#include <stdint.h>

#define RCC_BASE      0x40021000
#define GPIOA_BASE    0x50000000

#define RCC_IOPENR    (*(volatile uint32_t*)(RCC_BASE + 0x34))
#define GPIOA_MODER   (*(volatile uint32_t*)(GPIOA_BASE + 0x00))
#define GPIOA_IDR     (*(volatile uint32_t*)(GPIOA_BASE + 0x10)) 
#define GPIOA_ODR     (*(volatile uint32_t*)(GPIOA_BASE + 0x14))

#define SYST_CSR_ENABLE     (1U<<0)
#define SYST_CSR_CLKSOURCE  (1U<<2)
#define SYST_CSR_COUNTFLAG  (1U<<16)

#define SYST_CLK 48000000UL
#define BASE_VALUE ((SYST_CLK/1000)-1)

#define SYSTICK_BASE 0xE000E010UL

#define SYST_CSR (*(volatile uint32_t*)(SYSTICK_BASE + 0x00UL))
#define SYST_RVR (*(volatile uint32_t*)(SYSTICK_BASE + 0x04UL))
#define SYST_CVR (*(volatile uint32_t*)(SYSTICK_BASE + 0x08UL))

void delayMs(uint32_t delay){
    if(delay == 0) return;

    uint32_t reload = BASE_VALUE;
    if(reload > 0xFFFFFFUL) reload = 0xFFFFFFUL;

    SYST_CSR = 0U;
    SYST_RVR = reload;
    SYST_CVR = 0U;

    SYST_CSR = SYST_CSR_CLKSOURCE | SYST_CSR_ENABLE;

    while(delay--){
        while((SYST_CSR & SYST_CSR_COUNTFLAG) == 0U);
    }

    SYST_CSR = 0U;
    SYST_CVR = 0U;
}

int main(void) {
  
  const uint8_t pino_botao = 3;
  const uint8_t pinos_leds[3] = {0,1,2}; 
  int alarme = 0;

  RCC_IOPENR |= (1 << 0);

  GPIOA_MODER &= ~(3 << pino_botao*2);



  for(int i = 0; i < 3; i++){
    GPIOA_MODER &= ~(3 << pinos_leds[i]*2);
    GPIOA_MODER |= (1 << pinos_leds[i]*2);
  }


  int alerme = 0;

  while (1) {

    delayMs(50);

    if(!(GPIOA_IDR & (1 << pino_botao))){

      delayMs(50);

      alarme++;

      if(alarme > 3){
        
        alarme = 0;

        for(int i = 0; i < 2; i++){

          GPIOA_ODR &= ~(3 << pinos_leds[i]);

        }

      }

      if(alarme == 1){

        GPIOA_ODR |= (1 << pinos_leds[0]);

      }else if(alarme == 2){

        GPIOA_ODR |= (1 << pinos_leds[1]);

      }else if(alarme == 3){

        GPIOA_ODR |= (1 << pinos_leds[2]);

      }

      while(!(GPIOA_IDR & (1 << pino_botao)));
      
      delayMs(50);

    }
  
  }

}