refactor: improve calendar event handling and date management

saharsh-agrawal · saharsh-agrawal · commit 8a869d0b0630 · 2025-10-18T01:57:01.000+05:30
- Updated `generate_ics.py` to enhance class-off date handling and event creation.
- Refactored `google_calendar.py` to streamline calendar creation and event addition.
- Improved date generation logic in `dates.py` for better holiday and class-off date management.
- Enhanced timezone handling in `build_event.py` for accurate datetime representation.
diff --git a/gyft.py b/gyft.py
@@ -77,8 +77,12 @@ def main():
             )
     else:
         _, sso_token = erp.login(headers, session)
+        # sso_token = 'xxxx' # for testing purposes
+    
+    # print(sso_token) # for testing purposes
 
     roll_number = erp.ROLL_NUMBER
+    # roll_number = 'xxxx' # for testing purposes
 
     courses = get_courses(session, sso_token, roll_number)
 
diff --git a/timetable/generate_ics.py b/timetable/generate_ics.py
@@ -1,11 +1,9 @@
 from __future__ import print_function
 
 from icalendar import Calendar, Event
-from datetime import datetime, timedelta
+from datetime import timedelta
 from timetable import Course
-from utils import academic_calander_handler, dates, build_event_duration, generate_india_time, next_weekday
-
-WORKING_DAYS = dates.get_dates()
+from utils import academic_calander_handler, dates, build_event_duration, generate_india_time
 
 
 def generate_ics(courses: list[Course], output_filename, is_web=False):
@@ -14,55 +12,73 @@ def generate_ics(courses: list[Course], output_filename, is_web=False):
     """
     cal = Calendar()
     cal.add("prodid", "-//Your Timetable generated by GYFT//mxm.dk//")
-    cal.add("version", "1.0")
+    cal.add("version", "2.0")
+
+    # Build exhaustive list of class-off dates for the semester
+    class_off_days = dates.get_class_off_dates_in_semester()
+
+    # Helper: find first occurrence of course.day on/after SEM_BEGIN
+    def first_occurrence_of_day(day_name: str):
+        return dates.next_weekday(dates.SEM_BEGIN, day_name)
+
+    # For each course, create a single weekly recurring VEVENT with EXDATEs on class-off days
     for course in courses:
-        start_dates = []
-        end_dates = []
-        for x in WORKING_DAYS:
-            if next_weekday(x[0], course.day) <= x[1]:
-                start_dates.append(
-                    next_weekday(x[0], course.day)
-                )  # work only in the interval 'x' of WORKING_DAYS, avoiding recurring outside of it.
-                end_dates.append(x[1])
-        lecture_begins_stamps = [
-            generate_india_time(
-                start.year, start.month, start.day, course.start_time, 0
-            )
-            for start in start_dates
-        ]
+        first_day = first_occurrence_of_day(course.day)
+        lecture_begin = generate_india_time(
+            first_day.year, first_day.month, first_day.day, course.start_time, 0
+        )
+
+        # Recurrence end: last occurrence should not exceed END_TERM_BEGIN
+        until = dates.END_TERM_BEGIN
 
-        for lecture_begin, end in zip(lecture_begins_stamps, end_dates):
-            event = build_event_duration(
-                course.title,
-                course.code,
-                lecture_begin,
-                course.duration,
-                course.get_location(),
-                "weekly",
-                end,
-            )
+        event = build_event_duration(
+            course.title,
+            course.code,
+            lecture_begin,
+            course.duration,
+            course.get_location(),
+            "weekly",
+            until,
+        )
 
-            cal.add_component(event)
+        # Compute EXDATE list: class-off days that fall on the course weekday
+        # Build exclusion timestamps at the same local time as lecture_begin
+        exdates = []
+        for off_day in class_off_days:
+            if off_day.weekday() == first_day.weekday():
+                ex_dt = generate_india_time(
+                    off_day.year, off_day.month, off_day.day, course.start_time, 0
+                )
+                # Only exclude occurrences within [lecture_begin, until)
+                if lecture_begin <= ex_dt < until:
+                    exdates.append(ex_dt)
 
