NJU course schedule => iCalendar: A quick and dirty script to convert JSON data downloaded from NJU ehall containing course schedule to ICalendar file (.ics).

nju-course-to-ics.py

#!/usr/bin/env python3
import json
import uuid
import datetime as dt
from dataclasses import dataclass

firstDayOfTerm  = dt.date(year=2023, month=9, day=4)
lessonStartTime = list(map(dt.time.fromisoformat, ['08:00','09:00','10:10','11:10','14:00','15:00','16:10','17:10','18:30', '19:30','20:40','21:30']))
lessonDuration  = dt.timedelta(minutes=50)

def fmtDateTime(datetime):
    return f'TZID=/Asia/Shanghai:{datetime.strftime("%Y%m%dT%H%M%S")}'

def fmtUtcDateTime(datetime):
    return f'{datetime.strftime("%Y%m%dT%H%M%SZ")}'

@dataclass(frozen=True)
class Course:
    name: str
    weekDay: int
    firstWeek: int
    perWeeks: int
    times: int
    location: str
    description: str

print("""
Usage:
1. Login to https://ehall.nju.edu.cn/
2. Find the 课表 app
3. Open the developer tools/inspect element etc., and select the Network tab
4. Refresh the page and locate the request to xspkjgcx.do
5. In the response tab, locate datas.xspkjgcx.rows
6. Right click on it and choose Copy Value
7. Save clipboard content as courses.json. Its content should look like:
   {
       "rows": [
           {
   // ...
""")

decoder = json.decoder.JSONDecoder()
with open('courses.json', 'r') as f:
    resp = f.read()
dic = decoder.decode(resp)
outfn = f'course-schedule-{dt.datetime.today().isoformat()}.ics'
print(f'Trying to saving as {outfn}...\n')
with open(outfn, 'wb') as f:
    emit = lambda s: f.write((s + '\r\n').encode())
    emit('BEGIN:VCALENDAR')
    emit('VERSION:2.0')
    emit('PRODID:gen')
    emit('SUMMARY:课表')
    courses = {}
    for course in dic['rows']:
        weekDay = int(course["XQ"])
        assert 1 <= weekDay <= 7
        name = course["KCMC"]
        location = course["JASMC"]
        description = f"教师:{course['JSXM']}"
        key = (name, weekDay)
        firstWeek, lastWeek = course['ZCMC'][:-1].strip().split('-')
        firstWeek = int(firstWeek)
        lastWeek = int(lastWeek)
        perWeeks = 1 # TODO: ...
        times = (lastWeek - firstWeek) // perWeeks + 1
        obj = Course(
            name=name,
            weekDay=weekDay,
            firstWeek=firstWeek,
            perWeeks=perWeeks,
            times=times,
            location=location,
            description=description
        )
        if (lessons := courses.get(obj)) is None:
            lessons = courses[obj] = []
        lessons.append(int(course["KSJCDM"]))
    for lessons in courses.values():
        lessons.sort()
    for it in courses.items():
        print(it)
        course, lessons = it
        assert lessons == list(range(lessons[0], lessons[-1]+1)), lessons
        firstDay = firstDayOfTerm + dt.timedelta(days=7*(firstWeek - 1) + course.weekDay - 1)
        firstLessonStartDt = dt.datetime.combine(firstDay, lessonStartTime[lessons[0]-1])
        firstLessonEndDt   = dt.datetime.combine(firstDay, lessonStartTime[lessons[-1]-1]) + lessonDuration
        emit(f'BEGIN:VEVENT')
        emit(f'SUMMARY:{course.name}')
        emit(f'UID:{uuid.uuid1()}')
        emit(f'DTSTAMP:{fmtUtcDateTime(dt.datetime.utcnow())}')
        emit(f'DTSTART;{fmtDateTime(firstLessonStartDt)}')
        emit(f'DTEND;{fmtDateTime(firstLessonEndDt)}')
        emit(f'DESCRIPTION:{course.description}')
        emit(f'LOCATION:{course.location}')
        emit(f'RRULE:FREQ=WEEKLY;INTERVAL={course.perWeeks};COUNT={course.times}')
        emit(f'END:VEVENT')
    emit('END:VCALENDAR')