->ticker.attach_ms(GV->sampling, GVMonitorTask);      // Use Tasmota Scheduler (100) or Ticker (20..99,101..1000)
  }
  AddLog(LOG_LEVEL_DEBUG, PSTR("IOV: Connected"));
}

/*********************************************************************************************/

void GVHandleRelease(void) {
  String jsonResponse = "{\"release\":\"" + String(GVRelease) + "\"}";
  GVWebserverSendJson(jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVHandleFreePSRam(void) {
  String jsonResponse = "{\"freePSRAM\":\"";
#ifdef ESP32
  if (UsePSRAM()) {
    jsonResponse += String(ESP.getFreePsram() / 1024) + " KB\"}";
  } else
#endif  // ESP32
    jsonResponse += "No PSRAM\"}";
  GVWebserverSendJson(jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVHandleSampling(void) {
  String jsonResponse = "{\"sampling\":\"" + String(GV->sampling) + "\"}";
  GVWebserverSendJson(jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVHandleEspInfo(void) {
#ifdef GV_USE_ESPINFO
  String jsonResponse = "{\"chip_model\":\"" + GetDeviceHardware();
  jsonResponse += "\",\"cores_count\":\"" + String(ESP_getChipCores());
  jsonResponse += "\",\"chip_revision\":\"" + String(ESP_getChipRevision());
  jsonResponse += "\",\"cpu_frequency\":\"" + String(ESP.getCpuFreqMHz());
  jsonResponse += "\",\"cycle_count\":" + String(ESP.getCycleCount());
  jsonResponse += ",\"mac\":\"" + ESP_getEfuseMac();

  const FlashMode_t flashMode = ESP.getFlashChipMode(); // enum
  jsonResponse += "\",\"flash_mode\":" + String(flashMode);

#ifdef ESP8266
  jsonResponse += ",\"flash_chip_size\":" + String(ESP.getFlashChipRealSize());
#else   // ESP32
  jsonResponse += ",\"flash_chip_size\":" + String(ESP.getFlashChipSize());
#endif  // ESP32
  jsonResponse += ",\"flash_chip_speed\":" + String(ESP.getFlashChipSpeed());
  jsonResponse += ",\"heap_size\":" + String(ESP_getHeapSize());
  jsonResponse += ",\"heap_max_alloc\":" + String(ESP_getMaxAllocHeap());
  jsonResponse += ",\"psram_size\":" + String(ESP_getPsramSize());
  jsonResponse += ",\"free_psram\":" + String(ESP_getFreePsram());
  jsonResponse += ",\"psram_max_alloc\":" + String(ESP_getMaxAllocPsram());
  jsonResponse += ",\"free_heap\":" + String(ESP_getFreeHeap());
  jsonResponse += ",\"up_time\":\"" + String(millis());
  jsonResponse += "\",\"sketch_size\":" + String(ESP_getSketchSize());

#ifdef ESP8266
  String arduinoCoreVersion = "2.7.7";
#else   // ESP32
  String arduinoCoreVersion = "3.0.4";
#endif  // ESP32
#if defined(ESP_ARDUINO_VERSION_MAJOR) && defined(ESP_ARDUINO_VERSION_MINOR) && defined(ESP_ARDUINO_VERSION_PATCH)
  arduinoCoreVersion = String(ESP_ARDUINO_VERSION_MAJOR) + "." + String(ESP_ARDUINO_VERSION_MINOR) + "." + String(ESP_ARDUINO_VERSION_PATCH);
#endif  // ESP_ARDUINO_VERSION_
  jsonResponse += ",\"arduino_core_version\":\"" + arduinoCoreVersion;

  jsonResponse += "\",\"free_sketch\":" + String(ESP_getFreeSketchSpace());
  jsonResponse += "}";
#else   // No GV_USE_ESPINFO
  String jsonResponse = "{\"chip_model\":\"" + GetDeviceHardware() + "\"}";
#endif  // GV_USE_ESPINFO
  GVWebserverSendJson(jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVHandlePartition(void) {
  String jsonResponse = "["; // Start of JSON array
#ifdef ESP32
  bool firstEntry = true;    // Used to format the JSON array correctly

  esp_partition_iterator_t iter = esp_partition_find(ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_ANY, NULL);
//  esp_partition_iterator_t iter = esp_partition_find(ESP_PARTITION_TYPE_ANY, ESP_PARTITION_SUBTYPE_ANY, NULL);

  // Loop through partitions
  while (iter != NULL) {
    const esp_partition_t *partition = esp_partition_get(iter);

    // Add comma before the next entry if it's not the first
    if (!firstEntry)
    {
      jsonResponse += ",";
    }
    firstEntry = false;

