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C Programming for Everybody (CC4E)

Course materials for www.cc4e.com

See the file book/README.md for book-related details.

Setup On Localhost

Here are the steps to set this up on localhost on a Macintosh using MAMP.

Install MAMP (or similar) using https://www.wa4e.com/install

Check out this repo into a top level folder in htdocs

cd /Applications/MAMP/htdocs
git clone https://github.com/csev/cc4e.git

Go into the newly checked out folder and get a copy of Tsugi:

cd cc4e
git clone https://github.com/csev/tsugi.git

Create a database in your SQL server:

CREATE DATABASE tsugi DEFAULT CHARACTER SET utf8;
CREATE USER 'ltiuser'@'localhost' IDENTIFIED BY 'ltipassword';
GRANT ALL ON tsugi.* TO 'ltiuser'@'localhost';
CREATE USER 'ltiuser'@'127.0.0.1' IDENTIFIED BY 'ltipassword';
GRANT ALL ON tsugi.* TO 'ltiuser'@'127.0.0.1';

Still in the tsugi folder set up config.php:

cp config-dist.php config.php

Edit the config.php file, scroll through and set up all the variables. As you scroll through the file some of the following values are the values I use on my MAMP:

$wwwroot = 'http://localhost:8888/cc4e/tsugi';   // Embedded Tsugi localhost

...

$CFG->pdo = 'mysql:host=127.0.0.1;port=8889;dbname=tsugi'; // MAMP
$CFG->dbuser    = 'ltiuser';
$CFG->dbpass    = 'ltipassword';

...

$CFG->adminpw = 'short';

...

$CFG->apphome = 'http://localhost:8888/cc4e';
$CFG->context_title = "C Programming for Everybody";
$CFG->lessons = $CFG->dirroot.'/../lessons.json';

... 

$CFG->tool_folders = array("admin", "../tools", "../mod");
$CFG->install_folder = $CFG->dirroot.'./../mod'; // Tsugi as a store

...

$CFG->servicename = 'CC4E';

(Optional) If you want to use Google Login, go to https://console.developers.google.com/apis/credentials and create an "OAuth Client ID". Make it a "Web Application", give it a name, put the following into "Authorized JavaScript Origins":

    http://localhost

And these into Authorized redirect URIs:

http://localhost/cc4e/tsugi/login.php
http://localhost/cc4e/tsugi/login

Note: You do not need port numbers for either of these values in your Google configuration.

Google will give you a 'client ID' and 'client secret', add them to config.php as follows:

$CFG->google_client_id = '96..snip..oogleusercontent.com';
$CFG->google_client_secret = 'R6..snip..29a';

While you are there, you could "Create credentials", select "API key", and name the key "My Google MAP API Key" and put the API key into config.php like the following:

$CFG->google_map_api_key = 'AIza..snip..9e8';

Starting the Application

After the above configuration is done, navigate to your application:

http://localhost:8888/cc4e/tsugi/

It should complain that you have not created tables and suggest you use the Admin console to do that:

http://localhost:8888/cc4e/tsugi/admin

It will demand the $CFG->adminpw from config.php (above) before unlocking the admin console. Run the "Upgrade Database" option and it should create lots of tables in the database and the red warning message about bad database, should go away.

Alternately, you can create all the databases on the command line using:

cd cc4e/tsugi/admin
php upgrade.php

Keep refreshing the /cc4e/tsugi page until all the error messages go away. Once the error messages are gone, the main page should also have no errors.

http://localhost:8888/cc4e/

Go into the database and the lti_key table, find the row with the key_key of google.com and put a value in the secret column - anything will do - just don't leave it empty or the internal LTI tools will not launch.

You can always test the tools using the "App Store" at:

http://localhost:8888/cc4e/tools/

This allows you to do test launches as the instructor and student in a test environment using the key '12345'.

Setting up Emscripten

To compile, run, and autograde code, this site uses Emscripten which compiles C to Web Assembly:

https://emscripten.org/

Using this means that we can run student in their browser rather than on the server. This saves a bunch of compute resources, reliability issues, and security vulnerabilities when running student code on the server. The code is compiled to WASM and JS using emcc and then the code is sent to the browser for execution and the ouytput is thenn returned from the browser.

You need to install the Emscripten compiler. On Ubuntu:

 apt install emscripten

On Macintosh:

brew install emscripten

You also need to make a folder /var/www/compile where the student code will be stored and compiled and chown it to www-root:

mkdir /var/www/compile
chown -R www-data.www-data /var/www/compile

This folder will accumulate student programs and results. You probably want to make a cron job to clear out this folder for data more than a week old so it does not grow.

Here are the configuration options to setup the compiler for Ubuntu:

$CFG->setExtension('emcc_path', '/var/www/emsdk/upstream/emscripten/emcc');
$CFG->setExtension('emcc_folder', '/var/www/compile');
$CFG->setExtension('emcc_secret', 'changeme');

On Macintosh:

$CFG->setExtension('emcc_path', '/opt/homebrew/bin/emcc');
$CFG->setExtension('emcc_folder', '/tmp/zap');
$CFG->setExtension('emcc_secret', 'zap');

If you want to debug the Emscripten process, you can add this configuration option:

$CFG->setExtension('emcc_pause', 'true');

Instead of the spinner and flash, the process wqill pause sou you can look at the in-browser code to load and run the WASM and then send the output back to be graded or shown.

Using the Application

Navigate to:

http://localhost:8888/cc4e/

You should click around without logging in and see if things work.

Then log in with your Google account and the UI should change. In particular you should see 'Assignments' and in Lessons you should start seeing LTI autograders.