#include <gpio.h>
#include <stdint.h>

#define EXTI_INTENR REGISTER(0x40010400)
#define EXTI_RTENR REGISTER(0x40010408)
#define EXTI_FTENR REGISTER(0x4001040C)
#define EXTI_INTFR REGISTER(0x40010410)
#define AFIO_EXTICR (*(volatile uint32_t *)(0x40010008))

#define P_PIN 3

void configure_pd3_interrupt() {
  // Map EXTI line 3 to Port D (4 bits per line)
  AFIO_EXTICR &= ~(0xF << (4 * 3));
  AFIO_EXTICR |= (0x03 << (4 * 3));  // 0x03 for Port D

  // enable interrupt for gpio pin
  EXTI_INTENR |= PIN(3);
  EXTI_RTENR |= PIN(3);
  EXTI_FTENR |= PIN(3);

  EXTI_INTFR &= ~PIN(3);
  REGISTER(0xE000E100) |= PIN(20);  // Enable EXTI7_0 interrupt in PFIC (IRQ 20)
}

int main(void) {
  enable_APB2_peripheral(AFIOEN);  // enable alternative function
  enable_gpio_port(PORT_D);        // enable port D

  gpio_set_mode(PORT_D, 3, GPIO_MODE_INPUT_FLOATING);
  gpio_set_mode(PORT_D, 2, GPIO_MODE_OUTPUT_PP_50MHZ);

  configure_pd3_interrupt();

  while (1) {
    uint32_t flag_register_value = EXTI_INTFR;
    if (flag_register_value & PIN(3)) {
      EXTI_INTFR &= ~PIN(3);
      gpio_write(PORT_D, 2, 1);
    }
  }
}