Make next assignee reassignable

lib/chore_tracker/chores.ex

@@ -12,10 +12,11 @@ defmodule ChoreTracker.Chores do
 
   def list_chores do
     logs = from(log in ChoreLog, limit: 1)
-    from(chore in Chore, preload: [:assignees, logs: ^logs]) |> Repo.all()
+    from(chore in Chore, preload: [:assignees, :next_assignee, logs: ^logs]) |> Repo.all()
   end
 
-  def get_chore!(id), do: Repo.get!(Chore, id) |> Repo.preload([{:logs, :user}, :assignees])
+  def get_chore!(id),
+    do: Repo.get!(Chore, id) |> Repo.preload([{:logs, :user}, :assignees, :next_assignee])
 
   def create_chore(attrs \\ %{}) do
     %Chore{}
@@ -24,9 +25,12 @@ defmodule ChoreTracker.Chores do
   end
 
   def update_chore(%Chore{} = chore, attrs) do
-    chore
-    |> change_chore(attrs)
-    |> Repo.update()
+    Ecto.Multi.new()
+    |> Ecto.Multi.update(:chore, change_chore(chore, attrs))
+    |> Ecto.Multi.run(:update_next_assignee, fn _repo, _changeset ->
+      save_next_chore_assignee(chore)
+    end)
+    |> Repo.transaction()
   end
 
   def delete_chore(%Chore{} = chore) do
@@ -41,6 +45,14 @@ defmodule ChoreTracker.Chores do
     |> Changeset.put_assoc(:assignees, assignees)
   end
 
+  def update_chore_assignee(%Chore{} = chore, attrs) do
+    change_chore_assignee(chore, attrs) |> Repo.update()
+  end
+
+  def change_chore_assignee(%Chore{} = chore, attrs \\ %{}) do
+    chore |> Ecto.Changeset.cast(attrs, [:next_assignee_id])
+  end
+
   def get_last_chore_log_for_assignee(%Chore{} = chore, %User{} = user) do
     from(log in ChoreLog,
       where: log.chore_id == ^chore.id and log.user_id == ^user.id,
@@ -51,9 +63,15 @@ defmodule ChoreTracker.Chores do
   end
 
   def log_chore_execution(%User{} = user, %Chore{} = chore) do
-    %ChoreLog{}
-    |> ChoreLog.changeset(%{user_id: user.id, chore_id: chore.id})
-    |> Repo.insert()
+    Ecto.Multi.new()
+    |> Ecto.Multi.insert(
+      :log,
+      %ChoreLog{} |> ChoreLog.changeset(%{user_id: user.id, chore_id: chore.id})
+    )
+    |> Ecto.Multi.run(:chore, fn _repo, _change ->
+      save_next_chore_assignee(chore)
+    end)
+    |> Repo.transaction()
   end
 
   def update_chore_log(%ChoreLog{} = chore_log, attrs) do
@@ -83,6 +101,11 @@ defmodule ChoreTracker.Chores do
     chore.starts_at
   end
 
+  @doc """
+  Calculate next assignee for the chore.
+  Assigns the person who last did the task the longest time ago.
+  Returns `nil` if chore has no assignees.
+  """
   def next_chore_assignee(%Chore{} = chore) do
     chore.assignees
     |> Enum.map(&{&1, get_last_chore_log_for_assignee(chore, &1)})
@@ -98,4 +121,14 @@ defmodule ChoreTracker.Chores do
     |> Enum.map(fn {assignee, _log} -> assignee end)
     |> List.first()
   end
+
+  defp save_next_chore_assignee(%Chore{} = chore) do
+    next_assignee = next_chore_assignee(chore)
+
+    if next_assignee do
+      chore |> update_chore_assignee(%{next_assignee_id: next_assignee.id})
+    else
+      {:ok, nil}
+    end
+  end
 end

lib/chore_tracker/chores/chore.ex

@@ -1,6 +1,8 @@
 defmodule ChoreTracker.Chores.Chore do
   use Ecto.Schema
   import Ecto.Changeset
+  alias ChoreTracker.Chores
+  alias ChoreTracker.Accounts
 
   schema "chores" do
     field :name, :string
@@ -12,9 +14,11 @@ defmodule ChoreTracker.Chores.Chore do
 
     timestamps(type: :utc_datetime)
 
-    has_many :logs, ChoreTracker.Chores.ChoreLog, preload_order: [desc: :inserted_at]
+    has_many :logs, Chores.ChoreLog, preload_order: [desc: :inserted_at]
 
