#include <TimeLib.h>
#include <NTPClient.h>
#include <SoftwareSerial.h>
#include <ESP8266WiFi.h>
#include <ESP8266mDNS.h>
#include <ESP8266HTTPClient.h>
#include <WiFiUdp.h>
#include <ArduinoOTA.h>
#include <Button2.h>
#include <Timer.h>
#include "CRC16.h"
#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Fonts/Org_01.h>
#include <Adafruit_PCD8544.h>

// Function prototypes
void reboot();
time_t NTPgetTime();
void drawMenu();

// Time related settings
Timer t;
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "europe.pool.ntp.org", 3600, 10000);

// Display settings
//// Software SPI (slower updates, more flexible pin options):
//// pin 7 - Serial clock out (SCLK)
//// pin 6 - Serial data out (DIN)
//// pin 5 - Data/Command select (D/C)
//// pin 4 - LCD chip select (CS)
//// pin 3 - LCD reset (RST)
Adafruit_PCD8544 display = Adafruit_PCD8544(D7, D6, D5, D4, D3);
int tab = 0;
int tabCount = 3;

// LED settings
#define ledPin D8
int ledBrightness = 192;
void ledOff();
int ledTimeout;

// Button settings
#define buttonPin D2
Button2 button = Button2(buttonPin);

// Wifi Settings
const char *ssid = "*";
const char *password = "*";
const char *hostName = "ESPP1Meter";

// Server settings
const char *apiIP = "192.168.2.6";
const int apiPort = 3000;
const char *apiKey = "*";
const int gasIdx = 291;
const int energyIdx = 294;
const bool outputOnSerial = false;

// Statistics variables
unsigned long telegramsTotal = 0;
unsigned long telegramsInvalid = 0;
unsigned long postedTotal = 0;
unsigned long postedFailed = 0;

// Vars to store meter readings
long mEVLT = 0; //Meter reading Electrics - consumption low tariff
long mEVHT = 0; //Meter reading Electrics - consumption high tariff
long mEOLT = 0; //Meter reading Electrics - return low tariff
long mEOHT = 0; //Meter reading Electrics - return high tariff
long mEAV = 0;  //Meter reading Electrics - Actual consumption
long mEAT = 0;  //Meter reading Electrics - Actual return
long mGAS = 0;  //Meter reading Gas
long prevGAS = 0;

#define MAXLINELENGTH 128 // longest normal line is 47 char (+3 for \r\n\0)
char telegram[MAXLINELENGTH];
unsigned int currentCRC = 0;

// P1 Serial settings
#define SERIAL_RX D1                           // pin for SoftwareSerial RX
SoftwareSerial mySerial(SERIAL_RX, -1, false); // (RX, TX, inverted)

void setup()
{
  // Init Serial
  Serial.begin(115200);
  delay(50);

  // Init LED
  pinMode(ledPin, OUTPUT);
  analogWrite(ledPin, ledBrightness);

  // Init Button
  button.setReleasedHandler(press);

  // Init Display
  display.begin();
  display.setContrast(50);
  display.setFont(&Org_01);
  drawMenu();

  // Init WiFi
  WiFi.mode(WIFI_STA);

  display.println("Connecting to:");
  display.print(" ");
  display.println(ssid);
  display.display();

  WiFi.begin(ssid, password);

  while (WiFi.waitForConnectResult() != WL_CONNECTED)
  {
    Serial.println("Connection Failed! Rebooting...");
    drawMenu();
    display.println("Connection Failed!");
    display.display();
    delay(5000);
    ESP.restart();
  }

  // Init P1 Serial
  mySerial.begin(115200);

  // Init ArduinoOTA
  //// Port defaults to 8266
  ArduinoOTA.setPort(8266);

  //// Hostname defaults to esp8266-[ChipID]
  ArduinoOTA.setHostname(hostName);

  //// No authentication by default
  // ArduinoOTA.setPassword((const char *)"123");

  ArduinoOTA.onStart([]() {
    drawMenu();
    display.println("OTA Update");
    display.display();