-    # add holidays
+        if exdates:
+            # icalendar supports adding list of datetimes as EXDATE
+            event.add("exdate", exdates)
+
+        cal.add_component(event)
+
+    # add holidays (as all-day events in Asia/Kolkata)
     for holiday in dates.holidays:
         event = Event()
         event.add("summary", "INSTITUTE HOLIDAY : " + holiday[0])
-        event.add("dtstart", holiday[1])
-        event.add("dtend", holiday[1] + timedelta(days=1))
+        hdt = holiday[1]
+        hend = hdt + timedelta(days=1)
+        event.add("dtstart", hdt)
+        event.add("dtend", hend)
         cal.add_component(event)
 
     for entry in academic_calander_handler.get_academic_calendar(is_web):
         event = Event()
         event.add("summary", entry.event)
-        event.add("dtstart",entry.start_date)
-        event.add("dtend",entry.end_date)
+        event.add("dtstart", entry.start_date)
+        event.add("dtend", entry.end_date)
         cal.add_component(event)
-    
 
-    if output_filename != "":
+    if output_filename:
         with open(output_filename, "wb") as f:
             f.write(cal.to_ical())
             print("\nYour timetable has been written to %s" % output_filename)
-    
-    return cal.to_ical().decode('utf-8')
+
+    return cal.to_ical()
diff --git a/timetable/google_calendar.py b/timetable/google_calendar.py
@@ -12,11 +12,11 @@
 from utils import (
     END_TERM_BEGIN,
     SEM_BEGIN,
-    GYFT_RECUR_STRS,
-    get_rfc_time,
-    hdays,
     holidays,
+    dates,
+    generate_india_time,
 )
+from utils import academic_calander_handler
 from timetable import Course
 
 DEBUG = False
@@ -53,7 +53,7 @@ def get_credentials() -> client.Credentials:
     return credentials
 
