commit e6cbccaf6f99809706550a16be4ec89334afcb5e
Author: Mikko Ahlroth <mikko.ahlroth@gmail.com>
Date:   Mon May 27 06:02:42 2019 +0200

    Initial commit

diff --git a/backend/.formatter.exs b/backend/.formatter.exs
new file mode 100644
index 0000000..d2cda26
--- /dev/null
+++ b/backend/.formatter.exs
@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]
diff --git a/backend/.gitignore b/backend/.gitignore
new file mode 100644
index 0000000..55e7abb
--- /dev/null
+++ b/backend/.gitignore
@@ -0,0 +1,24 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+week_budget-*.tar
+
diff --git a/backend/README.md b/backend/README.md
new file mode 100644
index 0000000..efb4add
--- /dev/null
+++ b/backend/README.md
@@ -0,0 +1,21 @@
+# WeekBudget
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `week_budget` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:week_budget, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at [https://hexdocs.pm/week_budget](https://hexdocs.pm/week_budget).
+
diff --git a/backend/config/config.exs b/backend/config/config.exs
new file mode 100644
index 0000000..b324b03
--- /dev/null
+++ b/backend/config/config.exs
@@ -0,0 +1,38 @@
+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# This configuration is loaded before any dependency and is restricted
+# to this project. If another project depends on this project, this
+# file won't be loaded nor affect the parent project. For this reason,
+# if you want to provide default values for your application for
+# third-party users, it should be done in your "mix.exs" file.
+
+# You can configure your application as:
+#
+#     config :week_budget, key: :value
+#
+# and access this configuration in your application as:
+#
+#     Application.get_env(:week_budget, :key)
+#
+# You can also configure a third-party app:
+#
+#     config :logger, level: :info
+#
+
+# It is also possible to import configuration files, relative to this
+# directory. For example, you can emulate configuration per environment
+# by uncommenting the line below and defining dev.exs, test.exs and such.
+# Configuration from the imported file will override the ones defined
+# here (which is why it is important to import them last).
+#
+#     import_config "#{Mix.env()}.exs"
+
+config :week_budget,
+  ecto_repos: [WeekBudget.DB.Repo],
+  database_url: "ecto://weekbudget:week@127.0.0.1/weekbudget"
+
+config :ex_money,
+  exchange_rates_retrieve_every: :never,
+  default_cldr_backend: WeekBudget.Core.Cldr
diff --git a/backend/lib/api/server.ex b/backend/lib/api/server.ex
new file mode 100644
index 0000000..d3eb796
--- /dev/null
+++ b/backend/lib/api/server.ex
@@ -0,0 +1,87 @@
+defmodule WeekBudget.API.Server do
+  @moduledoc """
+  Simple server handling/delegating all API calls of the system.
+  """
+
+  require Logger
+  use Ace.HTTP.Service, port: 2019, cleartext: true
+  use Raxx.SimpleServer
+
+  @impl Raxx.SimpleServer
+  @spec handle_request(Raxx.Request.t(), %{}) :: Raxx.Response.t()
+  def handle_request(req, state)
+
+  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
+      wb
+      |> serialize_budget()
+      |> json_resp()
+    else
+      :error -> json_resp(:bad_request, %{error: "Malformed UUID."})
+      nil -> json_resp(:not_found, %{error: "Budget not found."})
+    end
+  end
+
+  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
+  end
+
+  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
+  end
+
+  def handle_request(req, _) do
+    Logger.debug("Failed request:")
+    Logger.debug(inspect(req))
+    json_resp(:not_found, %{error: "Unknown API path or invalid data."})
+  end
+
+  defp serialize_budget(%WeekBudget.DB.Budget{secret: secret, amount: amount, events: events}) do
+    # True amount is initial amount plus all event amounts
+    true_amount = Enum.reduce(events, amount, &Money.add!(&2, &1.amount))
+
+    %{
+      uuid: secret,
