Journal CLI

Mix.install([
  {:kino, github: "livebook-dev/kino", override: true},
  {:kino_lab, "~> 0.1.0-dev", github: "jonatanklosko/kino_lab"},
  {:vega_lite, "~> 0.1.4"},
  {:kino_vega_lite, "~> 0.1.1"},
  {:benchee, "~> 0.1"},
  {:ecto, "~> 3.7"},
  {:math, "~> 0.7.0"},
  {:faker, "~> 0.17.0"},
  {:utils, path: "#{__DIR__}/../utils"},
  {:tested_cell, git: "https://github.com/BrooklinJazz/tested_cell"}
])

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Setup

Ensure you type the ea keyboard shortcut to evaluate all Elixir cells before starting. Alternatively you can evaluate the Elixir cells as you read.

Journal CLI

You’re going to create a Command Line Interface Application, generally referred to as a CLI. This CLI will automate the process of creating daily journals with a markdown template.

Once complete, you will run the following in the command line:

./journal

Which will generate a markdown file based on the current date yyyy-mm-dd.md with a journal template.

Create A New Mix Project

Using the command line, create a new project in the projects folder called journal.

mix new journal

Configure the Project For the Command Line

We want to be able to use the command line to execute this project.

Command line applications run the main/1 function on a configured module.

First, add a main/1 function to the Journal module in journal.ex. We’re going to leave it with a blank IO.inspect/2 for now.

def main(args) do
  IO.inspect(args)
end

For a command line application, we need to tell Mix which module to run. Configure the :escript option with the :main_module. Tell Mix to use the Journal module in mix.exs.

def project do
  [
    app: :journal,
    version: "0.1.0",
    elixir: "~> 1.13",
    start_permanent: Mix.env() == :prod,
    deps: deps(),
    # Added this line
    escript: [main_module: Journal]
  ]
end

Under the hood, Elixir builds an executable file called an escript. This escript can be invoked from the command line directly rather than using the IEx Shell.

Run the following in the command line from the project folder to build the executable file. To pick up future changes, you will need to re-run this command.

mix escript.build

Execute the file with:

./journal

You should see it print an empty list. That’s because we haven’t passed in any arguments.

[]

Pass in arguments to see them in the list.

./journal argument1 argument2 --switch
["argument1", "argument2", "--switch"]

Create A Daily Journal

With no arguments provided, the ./journal command should create a markdown file yyyy-mm-dd.md in an entries/ folder.

The files contents should be blank except for a title matching todays date.

# yyyy-mm-dd

Implement the Journal.main/1 function when given no arguments. Once complete, run the following from the command line.

./journal

And ensure it generated a entries/yyyy-mm-dd.md file with the following content.

# yyyy-mm-dd

Where yyyy-mm-dd is the current date. i.e. 2022-05-25.

Add the –folder Switch

Command line applications use switches to alter functionality. You’ve already used a switch whenever you make a git commit.

git commit -m "my example commit"

-m is just an alias for message. So you could also use:

git commit --message "my example commit".

So --message is a switch for the git cli.

You’re going to create a --folder switch for our journal cli which will override the default entries folder. For example, the following will create a new file in the example_folder.

./journal --folder example_folder

You can use the built-in OptionParser module to parse switches. Specify the :switches in a keyword list with their values. For example, a --folder switch could be handled with:

# journal.ex
def main(args) do
  options = [switches: [folder: :string]]
  {opts, _, _} = OptionParser.parse(args, options)
  IO.inspect(opts)
end

Now opts for the following command would be: [folder: "example"].

./journal --folder example_folder

Implement the --folder switch to store journal entries in a different folder. Continue to use test_entries if the --folder switch is not provided.

Add the –file Switch

Implement the --file switch, which should override the default file name.

So the following would create a new file test.md.

./journal --file test

Add the –title Switch

Implement the --title switch, which should override the default file title.

So the following would create a new file test.md.

./journal --file test --title "My Title"

With the following content:

# My Title

Use the –template Switch

Test and implement the --template switch.

The template flag should allow users to use any custom template in a templates folder like so:

./journal --template bullet_journal

Where templates/bullet_journal.md is a markdown file with the following content:

# Bullet Journal
I am grateful for
-
-
-

Today I will
-
-
-

(BONUS) Handle An Existing Daily Journal

Warn users if they already have a daily journal or a journal with the same name. You can use IO.puts/2 to print a message to the user.

$ ./journal
Error, daily journal already exists. Open test_entries/yyyy-mm-dd.md to see todays journal.

(BONUS) Provide Custom Values in Templates

If a template defines some content in the format {DATE}, replace that content with todays date.

If a template defines some content in the format {TITLE} replace that value with the --title switch if it exists. If it does not exist, replace the {TITLE} with an empty string.

For example:

# {TITLE}
Created on {DATE}

When provided --title "My Title" Would become:

# My Title
Created on 2022-04-06

(Bonus) Search Entries

Implement a search command you can use to find files who’s file name contains the searched string.

./journal search "example"
/entries/example_file1.md
/entries/example_file2.md

You can use IO.puts/2 to print information in the console.

Commit Your Progress

Run the following in your command line from the project folder to track and save your progress in a Git commit.

$ git add .
$ git commit -m "finish journal cli exercise"