#!/usr/bin/env python3
"""
Read weather predictions for the next days, and if it's high enough,
recommend that Dennis buys witbier.
"""
import datetime
import json
import os
import textwrap
import smtplib
import sys
from collections import defaultdict
from email.message import EmailMessage
from urllib.request import urlopen


EMAIL_SENDER = 'Witbierbot <witbier@example.org>'
EMAIL_RECIPIENT = 'RECIPIENT'


def load_weather():
    url = 'https://api.openweathermap.org/data/2.5/forecast?q=Leiden' \
            + '&units=metric' \
            + '&appid=' + os.environ['API_KEY']

    result = urlopen(url)

    return json.load(result)


def get_maxima(weather):
    days = defaultdict(float)
    for day in weather['list']:
        instant = datetime.datetime.fromtimestamp(day['dt'])
        date = instant.date()
        days[date] = max(days[date], day['main']['temp_max'])

    return days


def notify(best_day, best_temp):
    best_day = best_day.strftime('%d/%m')

    message = f'''\
            Lief DB,

            De komende dagen wordt het wederom prachtig weer. Zo wordt het
            op {best_day} maar liefst {best_temp} °C!

            Met zulke mooie berichten kan het niet anders dan dat er
            binnenkort witbier verkocht wordt. Toch? Ik kijk er in ieder
            geval naar uit.

            Knuffels,

            Witbierbot.
            '''

    message = textwrap.dedent(message)

    report_date = datetime.datetime.now().strftime('%d/%m/%y')

    mail = EmailMessage()
    mail.set_content(message)
    mail['Subject'] = 'Witbier alert voor ' + report_date
    mail['To'] = EMAIL_RECIPIENT
    mail['From'] = EMAIL_SENDER

    with smtplib.SMTP('localhost') as smtp:
        smtp.send_message(mail)


def main():
    if len(sys.argv) > 1:
        with open(sys.argv[1]) as f:
            weather = json.load(f)
    else:
        weather = load_weather()

    maxima = get_maxima(weather)
    best, temp = max(maxima.items(), key=lambda x: x[1])
    if temp > 10:
        notify(best, temp)


if __name__ == '__main__':
    main()