/*
  ESP8266/ESP32 publish the RSSI as the WiFi signal strength to ThingSpeak channel.
  This example is for explaining how to use the AutoConnect library.

  In order to execute this example, the ThingSpeak account is needed. Sing up
  for New User Account and create a New Channel via My Channels.
  For details, please refer to the project page.
  https://hieromon.github.io/AutoConnect/examples/index.html#used-with-mqtt-as-a-client-application

  Also, this example uses AutoConnectAux menu customization which stored in SPIFFS.
  To evaluate this example, you upload the contents as mqtt_setting.json of
  the data folder with MkSPIFFS Tool ("ESP8266 Sketch Data Upload" in Tools menu
  in Arduino IDE).

  This example is based on the thinkspeak.com environment as of Dec. 20, 2018.
  Copyright (c) 2018 Hieromon Ikasamo.
  This software is released under the MIT License.
  https://opensource.org/licenses/MIT
*/

#if defined(ARDUINO_ARCH_ESP8266)
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#elif defined(ARDUINO_ARCH_ESP32)
#include <WiFi.h>
#include <SPIFFS.h>
#endif
#include <FS.h>
#include <PubSubClient.h>
#include <AutoConnect.h>

#define PARAM_FILE      "/param.json"
#define AUX_MQTTSETTING "/mqtt_setting"
#define AUX_MQTTSAVE    "/mqtt_save"
#define AUX_MQTTCLEAR   "/mqtt_clear"

AutoConnect  portal;
AutoConnectConfig config;
WiFiClient   wifiClient;
PubSubClient mqttClient(wifiClient);
String  serverName;
String  channelId;
String  userKey;
String  apiKey;
String  apid;
String  hostName;
unsigned int  updateInterval = 0;
unsigned long lastPub = 0;

#define MQTT_USER_ID  "anyone"

bool mqttConnect() {
  static const char alphanum[] = "0123456789"
                                 "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                 "abcdefghijklmnopqrstuvwxyz";  // For random generation of client ID.
  char    clientId[9];

  uint8_t retry = 10;
  while (!mqttClient.connected()) {
    if (serverName.length() <= 0)
      break;

    mqttClient.setServer(serverName.c_str(), 1883);
    Serial.println(String("Attempting MQTT broker:") + serverName);

    for (uint8_t i = 0; i < 8; i++) {
      clientId[i] = alphanum[random(62)];
    }
    clientId[8] = '\0';

    if (mqttClient.connect(clientId, MQTT_USER_ID, userKey.c_str())) {
      Serial.println("Established:" + String(clientId));
      return true;
    } else {
      Serial.println("Connection failed:" + String(mqttClient.state()));
      if (!--retry)
        break;
    }
    delay(3000);
  }
  return false;
}

void mqttPublish(String msg) {
  String path = String("channels/") + channelId + String("/publish/") + apiKey;
  int    tLen = path.length();
  char   topic[tLen];
  path.toCharArray(topic, tLen + 1);

  int    mLen = msg.length();
  char   payload[mLen];
  msg.toCharArray(payload, mLen + 1);

  mqttClient.publish(topic, payload);
}

int getStrength(uint8_t points) {
  uint8_t sc = points;
  long    rssi = 0;

  while (sc--) {
    rssi += WiFi.RSSI();
    delay(20);
  }
  return points ? static_cast<int>(rssi / points) : 0;
}

String loadParams(AutoConnectAux& aux, PageArgument& args) {
  (void)(args);
  SPIFFS.begin();
  File param = SPIFFS.open(PARAM_FILE, "r");
  if (param) {
    aux.loadElement(param);
    param.close();
  }
  else
    Serial.println(PARAM_FILE " open failed");
  SPIFFS.end();
  return "";
}

String saveParams(AutoConnectAux& aux, PageArgument& args) {
  serverName = args.arg("mqttserver");
  serverName.trim();

  channelId = args.arg("channelid");
  channelId.trim();
  
  userKey = args.arg("userkey");
  userKey.trim();
  
  apiKey = args.arg("apikey");
  apiKey.trim();
  
  String upd = args.arg("period");
  updateInterval = upd.substring(0, 2).toInt() * 1000;

  String uniqueid = args.arg("uniqueid");

  hostName = args.arg("hostname");
  hostName.trim();
  
  // In order to retrieve the elements of /mqtt_setting,
  // it is necessary to get the AutoConnectAux object of /mqtt_setting.
  SPIFFS.begin();
  File param = SPIFFS.open(PARAM_FILE, "w");
  portal.aux("/mqtt_setting")->saveElement(param, { "mqttserver", "channelid", "userkey", "apikey", "period", "uniqueid", "hostname" });
  param.close();
  SPIFFS.end();

