Skeleton Code for CompSci 316/516 Standard Course Project.

Originally created by Rickard Stureborg and Yihao Hu for Fall 2021. Amended by various teaching staff in subsequent years.

We assume you are in your course container shell. If you have a different setup, your mileage with the following instructions may vary.

Installing the Current Skeleton

1. One (and only one) team member should fork this repo by clicking the small 'Fork' button at the very top right on GitLab. It's important that you fork first, because if you clone this repo directly you won't be able to push changes (save your progress) back to this repo (which is owned by the teaching staff). Name your forked repo as you prefer.

   In your newly forked repo, find the blue "Clone" button. Copy the "Clone with SSH" text. Add your teammates as members of your project as "Maintainers." Share the copied text with your teammates so they have access to this repo too.

   The remaining steps should be carried out by all team members.

2. In your container shell, issue the command git clone THE_TEXT_YOU_JUST_COPIED (make sure to replace THE_TEXT_YOU_JUST_COPIED with the "Clone with SSH" text).

3. In your container shell, change into the repository directory and then run ./install.sh. This will install a bunch of things, set up an important file called .flashenv, and creates a simple PostgreSQL database named amazon.

Running/Stopping the Website

To run your website, in your container shell, go into the repository directory and issue the following commands:

poetry shell
flask run

The first command ensures that you are in the correct Python virtual environment managed by a tool called poetry (you can tell that your command-line prompt looks differently --- it would start with the name of the environment). The second command runs the Flask/web server. Do NOT run Flask outside the poetry environment; you will get errors.

You can now use your laptop's browser to explore the website. Point your browser to http://localhost:8080/

To stop your app, type CTRL-C in the container shell; that will take you back to the command-line prompt, still inside the poetry environment. If you are all done with this app for now, you can type exit to get out of the poetry environment and get back to the normal container shell.

Working with the Database

Your Flask server interacts with a PostgreSQL database called amazon behind the scene. As part of the installation procedure above, this database has been created automatically for you. You can access the database directly by running the command psql amazon in your VM.

For debugging, you can access the database while the Flask server is running. We recommend you open a second container shell to run psql amazon. After you perform some action on the website, you run a query inside psql to see the action has the intended effect on the database.

The db/ subdirectory of this repository contains files useful for (re-)initializing the database if needed. To (re-)initialize the database, first make sure that you are NOT running your Flask server or any psql sessions; then, from your repository directory, run db/setup.sh.

• You will see lots of text flying by --- make sure you go through them carefully and verify there was no errors. Any error in (re-)initializing the database will cause your Flask server to fail, so make sure you fix them.

• If you get ERROR: database "amazon" is being accessed by other users, that means you likely have Flask or another psql still running; terminate them and re-run db/setup.sh. If you cannot seem to find where you are running them, a sure way to get rid of them is to stop/start your container.

To change the database schema, modify db/create.sql and db/load.sql as needed. Make sure you run db/setup.sh to reflect the changes.

Under db/data/, you will find CSV files that db/load.sql uses to initialize the database contents when you run db/setup.sh. Under db/generated/, you will find alternate CSV files that will be used to initialize a bigger database instance when you run db/setup.sh generated; these files are automatically generated by running a script (which you can re-run by going inside db/data/generated/ and running python gen.py.

• Note that PostgreSQL does NOT store data inside these CSV files; it store data on disk files using an efficient, binary format. In other words, if you change your database contents through your website or through psql, you will NOT see these changes reflected in these CSV files (but you can see them through psql amazon).

• For safety, a database should never store password in plain text; instead it stores one-way hash of the password. This rule applies to the password value in the CSV files too. To see what hashed password value you should put in a CSV file, see db/data/gen.py for example of how to compute the hashed value.

Note on Hiding Credentials

Use the file .flaskenv for passwords/secret keys --- we are talking about passwords used to access your database server, for example (not user passwords for your website in CSV files for loading sample database). This file is NOT tracked by git and it was automatically generated when you first ran ./install.sh. Don't check it into git because your credentials would be exposed to everybody on GitLab if you are not careful.