+      init: Decimal.to_float(amount.amount),
+      amount: Decimal.to_float(true_amount.amount),
+      events: Enum.map(events, &serialize_event/1)
+    }
+  end
+
+  defp serialize_event(%WeekBudget.DB.Event{at: at, amount: amount}) do
+    %{at: DateTime.to_iso8601(at), amount: Decimal.to_float(amount.amount)}
+  end
+
+  defp json_resp(status \\ :ok, content) do
+    response(status)
+    |> set_header("content-type", "application/json")
+    |> set_body(Jason.encode!(content))
+  end
+end
diff --git a/backend/lib/core/application.ex b/backend/lib/core/application.ex
new file mode 100644
index 0000000..c817f1a
--- /dev/null
+++ b/backend/lib/core/application.ex
@@ -0,0 +1,30 @@
+defmodule WeekBudget.Core.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  def start(_type, _args) do
+    case Code.ensure_loaded(ExSync) do
+      {:module, ExSync = mod} ->
+        mod.start()
+
+      {:error, _} ->
+        :ok
+    end
+
+    port = Application.get_env(:week_budget, :port, 2019)
+
+    # List all child processes to be supervised
+    children = [
+      {WeekBudget.DB.Repo, []},
+      {WeekBudget.API.Server, [[], [port: port]]}
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: WeekBudget.Core.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end
diff --git a/backend/lib/core/cldr.ex b/backend/lib/core/cldr.ex
new file mode 100644
index 0000000..78a0153
--- /dev/null
+++ b/backend/lib/core/cldr.ex
@@ -0,0 +1,3 @@
+defmodule WeekBudget.Core.Cldr do
+  use Cldr, locales: ["en"], default_locale: "en"
+end
diff --git a/backend/lib/core/money_utils.ex b/backend/lib/core/money_utils.ex
new file mode 100644
index 0000000..9526e09
--- /dev/null
+++ b/backend/lib/core/money_utils.ex
@@ -0,0 +1,22 @@
+defmodule WeekBudget.Core.MoneyUtils do
+  @moduledoc """
+  Utilities to do with money operations.
+  """
+
+  @doc """
+  Create money from given integer or float and currency. Float is used to easier accept money from the
+  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()}}
+  def create(currency, amount)
+
+  def create(currency, amount) when is_integer(amount) do
+    Money.new(currency, amount)
+  end
+
+  def create(currency, amount) when is_float(amount) do
+    Money.from_float(currency, amount)
+  end
+end
diff --git a/backend/lib/db/budget.ex b/backend/lib/db/budget.ex
new file mode 100644
index 0000000..70f9d99
--- /dev/null
+++ b/backend/lib/db/budget.ex
@@ -0,0 +1,43 @@
+defmodule WeekBudget.DB.Budget do
+  @moduledoc """
+  A single budget that has a secret token that can be used to join it and an initial sum.
+
+  The final sum can be calculated by subtracting all the events from the initial sum.
+  """
+  use Ecto.Schema
+  import Ecto.Query, only: [from: 2]
+
+  @primary_key {:secret, :binary_id, autogenerate: true}
+
+  schema "budgets" do
+    field(:amount, Money.Ecto.Composite.Type)
+
+    timestamps()
+
+    has_many(:events, WeekBudget.DB.Event, foreign_key: :budget_id)
+  end
+
+  @doc """
+  Get budget by its secret, if any exists.
+  """
+  @spec get_by_secret(String.t()) :: __MODULE__.t() | nil
+  def get_by_secret(secret) do
+    from(w in __MODULE__,
+      where: w.secret == ^secret,
+      select: [:secret, :amount],
+      preload: [:events]
+    )
+    |> WeekBudget.DB.Repo.one()
+  end
+
+  @doc """
+  Create budget with given initial amount.
+  """
+  @spec create(Money.t()) :: {:ok, __MODULE__.t()} | {:error, Ecto.Changeset.t()}
+  def create(amount) do
+    %__MODULE__{
+      amount: amount
+    }
+    |> WeekBudget.DB.Repo.insert()
+  end
+end
diff --git a/backend/lib/db/event.ex b/backend/lib/db/event.ex
new file mode 100644
index 0000000..80b51b4
--- /dev/null
+++ b/backend/lib/db/event.ex
@@ -0,0 +1,32 @@
+defmodule WeekBudget.DB.Event do
+  @moduledoc """
+  A money spending event that occurred on the budget. If amount is positive, money was spent. If amount
+  is negative, money was received.
