Replace date-parser with log-parser (regular expressions)

[angelikatyborska]

Closes #941

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---

Automated comment created by PR Commenter 🤖.

[angelikatyborska]

I wanted to add some step that would require an interpolated regex with escaping a variable, but I couldn't come up with anything thematic that wouldn't be better done with String.starts_with? :/

[jiegillet]

How about adding a step to tag_with_user_name/1?
Maybe something like bolding the user names whenever they are mentioned without "User"?

LogParser.tag_with_user_name("[INFO] User Alice created a new project.")
# => "[USER] Alice [INFO] User Alice created a new project"
LogParser.tag_with_user_name("[INFO] User Alice created a new project. Alice has a reputation of 643.")
# => "[USER] Alice [INFO] User Alice created a new project. **Alice** has a reputation of 643."

[jiegillet]

Nice, I think it's definitely an improvement over the date-parser.

I left a couple of small suggestions, but I'm already approving. Ping me on Slack if you need another round of review, I might miss the notification otherwise.

Here is my solution as reference

defmodule LogParser do
  def valid_line?(line) do
    regex = ~r/^\[(DEBUG|INFO|WARNING|ERROR)\]/
    line =~ regex
  end 

  def split_line(line) do
    regex = ~r/<[~\*=-]*>/
    String.split(line, regex)
  end 

  def remove_artifacts(line) do
    regex = ~r/end-of-line\d+/i
    String.replace(line, regex, "") 
  end 

  def tag_with_user_name(line) do
    regex = ~r/User\s+(\S+)/

    case Regex.run(regex, line) do
      [_user_name, name] -> "[USER] #{name} " <> line
      _ -> line
    end 
  end 
end

[jiegillet]

I think we should add an example, something like

Regex.run(~r/test number (\d+)/, "This is test number 256")
# => ["test number 256", "256"]

[angelikatyborska]

Done: 394686e (#1148)

It also made me realize that the initial description was wrong :) the first element isn't always the whole input string, only the part of it that was a match for the regex.

[jiegillet]

Should we offer a link or two for those who don't?
To be honest, I just googled learning regex and found plenty of material, but there are also a bunch of links in the hints we could reuse.

[angelikatyborska]

Done: a133b42 (#1148)

[jiegillet]

We mention this point in the intro, but we don't practice it in an exercise.
Maybe we could have one exercise that involves parsing several / and ask them to use another delimiter for readability?

[angelikatyborska]

Good point. It would also be possible to do an analyzer check for the delimiter because that information is kept in the AST:

iex(2)> quote do
...(2)> ~r()
...(2)> end
{:sigil_r, [delimiter: "(", context: Elixir, import: Kernel],
 [{:<<>>, [], [""]}, []]}

[jiegillet]

How about adding a step to tag_with_user_name/1?
Maybe something like bolding the user names whenever they are mentioned without "User"?

LogParser.tag_with_user_name("[INFO] User Alice created a new project.")
# => "[USER] Alice [INFO] User Alice created a new project"
LogParser.tag_with_user_name("[INFO] User Alice created a new project. Alice has a reputation of 643.")
# => "[USER] Alice [INFO] User Alice created a new project. **Alice** has a reputation of 643."

[angelikatyborska]

I postponed the two improvement ideas (#1162) because I'm low on time and creativity at the moment, but I really want to get this out before the ExHort starts on 08.08.