/* How many shift register chips are daisy-chained.
*/
#define NUMBER_OF_SHIFT_CHIPS   4

/* Width of data (how many ext lines).
*/
#define DATA_WIDTH   NUMBER_OF_SHIFT_CHIPS * 8

/* Width of pulse to trigger the shift register to read and latch.
*/
#define PULSE_WIDTH_USEC   10

/* Optional delay between shift register reads.
*/
#define POLL_DELAY_MSEC   10

/* You will need to change the "int" to "long" If the
 * NUMBER_OF_SHIFT_CHIPS is higher than 2.
*/
#define BYTES_VAL_T unsigned long

int ploadPin        = 10;  // Connects to Parallel load pin the 165
int clockEnablePin  = 11;  // Connects to Clock Enable pin the 165
int dataPin         = 8; // Connects to the Q7 pin the 165
int clockPin        = 9; // Connects to the Clock pin the 165

BYTES_VAL_T pinValues;
BYTES_VAL_T oldPinValues;

/* This function is essentially a "shift-in" routine reading the
 * serial Data from the shift register chips and representing
 * the state of those pins in an unsigned integer (or long).
*/
#define BYTES_VAL_T unsigned long long

BYTES_VAL_T read_shift_regs()
{
    byte bitVal;
    BYTES_VAL_T bytesVal = 0;

    /* Trigger a parallel Load to latch the state of the data lines,
    */
    digitalWrite(clockEnablePin, HIGH);
    digitalWrite(ploadPin, LOW);
    delayMicroseconds(PULSE_WIDTH_USEC);
    digitalWrite(ploadPin, HIGH);
    digitalWrite(clockEnablePin, LOW);

    /* Loop to read each bit value from the serial out line
     * of the SN74HC165N for each shift register.
    */
    for (int shiftRegister = 0; shiftRegister < NUMBER_OF_SHIFT_CHIPS; shiftRegister++)
    {
        for (int i = 7; i >= 0; i--) // Adjusted the loop index
        {
            bitVal = digitalRead(dataPin);

            /* Set the corresponding bit in bytesVal.
            */
            bytesVal |= static_cast<BYTES_VAL_T>(bitVal) << ((shiftRegister * 8) + i);

            /* Pulse the Clock (rising edge shifts the next bit).
            */
            digitalWrite(clockPin, HIGH);
            delayMicroseconds(PULSE_WIDTH_USEC);
            digitalWrite(clockPin, LOW);
        }
    }

    return bytesVal;
}



/* Dump the list of zones along with their current status.
*/
void display_pin_values()
{
    for(int i = 0; i < DATA_WIDTH; i++)
    {
        if ((pinValues >> i) & 1 > (oldPinValues >> i) & 1) {
          Serial.print("Button ");
          Serial.print(i);
          Serial.print(" Down!");
          Serial.print("\r\n");
        }

        if ((pinValues >> i) & 1 < (oldPinValues >> i) & 1) {
          Serial.print("Button ");
          Serial.print(i);
          Serial.print(" Up!");
          Serial.print("\r\n");
        }
    }
}

void setup()
{
    Serial.begin(9600);

    /* Initialize our digital pins...
    */
    pinMode(ploadPin, OUTPUT);
    pinMode(clockEnablePin, OUTPUT);
    pinMode(clockPin, OUTPUT);
    pinMode(dataPin, INPUT);

    digitalWrite(clockPin, LOW);
    digitalWrite(ploadPin, HIGH);

    /* Read in and display the pin states at startup.
    */
    pinValues = read_shift_regs();
    display_pin_values();
    oldPinValues = pinValues;
}

void loop()
{
    /* Read the state of all zones.
    */
    pinValues = read_shift_regs();

    /* If there was a chage in state, display which ones changed.
    */
    if(pinValues != oldPinValues)
    {
        // Serial.print("*Pin value change detected*\r\n");
        display_pin_values();
        oldPinValues = pinValues;
    }

    delay(POLL_DELAY_MSEC);
}