#!/usr/bin/python3

import csv
import argparse
from datetime import datetime, date, timedelta
from matplotlib import pyplot as plt

'''
filename = 'log.csv'
Time,TS,CO2,Temp
21:02:02,0,661,24
21:02:08,5021,657,24

'''

def parsedatetime(timevalue, currentdate):
    dt = datetime.strptime(timevalue, '%H:%M:%S')
    return datetime.combine(currentdate, dt.time())

def main():
    parser = argparse.ArgumentParser('Plot log.csv.')
    parser.add_argument('filename', nargs='?', default='log.csv', help='Name of csv file')
    parser.add_argument('-s', '--startdate', nargs='?', default='2020-10-22', help='First date in csv file')
    parser.add_argument('-t', '--temperature', action='store_true', help='Include temperature plot')
    args = parser.parse_args()
    startdate = datetime.strptime(args.startdate, '%Y-%m-%d').date()

    with open(args.filename) as f:
        reader = csv.reader(f)
        headers = next(reader)

        time = []
        co2 = []
        temp = []
        for row in reader:
            dt = parsedatetime(row[0], startdate)
            if len(time) > 0 and dt - time[-1] < timedelta(hours=-2): # DST switch!
                startdate += timedelta(days=1)
                dt += timedelta(days=1)
            time.append(dt)
            co2.append(int(row[2]))
            temp.append(int(row[3]))

        plt.plot(time, co2, c = 'red')
        plt.title('CO₂')
        plt.xlabel('time')
        plt.ylabel('ppm')
        plt.tick_params(axis = 'both', which = 'major')
        if args.temperature is True:
            plt.gca().twinx()
            plt.plot(time, temp, c = 'blue')
        plt.show()

if __name__ == '__main__':
    main()