Timeline

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.8.0", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Timeline

You are building an application which creates a timeline of events. Users provide you with a list of Dates. You will provide the number of days between each date.

dates = [~D[2020-01-01], ~D[2020-01-02], ~D[2020-01-22]]

Timeline.from_dates(dates)
[1, 20]

BONUS: Timeline.from_strings/1.

As a bonus, implement the Timeline.from_strings/1 function which accepts a list of strings instead of a list of Dates.

date_strings = ["2020-01-01", "2020-01-02", "2020-01-22"]

Timeline.from_strings(date_strings)
[1, 20]

Example Solution

defmodule Timeline do
  
  def from_dates(dates) do
    Enum.chunk_every(dates, 2, 1, :discard)
    |> Enum.map(fn chunk ->
      [start, finish] = chunk
      Date.diff(finish, start)
    end)
  end

  def from_strings(date_strings) do
    date_strings
    |> Enum.map(&string_to_date/1)
    |> from_dates()
  end

  defp string_to_date(date_string) do
    [year, month, day] = String.split(date_string, "-")
    Date.new!(String.to_integer(year), String.to_integer(month), String.to_integer(day))
  end
end

Enter your solution below.

defmodule Timeline do
  @moduledoc """
  Documentation for `Timeline`
  """

  @doc """
  Given a list of [Date](https://hexdocs.pm/elixir/Date.html)s return a timeline of days between each date.

  ## Examples

    iex> Timeline.from_dates([~D[2020-01-01]])
    []

    iex> Timeline.from_dates([~D[2020-01-01], ~D[2020-01-02]])
    [1]

    iex> Timeline.from_dates([~D[2020-01-01], ~D[2020-01-02], ~D[2020-01-22]])
    [1, 20]
    
    iex> Timeline.from_dates([~D[2020-01-01], ~D[2020-01-10], ~D[2020-01-22], ~D[2020-01-24]])
    [9, 12, 2]
  """
  def from_dates(dates) do
  end

  @doc """
  Given a list of "YYYY-MM-DD" strings return a timeline of days between each date.
  Assume you will always be given two or more strings.

  ## Examples

    iex> Timeline.from_strings(["2020-01-01", "2020-01-02"])
    [1]

    iex> Timeline.from_strings(["2020-01-01", "2020-01-02", "2020-01-22"])
    [1, 20]
    
    iex> Timeline.from_strings(["2020-01-01", "2020-01-10", "2020-01-22", "2020-01-24"])
    [9, 12, 2]
  """
  def from_strings(date_strings) do
  end
end

Mark As Completed

file_name = Path.basename(Regex.replace(~r/#.+/, __ENV__.file, ""), ".livemd")

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "timeline_reading"
    "exercises" -> "timeline_exercise"
  end

progress_path = __DIR__ <> "/../progress.json"
existing_progress = File.read!(progress_path) |> Jason.decode!()

default = Map.get(existing_progress, save_name, false)

form =
  Kino.Control.form(
    [
      completed: input = Kino.Input.checkbox("Mark As Completed", default: default)
    ],
    report_changes: true
  )

Task.async(fn ->
  for %{data: %{completed: completed}} <- Kino.Control.stream(form) do
    File.write!(
      progress_path,
      Jason.encode!(Map.put(existing_progress, save_name, completed), pretty: true)
    )
  end
end)

form

Commit Your Progress

Run the following in your command line from the curriculum folder to track and save your progress in a Git commit. Ensure that you do not already have undesired or unrelated changes by running git status or by checking the source control tab in Visual Studio Code.

$ git checkout -b timeline-exercise
$ git add .
$ git commit -m "finish timeline exercise"
$ git push origin timeline-exercise

Create a pull request from your timeline-exercise branch to your solutions branch. Please do not create a pull request to the DockYard Academy repository as this will spam our PR tracker.

DockYard Academy Students Only:

Notify your teacher by including @BrooklinJazz in your PR description to get feedback. You (or your teacher) may merge your PR into your solutions branch after review.

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