  // Echo back saved parameters to AutoConnectAux page.
  AutoConnectText&  echo = aux.getElement<AutoConnectText>("parameters");
  echo.value = "Server: " + serverName + "<br>";
  echo.value += "Channel ID: " + channelId + "<br>";
  echo.value += "User Key: " + userKey + "<br>";
  echo.value += "API Key: " + apiKey + "<br>";
  echo.value += "Update period: " + String(updateInterval / 1000) + " sec.<br>";
  echo.value += "Use APID unique: " + uniqueid + "<br>";
  echo.value += "ESP host name: " + hostName + "<br>";

  return "";
}

void handleRoot() {
  String  content =
    "<html>"
    "<head>"
    "<meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">"
    "</head>"
    "<body>"
    "<iframe width=\"450\" height=\"260\" style=\"transform:scale(0.79);-o-transform:scale(0.79);-webkit-transform:scale(0.79);-moz-transform:scale(0.79);-ms-transform:scale(0.79);transform-origin:0 0;-o-transform-origin:0 0;-webkit-transform-origin:0 0;-moz-transform-origin:0 0;-ms-transform-origin:0 0;border: 1px solid #cccccc;\" src=\"https://thingspeak.com/channels/454951/charts/1?bgcolor=%23ffffff&color=%23d62020&dynamic=true&type=line\"></iframe>"
    "<p style=\"padding-top:10px;text-align:center\">" AUTOCONNECT_LINK(COG_24) "</p>"
    "</body>"
    "</html>";

#if defined(ARDUINO_ARCH_ESP8266)
  ESP8266WebServer& server = portal.host();
#elif defined(ARDUINO_ARCH_ESP32)
  WebServer&  server = portal.host();
#endif
  server.send(200, "text/html", content);
}

// Clear channel using Thingspeak's API.
void handleClearChannel() {
  HTTPClient  httpClient;
  String  endpoint = serverName;
  endpoint.replace("mqtt", "api");
  String  delUrl = "http://" + endpoint + "/channels/" + channelId + "/feeds.json?api_key=" + userKey;

  Serial.println(delUrl + ":" + String(httpClient.begin(delUrl)));
  Serial.println("res:" + String(httpClient.sendRequest("DELETE")));
  String  res = httpClient.getString();
  httpClient.end();

  // Returns the redirect response. The page is reloaded and its contents
  // are updated to the state after deletion.
#if defined(ARDUINO_ARCH_ESP8266)
  ESP8266WebServer& server = portal.host();
#elif defined(ARDUINO_ARCH_ESP32)
  WebServer&  server = portal.host();
#endif
  server.sendHeader("Location", String("http://") + server.client().localIP().toString() + String("/"));
  server.send(302, "text/plain", "");
  server.client().flush();
  server.client().stop();
}

// Load AutoConnectAux JSON from SPIFFS.
bool loadAux(const String auxName) {
  bool  rc = false;
  String  fn = auxName + ".json";
  File fs = SPIFFS.open(fn.c_str(), "r");
  if (fs) {
    rc = portal.load(fs);
    fs.close();
  }
  else
    Serial.println("SPIFFS open failed: " + fn);
  return rc;
}

void setup() {
  delay(1000);
  Serial.begin(115200);
  Serial.println();

  SPIFFS.begin();
  loadAux(AUX_MQTTSETTING);
  loadAux(AUX_MQTTSAVE);
  SPIFFS.end();

  AutoConnectAux* setting = portal.aux(AUX_MQTTSETTING);
  if (setting) {
    AutoConnectCheckbox&  uniqueidElm = setting->getElement<AutoConnectCheckbox>("uniqueid");
    AutoConnectInput&     hostnameElm = setting->getElement<AutoConnectInput>("hostname");
    if (uniqueidElm.checked) {
      config.apid = String("ESP") + "_" + String(ESP.getChipId(), HEX);
    }
    if (hostnameElm.value.length()) {
      config.hostName = hostnameElm.value;
    }
    config.bootUri = AC_ONBOOTURI_HOME;
    config.homeUri = "/";
    portal.config(config);

    portal.on(AUX_MQTTSETTING, loadParams);
    portal.on(AUX_MQTTSAVE, saveParams);
  }
  else
    Serial.println("aux. load error");

  Serial.print("WiFi ");
  if (portal.begin()) {
    Serial.println("connected:" + WiFi.SSID());
    Serial.println("IP:" + WiFi.localIP().toString());
  } else {
    Serial.println("connection failed:" + String(WiFi.status()));
    while (1) {
      delay(100);
      yield();
    }
  }

#if defined(ARDUINO_ARCH_ESP8266)
  ESP8266WebServer& server = portal.host();
#elif defined(ARDUINO_ARCH_ESP32)
  WebServer&  server = portal.host();
#endif
  server.on("/", handleRoot);
  server.on(AUX_MQTTCLEAR, handleClearChannel);
}

void loop() {
  if (updateInterval > 0) {
    if (millis() - lastPub > updateInterval) {
      if (!mqttClient.connected()) {
        mqttConnect();
      }
      String item = String("field1=") + String(getStrength(7));
      mqttPublish(item);
      mqttClient.loop();
      lastPub = millis();
    }
  }
  portal.handleClient();
}