from flask import Flask, jsonify
import serial
import os

app = Flask(__name__)

RELAY_DEV  = os.environ.get("RELAYCTL_DEV", "/dev/ttyUSB0")
RELAY_HOST = os.environ.get("RELAYCTL_HOST", "127.0.0.1")
RELAY_PORT = os.environ.get("RELAYCTL_PORT", "5050")
RELAY_BAUD = 9600
RELAY_ID = 1  # NOTE: multi relay boards are not supported (only relay id 1)

def get_cmd(state: bool):
    """
    LCUS relay 4-byte control command syntax is as follows:
    start: always 0xA0
    relay: id of relay (counts from 1)
    state: coil energized 0 or 1
    checksum: sum of previous 3 bytes
    """
    start = 0xA0
    relay = RELAY_ID
    state = int(state)
    checksum = start + relay + state
    return bytes((start, relay, state, checksum))

def get_serial():
    return serial.Serial(RELAY_DEV, RELAY_BAUD, timeout=1)

@app.route("/on", methods=["GET", "POST"])
def on():
    with get_serial() as ser:
        ser.write(get_cmd(True))
        return jsonify({"state": "ON"})

@app.route("/off", methods=["GET", "POST"])
def off():
    with get_serial() as ser:
        ser.write(get_cmd(False))
        return jsonify({"state": "OFF"})

@app.route("/status", methods=["GET"])
def status():
    with get_serial() as ser:
        ser.write(bytes((0xFF,)))  # write 0xFF to get status
        r = ser.readline()
        state = r.decode("utf-8").removeprefix("CH1: ").strip()
        return jsonify({"state": state})

def main():
    app.run(host=RELAY_HOST, port=int(RELAY_PORT))

if __name__ == "__main__":
    main()