 
-def create_calendar(courses: list[Course]) -> None:
+def create_calendar(courses: list[Course], is_web: bool = False) -> None:
     r"""
     Adds courses to Google Calendar
     Args:
@@ -62,77 +62,103 @@ def create_calendar(courses: list[Course]) -> None:
     credentials = get_credentials()
     http = credentials.authorize(httplib2.Http())
     service = discovery.build("calendar", "v3", http=http)
+
+    # Helper: get or create the dedicated 'IIT KGP' calendar
+    def get_or_create_calendar_id(name: str = "IIT KGP", tz: str = "Asia/Kolkata") -> str:
+        page_token = None
+        while True:
+            cl = service.calendarList().list(pageToken=page_token, maxResults=250).execute()
+            for item in cl.get("items", []):
+                if item.get("summary") == name and item.get("accessRole") in ("owner", "writer"):
+                    return item["id"]
+            page_token = cl.get("nextPageToken")
+            if not page_token:
+                break
+        # Create if not found
+        body = {"summary": name, "timeZone": tz}
+        created = service.calendars().insert(body=body).execute()
+        return created["id"]
+
+    calendar_id = get_or_create_calendar_id()
     batch = service.new_batch_http_request()  # To add events in a batch
+
+    # Build exhaustive class-off dates once
+    class_off_days = dates.get_class_off_dates_in_semester()
+
+    # Helper: first occurrence of the course weekday on/after SEM_BEGIN
+    def first_occurrence_of_day(day_name: str):
+        return dates.next_weekday(SEM_BEGIN, day_name)
+
     for course in courses:
+        first_day = first_occurrence_of_day(course.day)
+        lecture_begin_dt = generate_india_time(
+            first_day.year, first_day.month, first_day.day, course.start_time, 0
+        )
+        lecture_end_dt = lecture_begin_dt + timedelta(hours=course.duration)
+
+        # Build EXDATEs at the lecture start time for class-off days matching the course weekday
+        exdate_stamps: list[str] = []
+        for off_day in class_off_days:
+            if off_day.weekday() == first_day.weekday():
+                ex_dt = generate_india_time(
+                    off_day.year, off_day.month, off_day.day, course.start_time, 0
+                )
+                if lecture_begin_dt <= ex_dt < END_TERM_BEGIN:
+                    exdate_stamps.append(ex_dt.strftime("%Y%m%dT%H%M%S"))
+
         event = {
             "summary": course.title,
             "location": course.get_location(),
+            "description": course.code,
             "start": {
-                "dateTime": get_rfc_time(course.start_time, course.day)[:-7],
+                "dateTime": lecture_begin_dt.strftime("%Y-%m-%dT%H:%M:%S"),
                 "timeZone": "Asia/Kolkata",
             },
             "end": {
-                "dateTime": get_rfc_time(course.end_time, course.day)[:-7],
+                "dateTime": lecture_end_dt.strftime("%Y-%m-%dT%H:%M:%S"),
                 "timeZone": "Asia/Kolkata",
             },
-        }
-
-        ### making a string to pass in exdate. Changed the time of the string to class start time
-        exdate_str_dict = defaultdict(str)
-
-        for day in hdays[course.day]:
-            exdate_str_dict[course.day] += (
-                day.replace(hour=course.start_time).strftime("%Y%m%dT%H%M%S") + ","
-            )
-        if exdate_str_dict[course.day] != None:
-            exdate_str_dict[course.day] = exdate_str_dict[course.day][:-1]
-
-        if (
-            exdate_str_dict[course.day] != None
-        ):  ## if holiday exists on this recurrence, skip it with exdate
-            event["recurrence"] = [
-                "EXDATE;TZID=Asia/Kolkata:{}".format(exdate_str_dict[course.day]),
+            "recurrence": [
+                # Add EXDATE first if any
+                *( ["EXDATE;TZID=Asia/Kolkata:" + ",".join(exdate_stamps)] if exdate_stamps else [] ),
                 "RRULE:FREQ=WEEKLY;UNTIL={}".format(
                     END_TERM_BEGIN.strftime("%Y%m%dT000000Z")
                 ),
-            ]
-
-        else:
-            event["recurrence"] = [
-                "RRULE:FREQ=WEEKLY;UNTIL={}".format(
-                    END_TERM_BEGIN.strftime("%Y%m%dT000000Z")
-                )
-            ]
+            ],
+        }
 
-        batch.add(service.events().insert(calendarId="primary", body=event))
+        batch.add(service.events().insert(calendarId=calendar_id, body=event))
         print("Added " + event["summary"])
-
     batch.execute()  ## execute batch of timetable
 
