// Ch1 : Left
#define DIR_1 8
#define ST_1 9
#define PWM_1 45
#define ENCA_1 2
#define ENCB_1 3

// Ch2 : Right
#define DIR_2 22
#define ST_2 24
#define PWM_2 44
#define ENCA_2 18
#define ENCB_2 19

int setRPM1 = 0;
int setRPM2 = 0;

double kp1 = 0.5, ki1 = 3.0, kd1 = 0.085;
double kp2 = 0.5, ki2 = 3.0, kd2 = 0.085;
double kb1 = 3, kb2 = 3;
double alpha = 0.3;

volatile long encoderPos1 = 0, encoderPos2 = 0;
double v = 0, w = 0;
double rpm1 = 0, rpm2 = 0;
int calPWM1 = 0, calPWM2 = 0;
double error1 = 0, prevError1 = 0, integral1 = 0, derivative1 = 0;
double error2 = 0, prevError2 = 0, integral2 = 0, derivative2 = 0;
double prevRPM1 = 0, prevRPM2 = 0;
double backError1 = 0, backError2 = 0;

const unsigned long interval = 30;
unsigned long prevTime = 0;
double dt = interval / 1000.0;

const double WHEEL_RADIUS = 0.065; // 65mm
const double WHEEL_DISTANCE = 0.437; // 437mm

void doEncoderA1() { if (digitalRead(ENCB_1) == LOW) encoderPos1--; else encoderPos1++; }
void doEncoderB1() { if (digitalRead(ENCA_1) == HIGH) encoderPos1--; else encoderPos1++; }
void doEncoderA2() { if (digitalRead(ENCB_2) == LOW) encoderPos2++; else encoderPos2--; }
void doEncoderB2() { if (digitalRead(ENCA_2) == HIGH) encoderPos2++; else encoderPos2--; }

double calculateRPM(long counts) {
  return ((double)counts / (4096.0 * 2)) * (60.0 / dt);
}

int computePID(double currentRPM, double &error, double &prevError,
               double &integral, double &derivative, int targetRPM,
               double kp, double ki, double kd, bool isMotor1) {
  double absTarget = abs(targetRPM);
  double absCurrent = abs(currentRPM);
  error = absTarget - absCurrent;
  integral += error * dt;

  double rawDerivative = -(absCurrent - (isMotor1 ? prevRPM1 : prevRPM2)) / dt;
  double filteredDeriv = alpha * rawDerivative + (1 - alpha) * (isMotor1 ? derivative1 : derivative2);
  if (isMotor1) prevRPM1 = absCurrent; else prevRPM2 = absCurrent;

  double P = kp * error;
  double I = ki * integral;
  double D = kd * filteredDeriv;
  double output = P + I + D;
  double outputSat = constrain(output, 0, 255);
  double backError = outputSat - output;
  integral += (isMotor1 ? kb1 : kb2) * backError * dt;

  Serial.print(abs(targetRPM)); Serial.print('\t');
  Serial.print(currentRPM, 2); Serial.print('\t');
  if (isMotor1) {
    Serial.print("P1 : "); Serial.print(P, 2); Serial.print('\t');
    Serial.print("I1 : "); Serial.print(I, 2); Serial.print('\t');
    Serial.print("D1 : "); Serial.print(D, 2); Serial.println('\t');
  } else {
    Serial.print("P2 : "); Serial.print(P, 2); Serial.print('\t');
    Serial.print("I2 : "); Serial.print(I, 2); Serial.print('\t');
    Serial.print("D2 : "); Serial.print(D, 2); Serial.println('\t');
    Serial.println("---------------------------------------------------------");
  }

  return (int)(P + I + D);
}

void serialSetTwist() {
  if (Serial.available()) {
    String input = Serial.readStringUntil('\n');
    input.trim();

    int vIndex = input.indexOf('V');
    int wIndex = input.indexOf('W');

    bool vUpdated = false;
    bool wUpdated = false;

    if (vIndex != -1) {
      int end = (wIndex != -1 && wIndex > vIndex) ? wIndex : input.length();
      String vStr = input.substring(vIndex + 1, end);
      vStr.trim();
      double parsedV = vStr.toFloat();
      if (String(parsedV) == vStr || vStr.length() > 0) {
        v = parsedV;
        vUpdated = true;
      }
    }