-    many_to_many :assignees, ChoreTracker.Accounts.User,
+    belongs_to :next_assignee, Accounts.User
+
+    many_to_many :assignees, Accounts.User,
       join_through: "chore_assignees",
       on_replace: :delete
   end
@@ -22,7 +26,15 @@ defmodule ChoreTracker.Chores.Chore do
   @doc false
   def changeset(chore, attrs) do
     chore
-    |> cast(attrs, [:name, :description, :emoji, :period, :period_unit, :starts_at])
+    |> cast(attrs, [
+      :name,
+      :description,
+      :emoji,
+      :period,
+      :period_unit,
+      :starts_at,
+      :next_assignee_id
+    ])
     |> validate_required([:name, :emoji, :period, :period_unit, :starts_at])
     |> validate_length(:emoji, min: 1, max: 1)
   end

lib/chore_tracker_web/live/chore_live/show.ex

@@ -1,4 +1,5 @@
 defmodule ChoreTrackerWeb.ChoreLive.Show do
+  alias ChoreTracker.Repo
   use ChoreTrackerWeb, :live_view
 
   alias ChoreTracker.Chores
@@ -11,15 +12,18 @@ defmodule ChoreTrackerWeb.ChoreLive.Show do
 
   @impl true
   def handle_params(%{"id" => id}, _, socket) do
+    chore = Chores.get_chore!(id)
+
     {:noreply,
      socket
      |> assign(:page_title, page_title(socket.assigns.live_action))
-     |> assign(:chore, Chores.get_chore!(id))}
+     |> update_state(chore)}
   end
 
   defp page_title(:show), do: "Show Chore"
   defp page_title(:edit), do: "Edit Chore"
 
+  @impl true
   def handle_event("log_execution", _params, socket) do
     %{current_user: user, chore: chore} = socket.assigns
 
@@ -28,7 +32,31 @@ defmodule ChoreTrackerWeb.ChoreLive.Show do
         {:noreply,
          socket
          |> put_flash(:info, "Chore execution logged.")
-         |> assign(:chore, Chores.get_chore!(chore.id))}
+         |> update_state(Chores.get_chore!(chore.id))}
     end
   end
+
+  @impl true
+  def handle_event("change_assignee", params, socket) do
+    %{"chore" => chore_params} = params
+    chore = socket.assigns.chore
+
+    case Chores.update_chore_assignee(chore, chore_params) do
+      {:ok, chore} ->
+        {:noreply,
+         socket
+         |> put_flash(:info, "Assignee changed")
+         |> update_state(chore)}
+    end
+  end
+
+  def assignee_options() do
+    Accounts.list_users() |> Enum.map(&{Accounts.display_user(&1), &1.id})
+  end
+
+  defp update_state(socket, chore) do
+    socket
+    |> assign(:chore, chore |> Repo.preload(:next_assignee))
+    |> assign(:assignee_form, to_form(Chores.change_chore_assignee(chore)))
+  end
 end

lib/chore_tracker_web/live/chore_live/show.html.heex

@@ -59,13 +59,22 @@
   </div>
 
   <div class="col-span-6">
-    <p class="text-sm font-medium text-zinc-500 mb-2">Next assignee</p>
-
-    <%= if next_assignee = Chores.next_chore_assignee(@chore) do %>
-      <p><%= Accounts.display_user(next_assignee) %></p>
-    <% else %>
-      <p>None</p>
-    <% end %>
+    <label for="chore_next_assignee_id" class="text-sm font-medium text-zinc-500">
+      Next assignee
+    </label>
+    <.form
+      for={@assignee_form}
+      class="flex flex-wrap gap-2 items-end"
+      phx-submit="change_assignee"
+    >
+      <.input
+        field={@assignee_form[:next_assignee_id]}
+        prompt="None"
+        type="select"
+        options={assignee_options()}
+      />
+      <.button type="submit">Save</.button>
+    </.form>
   </div>
 
   <div class="col-span-12">

lib/chore_tracker_web/live/overview_live.ex

@@ -36,7 +36,7 @@ defmodule ChoreTrackerWeb.OverviewLive do
         <p><%= display_relative(next_date) %></p>
       </:col>
       <:col :let={chore} label="Next assignee">
-        <%= case Chores.next_chore_assignee(chore) do
+        <%= case chore.next_assignee do
           nil -> "No assignee"
           %Accounts.User{} = user -> Accounts.display_user(user)
         end %>

priv/repo/migrations/20240807222134_create_chores.exs

@@ -9,6 +9,7 @@ defmodule ChoreTracker.Repo.Migrations.CreateChores do
       add :period, :integer
       add :period_unit, :string
       add :starts_at, :date
+      add :next_assignee_id, references(:users, on_delete: :nilify_all)
 
       timestamps(type: :utc_datetime)
     end