# ============================================================
# SMART WASTE BIN MONITORING SYSTEM - COMPLETE PRODUCTION CODE
# Target Platform: Raspberry Pi Pico W
# Configured for: MQ2 + HC-SR04 + OLED + 4-Pin Tactile Button
# ============================================================

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

# ============================================================
# PHYSICAL HARDWARE PIN ASSIGNMENTS
# ============================================================

# 1. MQ2 Gas Sensor (Yellow wire -> GP26 / ADC0)
mq2 = ADC(26)              

# 2. HC-SR04 Ultrasonic Sensor (Trig -> GP16, Echo -> GP17 via Voltage Divider)
trig = Pin(16, Pin.OUT)    
echo = Pin(17, Pin.IN)     

# 3. Piezo Buzzer (Positive Leg -> GP15)
buzzer = Pin(15, Pin.OUT)  

# 4. Push Button (Pin 1L -> GP14, Pin 2L -> 3.3V)
# Internal microchip Pull-Down keeps logic safely at 0 until pressed
button = Pin(14, Pin.IN, Pin.PULL_DOWN)

# ============================================================
# OLED DISPLAY CONFIGURATION & ERROR-SAFE BUS INITIALIZATION
# ============================================================
oled = None

print("Checking display hardware connection...")
try:
    # Attempt Primary Map (SDA -> GP2, SCL -> GP3 on I2C1)
    i2c = I2C(1, scl=Pin(3), sda=Pin(2), freq=400000)
    oled = ssd1306.SSD1306_I2C(128, 64, i2c)
    print("-> OLED Success: Connected on I2C Bus 1 (GP2/GP3)")
except Exception:
    try:
        # Fallback Standard Map (SDA -> GP0, SCL -> GP1 on I2C0)
        i2c = I2C(0, scl=Pin(1), sda=Pin(0), freq=400000)
        oled = ssd1306.SSD1306_I2C(128, 64, i2c)
        print("-> OLED Success: Connected on I2C Bus 0 (GP0/GP1)")
    except Exception as error_msg:
        print("!! SCREEN ALERT: Could not bind to I2C interface.")
        print("   Verify VCC/GND power tracks or missing 'ssd1306.py' file.")
        print("   Details:", error_msg)

# ============================================================
# CONTEXT CALIBRATION VARIABLES
# ============================================================
BIN_HEIGHT = 40          # Depth/Height of your physical waste bin in cm
FULL_LEVEL = 80          # The fill percentage that triggers a "BIN FULL" alert
MQ2_THRESHOLD = 28000    # Calibrated 16-bit analog boundary for organic odor spikes

# ============================================================
# HELPER ACTIONS / FUNCTIONS
# ============================================================

def beep(duration):
    """Flashes the pin high to trigger the piezo element alert tone"""
    buzzer.high()
    time.sleep(duration)
    buzzer.low()

def get_distance():
    """Triggers the ultrasonic sensor module and records return travel duration"""
    trig.low()
    time.sleep_us(2)
    
    # Send high ultrasonic pulse burst
    trig.high()
    time.sleep_us(10)
    trig.low()

    try:
        # Echo pin waits for high return pulse timeout capped at 30ms max
        duration = time_pulse_us(echo, 1, 30000)
        if duration < 0:
            return -1 # Hardware readout fault indicator
        
        # Speed of sound parsing formula to evaluate range boundary
        distance = (duration * 0.0343) / 2
        return distance
    except:
        return -1

def get_fill_percentage(distance):
    """Translates free-space distance to total internal mass capacity percentage"""
    if distance < 0:
        return 0

    fill = ((BIN_HEIGHT - distance) / BIN_HEIGHT) * 100
    
    # Strict clamp safety boundaries (Keep value within 0% - 100%)
    if fill < 0:   fill = 0
    if fill > 100: fill = 100
    return fill

def display_data(gas, distance, fill, status):
    """Refreshes the memory matrix on the screen and prints layout"""
    if oled is None:
        return
    oled.fill(0)
    oled.text("SMART WASTE BIN", 0, 0)
    oled.text("Gas Vol: {}".format(gas), 0, 16)
    oled.text("Dist:    {:.1f}cm".format(distance), 0, 30)
    oled.text("Fill:    {:.1f}%".format(fill), 0, 44)
    oled.text("SYS:     {}".format(status), 0, 56)
    oled.show()

# ============================================================
# BOOT EXECUTION SPLASH
# ============================================================
if oled:
    oled.fill(0)
    oled.text("SMART WASTE BIN", 0, 20)
    oled.text("SYSTEM ONLINE", 0, 38)
    oled.show()

print("\n=========================================")
print("      WASTE MONITOR ACTIVE & READY       ")
print("=========================================")
time.sleep(1.5)

# ============================================================
# MAIN APPLICATION LOOP
# ============================================================
while True:
    # Idle Waiting Prompt Frame
    if oled:
        oled.fill(0)
        oled.text("  [ STATUS IDLE ] ", 0, 15)
        oled.text("PRESS BUTTON TO", 5, 35)
        oled.text("SCAN CAPACITIES", 5, 48)
        oled.show()

    # Smooth clock baseline loop cadence to prevent tracking bounces
    time.sleep(0.05)

    # Detect pull-up state shift (Button Pressed)
    if button.value() == 1:
        print("\n--- Gathering Real-Time Environment Metrics ---")

        # Read Current Values
        gas_value = mq2.read_u16()
        distance = get_distance()

        # Error fallbacks if ultrasonic is completely blocked or unplugged
        if distance == -1:
            distance = BIN_HEIGHT

        fill_percent = get_fill_percentage(distance)

        # Output Data Struct Directly to IDE Console Log
        print("Gas Registry Value (16-bit ADC):", gas_value)
        print("Target Object Distance         :", round(distance, 1), "cm")
        print("Computed Mass Capacity         :", round(fill_percent, 1), "%")

        # Decision Matrix evaluation logic
        if fill_percent >= FULL_LEVEL:
            status = "BIN FULL!"
            print("ALERT NOTIFICATION -> Capacity Threshold Exceeded!")
            beep(1.0) # Long tone warning

        elif gas_value >= MQ2_THRESHOLD:
            status = "BAD SMELL!"
            print("ALERT NOTIFICATION -> High Accumulation Odor Spike!")
            beep(0.5) # Short warning tone

        else:
            status = "NORMAL OPER."
            print("STATUS -> Environment vectors within normal limits.")

        # Push data payload structures directly into display update logic
        display_data(gas_value, distance, fill_percent, status)

        # Retain measured info visible window for user review before resetting frame
        time.sleep(4.5)