    Serial.println("Start");
  });
  ArduinoOTA.onEnd([]() {
    Serial.println("\nEnd");
  });
  ArduinoOTA.onProgress([](unsigned int progress, unsigned int total) {
    drawMenu();
    display.println("OTA Update");
    display.printf("Progress: %u%%\r", (progress / (total / 100)));
    display.display();

    Serial.printf("Progress: %u%%\r", (progress / (total / 100)));
  });
  ArduinoOTA.onError([](ota_error_t error) {
    drawMenu();
    display.println("OTA Update");
    display.printf("Error[%u]: ", error);
    display.display();

    Serial.printf("Error[%u]: ", error);
    if (error == OTA_AUTH_ERROR)
      Serial.println("Auth Failed");
    else if (error == OTA_BEGIN_ERROR)
      Serial.println("Begin Failed");
    else if (error == OTA_CONNECT_ERROR)
      Serial.println("Connect Failed");
    else if (error == OTA_RECEIVE_ERROR)
      Serial.println("Receive Failed");
    else if (error == OTA_END_ERROR)
      Serial.println("End Failed");
  });
  ArduinoOTA.begin();

  // Init Time
  timeClient.begin();

  time_t test = NTPgetTime();
  while (test < 10000)
  {
    test = NTPgetTime();
  }

  setTime(NTPgetTime());
  getExternalTime NtpTime = &NTPgetTime;
  setSyncProvider(NtpTime);
  setSyncInterval(3600);

  display.println("Time set");
  display.display();
  delay(1000);

  // Exit setup
  drawTab(2);
  ledTimeout = t.after(5000, ledOff, (void *)0);
}

// Reboot the ESP
void reboot()
{
  drawMenu();
  display.println("Scheduled reboot");
  display.display();
  delay(5000);
  ESP.restart();
}

// Update Time
time_t NTPgetTime()
{
  timeClient.update();
  return timeClient.getEpochTime();
}

// Turn of the backlight LEDs
void ledOff(void *context)
{
  tab = 0;
  drawTab(tab);
  analogWrite(ledPin, 0);
}

// Button action
void press(Button2 &btn)
{
  analogWrite(ledPin, ledBrightness);
  t.stop(ledTimeout);
  ledTimeout = t.after(10000, ledOff, (void *)0);

  if ((tab + 1) == tabCount)
  {
    tab = 0;
  }
  else
  {
    tab++;
  }
  drawTab(tab);
}

// Draw top bar
void drawMenu()
{
  display.clearDisplay();
  display.setCursor(0, 4);
  display.println("P1 Reader");
  display.drawLine(0, 6, 84, 6, 1);

  display.display();
  display.setCursor(0, 12);
}

void drawTab(int no)
{
  drawMenu();
  switch (no)
  {
  // Network
  case 0:
    drawMenu();

    // SSID
    display.println("Connected to:");
    display.print(" ");
    display.println(ssid);

    // Own IP
    display.println("IP address: ");
    display.print(" ");
    display.println(WiFi.localIP());

    // Target server
    display.println("Target host: ");
    display.print(" ");
    display.println(String(apiIP) + ":" + String(apiPort));
    break;

  // Stats
  case 1:
    drawMenu();

    // Telegrams
    display.println("Telegrams");
    display.print(" Total: ");
    display.println(String(telegramsTotal));
    display.print(" Invalid: ");
    display.println(String(telegramsInvalid));

    // Posted
    display.println("Posted");
    display.print(" Total: ");
    display.println(String(postedTotal));
    display.print(" Failed: ");
    display.println(String(postedFailed));
    break;

  // Time
  case 2:
    display.println("Current time:");

    // Time
    display.print(" ");
    if (hour() < 10)
    {
      display.print("0");
    }
    display.print(hour());
    display.print(":");
    if (minute() < 10)
    {
      display.print("0");
    }
    display.println(minute());

    // Date
    display.print(" ");
    if (day() < 10)
    {
      display.print("0");
    }
    display.print(day());
    display.print("-");
    if (month() < 10)
    {
      display.print("0");
    }
    display.print(month());
    display.print("-");
    display.println(year());
    break;
  }
  display.display();
}

