#!/usr/bin/env python3

import serial
import json
import re

class Usv(object):
    def __init__(self, device, baudrate, json_file):
        self._serial_port = serial.Serial(device,
                baudrate=baudrate,
                timeout=0.8)

        # force a clean prompt
        #self._serial_port.write(b"\r")
        self._read_until_prompt("\r")
        #print("cleaned prompt")
        with open(json_file) as fhandle:
            self.json_params = json.load(fhandle)


    def _read_until_prompt(self, outbuf):
        # match on "\n=>"
        self._serial_port.write(outbuf.encode())
        
        inbuf = self._serial_port.read(100)
        sbuf = inbuf.decode("utf-8") 

        #prompt = False
        #inbuf = []
        #while not prompt:
        #    pending = self._serial_port.read(1)
        #    if len(pending) == 0:
        #        self._serial_port.write(b"\r")
        #    else:
        #        inbuf.append(pending)
        #        print(pending)
        #if len(sbuf) > 2:
        #    if sbuf[-3] == "\n" and \
        #        sbuf[-2] == "=" and sbuf[-1] == ">":
        #        return sbuf
        #    else:
        #        sbuf = self._read_until_prompt(outbuf)
                
        return sbuf
    
    def get_parameters(self):
        # [{'name': 'acvoltsin', 'index': 1}, 
        results = {}

        for parameter in self.json_params:
            outbuf = "d %s\r" % parameter['num']
            inbuf = self._read_until_prompt(outbuf)
            
            regex = parameter['regex']
            match = re.search(regex, inbuf, re.MULTILINE)
            
            if match:
                name = parameter['name']
                value = float(match.group(1))

                results.setdefault(name, value)
                #print("MATCH: %s: %f" % (name,value))

        return results
          


if __name__ == "__main__":
    import pprint

    usv = Usv("/dev/ttyU0", 600, "usv_param.json")
    parameters = usv.get_parameters()
    pprint.pprint(parameters)