    // Append partition information in JSON format
    jsonResponse += "{";
    jsonResponse += "\"label\":\"" + String(partition->label) + "\",";
    jsonResponse += "\"type\":" + String(partition->type) + ",";
    jsonResponse += "\"subtype\":" + String(partition->subtype) + ",";
    jsonResponse += "\"address\":\"0x" + String(partition->address, HEX) + "\",";
    jsonResponse += "\"size\":" + String(partition->size);
    jsonResponse += "}";

    // Move to next partition
    iter = esp_partition_next(iter);
  }

  // Clean up the iterator
  esp_partition_iterator_release(iter);
#endif  // ESP32

  jsonResponse += "]"; // End of JSON array
  GVWebserverSendJson(jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVHandlePinModes(void) {
  String jsonResponse = "["; // Start of JSON array
  bool firstEntry = true;    // Used to format the JSON array correctly

  for (int i = 0; i < MAX_GPIO_PIN; i++) {
    if (GV->pinmode[i] != GV_NOT_USED) {
      if (!firstEntry)
      {
        jsonResponse += ",";
      }
      firstEntry = false;
      jsonResponse += "{";
      jsonResponse += "\"pin\":\"" + String(i) + "\",";
      jsonResponse += "\"mode\":\"" + String(GV->pinmode[i]) + "\"";
      jsonResponse += "}";
    }
  }
  jsonResponse += "]"; // End of JSON array
  GVWebserverSendJson(jsonResponse);
}

/*-------------------------------------------------------------------------------------------*/

void GVStartPinFunction(const char *pinFunction, String *json) {
  *json += "{\"name\":\"" + String(pinFunction) + "\",\"functions\":[";
}

void GVAddPinFunction(const char *pinName, int pin, String *json) {
  if (!json->endsWith("["))
  {
     *json += ",";
  }

  *json += "{\"function\":\"" + String(pinName) + "\",\"pin\":" + String(pin) + "}";
}

void GVHandlePinFunctions(void) {
  String jsonResponse = "{\"boardpinsfunction\":[";

  // ADC pins
  GVStartPinFunction("ADC", &jsonResponse);
  for (int i = 0; i < GV->ADCPinsCount; i++)
  {
    GVAddPinFunction("ADC", GV->ADCPins[i], &jsonResponse);
  }
  jsonResponse += "]}";

#ifdef ESP32
  // Touch pins
  jsonResponse += ",";
  GVStartPinFunction("Touch", &jsonResponse);
  for (int i = 0; i < GV->TouchPinsCount; i++)
  {
    GVAddPinFunction("Touch", GV->TouchPins[i], &jsonResponse);
  }
  jsonResponse += "]}";
#endif  // ESP32

  jsonResponse += "]}";
  GVWebserverSendJson(jsonResponse);
}

/*********************************************************************************************/

void GVEventDisconnected(void) {
  if (GV->sse_ready) {
    AddLog(LOG_LEVEL_DEBUG, PSTR("IOV: Disconnected"));
  }
  GV->sse_ready = false;                                    // This just stops the event to be restarted by opening root page again
  GV->ticker.detach();
}

/*-------------------------------------------------------------------------------------------*/

void GVCloseEvent(void) {
  if (GV->WebServer) {
    GVEventSend("{}", "close", millis());                   // Closes web page
    GVEventDisconnected();
  }
}

/*-------------------------------------------------------------------------------------------*/

//void GVEventSend(const char *message, const char *event=NULL, uint32_t id=0, uint32_t reconnect=0);
void GVEventSend(const char *message, const char *event, uint32_t id) {
  if (GVWebClient.connected()) {
    // generateEventMessage() in AsyncEventSource.cpp
//    GVWebClient.printf_P(PSTR("retry:1000\nid:%u\nevent:%s\ndata:%s\n\n"), id, event, message);
    GVWebClient.printf_P(PSTR("id:%u\nevent:%s\ndata:%s\n\n"), id, event, message);
  } else {
    GVEventDisconnected();
  }
}

/*********************************************************************************************/

void GVMonitorTask(void) {
  // Monitor GPIO Values
  if (GV->mutex) { return; }
  GV->mutex = true;

  uint32_t originalValue;
  uint32_t pintype;
  bool hasChanges = false;

  String jsonMessage = "{";
  for (uint32_t pin = 0; pin < MAX_GPIO_PIN; pin++) {
    int pinmode = GV_NOT_USED;
    int currentState = 0;

#ifdef ESP32
    // Read PWM GPIO
    int pwm_resolution = ledcReadDutyResolution(pin);
    if (pwm_resolution > 0) {
      pintype = GV_PWMPin;
      pinmode = GV_OUTPUT;
      originalValue = ledcRead2(pin);
      currentState = changeUIntScale(originalValue, 0, pwm_resolution, 0, 255);   // Bring back to 0..255
    }
#endif  // ESP32

