'''
Live read of the AMS CCS811 air-quality sensor (used by the web "Get Data" button).
Prints a JSON object: {"eCO2": <int_ppm>, "TVOC": <int_ppb>} or {"error": "<message>"}.

CCS811 is a MOX gas sensor: it outputs an equivalent CO2 (eCO2, derived from VOCs)
and a Total VOC (TVOC). It is NOT an NDIR CO2 sensor like the S88. TVOC is the
primary measurement of interest here.

I2C, library adafruit-circuitpython-ccs811. Address read from config_table
(key CCS811_address, e.g. "0x5A" Adafruit / "0x5B" SparkFun), default 0x5A.

Usage: /usr/bin/python3 /var/www/nebuleair_pro_4g/CCS811/get_data.py [address]
'''

import json
import sqlite3
import sys
import time

DB_PATH = "/var/www/nebuleair_pro_4g/sqlite/sensors.db"
DEFAULT_ADDRESS = 0x5A
# CCS811 produces a fresh sample every 1 s in drive mode 1. Poll data_ready a few
# times to cover the case where the driver was just (re)initialised.
DATA_READY_RETRIES = 30
DATA_READY_DELAY = 0.2  # seconds


def get_address_from_config():
    try:
        conn = sqlite3.connect(DB_PATH)
        cursor = conn.cursor()
        cursor.execute("SELECT value FROM config_table WHERE key = ?", ("CCS811_address",))
        row = cursor.fetchone()
        conn.close()
        if row and row[0]:
            return int(str(row[0]), 16)
    except Exception:
        pass
    return DEFAULT_ADDRESS


def main():
    if len(sys.argv) > 1:
        try:
            address = int(sys.argv[1], 16)
        except ValueError:
            print(json.dumps({"error": f"invalid address {sys.argv[1]}"}))
            return
    else:
        address = get_address_from_config()

    try:
        import board
        import busio
        import adafruit_ccs811
    except Exception as e:
        print(json.dumps({"error": f"library import failed: {e}"}))
        return

    try:
        i2c = busio.I2C(board.SCL, board.SDA)
        ccs811 = adafruit_ccs811.CCS811(i2c, address=address)
    except Exception as e:
        print(json.dumps({"error": f"cannot init CCS811 at {hex(address)}: {e}"}))
        return

    try:
        ready = False
        for _ in range(DATA_READY_RETRIES):
            if ccs811.data_ready:
                ready = True
                break
            time.sleep(DATA_READY_DELAY)

        if not ready:
            print(json.dumps({"error": "CCS811 data not ready (warming up?)"}))
            return

        eco2 = int(ccs811.eco2)
        tvoc = int(ccs811.tvoc)
        # eCO2 floor is 400 ppm; a sub-400 value is a not-yet-settled sample.
        if eco2 < 400:
            print(json.dumps({"error": "CCS811 reading not settled (warming up?)"}))
            return
        print(json.dumps({"eCO2": eco2, "TVOC": tvoc}))
    except Exception as e:
        print(json.dumps({"error": f"CCS811 read error: {e}"}))


if __name__ == "__main__":
    main()