+  """
+  use Ecto.Schema
+
+  schema "events" do
+    field(:amount, Money.Ecto.Composite.Type)
+    field(:at, :utc_datetime)
+
+    belongs_to(:budget, WeekBudget.DB.Budget,
+      references: :secret,
+      foreign_key: :budget_id,
+      type: :binary_id
+    )
+  end
+
+  @doc """
+  Create a new event with the given amount. Note that normally the amount should be negative.
+  """
+  @spec create(WeekBudget.DB.Budget.t(), Money.t()) ::
+          {:ok, __MODULE__.t()} | {:error, Ecto.Changeset.t()}
+  def create(%WeekBudget.DB.Budget{} = budget, %Money{} = amount) do
+    %__MODULE__{
+      amount: amount,
+      budget: budget,
+      at: DateTime.utc_now() |> DateTime.truncate(:second)
+    }
+    |> WeekBudget.DB.Repo.insert()
+  end
+end
diff --git a/backend/lib/db/repo.ex b/backend/lib/db/repo.ex
new file mode 100644
index 0000000..b2378a5
--- /dev/null
+++ b/backend/lib/db/repo.ex
@@ -0,0 +1,9 @@
+defmodule WeekBudget.DB.Repo do
+  use Ecto.Repo,
+    otp_app: :week_budget,
+    adapter: Ecto.Adapters.Postgres
+
+  def init(_type, config) do
+    {:ok, Keyword.put(config, :url, Application.get_env(:week_budget, :database_url))}
+  end
+end
diff --git a/backend/mix.exs b/backend/mix.exs
new file mode 100644
index 0000000..77980de
--- /dev/null
+++ b/backend/mix.exs
@@ -0,0 +1,37 @@
+defmodule WeekBudget.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :week_budget,
+      version: "0.1.0",
+      elixir: "~> 1.8",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {WeekBudget.Core.Application, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:raxx, "~> 1.0.1"},
+      {:raxx_logger, "~> 0.2.2"},
+      {:ace, "~> 0.18.8"},
+      {:ecto, "~> 3.1.4"},
+      {:ecto_sql, "~> 3.1.3"},
+      {:jason, "~> 1.1.2"},
+      {:observer_cli, "~> 1.5.0"},
+      {:postgrex, ">= 0.0.0"},
+      {:ex_money, "~> 3.4.2"},
+      {:exsync, "~> 0.2.3", only: :dev}
+    ]
+  end
+end
diff --git a/backend/mix.lock b/backend/mix.lock
new file mode 100644
index 0000000..97c0576
--- /dev/null
+++ b/backend/mix.lock
@@ -0,0 +1,26 @@
+%{
+  "ace": {:hex, :ace, "0.18.8", "9853110247f769e7d1600be7cd2abd638b53391c8c7b1ab11baad15184cb95d4", [:mix], [{:hpack, "~> 0.2.3", [hex: :hpack_erl, repo: "hexpm", optional: false]}, {:raxx, "~> 0.17.0 or ~> 0.18.0 or ~> 1.0", [hex: :raxx, repo: "hexpm", optional: false]}], "hexpm"},
+  "cldr_utils": {:hex, :cldr_utils, "2.2.0", "4f6ac090fc1871037ac41265c98bf0f785b2a4ede144dd2a5282986a5311dd14", [:mix], [{:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}], "hexpm"},
+  "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], [], "hexpm"},
+  "db_connection": {:hex, :db_connection, "2.0.6", "bde2f85d047969c5b5800cb8f4b3ed6316c8cb11487afedac4aa5f93fd39abfa", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}], "hexpm"},
+  "decimal": {:hex, :decimal, "1.7.0", "30d6b52c88541f9a66637359ddf85016df9eb266170d53105f02e4a67e00c5aa", [:mix], [], "hexpm"},
+  "ecto": {:hex, :ecto, "3.1.4", "69d852da7a9f04ede725855a35ede48d158ca11a404fe94f8b2fb3b2162cd3c9", [:mix], [{:decimal, "~> 1.6", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm"},
