Mensa UPB Command-line tool | Portfolio Moritz Hölting

A small tool I wrote in Rust for checking which meals I can eat at university.

Demo of the tool

Allows choosing the day, the locations and which prices to show.

It works by parsing the command-line arguments with clap and asynchronously requesting and scraping the webpage. The gathered data is filtered and displayed as a table.

Usage

Show the menu for today
```
mensa-upb-cli
```
Show the help screen
```
mensa-upb-cli --help
```
Show the menu of the third next day
```
mensa-upb-cli -d 3
```
Show the menu of a different mensa
```
mensa-upb-cli -m grill-cafe
```
Show the only the prices for students
```
mensa-upb-cli -p student
```

How it is made

My university has multiple cafeterias and a website with the menu of each one. I did not like checking multiple pages when choosing what and where to eat.

Therefore I decided to build an application that would make this process easier. My solution had 4 steps:

Read the user input
Fetch the data
Filter the data based on user input
Output the data in a readable way

1. Reading user input

For reading the cli arguments, I choose clap which is a popular library and very easy to use by deriving the traits.

#[derive(Parser)]
#[command(author, version, about, long_about = None)]
struct Cli {
    /// Choose the mensa
    #[arg(short, long, value_enum, default_values_t = [Mensa::Forum, Mensa::Academica])]
    mensa: Vec<Mensa>,
    /// Choose the price level
    #[arg(short, long)]
    price_level: Option<PriceLevel>,
    /// Choose how many days in the future to fetch
    #[arg(short, long)]
    days_ahead: Option<u64>,
    /// Filter by extras
    #[arg(short, long)]
    extras: Vec<String>,
}

2. Fetch the data

Because there is no API for our cafeteria, I had to scrape the website. The tools I used are reqwest for fetching the html and scraper for extracting the required information from the html.

3. Filter the data based on user input

Filtering is done at multiple places:

only fetch and parse the pages of the cafeterias requested and the day selected
filter which price level to show (student, employee, guest)
filter which meals match the selected extra (vegetarian, vegan)

4. Output the data in a readable way

For readability, I choose to display the meals in a table. Also I wanted to group the meals by categorie (main dishes, side dishes and desserts). A nice library I found for printing tables to the terminal is comfy-table. It allows customizing the borders and alignment of each cell.

let mut desserts_row = Row::new();
desserts_row.add_cell(
    Cell::from("Desserts")
        .set_alignment(CellAlignment::Center)
        .add_attribute(comfy_table::Attribute::Underlined)
        .add_attribute(comfy_table::Attribute::OverLined),
);

Source Code

If you want to take a look at the source code, it is available on my GitHub. You could even try to adapt the web requesting and scraping to the cafeteria you go to.