#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Stepper.h>

#define SCREEN_WIDTH 128 // OLED width,  in pixels
#define SCREEN_HEIGHT 64 // OLED height, in pixels
Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

#define ENCODER_CLK 32
#define ENCODER_DT  33
int encoder_value      =  0;
int encoder_value_last = -1;

#define STEP 200
Stepper myStepper(STEP, 5, 17, 16, 4);

void read_encoder_value() {
  int dtValue = digitalRead(ENCODER_DT);

  if      (dtValue == HIGH && encoder_value != 100) encoder_value += 5;
  else if (dtValue == LOW  && encoder_value != 0)   encoder_value -= 5;

  Serial.print("encoder_value -> ");
  Serial.println(encoder_value);
}

void draw_encoder_value() {
  // https://adafruit.github.io/Adafruit-GFX-Library/html/class_adafruit___g_f_x.html#a6f6f1abccf677eac244fa17d105133ea
  oled.clearDisplay();

  oled.setCursor(14, 1);
  oled.println("0");
  oled.setCursor(49, 1);
  oled.println("speed");
  oled.setCursor(97, 1);
  oled.println("100");

  oled.drawRect(14, 10, 100, 18, SSD1306_WHITE);
  oled.fillRect(16, 12, (int) (96 * (encoder_value / 100.0)),  14, SSD1306_WHITE);

  oled.display();
}



void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");

  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("failed to start SSD1306 OLED"));
    while (1);
  }
  
  oled.setTextSize(1);
  oled.setTextColor(WHITE);

  pinMode(ENCODER_CLK, INPUT);
  pinMode(ENCODER_DT, INPUT);
  attachInterrupt(digitalPinToInterrupt(ENCODER_CLK), read_encoder_value, FALLING);
}

void loop() {
  // put your main code here, to run repeatedly:
  if (encoder_value != encoder_value_last) {
    draw_encoder_value();
    encoder_value_last = encoder_value;
  }

  if (encoder_value != 0) {
    myStepper.setSpeed((int) (encoder_value * 1.5));
    myStepper.step(STEP/10);
  }

  delay(5); // this speeds up the simulation
}