#include <libopencm3/cm3/nvic.h>
#include <libopencm3/cm3/systick.h>
#include <libopencm3/stm32/flash.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/rcc.h>
#include <stdint.h>

volatile uint64_t ticks;

static void gpio_setup(void) {
    rcc_periph_clock_enable(RCC_GPIOC);
    gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
}

void sys_tick_handler(void) { ticks++; }

static void sys_tick_setup(void) {
    ticks = 0;
    // rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE16_72MHZ]);

    // systick_set_clocksource(STK_CSR_CLKSOURCE_AHB_DIV8);
    systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);

    // systick_set_reload(48000 - 1);
    systick_set_frequency(1000, 72000000);

    systick_clear();

    systick_interrupt_enable();
    systick_counter_enable();

    return;
}

static uint64_t sys_ticks_get(void) { return ticks; }

static void delay(volatile uint32_t count) {
    while (count-- > 0) {
        __asm__("nop");
    }
}

int main(void) {
    rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
    // rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSI_48MHZ]);
    gpio_setup();
    sys_tick_setup();

    gpio_clear(GPIOC, GPIO13);
    gpio_set(GPIOC, GPIO13);
    // gpio_set(GPIOB, GPIO6);    /* LED2 off */

    // ticks = 0;

    uint64_t init = sys_ticks_get();
    while (sys_ticks_get() == init);

    /* We call this handler every 1ms so 1000ms = 1s on/off. */
    uint64_t ref = 0;
    while (1) {
        if (sys_ticks_get() > ref) {
            ref += 500;
            gpio_toggle(GPIOC, GPIO13);
            // while (sys_ticks_get() % 1000 == 0);
        }
    }

    while (1);

    return 0;
}