#include <EEPROM.h>//https://github.com/espressif/arduino-esp32/tree/master/libraries/EEPROM

const int trigPin = 5;
const int echoPin = 18;
const int FULL_ADD = 1;
const int EMPTY_ADD = 2;
char* FULL_MODE = "F";
char* EMPTY_MODE = "E";
char* NONE_MODE = "N";

//define sound speed in cm/uS
#define SOUND_SPEED 0.034

long duration;
float distanceCm;
float dist = 0;
float cm = 0;
float perc = 0;
float vol = 0;
char* mode;

int full = 10;
int empty = 150;

void setup() {
  mode = NONE_MODE;

  Serial.begin(115200); // Starts the serial communication
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT); // Sets the echoPin as an Input


  full = EEPROM.read(FULL_ADD);
  if (!full) full = 10;
  empty = EEPROM.read(EMPTY_ADD);
  if (!empty) empty = 150;
}

void loop() {

  serialReadVal();
  serialReadMode();

  dist = getDistance();
  if (dist > empty) {
    dist = empty;
  }

  cm = (empty - full) - (dist - full);
  perc = cm / (empty - full) * 100;
  vol = 1500 * perc / 100;

  printData();

  delay(5000);
}

void serialReadVal() {
  if (Serial.available() > 0 && (mode ==  EMPTY_MODE || mode == FULL_MODE) ) {
    Serial.println("READ VAL MODE");
    int serialIn = Serial.read();
    // say what you got:
    Serial.print("I received: ");
    Serial.println(serialIn, DEC);

    if (mode == EMPTY_MODE) {
      empty = 150;
      EEPROM.write(EMPTY_ADD, empty);
    } else if (mode ==  FULL_MODE) {
      full = 10;
      EEPROM.write(FULL_ADD, full);
    }
  }
}

void serialReadMode() {
  if (Serial.available() > 0 && mode == NONE_MODE) {
    String serialIn = Serial.readString();
    serialIn.trim();

    if (serialIn[0] == 'E' ) {
      mode = EMPTY_MODE;
      Serial.println("Set mode E");
    } else if ( serialIn ==  "F") {
      mode = FULL_MODE;
      Serial.println("Set mode F");
    } else {
      Serial.println("Nothing to do with this mode ! " );
    }
  }
}

void printData() {
  Serial.print(dist);
  Serial.println("cm (detected)");

  Serial.print(cm);
  Serial.println("cm of fuel");
  Serial.print(perc);
  Serial.println("% of fuel");
  Serial.print(vol);
  Serial.println("l of fuel");


  Serial.print("Tank is full when ");
  Serial.print(full);
  Serial.println("cm is detected");
  Serial.print("Tank is empty when ");
  Serial.print(empty);
  Serial.println("cm is detected");


  Serial.println("-----------------------------");
}

long getDistance() {
  // Clears the trigPin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);

  // Calculate the distance
  distanceCm = duration * SOUND_SPEED / 2;
  return distanceCm;
}