from machine import Pin, I2C
import ssd1306
import time
import machine

# -------------------------
# OLED DISPLAY SETUP
# -------------------------
i2c = I2C(0, scl=Pin(5), sda=Pin(4))
oled = ssd1306.SSD1306_I2C(128, 64, i2c)

# -------------------------
# ULTRASONIC SENSOR PINS
# -------------------------
trigger = Pin(3, Pin.OUT)
echo = Pin(2, Pin.IN)

# -------------------------
# OUTPUT DEVICES PINS
# -------------------------
led = Pin(15, Pin.OUT)
relay = Pin(16, Pin.OUT)
buzzer = Pin(17, Pin.OUT)

# -------------------------
# TANK PARAMETERS
# -------------------------
tank_height = 100
status = "STARTING"

# -------------------------
# MEASURE DISTANCE FUNCTION
# -------------------------
def measure_distance():
    trigger.low()
    time.sleep_us(2)
    
    trigger.high()
    time.sleep_us(10)
    trigger.low()

    # Safe pulse-timing function to keep Wokwi from freezing
    time_passed = machine.time_pulse_us(echo, 1, 30000)
    
    if time_passed < 0:
        return tank_height # Timeout default (assumes empty tank)

    distance = (time_passed * 0.0343) / 2
    return distance

# -------------------------
# MAIN PROGRAM LOOP
# -------------------------
while True:
    distance = measure_distance()
    water_level = tank_height - distance

    if water_level < 0:
        water_level = 0

    percentage = int((water_level / tank_height) * 100)

    if percentage > 100:
        percentage = 100

    print("Water Level:", percentage, "%")

    # LOW WATER CONDITION (Trigger Fill)
    if percentage < 30:
        led.on()
        relay.on()
        buzzer.on()
        status = "FILLING"

    # FULL TANK CONDITION (Stop Fill)
    elif percentage >= 90:
        led.off()
        relay.off()
        buzzer.off()
        status = "FULL"

    # NORMAL OPERATING CONDITION
    else:
        buzzer.off()
        # Hysteresis: Keep pump running if filling, keep off if draining naturally
        if relay.value() == 1:
            status = "FILLING"
            led.on()
        else:
            status = "NORMAL"
            led.off()

    # -------------------------
    # OLED DISPLAY REFRESH
    # -------------------------
    oled.fill(0) # Clear Screen
    
    oled.text("SMART TANK", 0, 0)
    oled.text("LEVEL:", 0, 20)
    oled.text(str(percentage) + "%", 60, 20)
    oled.text("STATUS: " + status, 0, 45)
    
    oled.show() # Update display hardware

    time.sleep(1)