Create prerequisite for courses

[karbassi]

Allow Courses to have prerequisites.

For example, JS 1 has no other course prerequisites. However, JS 2 has a prerequisite of JS 1. JS 3 has JS 2, and so on.

To Do

• Modify the Course model to allow for specifying a classes prerequisites
• When a guardian goes to register a student for a session, allow the registration only if the student has met the class prerequisites, which should use the criteria:
  • Student has at least one order for an active session that was a prerequisite class
  • And that session was in the past
  • And there is a non null check-in date
• Update the programs template, removing hardcoded prerequisites and replacing with the prerequisites defined via the data model
  • ./website/weallcode/templates/weallcode/programs.html
• Display the required prerequisites in the class template
  • ./website/weallcode/templates/weallcode/snippets/class.html

Research

• http://www.softwaregems.com.au/Documents/Student%20Resolutions/Swartz%20DM.pdf
• https://stackoverflow.com/a/4150138
• https://github.com/django-danceschool/django-danceschool/blob/master/danceschool/prerequisites/models.py (this is crazy details and overkill for what we need)

[rgroves]

@karbassi what is the scope of this Issue? Should it encompass all of the following:

• Modifying the Course model to allow for specifying a classes prerequisites
• When a guardian goes to register a student for a session, allow the registration only if the student has met the class prerequisites
• Update the programs template, removing hardcoded prerequisites and replacing with the prereqs defined via the data model
  • ./website/weallcode/templates/weallcode/programs.html
• Display the required prerequisites in the class template
  • ./website/weallcode/templates/weallcode/snippets/class.html

Does that cover it in terms of scope or is something missing?

Also, what should be considered the correct criteria for determining if a student has met a prerequisite? I assume it starts with the criteria:

• Student has at least one order for a session that was for a prerequisite class
• And that session was in the past

What determines if the student was actually in attendance and completed the session? Is the check_in date something that needs to be checked for that?

What else, if anything, should be considered?

[rgroves]

I've updated the first comment in the thread with scope items discussed last week over Slack.
Will be submitting a PR for review shortly.

[rgroves]

The one remaining item for this issue not addressed by #858 is "Update the programs template, removing hardcoded prerequisites and replacing with the prerequisites defined via the data model".

It should be easy enough to generate the list of courses under the Courses section of the Programs page, but I wasn't sure of a few things that are ambiguous or currently require further changes and would like some guidance on them:

• If we generate based on the Courses data in the DB instead of hardcoding, how do you want to handle ordering of the courses (e.g. by course code alphabetically? some other way?)
• The Pathways listed for the courses seem not to exist in the DB, if we are to generate them programmatically a model for Pathways and a relationship to Courses will be required.
• I wasn't sure if the course info currently hardcoded in the programs template (./website/weallcode/templates/weallcode/programs.html) was actually up-to-date in the Courses data in the database (something we need to consider/verify before deploying I guess)
• I assume the Grade restriction notes will have to be determined by the Age restriction since there isn't anything in the Course model related to Grade levels (only Age), or should a minimum grade level be added to the Course model?