// a simple traffic light system using GPIO pins to control LEDs.

#define LED_RED_1    2
#define LED_YELLOW_1 3
#define LED_GREEN_1  4

#define LED_RED_2    8
#define LED_YELLOW_2 9
#define LED_GREEN_2  10

// These lines define constants for the GPIO pins connected to the LEDs. 
// LED_RED_1 is connected to pin 2, LED_YELLOW_1 to pin 3, and LED_GREEN_1 to pin 4. 
// Similarly, LED_RED_2 is connected to pin 8, LED_YELLOW_2 to pin 9, and LED_GREEN_2 to pin 10.

int main() {
    // The main function where the program execution starts.
    _gpio_init(LED_RED_1);
    gpio_set_dir(LED_RED_1, GPIO_OUT);

    _gpio_init(LED_YELLOW_1);
    gpio_set_dir(LED_YELLOW_1, GPIO_OUT);

    _gpio_init(LED_GREEN_1);
    gpio_set_dir(LED_GREEN_1, GPIO_OUT);

    _gpio_init(LED_RED_2);
    gpio_set_dir(LED_RED_2, GPIO_OUT);

    _gpio_init(LED_YELLOW_2);
    gpio_set_dir(LED_YELLOW_2, GPIO_OUT);

    _gpio_init(LED_GREEN_2);
    gpio_set_dir(LED_GREEN_2, GPIO_OUT);

    // These lines initialize the GPIO pins for the LEDs 
    // and set their direction to output. _gpio_init initializes the pin, and gpio_set_dir sets the pin direction to output.

    while (1) {
      // This starts an infinite loop, meaning the code inside will run repeatedly
      gpio_put(LED_RED_1, 1);
      gpio_put(LED_YELLOW_1, 0);
      gpio_put(LED_GREEN_1, 0);

      gpio_put(LED_RED_2, 1);
      gpio_put(LED_YELLOW_2, 0);
      gpio_put(LED_GREEN_2, 0);

      // Turns on the red LEDs and turns off the yellow and green LEDs for both traffic lights. Then, it waits for 1 second.
      sleep_ms(1000);

      gpio_put(LED_RED_1, 0);

      gpio_put(LED_GREEN_1, 1);

      // Turns off the red LED and turns on the green LED for the first traffic light. Then, it waits for 3 seconds.
      sleep_ms(3000);
      

      gpio_put(LED_GREEN_1, 0);
      gpio_put(LED_YELLOW_1, 1);
      // Turns off the green LED and turns on the yellow LED for the first traffic light. Then, it waits for 1 second.
      sleep_ms(1000);

    
      gpio_put(LED_YELLOW_1, 0);
      gpio_put(LED_RED_1, 1);
      gpio_put(LED_RED_2, 1);

      // Turns off the yellow LED and turns on the red LEDs for both traffic lights. Then, it waits for 1 second.
      sleep_ms(1000);

      // Turns off the red LED and turns on the green LED for the second traffic light. Then, it waits for 3 seconds.
      gpio_put(LED_RED_2, 0);

      gpio_put(LED_GREEN_2, 1);

      sleep_ms(3000);

      // Turns off the green LED and turns on the yellow LED for the second traffic light. Then, it waits for 1 second.

      gpio_put(LED_GREEN_2, 0);
      gpio_put(LED_YELLOW_2, 1);

      sleep_ms(1000);

      // The loop repeats indefinitely.
    }
    // The program returns 0, indicating successful execution, though this line is never reached due to the infinite loop.
    return (0);

}