// https://wokwi.com/projects/410458155479810049

#define pin_LED 18
#define pin_BTN_red 25
#define pin_BTN_yellow 26
#define pin_BTN_green 27

long timer = 0;
const long period_sleep   = 10000;
const long period_warmup  =  4000;
const long period_measure =  7000;

String mode = "uninitialized"; 
String mode_new = "cyclic";
String state = "uninitialized";

int btn_red, btn_yellow, btn_green;

void setup() {
  Serial.begin(115200);

  // config GPIO21 as input pin and enable the internal pull-up resistor
  pinMode(pin_BTN_green, INPUT_PULLUP); 
  pinMode(pin_BTN_yellow, INPUT_PULLUP); 
  pinMode(pin_BTN_red, INPUT_PULLUP); 
  pinMode(pin_LED, OUTPUT);
}

void loop() {

  if (digitalRead(pin_BTN_green) == LOW) { mode_new = "on"; };
  if (digitalRead(pin_BTN_yellow) == LOW) { mode_new = "cyclic"; };
  if (digitalRead(pin_BTN_red) == LOW) { mode_new = "off"; };

  if (mode_new != mode) {
    mode = mode_new;
    if ((mode == "on") or (mode == "cyclic")) { 
      if ((state != "measure") and (state != "go.warmup") and (state != "warmup")) {
        state = "go.warmup"; 
      }
    }
    if (mode == "off") { 
      if ((state != "sleep") and (state != "go.sleep")) { state = "go.sleep"; }
    }
    Serial.print("--> CHANGE MODE to mode="); Serial.print(mode); Serial.print(" | state="); Serial.println(state);
  }

  if (state == "go.warmup") { 
    state = "warmup";
    timer = millis() + period_warmup;
    digitalWrite(pin_LED, HIGH); // start device
  }

  if ((state == "warmup") and (millis() > timer)) {
    state = "measure";
    timer = millis() + period_measure;
  }

  if ((state == "measure") and (mode == "cyclic") and (millis() > timer)) {
    state = "go.sleep";
  }

  if (state == "go.sleep") {
    state = "sleep";
    timer = millis() + period_sleep;
    digitalWrite(pin_LED, LOW); // stop device
  }

  if ((state == "sleep") and (mode == "cyclic") and (millis() > timer)) {
    state = "go.warmup";
  }

  if (state == "warmup") {
      Serial.println("... emptying the stream");
      //delay(1000);
  }
    if (state == "measure") {
      Serial.println("... do measurement");
      //delay(1000);
  }

  Serial.print("mode="); Serial.print(mode); Serial.print(" state="); Serial.print(state); Serial.print(" | "); 
  Serial.print(timer);  Serial.print(" "); Serial.print(millis()); Serial.println("");
  delay(1000);
    
}