+  "ecto_sql": {:hex, :ecto_sql, "3.1.3", "2c536139190492d9de33c5fefac7323c5eaaa82e1b9bf93482a14649042f7cd9", [:mix], [{:db_connection, "~> 2.0", [hex: :db_connection, repo: "hexpm", optional: false]}, {:ecto, "~> 3.1.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:mariaex, "~> 0.9.1", [hex: :mariaex, repo: "hexpm", optional: true]}, {:myxql, "~> 0.2.0", [hex: :myxql, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.14.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm"},
+  "ex_cldr": {:hex, :ex_cldr, "2.7.0", "be0f1c88f1baeb8364395df7d3266a8d7f075ebaeb00d20db743b1d72fa47e55", [:mix], [{:cldr_utils, "~> 2.1", [hex: :cldr_utils, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}, {:gettext, "~> 0.13", [hex: :gettext, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:nimble_parsec, "~> 0.5", [hex: :nimble_parsec, repo: "hexpm", optional: false]}, {:plug, "~> 1.4", [hex: :plug, repo: "hexpm", optional: true]}], "hexpm"},
+  "ex_cldr_currencies": {:hex, :ex_cldr_currencies, "2.3.0", "bffae489416b8b05d4683403263f5d62aae17de70c24ff915a533541fea514de", [:mix], [{:ex_cldr, "~> 2.6", [hex: :ex_cldr, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm"},
+  "ex_cldr_numbers": {:hex, :ex_cldr_numbers, "2.6.0", "431c744058a3980f561878f4886b78871d4067c6d9039ce78335ed9a41c831f8", [:mix], [{:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}, {:ex_cldr, "~> 2.6", [hex: :ex_cldr, repo: "hexpm", optional: false]}, {:ex_cldr_currencies, "~> 2.3", [hex: :ex_cldr_currencies, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm"},
+  "ex_money": {:hex, :ex_money, "3.4.2", "7da06947ed92fab7ad265f7fe1f6d36b30404f2b33c7b46de54670921dfe3420", [:mix], [{:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}, {:ecto_sql, "~> 3.0", [hex: :ecto_sql, repo: "hexpm", optional: true]}, {:ex_cldr, "~> 2.6", [hex: :ex_cldr, repo: "hexpm", optional: false]}, {:ex_cldr_numbers, "~> 2.6", [hex: :ex_cldr_numbers, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_html, "~> 2.0", [hex: :phoenix_html, repo: "hexpm", optional: true]}], "hexpm"},
+  "ex_sync": {:hex, :ex_sync, "0.0.4", "468839964dead69df738a3698e4318d18fa3322e4f684adf98d5441704d1bc8c", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: false]}], "hexpm"},
+  "exsync": {:hex, :exsync, "0.2.3", "a1ac11b4bd3808706003dbe587902101fcc1387d9fc55e8b10972f13a563dd15", [:mix], [{:file_system, "~> 0.2", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm"},
+  "file_system": {:hex, :file_system, "0.2.7", "e6f7f155970975789f26e77b8b8d8ab084c59844d8ecfaf58cbda31c494d14aa", [:mix], [], "hexpm"},
+  "hpack": {:hex, :hpack_erl, "0.2.3", "17670f83ff984ae6cd74b1c456edde906d27ff013740ee4d9efaa4f1bf999633", [:rebar3], [], "hexpm"},
+  "jason": {:hex, :jason, "1.1.2", "b03dedea67a99223a2eaf9f1264ce37154564de899fd3d8b9a21b1a6fd64afe7", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm"},
+  "nimble_parsec": {:hex, :nimble_parsec, "0.5.0", "90e2eca3d0266e5c53f8fbe0079694740b9c91b6747f2b7e3c5d21966bba8300", [:mix], [], "hexpm"},
+  "observer_cli": {:hex, :observer_cli, "1.5.0", "9944882b71f55b2503663d9cb54d3f1c7bbdf7cc6dd01cc40ea8ef51207601ec", [:mix, :rebar3], [{:recon, "2.5.0", [hex: :recon, repo: "hexpm", optional: false]}], "hexpm"},