// Send data to server
bool Send(int idx, int nValue, char *sValue)
{
  HTTPClient http;
  bool retVal = false;
  char httpRequestData[255];

  // "http://%s:%d/json.htm?type=command&param=udevice&idx=%d&nvalue=%d&svalue=%s"
  // "api_key=tPmAT5Ab3j7F9&sensor=BME280&value1=24.25&value2=49.54&value3=1005.14"
  sprintf(httpRequestData, "api_key=%s&type=%d&nval=%d&sval=%s", apiKey, idx, nValue, sValue);

  Serial.printf("[HTTP] GET... URL: %s\n", httpRequestData);

  http.begin(String("http://" + String(apiIP) + ":" + String(apiPort))); //HTTP
  http.addHeader("Content-Type", "application/x-www-form-urlencoded");

  postedTotal++;
  int httpCode = http.POST(httpRequestData);
  // httpCode will be negative on error
  if (httpCode > 0)
  { // HTTP header has been send and Server response header has been handled
    Serial.printf("[HTTP] GET... code: %d\n", httpCode);

    // file found at server
    if (httpCode == HTTP_CODE_OK)
    {
      String payload = http.getString();
      retVal = true;
    }
  }
  else
  {
    postedFailed++;
    Serial.printf("[HTTP] GET... failed, error: %s\n", http.errorToString(httpCode).c_str());
  }
  http.end();
  return retVal;
}

// Update Gas info
void UpdateGas()
{
  if (prevGAS != mGAS)
  {
    char sValue[10];
    sprintf(sValue, "%d", mGAS);
    if (Send(gasIdx, 0, sValue))
      prevGAS = mGAS;
  }
}

// Update Electricity info
void UpdateElectricity()
{
  char sValue[255];
  sprintf(sValue, "%d;%d;%d;%d;%d;%d", mEVLT, mEVHT, mEOLT, mEOHT, mEAV, mEAT);
  Send(energyIdx, 0, sValue);
}

// Check if value is number
bool isNumber(char *res, int len)
{
  for (int i = 0; i < len; i++)
  {
    if (((res[i] < '0') || (res[i] > '9')) && (res[i] != '.' && res[i] != 0))
    {
      return false;
    }
  }
  return true;
}

// Find char in array
int FindCharInArrayRev(char array[], char c, int len)
{
  for (int i = len - 1; i >= 0; i--)
  {
    if (array[i] == c)
    {
      return i;
    }
  }
  return -1;
}

// Check if value is valid
long getValidVal(long valNew, long valOld, long maxDiffer)
{
  //check if the incoming value is valid
  if (valOld > 0 && ((valNew - valOld > maxDiffer) && (valOld - valNew > maxDiffer)))
    return valOld;
  return valNew;
}

// Get value from char buffer
long getValue(char *buffer, int maxlen)
{
  int s = FindCharInArrayRev(buffer, '(', maxlen - 2);
  if (s < 8)
    return 0;
  if (s > 32)
    s = 32;
  int l = FindCharInArrayRev(buffer, '*', maxlen - 2) - s - 1;
  if (l < 4)
    return 0;
  if (l > 12)
    return 0;
  char res[16];
  memset(res, 0, sizeof(res));

  if (strncpy(res, buffer + s + 1, l))
  {
    if (isNumber(res, l))
    {
      return (1000 * atof(res));
    }
  }
  return 0;
}

