'''
Live read of the Senseair S88 CO2 sensor (used by the web "Get Data" button).
Prints a JSON object: {"CO2": <int_ppm>} or {"error": "<message>"}.

Usage: /usr/bin/python3 /var/www/nebuleair_pro_4g/S88/get_data.py [port]
If no port is given, the script reads S88_port from config_table.
'''

import json
import sqlite3
import sys

import serial

DB_PATH = "/var/www/nebuleair_pro_4g/sqlite/sensors.db"
DEFAULT_PORT = "/dev/ttyAMA5"
BAUDRATE = 9600


def get_port_from_config():
    try:
        conn = sqlite3.connect(DB_PATH)
        cursor = conn.cursor()
        cursor.execute("SELECT value FROM config_table WHERE key = ?", ("S88_port",))
        row = cursor.fetchone()
        conn.close()
        return row[0] if row else DEFAULT_PORT
    except Exception:
        return DEFAULT_PORT


def read_co2(ser):
    # TODO: implement the Senseair S88 read protocol once the datasheet is provided.
    # Expected return: integer CO2 concentration in ppm, or None on failure.
    raise NotImplementedError("Senseair S88 read protocol not implemented yet")


def main():
    port = sys.argv[1] if len(sys.argv) > 1 else get_port_from_config()

    try:
        ser = serial.Serial(
            port=port,
            baudrate=BAUDRATE,
            parity=serial.PARITY_NONE,
            stopbits=serial.STOPBITS_ONE,
            bytesize=serial.EIGHTBITS,
            timeout=1,
        )
    except Exception as e:
        print(json.dumps({"error": f"Cannot open {port}: {e}"}))
        return

    try:
        co2 = read_co2(ser)
        if co2 is None:
            print(json.dumps({"error": "No data from S88"}))
            return
        print(json.dumps({"CO2": int(round(co2))}))
    except NotImplementedError as e:
        print(json.dumps({"error": str(e)}))
    except Exception as e:
        print(json.dumps({"error": f"S88 read error: {e}"}))
    finally:
        try:
            ser.close()
        except Exception:
            pass


if __name__ == "__main__":
    main()