#include "stm32c0xx.h"

#define BUTTON_PIN   (1<<10)   // PA10 -> D2
#define VEHICLE_LED  (1<<3)    // PB3 -> D3
#define BUZZER_PIN   (1<<5)    // PB5 -> D4
#define WARNING_LED  (1<<4)    // PB4 -> D5

volatile uint32_t systemTime = 0;
uint32_t pressStart = 0;

void delay_ms(uint32_t ms){
  for(uint32_t i=0;i<ms*4000;i++);
}

void showMessage(char *msg){
  Serial.println(msg);
}

uint32_t getTime(){
  return systemTime;
}

void setup() {

  Serial.begin(9600);

  // Enable GPIOA and GPIOB clock
  RCC->IOPENR |= (1<<0);   // GPIOA
  RCC->IOPENR |= (1<<1);   // GPIOB

  // PA10 input
  GPIOA->MODER &= ~(3<<(10*2));

  // PB3 PB4 PB5 output
  GPIOB->MODER &= ~((3<<(3*2)) | (3<<(4*2)) | (3<<(5*2)));
  GPIOB->MODER |=  ((1<<(3*2)) | (1<<(4*2)) | (1<<(5*2)));

  // Initial state
  GPIOB->ODR |= VEHICLE_LED;
  GPIOB->ODR &= ~WARNING_LED;
  GPIOB->ODR &= ~BUZZER_PIN;

  showMessage("DRIVER SAFE - Vehicle Running");
}

void loop() {

  delay_ms(1);
  systemTime++;

  // Button pressed
  if(!(GPIOA->IDR & BUTTON_PIN)) {

    if(pressStart == 0){
      pressStart = getTime();
    }

    uint32_t elapsed = getTime() - pressStart;

    if(elapsed >= 1000){
      GPIOB->ODR &= ~VEHICLE_LED;
      showMessage("WARNING - Eyes Closed");
    }

    if(elapsed >= 2000){
      GPIOB->ODR |= WARNING_LED;
      showMessage("DROWSINESS DETECTED");
    }

    if(elapsed >= 3000){
      GPIOB->ODR |= BUZZER_PIN;
      showMessage("ALERT ACTIVE - STOP VEHICLE");
    }
  }

  else {

    pressStart = 0;

    GPIOB->ODR |= VEHICLE_LED;
    GPIOB->ODR &= ~WARNING_LED;
    GPIOB->ODR &= ~BUZZER_PIN;

    showMessage("DRIVER SAFE - Vehicle Running");
  }
}