Convert tide times to ICS calendar

tides-csv2ics.py

#!/usr/bin/env python3

import argparse
import datetime


# Tides from
# https://www.linz.govt.nz/products-services/tides-and-tidal-streams/tide-predictions
# get converted to .ics files which can be imported into Google Calendar.


def main():

    parser = argparse.ArgumentParser(
        prog="Tides CSV to ICS converter")

    parser.add_argument('input_file', help="CSV file")
    parser.add_argument('output_file', help="ICS file")
    args = parser.parse_args()

    ics = Ics()

    with open(args.input_file, 'rb') as csvfile:
        # ignore first 3 lines which are comments
        for line in csvfile.readlines()[3:-1]:
            parse_line(ics, line.decode('utf-8').strip())

    with open(args.output_file, 'w') as icsfile:
        icsfile.write(ics.render())


class Event:
    def __init__(self, time, height):
        self.is_high = height > 1.5
        self.time = time
        self.height = height


class Ics:
    def __init__(self):
        self.events = []

    def add(self, year, month, day, time, height):
        if (len(time) > 0 and len(height) > 0):
            hours, mins = time.split(":")
            self.events.append(
                    Event(
                        datetime.datetime(
                            int(year),
                            int(month),
                            int(day),
                            int(hours),
                            int(mins)),
                        float(height)))

    def render(self):
        content = self.header()
        for event in self.events:
            if (not event.is_high):
                continue
            content += "BEGIN:VEVENT\n"
            content += f"SUMMARY:High tide {event.height}m\n"

            icsdatefmt = "%Y%m%dT%H%M%S"

            before = (event.time - datetime.timedelta(hours=1)) \
                .strftime(icsdatefmt)
            after = (event.time + datetime.timedelta(hours=1)) \
                .strftime(icsdatefmt)
            at = event.time.strftime("%H:%M")

            content += f"DTSTART;TZID=Pacific/Auckland:{before}\n"
            content += f"DTEND;TZID=Pacific/Auckland:{after}\n"
            content += f"DESCRIPTION: High tide at {at}.\n"
            content += "ACTION:DISPLAY\n"

            content += "END:VEVENT\n"
        content += self.footer()
        return content

    def header(self):
        return "BEGIN:VCALENDAR\nVERSION:2.0\nCALSCALE:GREGORIAN\n"

    def footer(self):
        return "END:VCALENDAR\n"


def parse_line(ics, line):
    day, _, month, year, time1, height1, time2, height2, \
        time3, height3, time4, height4 = line.split(',')
    ics.add(year, month, day, time1, height1)
    ics.add(year, month, day, time2, height2)
    ics.add(year, month, day, time3, height3)
    ics.add(year, month, day, time4, height4)


if __name__ == '__main__':
    main()