-    # add holidays to calender as events
+    # add holidays to calendar as all-day events (Asia/Kolkata midnight)
     for holiday in holidays:
-        if (
-            holiday[1].date() >= date.today()
-            and holiday[1].date() <= END_TERM_BEGIN.date()
-        ):
-            holiday_event = {
-                "summary": "INSTITUTE HOLIDAY : " + holiday[0],
-                "start": {
-                    "dateTime": holiday[1].strftime("%Y-%m-%dT00:00:00"),
-                    "timeZone": "Asia/Kolkata",
-                },
-                "end": {
-                    "dateTime": (holiday[1] + timedelta(days=1)).strftime(
-                        "%Y-%m-%dT00:00:00"
-                    ),
-                    "timeZone": "Asia/Kolkata",
-                },
-            }
-            insert = (
-                service.events()
-                .insert(calendarId="primary", body=holiday_event)
-                .execute()
-            )
+        hdt = holiday[1]
+        start_str = generate_india_time(hdt.year, hdt.month, hdt.day, 0, 0).strftime("%Y-%m-%dT00:00:00")
+        end_dt = generate_india_time(hdt.year, hdt.month, hdt.day, 0, 0) + timedelta(days=1)
+        holiday_event = {
+            "summary": "INSTITUTE HOLIDAY : " + holiday[0],
+            "start": {
+                "dateTime": start_str,
+                "timeZone": "Asia/Kolkata",
+            },
+            "end": {
+                "dateTime": end_dt.strftime("%Y-%m-%dT00:00:00"),
+                "timeZone": "Asia/Kolkata",
+            },
+        }
+        service.events().insert(calendarId=calendar_id, body=holiday_event).execute()
+
+    # add academic calendar entries as all-day events
+    for entry in academic_calander_handler.get_academic_calendar(is_web):
+        start_str = entry.start_date.strftime("%Y-%m-%dT00:00:00")
+        end_str = entry.end_date.strftime("%Y-%m-%dT00:00:00")
+        event = {
+            "summary": entry.event,
+            "start": {"dateTime": start_str, "timeZone": "Asia/Kolkata"},
+            "end": {"dateTime": end_str, "timeZone": "Asia/Kolkata"},
+        }
+        service.events().insert(calendarId=calendar_id, body=event).execute()
 
     print("\nAll events added successfully!\n")
 
@@ -144,28 +170,24 @@ def delete_calendar():
     credentials = get_credentials()
     http = credentials.authorize(httplib2.Http())
     service = discovery.build("calendar", "v3", http=http)
-    batch = service.new_batch_http_request()  # To add events in a batch
-    print("Getting the events")
-    events_result = (
-        service.events()
-        .list(
-            calendarId="primary",
-            timeMin=SEM_BEGIN.strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
-            singleEvents=False,
-            timeMax=END_TERM_BEGIN.strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
-            maxResults=2500,
-        )
-        .execute()
-    )
-    events = events_result.get("items", [])
-    if not events or len(events) == 0:
-        print("No upcoming events found.")
+
+    # Find the IIT KGP calendar and delete it entirely
+    target_name = "IIT KGP"
+    page_token = None
+    calendar_id = None
+    while True:
+        cl = service.calendarList().list(pageToken=page_token, maxResults=250).execute()
+        for item in cl.get("items", []):
+            if item.get("summary") == target_name and item.get("accessRole") in ("owner", "writer"):
+                calendar_id = item["id"]
+                break
+        if calendar_id or not cl.get("nextPageToken"):
+            break
+        page_token = cl.get("nextPageToken")
+
+    if not calendar_id:
+        print(f"Calendar '{target_name}' not found. Nothing to delete.")
         return
-    for event in events:
-        if event.get("recurrence", "NoRecur") in GYFT_RECUR_STRS:
-            batch.add(
-                service.events().delete(calendarId="primary", eventId=event["id"])
-            )
-            print("Deleted: ", event["summary"], event["start"])
-    batch.execute()
-    print("Deletion done!")
+
+    service.calendars().delete(calendarId=calendar_id).execute()
+    print(f"Calendar '{target_name}' deleted.")
diff --git a/utils/build_event.py b/utils/build_event.py
@@ -34,4 +34,10 @@ def build_event_duration(summary: str, description: str, start: datetime, durati
 
 # Converts time to datetime object for India/Asia/Kolkata timezone
 def generate_india_time(year: int, month: int, date: int, hour: int, minutes: int):
-    return datetime(year, month, date, hour, minutes, tzinfo=pytz.timezone('Asia/Kolkata'))
+    """
+    Create a timezone-aware datetime in Asia/Kolkata.
+    Note: Use tz.localize to avoid incorrect LMT offsets from assigning tzinfo directly.
+    """
+    tz = pytz.timezone('Asia/Kolkata')
+    naive = datetime(year, month, date, hour, minutes)
+    return tz.localize(naive)
diff --git a/utils/dates.py b/utils/dates.py
