Add reset to backend

backend/.gitignore

@@ -22,3 +22,5 @@ erl_crash.dump
 # Ignore package tarball (built via "mix hex.build").
 week_budget-*.tar
 
+.elixir_ls
+

backend/lib/api/server.ex

@@ -11,6 +11,7 @@ defmodule WeekBudget.API.Server do
   @spec handle_request(Raxx.Request.t(), %{}) :: Raxx.Response.t()
   def handle_request(req, state)
 
+  # GET budget information
   def handle_request(%{method: :GET, path: ["budgets", uuid]}, _state) when uuid != "" do
     with {:ok, _} <- Ecto.UUID.dump(uuid),
          %WeekBudget.DB.Budget{} = wb <- WeekBudget.DB.Budget.get_by_secret(uuid) do
@@ -23,38 +24,71 @@ defmodule WeekBudget.API.Server do
     end
   end
 
+  # POST new event into budget
   def handle_request(%{method: :POST, path: ["budgets", uuid, "events"], body: body}, _state)
       when uuid != "" and body != "" do
-    with {:uuid, {:ok, _}} <- {:uuid, Ecto.UUID.dump(uuid)},
-         {:wb, %WeekBudget.DB.Budget{} = wb} <- {:wb, WeekBudget.DB.Budget.get_by_secret(uuid)},
-         {:json, {:ok, %{"amount" => amnt}}} when is_number(amnt) <- {:json, Jason.decode(body)},
-         {:currency, {:ok, curr}} <- {:currency, Money.validate_currency(wb.amount.currency)},
-         {:money, %Money{} = money} <- {:money, WeekBudget.Core.MoneyUtils.create(curr, -amnt)} do
-      {:ok, event} = WeekBudget.DB.Event.create(wb, money)
-      event_json = serialize_event(event)
-      json_resp(:created, event_json)
-    else
-      {:uuid, _} -> json_resp(:bad_request, %{error: "Malformed UUID."})
-      {:wb, _} -> json_resp(:not_found, %{error: "Budget not found."})
-      {:json, _} -> json_resp(:bad_request, %{error: "Cannot parse JSON."})
-      {:currency, _} -> json_resp(:bad_request, %{error: "Invalid currency."})
-      {:money, _} -> json_resp(:internal_server_error, %{error: "Cannot create money."})
-    end
+    {status, data} =
+      with {:uuid, {:ok, _}} <- {:uuid, Ecto.UUID.dump(uuid)},
+           {:wb, %WeekBudget.DB.Budget{} = wb} <- {:wb, WeekBudget.DB.Budget.get_by_secret(uuid)},
+           {:json, {:ok, %{"amount" => amnt}}} when is_number(amnt) <-
+             {:json, Jason.decode(body)},
+           {:money, %Money{} = money} <-
+             {:money, WeekBudget.Core.MoneyUtils.create(wb.amount.currency, -amnt)} do
+        {:ok, event} = WeekBudget.DB.Event.create(wb, money)
+        event_json = serialize_event(event)
+        {:created, event_json}
+      else
+        {:uuid, _} -> {:bad_request, %{error: "Malformed UUID."}}
+        {:wb, _} -> {:not_found, %{error: "Budget not found."}}
+        {:json, _} -> {:bad_request, %{error: "Cannot parse JSON."}}
+        {:currency, _} -> {:bad_request, %{error: "Invalid currency."}}
+        {:money, _} -> {:internal_server_error, %{error: "Cannot create money."}}
+      end
+
+    json_resp(status, data)
   end
 
