#include <stm32c0xx_hal.h>

#define LED_RED_PIN       GPIO_PIN_4   // LSB
#define LED_GREEN_PIN     GPIO_PIN_11
#define LED_TEAL_PIN      GPIO_PIN_9
#define LED_WHITE_PIN     GPIO_PIN_15  // MSB
#define BUTTON_PIN        GPIO_PIN_0
#define BUTTON_PORT       GPIOA

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
void display_counter(uint8_t count);

int main(void)
{
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();

    uint8_t counter = 0;

    while (1)
    {
        if (HAL_GPIO_ReadPin(BUTTON_PORT, BUTTON_PIN) == GPIO_PIN_SET) // Not pressed (active-low)
        {
            display_counter(counter);
            counter = (counter + 1) % 16; // 4-bit rollover
            HAL_Delay(500); // delay between counts
        }
        else
        {
            // Button pressed -> pause counter (no change)
            HAL_Delay(10); // small debounce delay
        }
    }
}

void display_counter(uint8_t count)
{
    HAL_GPIO_WritePin(GPIOA, LED_RED_PIN,   (count & 0x01) ? GPIO_PIN_SET : GPIO_PIN_RESET);
    HAL_GPIO_WritePin(GPIOA, LED_GREEN_PIN, (count & 0x02) ? GPIO_PIN_SET : GPIO_PIN_RESET);
    HAL_GPIO_WritePin(GPIOA, LED_TEAL_PIN,  (count & 0x04) ? GPIO_PIN_SET : GPIO_PIN_RESET);
    HAL_GPIO_WritePin(GPIOA, LED_WHITE_PIN, (count & 0x08) ? GPIO_PIN_SET : GPIO_PIN_RESET);
}

void SystemClock_Config(void)
{
    RCC_OscInitTypeDef RCC_OscInitStruct = {0};
    RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
    RCC_OscInitStruct.HSIState = RCC_HSI_ON;
    RCC_OscInitStruct.HSIDiv = RCC_HSI_DIV1;
    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
        Error_Handler();
    }

    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_PCLK1;
    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
    RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
    RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV1;
    RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV1;

    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK) {
        Error_Handler();
    }
}

static void MX_GPIO_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStruct = {0};
    __HAL_RCC_GPIOA_CLK_ENABLE();

    // LED pins
    GPIO_InitStruct.Pin = LED_RED_PIN | LED_GREEN_PIN | LED_TEAL_PIN | LED_WHITE_PIN;
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    // Button pin
    GPIO_InitStruct.Pin = BUTTON_PIN;
    GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
    GPIO_InitStruct.Pull = GPIO_PULLUP;  // Pull-up so we can connect button to GND
    HAL_GPIO_Init(BUTTON_PORT, &GPIO_InitStruct);
}

void Error_Handler(void)
{
    while (1) {
        // Stay here on error
    }
}