#include "stm32l0xx_hal.h"

/* Private variables */
static uint32_t lastDebounceTime = 0;    // Last time the button state changed
static const uint32_t debounceDelay = 50; // Debounce time in milliseconds
static uint8_t lastStableButtonState = GPIO_PIN_SET; // Assume button is not pressed initially
static uint8_t ledState = 0;             // Track LED state (0=OFF, 1=ON)

/* Function prototypes */
void SystemClock_Config(void);
static void MX_GPIO_Init(void);

int main(void) {
    HAL_Init();           // Initialize HAL library
    SystemClock_Config(); // Configure system clock
    MX_GPIO_Init();       // Initialize GPIO

    uint8_t lastButtonState = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_5); // Read initial button state

    while (1) {
        uint8_t currentButtonState = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_5); // Read current button state

        // Check if button state has changed
        if (currentButtonState != lastButtonState) {
            lastDebounceTime = HAL_GetTick(); // Reset debouncing timer
        }

        // If the state has been stable for longer than the debounce delay
        if ((HAL_GetTick() - lastDebounceTime) > debounceDelay) {
            // If the stable state is different from the last stable state and button is pressed
            if (currentButtonState != lastStableButtonState) {
                lastStableButtonState = currentButtonState;
                
                // If button is pressed (assuming active low: GPIO_PIN_RESET when pressed)
                if (lastStableButtonState == GPIO_PIN_RESET) {
                    // Toggle LED state
                    ledState = !ledState;
                    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, ledState ? GPIO_PIN_SET : GPIO_PIN_RESET);
                }
            }
        }

        lastButtonState = currentButtonState; // Save current state for next comparison
    }
}

// GPIO initialization function
static void MX_GPIO_Init(void) {
    GPIO_InitTypeDef GPIO_InitStruct = {0};

    __HAL_RCC_GPIOB_CLK_ENABLE(); // Enable GPIOB clock

    // Configure LED pin (PB4) as output
    GPIO_InitStruct.Pin = GPIO_PIN_4;
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;      // Push-pull output
    GPIO_InitStruct.Pull = GPIO_NOPULL;              // No pull-up or pull-down
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;     // Low speed for LED
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

    // Configure button pin (PB5) as input
    GPIO_InitStruct.Pin = GPIO_PIN_5;
    GPIO_InitStruct.Mode = GPIO_MODE_INPUT;          // Input mode
    GPIO_InitStruct.Pull = GPIO_PULLUP;              // Internal pull-up resistor
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;     // Low speed for button
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

    // Initialize LED to be off
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, GPIO_PIN_RESET);
}