#!/usr/bin/env python3

import argparse
import base64
import os
import sys
import time
import urllib.error
import urllib.parse
import urllib.request

import yaml
from pymodbus.exceptions import ConnectionException

from solaredge_modbus_mqtt import MyInverter
from solaredge_modbus_mqtt import SolarData
from solaredge_modbus_mqtt import to_line_protocol

SPOOL_FILE = 'spool.txt'
SPOOL_MAX_LINES = 20000  # ~16h of backlog at a 3s poll interval


def send_to_influx(lines, influx):
    url = '{0}/write?db={1}&precision=ns'.format(
        influx['url'].rstrip('/'),
        urllib.parse.quote(influx['db'], safe='')
    )
    request = urllib.request.Request(url, data='\n'.join(lines).encode('utf-8'), method='POST')
    if influx.get('user'):
        credentials = '{0}:{1}'.format(influx['user'], influx.get('pass') or '')
        token = base64.b64encode(credentials.encode('utf-8')).decode('utf-8')
        request.add_header('Authorization', 'Basic ' + token)
    urllib.request.urlopen(request, timeout=5)


def publish(line, influx):
    '''Write one line to InfluxDB. On failure, spool it to disk and replay the
    spool together with the next successful write (capped at SPOOL_MAX_LINES).'''
    try:
        backlog = []
        if os.path.exists(SPOOL_FILE):
            with open(SPOOL_FILE, 'r') as f:
                backlog = f.read().splitlines()[-SPOOL_MAX_LINES:]
        send_to_influx(backlog + [line], influx)
        if backlog:
            os.remove(SPOOL_FILE)
    except urllib.error.HTTPError as err:
        body = err.read().decode('utf-8', 'replace')[:200]
        if err.code == 400:
            # Permanently rejected (malformed line or field type conflict).
            # Re-spooling would poison every future write, so drop the batch.
            print('InfluxDB rejected the write, dropping {0} spooled line(s): {1}'.format(len(backlog) + 1, body))
            if os.path.exists(SPOOL_FILE):
                os.remove(SPOOL_FILE)
        else:
            print('InfluxDB write failed (HTTP {0}), spooling line: {1}'.format(err.code, body or err))
            with open(SPOOL_FILE, 'a') as f:
                f.write(line + '\n')
    except Exception as err:
        print('InfluxDB write failed, spooling line: {0}'.format(err))
        with open(SPOOL_FILE, 'a') as f:
            f.write(line + '\n')


if __name__ == '__main__':
    argparser = argparse.ArgumentParser()
    argparser.add_argument('--config', type=str, default=os.environ.get('CONFIG_FILE', 'config.yaml'), help='Path to the config.yaml')
    args = argparser.parse_args()

    with open(args.config, 'r') as stream:
        try:
            config = yaml.safe_load(stream)
        except yaml.YAMLError as exc:
            print(exc)
            sys.exit(1)

    inverter = MyInverter(
        host=config['modbus']['host'],
        port=config['modbus']['port'],
        timeout=config['modbus']['timeout'],
        unit=config['modbus']['unit']
    )

    while True:
        try:
            raw = inverter.read()
            solar_data = SolarData(raw)
            line = to_line_protocol(solar_data.data, config['influx'].get('measurement', 'solaredge'))
            if line:
                publish(line, config['influx'])
        except ConnectionException as err:
            print('Cannot connect to SolarEdge Modbus server on {0}:{1}, error: {2}'.format(
                config['modbus']['host'], config['modbus']['port'], err))

        time.sleep(config['poll_interval'])