ETS Inventory Management

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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ETS Inventory

You’re going to build an in-memory inventory management application using :ets.

Example Solution

defmodule Inventory do
  def new(opts \\ []) do
    :ets.new(:inventory, opts)
  end

  def get_quantity(ref, item) do
    case :ets.lookup(ref, item) do
      [{_item, quantity}] -> quantity
      _ -> 0
    end
  end

  def store(ref, item, quantity) do
    existing_quantity = get_quantity(ref, item)
    :ets.insert(ref, {item, quantity + existing_quantity})
  end
end

Implement the Inventory module as documented.

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

  ## Examples

      Single quantity.

      iex> ref = Inventory.new()
      iex> Inventory.store(ref, :apples, 5)
      iex> Inventory.get_quantity(ref, :apples)
      5

      Multiple stores.

      iex> ref = Inventory.new()
      iex> Inventory.store(ref, :apples, 5)
      iex> Inventory.store(ref, :apples, 2)
      iex> Inventory.get_quantity(ref, :apples)
      7
  """
  @doc """
  Create a new Inventory :ets table.

  ## Examples

      iex> ref = Inventory.new()
      iex> is_reference(ref)
      true
  """
  def new() do
  end

  @doc """
  Retrieve the current quantity of an item in inventory.

  ## Examples
        
      iex> ref = Inventory.new()
      iex> Inventory.get_quantity(ref, :apples)
      0
  """
  def get_quantity(ref, item) do
  end

  @doc """
  Store an item in inventory.
  If item exists, add amount to existing total.

  ## Examples

      iex> ref = Inventory.new()
      iex> Inventory.store(ref, :apples, 5)
      true
  """
  def store(ref, item, quantity) do
  end
end

Bonus: Warehouse

You’re going to build a warehouse management application using :ets. Now, instead of having a single quantity for each item, every item can be stored in multiple boxes, each with their own quantity of that item.

Hint

Consider using the :duplicate_bag Table Type.

Example Solution

defmodule Warehouse do
  def new() do
    :ets.new(:warehouse, [:duplicate_bag])
  end

  def get_quantity(ref, item) do
    :ets.lookup(ref, item)
  end

  def store(ref, item, quantity) do
    :ets.insert(ref, {item, quantity})
  end
end

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

  ## Examples

      Existing quantity.

      iex> ref = Warehouse.new()
      iex> Warehouse.store(ref, :apples, 5)
      iex> Warehouse.get_boxes(ref, :apples)
      [apples: 5]

      Multiple Boxes.

      iex> ref = Warehouse.new()
      iex> Warehouse.store(ref, :apples, 1)
      iex> Warehouse.store(ref, :apples, 3)
      iex> Warehouse.get_boxes(ref, :apples)
      [apples: 1, apples: 3]
  """

  @doc """
  Create a new Warehouse :ets table.

  ## Examples

      iex> ref = Warehouse.new()
      iex> is_reference(ref)
      true
  """
  def new(opts \\ []) do
  end

  @doc """
  Retrieve all boxes of an item and the associated quantity in each box.

  ## Examples

      iex> ref = Warehouse.new()
      iex> Warehouse.get_boxes(ref, :apples)
      []
  """
  def get_boxes(ref, item) do
  end

  @doc """
  Store an item in the warehouse.
  If item exists, add amount to existing total.

    ## Examples

      iex> ref = Warehouse.new()
      iex> Warehouse.store(ref, :apples, 5)
      true
  """
  def store(ref, item, quantity) do
  end
end

Mark As Completed

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

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "inventory_management_reading"
    "exercises" -> "inventory_management_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 inventory-management-exercise
$ git add .
$ git commit -m "finish inventory management exercise"
$ git push origin inventory-management-exercise

Create a pull request from your inventory-management-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.

If you are interested in joining the next academy cohort, sign up here to receive more news when it is available.

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