// STM32 Nucleo-L031K6 HAL Blink Example using SysTick Timer
// The LED (PB3) blinks every 1 second using HAL and SysTick-based interrupts

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include "stm32l0xx_hal.h"

// ============================================
// Define the LED port and pin (PB3 = user LED)
// ============================================
#define LED_PORT              GPIOB
#define LED_PIN               GPIO_PIN_3
#define LED_PORT_CLK_ENABLE   __HAL_RCC_GPIOB_CLK_ENABLE

// ===========================
// Function Prototypes
// ===========================
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
void HAL_SYSTICK_Callback(void);

// ===========================
// Main Program Entry
// ===========================
int main(void)
{
    // 1. Initialize the HAL Library (sets up SysTick timer and basic config)
    HAL_Init();

    // 2. Configure system clock (to 32 MHz using PLL)
    SystemClock_Config();

    // 3. Initialize GPIO pin for LED
    MX_GPIO_Init();

    // 4. Main loop does nothing – blinking is done in interrupt
    while (1) { }

    return 0;
}

// ==================================================
// SysTick Interrupt Callback (called every 1 ms)
// Toggles the LED every 1000 ms (1 second)
// ==================================================
void HAL_SYSTICK_Callback(void)
{
    static uint32_t counter = 0;
    counter++;

    if (counter >= 1000) // 1000 ms = 1 second
    {
        HAL_GPIO_TogglePin(LED_PORT, LED_PIN); // Toggle LED
        counter = 0; // Reset counter
    }
}

// ==================================================
// GPIO Initialization Function
// Configures PB3 as digital output
// ==================================================
static void MX_GPIO_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStruct = {0};

    // Enable clock to GPIOB peripheral
    __HAL_RCC_GPIOB_CLK_ENABLE();

    // Configure PB3 as push-pull output, no pull-up/down
    GPIO_InitStruct.Pin = LED_PIN;
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;

    // Initialize the GPIO with the settings
    HAL_GPIO_Init(LED_PORT, &GPIO_InitStruct);
}

// ==================================================
// System Clock Configuration Function
// Uses HSI (16 MHz) -> PLL x4 / 2 = 32 MHz SYSCLK
// ==================================================
void SystemClock_Config(void)
{
    RCC_OscInitTypeDef RCC_OscInitStruct = {0};
    RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

    // Enable power interface clock
    __HAL_RCC_PWR_CLK_ENABLE();

    // Set voltage scaling for high-speed operation
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    // Configure oscillator: use internal HSI (High-Speed Internal) oscillator
    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
    RCC_OscInitStruct.HSIState = RCC_HSI_ON;
    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;

    // Enable PLL: HSI x4 / 2 = 32 MHz
    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
    RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL4;
    RCC_OscInitStruct.PLL.PLLDIV = RCC_PLL_DIV2;

    // Apply oscillator config
    HAL_RCC_OscConfig(&RCC_OscInitStruct);

    // Configure clock dividers and system source
    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                                 | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

    // Apply clock config with 1 wait state for Flash memory
    HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);
}