Soh Jason - Project Portfolio

We have chosen the second option for the ease of storage management and low access times. To store the schedule, a unique approach of using bit counters is used. Each bit stores a 30 minute block, totalling to 24 hours * 2 30-mins * 7 days = 336 bits. 1-bit signifies an occupied slot while a 0-bit signifies an empty slot. This 336 bit-string is then stored as a string in the xml. However, in the application, it will stored as a two-dimensional array [7][48]. This allows O(1) access times for each slot, while only requiring O(n) on startup to reload the bit-string into an array.

Each bit string is then translated into a Slot, detailing its time of the day and the day of the week, to be used by the application

As manipulating bit strings may be complicated, getter, setter and merger methods are provided for any external access to the schedule. This allows easy use of the specific slots in the schedule without heavy calculation and memorisation of bits.

To effect a schedule update, a pair of strings representing the time of the day and the day of the week are to be entered. The strings are then converted into a Slot(which contains Time and Day objects). The setter methods of schedule is then called to effect the change. Note that this is a "bit flip" operation, so it will set a free Slot to an occupied Slot and vice versa.

Similarly, as bitwise operations are allowed, two or more persons' schedule are or-ed together to form a new schedule object. This Schedule object is then translated into slots and print back to the application.

Noted that we have 336 Slots thus it is highly possible that maxSchedule command will return a large number of free time slots. Thus the sl/ tag is used to limit the range of free time displayed. It is implemented in the format of XXXX-XXXX where XXXX is the time slot in 24 hour format.

The sequence diagram of MaxSchedule command is illustrated below.

As noted from the schedule component, MaxSchedule command passes a Time object into the schedule. This abstraction of Time/Day objects reduces the possibility of invalid input resulting from the user input in MaxSchedule command.

NusMods will be used to provide academic events for the student. As for their non-academic events, he can use schedule update to manually update those slots. This way, we will be able to provide the most convenient way for the student to populate the schedule.

As nusmods.com is an external web server, internet access needs to be checked first. Following up, the nusmods.com gives the user a modsn.com shortlink which can translated back to a nusmods.com/…​ full link, if he wants to share his timetable with himself or others. Finally, a valid nusmods.com timetable would include json data in its GET parameters. All of these must be fulfilled or else a Invalid Nusmods link will be returned to the application.

The sequence diagram for the timetable download is illustrated below.

This is the valid short link of the nusmod timetable.

The above short link will be parsed into the full nusmods link as followed:

Breakdown on how to obtain the full timetable and convert it into a Schedule.

Step 1. We can easily obtain the person’s timetable by splitting the GET parameters by ';' delimiter. The resulting array would contain Module Code /=/ Lesson Type /:/ Number Slot.

Step 2. Then, to obtain the full details of the module (including all lessons and all slots), we can use the NUSMODS API detailed here https://github.com/nusmodifications/nusmods-api.

Step 3. We will then filter out the lessons obtained in step 1 from the full detail in step 2.

Step 4. The filtered lessons is then converted into a list of Slot.

Step 5. The list of Slot will be passed in a Schedule constructor to generate a new Schedule.

Step 6. The new Schedule object is returned to the application.