#ifdef ESP8266
    // Read PWM GPIO
    int pwm_value = AnalogRead(pin);
    if (pwm_value > -1) {
      pintype = GV_PWMPin;
      pinmode = GV_OUTPUT;
      originalValue = pwm_value;
      currentState = changeUIntScale(originalValue, 0, Settings->pwm_range, 0, 255);  // Bring back to 0..255
    }
#endif  // ESP8266

#ifdef USE_ADC
    else if (AdcPin(pin)) {
      // Read Analog (ADC) GPIO
      pintype = GV_AnalogPin;
//      pinmode = GV_ANALOG;
      pinmode = GV_INPUT_PULLUP;  // See Note 20240506
/*
#ifdef ESP32
      originalValue = AdcRead(pin, 2);
#endif  // ESP32
#ifdef ESP8266
      // Fix exception 9 if using ticker - GV.sampling != 100 caused by delay(1) in AdcRead() (CallChain: (phy)pm_wakeup_init, (adc)test_tout, ets_timer_arm_new, delay, AdcRead, String6concat, MonitorTask)
      originalValue = (GV.sampling != 100) ? analogRead(pin) : AdcRead(pin, 1);
#endif  // ESP8266
*/
      originalValue = AdcRead1(pin);
      currentState = changeUIntScale(originalValue, 0, AdcRange(), 0, 255);   // Bring back to 0..255
    }
#endif  // USE_ADC

    else {
      // Read digital GPIO
      int value = digitalRead(pin);
      originalValue = value;
      if (value == 1) {
        currentState = 256;
//      } else {
//        currentState = 0;
      }
      pintype = GV_DigitalPin;
      pinmode = GetPinMode(pin);
    }

    if (GV->init_done) {
      uint32_t pin_type = GetPin(pin) / 32;
      GV->lastPinStates[pin] = (pin_type != GPIO_NONE) ? -1 : originalValue;  // During init provide configured GPIOs fixing slow browsers
    }
    if (originalValue != GV->lastPinStates[pin]) { 
      GV->pinmode[pin] = pinmode;
      if (hasChanges) { jsonMessage += ","; }
      jsonMessage += "\"" + String(pin) + "\":{\"s\":" + currentState + ",\"v\":" + originalValue + ",\"t\":" + pintype + "}";
      GV->lastPinStates[pin] = originalValue;
      hasChanges = true;
    }
  }
  jsonMessage += "}";
  if (hasChanges) {
    GVEventSend(jsonMessage.c_str(), "gpio-state", millis());
  }

  if (GV->init_done) {
    GV->init_done--;
  }

  uint32_t heap = ESP_getFreeHeap();
  if (heap != GV->freeHeap) {
    // Send freeHeap
    GV->freeHeap = heap;
    char temp[20];
    snprintf_P(temp, sizeof(temp), PSTR("%d KB"), heap / 1024);
    GVEventSend(temp, "free_heap", millis());
    hasChanges = true;
  }

#ifdef ESP32
  if (UsePSRAM()) {
    // Send freePsram
    uint32_t psram = ESP.getFreePsram();
    if (psram != GV->freePSRAM) {
      GV->freePSRAM = psram;
      char temp[20];
      snprintf_P(temp, sizeof(temp), PSTR("%d KB"), psram / 1024);
      GVEventSend(temp, "free_psram", millis());
      hasChanges = true;
    }
  }
#endif  // ESP32

  if (!hasChanges) {
    // Send freeHeap as keepAlive
    uint32_t last_sent = millis() - GV->lastSentWithNoActivity;
    if (last_sent > GV_KEEP_ALIVE) {
      // No activity, resending for pulse
      char temp[20];
      snprintf_P(temp, sizeof(temp), PSTR("%d KB"), heap / 1024);
      GVEventSend(temp, "free_heap", millis());
      GV->lastSentWithNoActivity = millis();
    }
  } else {
    GV->lastSentWithNoActivity = millis();
  }

  GV->mutex = false;
}

/*********************************************************************************************\
 * Commands
\*********************************************************************************************/

const char kGVCommands[] PROGMEM = "GV|"   // Prefix
  "Viewer|Sampling|Port|Url";

void (* const GVCommand[])(void) PROGMEM = {
  &CmndGvViewer, &CmndGvSampling, &CmndGvPort, &CmndGvUrl };

