#include "stm32l0xx_hal.h"

// Define LED pin and port
#define LED_GPIO_PORT           GPIOB
#define RED_PIN                 GPIO_PIN_3
#define YELLOW_PIN              GPIO_PIN_4
#define GREEN_PIN               GPIO_PIN_5
#define BUTTON                  GPIO_PIN_6
#define LED_GPIO_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
int main(void) {
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();

    // Infinite loop (LED blinking is interrupt-driven)
    while (1) {
        // Do nothing, LED toggling handled by SysTick interrupt
    }
}

// SysTick interrupt callback (every 1 ms)
void HAL_SYSTICK_Callback(void) {
    static uint32_t counter = 0;
    static uint8_t state = 0;

    counter++;
    if (counter >= 1450) { // 1000 ms = 1 second
           counter = 0;

        // Turn off all LEDs first
        HAL_GPIO_WritePin(GPIOB, RED_PIN | YELLOW_PIN | GREEN_PIN, GPIO_PIN_RESET);
        if (state == 0){
          HAL_GPIO_WritePin(GPIOB, RED_PIN, GPIO_PIN_RESET);
          HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_3);
          state = 1;
        }
        else if (state == 1){
          HAL_GPIO_WritePin(GPIOB, GREEN_PIN, GPIO_PIN_RESET);
          HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_4);
          state = 3;
        }
        else{
          HAL_GPIO_WritePin(GPIOB, YELLOW_PIN, GPIO_PIN_RESET);
          HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_5);
          state = 0;
        }
        
    }

}

// Initialize GPIO pin for LED
static void MX_GPIO_Init(void) {
    GPIO_InitTypeDef GPIO_InitStruct = {0};

    // Enable clock for GPIO port
    LED_GPIO_CLK_ENABLE();

    // Configure GPIO pin Output Level
   HAL_GPIO_WritePin(GPIOB, RED_PIN | YELLOW_PIN | GREEN_PIN, GPIO_PIN_RESET);
    // Configure GPIO pin : PB3,4,5 as output
    GPIO_InitStruct.Pin = RED_PIN | YELLOW_PIN | GREEN_PIN;
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;

    HAL_GPIO_Init(LED_GPIO_PORT, &GPIO_InitStruct);
}

// Configure system clock to 32 MHz (internal oscillator + PLL)
void SystemClock_Config(void) {
    RCC_OscInitTypeDef RCC_OscInitStruct = {0};
    RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

    // Enable power controller and set voltage scaling
    __HAL_RCC_PWR_CLK_ENABLE();
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    // Configure PLL to generate 32 MHz from internal 16 MHz HSI oscillator
    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
    RCC_OscInitStruct.HSIState = RCC_HSI_ON;
    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
    RCC_OscInitStruct.PLL.PLLMUL = RCC_PLLMUL_4;
    RCC_OscInitStruct.PLL.PLLDIV = RCC_PLLDIV_2;
    HAL_RCC_OscConfig(&RCC_OscInitStruct);

    // Configure clock dividers
    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;
    HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);
}