# Import necessary libraries
# These libraries provide essential tools for managing time, accessing pin definitions, reading digital pulses, and controlling haptic feedback motors.
import time
import board
import digitalio
import adafruit_drv2605

# Configure HC-SR04 sensor pins
# Define trigger and echo pins on the microcontroller to interface with the HC-SR04 ultrasonic sensor.
trig_pin = board.D5  # The 'trig_pin' is set to D5, representing the trigger pin of the ultrasonic sensor.
echo_pin = board.D6  # The 'echo_pin' is set to D6, representing the echo pin of the ultrasonic sensor.
# Prepare to listen to the ultrasonic sensor's echo pin
# We use the 'DigitalInOut' tool to listen for signals (high or low) coming from the echo pin.
sonar = digitalio.DigitalInOut(echo_pin)
#'sonar' is set up to tell us if the echo pin is sending a strong signal (high) or not (low).
# This helps us measure distances because the sensor sends a signal, and 'sonar' lets us know when it comes back.

# Set up the echo pin as an input
# We are telling our sonar to listen attentively by setting the direction of the echo pin (D6) as 'INPUT'.
sonar.direction = digitalio.Direction.INPUT
# sonar is ready to notice any signals (changes from high to low or vice versa) coming from the echo pin.

# Initialize I2C bus and DRV2605 module
# Create an I2C communication bus and initialize the DRV2605 haptic feedback motor driver using that bus.
i2c = board.I2C()  # 'i2c' is an I2C communication bus used for communication with the DRV2605.
drv = adafruit_drv2605.DRV2605(i2c)  # 'drv' is an instance of the DRV2605 driver, enabling control over haptic feedback.

# Configure digital output for trigger pin
# Create a digital output object for the trigger pin and set it as an output. This pin is used to trigger the ultrasonic sensor.
trig = digitalio.DigitalInOut(trig_pin)  # 'trig' is a digital output object created for the trigger pin.
trig.direction = digitalio.Direction.OUTPUT  # The trigger pin is configured as an output.

# Main loop for running haptic feedback when an object is within two feet
# This loop continuously triggers the ultrasonic sensor to measure distance and activates haptic feedback if an object is within two feet.
effect_id = 119  # 'effect_id' represents the feedback effect ID to be played by the haptic motor.
while True:  # Infinite loop for continuous operation.

    # Trigger the ultrasonic sensor to measure distance
    trig.value = True  # Setting the trigger pin high initiates the ultrasonic sensor's pulse transmission.
    time.sleep(0.001)  # A brief pause (1 millisecond) to allow the sensor's pulse to propagate.
    trig.value = False  # Setting the trigger pin low stops the pulse transmission.

    # Measure distance using the ultrasonic sensor
    while sonar.value == False:  # Wait for the echo pin to go high.
        pulse_start = time.monotonic()  # Record the start time before the echo pin goes high.
    while sonar.value == True:  # Wait for the echo pin to go low.
        pulse_end = time.monotonic()  # Record the end time before the echo pin goes low.

    pulse_duration = pulse_end - pulse_start  # Calculate the duration of the pulse in seconds.
    distance = (pulse_duration * 34300) / 2  # Use the pulse duration to calculate the distance in centimeters (speed of sound = 34300 cm/s).
    print("Distance: {0} cm".format(distance))  # Print the measured distance.

    # Check if the distance is within two feet
    if (0 < distance < 60 or distance > 120):  # Check if the distance is within the specified range (0 to 60.96 cm).
        # Trigger haptic feedback with the specified effect ID
        print("Within two feet or 4 feet. Playing effect #{0}".format(effect_id))  # Display a message indicating the object is within two feet.
        drv.sequence[0] = adafruit_drv2605.Effect(effect_id)  # Set the haptic feedback effect.
        drv.play()  # Play the haptic feedback effect.
        time.sleep(0.5)  # Wait for a short duration (0.5 seconds).
        drv.stop()  # Stop the haptic feedback.

    # Pause for 1 second before the next iteration
    time.sleep(1)  # Wait for 1 second before taking the next distance measurement.