# ============================================================
# 🧪 Experiment 2: Room Monitoring System (CSV Logging Version)
# Raspberry Pi Pico W + LDR (Lux) + DHT22 (Temp & Humidity)
# Uploads to ThingSpeak Fields 3, 4, and 5
# Records all data into readings.csv
# ============================================================

import machine, time, math, network, urequests, ujson, dht

# ---------- ThingSpeak ----------
THINGSPEAK_API_KEY = "FTPW74F3RMWELQH8"
THINGSPEAK_URL = "http://api.thingspeak.com/update"

# ---------- Wi-Fi ----------
WIFI_SSID = "UniMAP-WiFi"
WIFI_PASSWORD = "2210600121"

# ---------- LDR (Analog) ----------
ldr = machine.ADC(1)           # GPIO27 = ADC1
VCC = 3.3
R_FIXED = 10000.0              # 10 kΩ resistor
GAMMA = 0.7
RL10  = 50.0                   # kΩ at 10 Lux

# ---------- DHT22 (Digital) ----------
dht_sensor = dht.DHT22(machine.Pin(4))  # DATA pin on GPIO4

# ---------- Wi-Fi connection ----------
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(WIFI_SSID, WIFI_PASSWORD)
print("Connecting to Wi-Fi...", end="")
while not wlan.isconnected():
    print(".", end="")
    time.sleep(1)
print("\n✅ Connected:", wlan.ifconfig())

# ---------- Helper Functions ----------
def read_lux():
    adc_val = ldr.read_u16()
    voltage = adc_val / 65535.0 * VCC
    if voltage <= 0.01 or voltage >= VCC - 0.01:
        return 0.0
    r_ldr = R_FIXED * voltage / (VCC - voltage)
    lux = math.pow(RL10 * 1e3 * math.pow(10, GAMMA) / r_ldr, 1.0 / GAMMA)
    return round(lux, 2)

def read_dht():
    try:
        dht_sensor.measure()
        temp = dht_sensor.temperature()
        hum  = dht_sensor.humidity()
        return round(temp, 2), round(hum, 2)
    except OSError:
        return None, None

def send_to_thingspeak(lux, temp, hum):
    data = {
        "api_key": THINGSPEAK_API_KEY,
        "field3": lux,
        "field4": temp,
        "field5": hum
    }
    try:
        r = urequests.post(
            THINGSPEAK_URL,
            data=ujson.dumps(data),
            headers={"Content-Type": "application/json"}
        )
        print(f"✅ Data sent → Lux: {lux}, Temp: {temp}, Hum: {hum}")
        r.close()
    except Exception as e:
        print("⚠️ ThingSpeak error:", e)

# ---------- Prepare CSV file ----------
file_name = "readings.csv"
with open(file_name, "w") as f:
    f.write("time,lux,temp,hum,measured_delay\n")  # header line

# ---------- Main Loop ----------
DELAY = 10  # 🔸 Change to 10,15,20,30,60 for Q5
previous_time = None
previous_ticks = None

while True:
    start_ticks = time.ticks_ms()

    # --- Sensor readings ---
    lux = read_lux()
    temp, hum = read_dht()
    timestamp = time.localtime()
    current_time = f"{timestamp[3]:02d}:{timestamp[4]:02d}:{timestamp[5]:02d}"

    # --- Calculate measured delay ---
    if previous_ticks is not None:
        delay_ms = time.ticks_diff(start_ticks, previous_ticks)
        delay_s = delay_ms / 1000.0
        print(f"\n⏱ Current: {current_time} | Previous: {previous_time} | Measured Delay = {delay_s:.2f} s")
    else:
        delay_s = 0.0
        print(f"\n⏱ Current: {current_time} | Previous: --- (first reading)")

    # --- Display readings ---
    print(f"Lux={lux} lx | Temp={temp} °C | Hum={hum}%")

    # --- Send to ThingSpeak ---
    if temp is not None and hum is not None:
        send_to_thingspeak(lux, temp, hum)
    else:
        print("⚠️ DHT22 read failed, skipping upload")

    # --- Save to CSV file ---
    try:
        with open(file_name, "a") as f:
            f.write(f"{current_time},{lux},{temp},{hum},{delay_s:.2f}\n")
    except Exception as e:
        print("⚠️ CSV write error:", e)

    # --- Adjust sleep to maintain total delay ---
    elapsed_ms = time.ticks_diff(time.ticks_ms(), start_ticks)
    elapsed_s = elapsed_ms / 1000.0
    sleep_time = max(0, DELAY - elapsed_s)
    print(f"⏳ Adjusted sleep = {sleep_time:.2f} s (Target delay = {DELAY}s)\n")

    previous_time = current_time
    previous_ticks = start_ticks

    time.sleep(sleep_time)