import paho.mqtt.client as mqtt
import threading
import re
import datetime
import copy

con = mqtt.Client()
con.connect('10.8.1.16')
con.subscribe('iot/+/+/energy')

class Meters:
    class Meter:
        def __init__(self, _id, history_size = 10):
            self.id = _id
            self.energy = []
            self.history_size = 10

        def add_energy_measurement(self, energy):
            self.energy.append((datetime.datetime.now(), energy))
            self.energy = self.energy[-self.history_size:]

        def get_metrics(self):
            if len(self.energy) > 0:
                last = self.energy[-1]
                s = ('energy{{node="esp8266-{mid:s}"}}  {energy:f} '
                    '{epoch:d}\n').format(mid=self.id, energy=last[1],
                    epoch=int(last[0].timestamp() * 1000))
                return s
            else:
                return ''
    def __init__(self):
        self._meters = {}
        self._lock = threading.Lock()

    def _get_meter_by_id(self, _id):
        if _id not in self._meters:
            self._meters[_id] = self.Meter(_id)
        return self._meters[_id]

    def add_energy_measurement(self, meter_id, energy):
        with self._lock:
            meter = self._get_meter_by_id(meter_id)
            meter.add_energy_measurement(energy)

    def get_metrics(self):
        with self._lock:
            s = ''
            for meter in self._meters.values():
                s += meter.get_metrics()
        return s

meters = Meters()

def on_message(client, userdata, message):
    m = re.match('iot/(?P<id>[^/]+)/[^/]+/energy', message.topic)
    if m is not None:
        try:
            energy = int(re.match('^(?P<joules>[0-9]*) J', message.payload.decode('ASCII')).group('joules'))
        except AttributeError:
            pass
        else: 
            if message.retain == 0:
                mid = m.group('id')
                meters.add_energy_measurement(mid, energy)
    
con.on_message = on_message
con.loop_start()

import flask
app = flask.Flask(__name__)

@app.route('/metrics')
def metrics():
    r = ""
    r += "# HELP energy energy in joules\n"
    r += "# TYPE energy counter\n"
    r += meters.get_metrics()
    return flask.Response(r, mimetype='text/plain; version=0.0.4')

app.run('0.0.0.0')