void CmndGvViewer(void) {
  /* GvViewer    - Show current viewer state
     GvViewer 0  - Turn viewer off
     GvViewer 1  - Turn viewer on
     GvViewer 2  - Toggle viewer state
  */
  if (!GVInit()) { return; }
  if ((XdrvMailbox.payload >= 0) && (XdrvMailbox.payload <= 2)) {
    uint32_t state = XdrvMailbox.payload;
    if (2 == state) {                      // Toggle
      state = (GV->WebServer == nullptr) ^1;
    }
    if (state) {                           // On
      GVBegin();
    } else {                               // Off
      GVCloseEvent();                      // Stop current updates
      GVStop();
    }
  }
  if (GV->WebServer) {
    Response_P(PSTR("{\"%s\":\"Active on http://%s:%d/\"}"), XdrvMailbox.command, NetworkAddress().toString().c_str(), GV->port);
  } else {
    ResponseCmndChar_P(PSTR("Stopped"));
  }
}

void CmndGvSampling(void) {
  /* GvSampling             - Show current sampling interval
     GvSampling 1           - Set default sampling interval
     GvSampling 20 .. 1000  - Set sampling interval
  */
  if (!GVInit()) { return; }
  if ((SC_DEFAULT == XdrvMailbox.payload) || ((XdrvMailbox.payload >= 20) && (XdrvMailbox.payload <= 1000))) {
    GVCloseEvent();                        // Stop current updates
    GV->sampling = (SC_DEFAULT == XdrvMailbox.payload) ? GV_SAMPLING_INTERVAL : XdrvMailbox.payload;  // 20 - 1000 milliseconds
  }
  ResponseCmndNumber(GV->sampling);
}

void CmndGvPort(void) {
  /* GvPort      - Show current port
     GvPort 1    - Select default port
     GvPort 5557 - Set port
  */
  if (!GVInit()) { return; }
  if ((XdrvMailbox.payload > 0) && (XdrvMailbox.payload < 65536)) {
    GVCloseEvent();                        // Stop current updates
    GV->port = (SC_DEFAULT == XdrvMailbox.payload) ? GV_PORT : XdrvMailbox.payload;
  }
  ResponseCmndNumber(GV->port);
}

void CmndGvUrl(void) {
  /* GvUrl       - Show current url
     GvUrl 1     - Select default url
     GvUrl https://thelastoutpostworkshop.github.io/microcontroller_devkit/gpio_viewer_1_5/
  */
  if (!GVInit()) { return; }
  if (XdrvMailbox.data_len > 0) {
    GVCloseEvent();                        // Stop current updates
    GV->baseUrl = (SC_DEFAULT == XdrvMailbox.payload) ? GV_BASE_URL : XdrvMailbox.data;
  }
  ResponseCmndChar(GV->baseUrl.c_str());
}

/*********************************************************************************************\
 * GUI
\*********************************************************************************************/
#ifdef USE_WEBSERVER
#define WEB_HANDLE_GV "gv"

const char HTTP_BTN_MENU_GV[] PROGMEM =
  "<p><form action='" WEB_HANDLE_GV "' method='get' target='_blank'><button>" D_GPIO_VIEWER "</button></form></p>";

void GVSetupAndStart(void) {
  if (!HttpCheckPriviledgedAccess()) { return; }

  AddLog(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_GPIO_VIEWER));

  if (!GVInit()) { return; }
  GVBegin();                               // Start WebServer

  char redirect[100];
  snprintf_P(redirect, sizeof(redirect), PSTR("http://%s:%d/"), NetworkAddress().toString().c_str(), GV->port);
  Webserver->sendHeader(F("Location"), redirect);
  Webserver->send(303);
}
#endif  // USE_WEBSERVER

/*********************************************************************************************\
 * Interface
\*********************************************************************************************/

bool Xdrv121(uint32_t function) {
  bool result = false;

  switch (function) {
    case FUNC_COMMAND:
      result = DecodeCommand(kGVCommands, GVCommand);
      break;
#ifdef USE_WEBSERVER
    case FUNC_WEB_ADD_MANAGEMENT_BUTTON:
      if (XdrvMailbox.index) {
        XdrvMailbox.index++;
      } else {
        WSContentSend_PD(HTTP_BTN_MENU_GV);
      }
      break;
    case FUNC_WEB_ADD_HANDLER:
      WebServer_on(PSTR("/" WEB_HANDLE_GV), GVSetupAndStart);
      break;
#endif  // USE_WEBSERVER
  }
  if (GV && (GV->WebServer)) {
    switch (function) {
      case FUNC_LOOP:
        GV->WebServer->handleClient();
        break;
      case FUNC_EVERY_100_MSECOND:
        if (GV->sse_ready && (100 == GV->sampling)) {
          GVMonitorTask();
        }
        break;
      case FUNC_SAVE_BEFORE_RESTART:
        GVCloseEvent();                    // Stop current updates
        break;
      case FUNC_ACTIVE:
        result = true;
        break;
    }
  }
  return result;
}

#endif  // USE_GPIO_VIEWER