// Decode P1 telegram
bool decodeTelegram(int len)
{
  //need to check for start
  int startChar = FindCharInArrayRev(telegram, '/', len);
  int endChar = FindCharInArrayRev(telegram, '!', len);
  bool validCRCFound = false;
  if (startChar >= 0)
  {
    //start found. Reset CRC calculation
    currentCRC = CRC16(0x0000, (unsigned char *)telegram + startChar, len - startChar);
    if (outputOnSerial)
    {
      for (int cnt = startChar; cnt < len - startChar; cnt++)
        Serial.print(telegram[cnt]);
    }
    Serial.println("Start found!");
    telegramsTotal++;
  }
  else if (endChar >= 0)
  {
    //add to crc calc
    currentCRC = CRC16(currentCRC, (unsigned char *)telegram + endChar, 1);
    char messageCRC[5];
    strncpy(messageCRC, telegram + endChar + 1, 4);
    messageCRC[4] = 0; //thanks to HarmOtten (issue 5)
    if (outputOnSerial)
    {
      for (int cnt = 0; cnt < len; cnt++)
        Serial.print(telegram[cnt]);
    }
    validCRCFound = (strtol(messageCRC, NULL, 16) == currentCRC);
    if (validCRCFound)
    {
      Serial.println("\nVALID CRC FOUND!");
    }
    else
    {
      Serial.println("\nINVALID CRC FOUND!");
      telegramsInvalid++;
    }
    currentCRC = 0;
  }
  else
  {
    currentCRC = CRC16(currentCRC, (unsigned char *)telegram, len);
    if (outputOnSerial)
    {
      for (int cnt = 0; cnt < len; cnt++)
        Serial.print(telegram[cnt]);
    }
  }

  long val = 0;
  long val2 = 0;
  // 1-0:1.8.1(000992.992*kWh)
  // 1-0:1.8.1 = Elektra verbruik laag tarief (DSMR v4.0)
  if (strncmp(telegram, "1-0:1.8.1", strlen("1-0:1.8.1")) == 0)
    mEVLT = getValue(telegram, len);

  // 1-0:1.8.2(000560.157*kWh)
  // 1-0:1.8.2 = Elektra verbruik hoog tarief (DSMR v4.0)
  if (strncmp(telegram, "1-0:1.8.2", strlen("1-0:1.8.2")) == 0)
    mEVHT = getValue(telegram, len);

  // 1-0:2.8.1(000348.890*kWh)
  // 1-0:2.8.1 = Elektra opbrengst laag tarief (DSMR v4.0)
  if (strncmp(telegram, "1-0:2.8.1", strlen("1-0:2.8.1")) == 0)
    mEOLT = getValue(telegram, len);

  // 1-0:2.8.2(000859.885*kWh)
  // 1-0:2.8.2 = Elektra opbrengst hoog tarief (DSMR v4.0)
  if (strncmp(telegram, "1-0:2.8.2", strlen("1-0:2.8.2")) == 0)
    mEOHT = getValue(telegram, len);

  // 1-0:1.7.0(00.424*kW) Actueel verbruik
  // 1-0:2.7.0(00.000*kW) Actuele teruglevering
  // 1-0:1.7.x = Electricity consumption actual usage (DSMR v4.0)
  if (strncmp(telegram, "1-0:1.7.0", strlen("1-0:1.7.0")) == 0)
    mEAV = getValue(telegram, len);

  if (strncmp(telegram, "1-0:2.7.0", strlen("1-0:2.7.0")) == 0)
    mEAT = getValue(telegram, len);

  // 0-1:24.2.1(150531200000S)(00811.923*m3)
  // 0-1:24.2.1 = Gas (DSMR v4.0) on Kaifa MA105 meter
  if (strncmp(telegram, "0-1:24.2.1", strlen("0-1:24.2.1")) == 0)
    mGAS = getValue(telegram, len);

  return validCRCFound;
}

// Read P1 telegram
void readTelegram()
{
  if (mySerial.available())
  {
    memset(telegram, 0, sizeof(telegram));
    while (mySerial.available())
    {
      int len = mySerial.readBytesUntil('\n', telegram, MAXLINELENGTH);
      telegram[len] = '\n';
      telegram[len + 1] = 0;
      yield();
      if (decodeTelegram(len + 1))
      {
        UpdateElectricity();
        UpdateGas();
      }
    }
  }
}

void loop()
{
  if (hour() == 0 && minute() == 0 && second() == 0)
  {
    reboot();
  }

  readTelegram();

  button.loop();

  t.update();

  ArduinoOTA.handle();
}