+  # PATCH budget with a new amount, deleting all events
+  def handle_request(%{method: :PATCH, path: ["budgets", uuid], body: body}, _state)
+      when uuid != "" and body != "" do
+    {status, data} =
+      with {:uuid, {:ok, _}} <- {:uuid, Ecto.UUID.dump(uuid)},
+           {:wb, %WeekBudget.DB.Budget{} = wb} <- {:wb, WeekBudget.DB.Budget.get_by_secret(uuid)},
+           {:json, {:ok, %{"amount" => amnt}}} when is_number(amnt) <-
+             {:json, Jason.decode(body)},
+           {:money, %Money{} = money} <-
+             {:money, WeekBudget.Core.MoneyUtils.create(wb.amount.currency, amnt)} do
+        {:ok, %{amount_update: budget}} = WeekBudget.DB.Budget.reset(wb, money)
+        budget_json = serialize_budget(%WeekBudget.DB.Budget{budget | events: []})
+        {:ok, budget_json}
+      else
+        {:uuid, _} -> {:bad_request, %{error: "Malformed UUID."}}
+        {:wb, _} -> {:not_found, %{error: "Budget not found."}}
+        {:json, _} -> {:bad_request, %{error: "Cannot parse JSON."}}
+        {:currency, _} -> {:bad_request, %{error: "Invalid currency."}}
+        {:money, _} -> {:internal_server_error, %{error: "Cannot create money."}}
+      end
+
+    json_resp(status, data)
+  end
+
+  # POST to create a new budget
   def handle_request(%{method: :POST, path: ["budgets"], body: body}, _state) when body != "" do
-    with {:json, {:ok, %{"amount" => amnt, "currency" => curr_str}}}
-         when is_number(amnt) and is_binary(curr_str) <- {:json, Jason.decode(body)},
-         {:currency, {:ok, curr}} <- {:currency, Money.validate_currency(curr_str)},
-         {:money, %Money{} = money} <- {:money, WeekBudget.Core.MoneyUtils.create(curr, amnt)} do
-      {:ok, budget} = WeekBudget.DB.Budget.create(money)
-      budget_json = serialize_budget(%WeekBudget.DB.Budget{budget | events: []})
-      json_resp(:created, budget_json)
-    else
-      {:json, _} -> json_resp(:bad_request, %{error: "Cannot parse JSON."})
-      {:currency, _} -> json_resp(:bad_request, %{error: "Invalid currency."})
-      {:money, _} -> json_resp(:internal_server_error, %{error: "Cannot create money."})
-    end
+    {status, data} =
+      with {:json, {:ok, %{"amount" => amnt, "currency" => curr_str}}}
+           when is_number(amnt) and is_binary(curr_str) <- {:json, Jason.decode(body)},
+           {:currency, {:ok, curr}} <- {:currency, Money.validate_currency(curr_str)},
+           {:money, %Money{} = money} <- {:money, WeekBudget.Core.MoneyUtils.create(curr, amnt)} do
+        {:ok, budget} = WeekBudget.DB.Budget.create(money)
+        budget_json = serialize_budget(%WeekBudget.DB.Budget{budget | events: []})
+        {:created, budget_json}
+      else
+        {:json, _} -> {:bad_request, %{error: "Cannot parse JSON."}}
+        {:currency, _} -> {:bad_request, %{error: "Invalid currency."}}
+        {:money, _} -> {:internal_server_error, %{error: "Cannot create money."}}
+      end
+
+    json_resp(status, data)
   end
 
   def handle_request(req, _) do

backend/lib/core/money_utils.ex

@@ -8,8 +8,7 @@ defmodule WeekBudget.Core.MoneyUtils do
   frontends. It is normalised to a Money instance at first opportunity so it is believed that the
   impact and potential for errors is minimal.
   """
-  @spec create(atom | string, integer | float) ::
-          {:ok, Money.t()} | {:error, {module, String.t()}}
+  @spec create(atom | String.t(), integer | float) :: Money.t() | {:error, {module, String.t()}}
   def create(currency, amount)
 
   def create(currency, amount) when is_integer(amount) do

backend/lib/db/budget.ex

@@ -40,4 +40,20 @@ defmodule WeekBudget.DB.Budget do
     }
     |> WeekBudget.DB.Repo.insert()
   end
+
+  @doc """
+  Reset budget to given amount an delete all events.
+  """
+  @spec reset(__MODULE__.t(), Money.t()) ::
+          {:ok, %{amount_update: __MODULE__.t(), delete_events: any()}} | {:error, any()}
+  def reset(budget, amount) do
+    update_cset =
+      budget
+      |> Ecto.Changeset.cast(%{amount: amount}, [:amount])
+
+    Ecto.Multi.new()
+    |> Ecto.Multi.update(:amount_update, update_cset)
+    |> Ecto.Multi.delete_all(:delete_events, Ecto.assoc(budget, :events))
+    |> WeekBudget.DB.Repo.transaction()
+  end
 end