// For: 
//   https://forum.arduino.cc/t/arduino-photo-interrupter-stepper-motor-project/1040942
//
// Using the "StepperOneStepAtATime" from:
//   https://docs.arduino.cc/learn/electronics/stepper-motor
//
//
// Something bad happened here. I started coding and coding and coding, 
// but in the end there was no real plan for the structure or a full safety check.
// That's just wrong. This is a beginners sketch.
//

#include <Stepper.h>

const int stepsPerRevolution = 200;  // depends on the stepper motor

Stepper myStepper(stepsPerRevolution, 11, 12, 10, 9);

const int ledPin = 3;         // A PWM pin for the LED
const int buttonPin = 5;      // HIGH if pressed
const int photoUpperPin = 6;  // Upper photointerrupter, active LOW
const int photoLowerPin = 4;  // Lower photointerrupter, active LOW

int state;                    // +1 is up, -1 is down, 0 is not moving
int count;                    // counts the number of steps

int lastButtonState;          // for the State Change Detection for the button

const int safetyDistancePhoto = 200;  // steps to be sure that photointerruptor is released

void setup() 
{
  Serial.begin(115200);
  Serial.println( F("Hello, the sketch is running."));
  Serial.println( F("Slide the switches to the left to for the upper and lower signals."));

  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
  pinMode(photoUpperPin, INPUT_PULLUP);
  pinMode(photoLowerPin, INPUT_PULLUP);

  myStepper.setSpeed(20);     // This also works with single steps

  // Initialize variables.
  // Normally, the stepper motor should go to the default position if it is in the middel.
  // Check if it is already in a position.
  state = 0;                  // default, not moving
  count = 0;
  lastButtonState = LOW;      // active HIGH, assuming button is not pressed.

  // Blink the led, just for fun.
  for( int i=0; i<5; i++)
  {
    digitalWrite( ledPin, HIGH);
    delay( 200);
    digitalWrite( ledPin, LOW);
    delay( 200);
  }

  Serial.println( F("Press the button to move up."));
}

void loop()
{
  if( state == 0)                                  // not moving ?
  {
    // The stepper motor is not moving.
    // The position should be in the upper or lower position.
    // Check if the button is pressed.

    int buttonState = digitalRead( buttonPin);     // debouncing later on with delay
    if( buttonState == HIGH and lastButtonState == LOW)  // button was just pressed ?
    {
      // Check the photointerruptors to see where it is
      int photoUp = digitalRead( photoUpperPin);   // upper photointerruptor
      int photoDown = digitalRead( photoLowerPin); // lower photointerruptor

      if( photoUp == LOW and photoDown == HIGH)    // in highest position ?
      {
        state = -1;                                // going down
        count = 0;                                 // count the steps
        Serial.println( F("Going down..."));
      }
      else if( photoUp == HIGH and photoDown == LOW)  // in lowest position ?
      {
        state = +1;                                // going up
        count = 0;                                 // count the steps
        Serial.println( F("Going up..."));
      }
      else if( photoUp == LOW and photoDown == LOW)
      {
        Serial.println( F("Error, both photointerruptors are active."));
        Serial.println( F("Not moving for safety."));
      }
      else if( photoUp == HIGH and photoDown == HIGH)
      {
        Serial.println( F("Error, position unknown."));
        Serial.println( F("No photointerruptor is active."));
        Serial.println( F("Not moving for safety."));
      }
    }
    lastButtonState = buttonState;
    delay( 20);                                    // an ugly way to debounce the button
  }
  else
  {
    // The stepper is moving, check the photointerruptors after each step.
    myStepper.step( state);                        // make one step
    count++;                                       // increment number of steps

    int photoUp = digitalRead( photoUpperPin);     // upper photointerruptor
    int photoDown = digitalRead( photoLowerPin);   // lower photointerruptor
    
    if( state == +1 and photoUp == LOW)            // reached the upper limit ?
    {
      state = 0;                                   // stop the stepper
      Serial.print( F("Reached Upper after "));
      Serial.print( count);
      Serial.println( F(" steps."));
      Serial.println( F("Press the button to move down."));
    }
    else if( state == -1 and photoDown == LOW)    // reached the lower limit ?
    {
      state = 0;
      Serial.print( F("Reached Lower after "));
      Serial.print( count);
      Serial.println( F(" steps."));
      Serial.println( F("Press the button to move up."));
    }
    else if( state == +1 and photoDown == LOW and count > safetyDistancePhoto)
    {
      Serial.println( F("Error, lower switch did not release while going up."));
      Serial.println( F("Stopped for safety."));
      state = 0;
    }
    else if( state == -1 and photoUp == LOW and count > safetyDistancePhoto)
    {
      Serial.println( F("Error, upper switch did not release while going down."));
      Serial.println( F("Stopped for safety."));
      state = 0;
    }
    else if( photoUp == LOW and photoDown == LOW)
    {
      Serial.println( F("Error, both photointerruptors activated."));
      Serial.println( F("Stopped for safety."));
      state = 0;
   }
  }
}