    if (wIndex != -1) {
      int end = (vIndex != -1 && vIndex > wIndex) ? vIndex : input.length();
      String wStr = input.substring(wIndex + 1, end);
      wStr.trim();
      double parsedW = wStr.toFloat();
      if (String(parsedW) == wStr || wStr.length() > 0) {
        w = parsedW;
        wUpdated = true;
      }
    }

    if (vUpdated || wUpdated) {
      double pkjR = 1;
      double pkjL = 1;
      double rpm_r = (v + (WHEEL_DISTANCE / 2.0) * w) / WHEEL_RADIUS * 60.0 / (2 * PI);
      double rpm_l = (v - (WHEEL_DISTANCE / 2.0) * w) / WHEEL_RADIUS * 60.0 / (2 * PI);
      setRPM1 = (int)(rpm_r * pkjR);
      setRPM2 = (int)(rpm_l * pkjL);

//      Serial.print("Target Updated → ");
//      Serial.print("V: "); Serial.print(v, 3);
//      Serial.print("  W: "); Serial.print(w, 3);
//      Serial.print("  R: "); Serial.print(setRPM1);
//      Serial.print("  L: "); Serial.println(setRPM2);
//    } else {
//      Serial.println("Error : Enter in V0.3 or W-0.2 format.");
    }
  }
}

void setup() {
  Serial.begin(115200);
  pinMode(DIR_1, OUTPUT); pinMode(PWM_1, OUTPUT); pinMode(ST_1, OUTPUT);
  pinMode(ENCA_1, INPUT_PULLUP); pinMode(ENCB_1, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(ENCA_1), doEncoderA1, RISING);
  attachInterrupt(digitalPinToInterrupt(ENCB_1), doEncoderB1, RISING);

  pinMode(DIR_2, OUTPUT); pinMode(PWM_2, OUTPUT); pinMode(ST_2, OUTPUT);
  pinMode(ENCA_2, INPUT_PULLUP); pinMode(ENCB_2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(ENCA_2), doEncoderA2, RISING);
  attachInterrupt(digitalPinToInterrupt(ENCB_2), doEncoderB2, RISING);

  digitalWrite(ST_1, LOW); digitalWrite(ST_2, LOW);
  prevTime = millis();
}

void loop() {
  unsigned long now = millis();
  if (now - prevTime >= interval) {
    prevTime += interval;

    noInterrupts(); long cnt1 = encoderPos1; encoderPos1 = 0;
                   long cnt2 = encoderPos2; encoderPos2 = 0; interrupts();
    rpm1 = calculateRPM(cnt1);
    rpm2 = calculateRPM(cnt2);

  static int zeroRPMCount = 0;
  const int maxZeroRPMCount = 10;  // 10*30ms = 300ms

  if (rpm1 == 0 && rpm2 == 0 && (setRPM1 != 0 || setRPM2 != 0)) {
    zeroRPMCount++;
  } else if (rpm1 == 0 && rpm2 == 0 && setRPM1 == 0 && setRPM2 == 0) {
    if (integral1 != 0 || integral2 != 0) {
      integral1 = 0;
      integral2 = 0;
    }
  } else {
    zeroRPMCount = 0;
  }
  
  if (zeroRPMCount > maxZeroRPMCount) {
    setRPM1 = 0;
    setRPM2 = 0;
    integral1 = 0;
    integral2 = 0;
    calPWM1 = 0;
    calPWM2 = 0;
  }

    calPWM1 = computePID(rpm1, error1, prevError1, integral1, derivative1, setRPM1, kp1, ki1, kd1, true);
    calPWM2 = computePID(rpm2, error2, prevError2, integral2, derivative2, setRPM2, kp2, ki2, kd2, false);

    digitalWrite(DIR_1, setRPM1 >= 0 ? LOW : HIGH);
    digitalWrite(DIR_2, setRPM2 >= 0 ? LOW : HIGH);
    analogWrite(PWM_1, constrain(abs(calPWM1), 0, 255));
    analogWrite(PWM_2, constrain(abs(calPWM2), 0, 255));
  }
  serialSetTwist();
}