+  "poolboy": {:hex, :poolboy, "1.5.2", "392b007a1693a64540cead79830443abf5762f5d30cf50bc95cb2c1aaafa006b", [:rebar3], [], "hexpm"},
+  "postgrex": {:hex, :postgrex, "0.14.3", "5754dee2fdf6e9e508cbf49ab138df964278700b764177e8f3871e658b345a1e", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 2.0", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm"},
+  "raxx": {:hex, :raxx, "1.0.1", "8c51ec5227c85f999360fc844fc1d4e2e5a2adf2b0ce068eb56243ee6b2f65e3", [:mix], [], "hexpm"},
+  "raxx_logger": {:hex, :raxx_logger, "0.2.2", "51bbce9371298e7329de028fe13cf050bf59547bc8f1926910d479ba4b31c4b4", [:mix], [{:raxx, "~> 0.17.5 or ~> 0.18.0 or ~> 1.0", [hex: :raxx, repo: "hexpm", optional: false]}], "hexpm"},
+  "recon": {:hex, :recon, "2.5.0", "2f7fcbec2c35034bade2f9717f77059dc54eb4e929a3049ca7ba6775c0bd66cd", [:mix, :rebar3], [], "hexpm"},
+  "telemetry": {:hex, :telemetry, "0.4.0", "8339bee3fa8b91cb84d14c2935f8ecf399ccd87301ad6da6b71c09553834b2ab", [:rebar3], [], "hexpm"},
+}
diff --git a/backend/priv/repo/migrations/20190523122128_add_money_with_currency_type_to_postgres.exs b/backend/priv/repo/migrations/20190523122128_add_money_with_currency_type_to_postgres.exs
new file mode 100644
index 0000000..bbbce4b
--- /dev/null
+++ b/backend/priv/repo/migrations/20190523122128_add_money_with_currency_type_to_postgres.exs
@@ -0,0 +1,11 @@
+defmodule WeekBudget.DB.Repo.Migrations.AddMoneyWithCurrencyTypeToPostgres do
+  use Ecto.Migration
+
+  def up do
+    execute("CREATE TYPE public.money_with_currency AS (currency_code char(3), amount numeric);")
+  end
+
+  def down do
+    execute("DROP TYPE public.money_with_currency;")
+  end
+end
\ No newline at end of file
diff --git a/backend/priv/repo/migrations/20190523122356_init.exs b/backend/priv/repo/migrations/20190523122356_init.exs
new file mode 100644
index 0000000..e981b5c
--- /dev/null
+++ b/backend/priv/repo/migrations/20190523122356_init.exs
@@ -0,0 +1,12 @@
+defmodule WeekBudget.DB.Repo.Migrations.Init do
+  use Ecto.Migration
+
+  def change do
+    create table(:budgets, primary_key: false) do
+      add(:secret, :binary_id, primary_key: true)
+      add(:amount, :money_with_currency)
+
+      timestamps()
+    end
+  end
+end
diff --git a/backend/priv/repo/migrations/20190523123548_add_events.exs b/backend/priv/repo/migrations/20190523123548_add_events.exs
new file mode 100644
index 0000000..2306c84
--- /dev/null
+++ b/backend/priv/repo/migrations/20190523123548_add_events.exs
@@ -0,0 +1,18 @@
+defmodule WeekBudget.DB.Repo.Migrations.AddEvents do
+  use Ecto.Migration
+
+  def change do
+    create table(:events) do
+      add(:amount, :money_with_currency, null: false)
+      add(:at, :utc_datetime, null: false)
+
+      add(
+        :budget,
+        references("budgets", column: :secret, type: :binary_id, on_delete: :delete_all),
+        null: false
+      )
+    end
+
+    create(index("events", :budget))
+  end
+end
diff --git a/backend/priv/repo/migrations/20190525204914_budget_fkey_name.exs b/backend/priv/repo/migrations/20190525204914_budget_fkey_name.exs
new file mode 100644
index 0000000..59d1672
--- /dev/null
+++ b/backend/priv/repo/migrations/20190525204914_budget_fkey_name.exs
@@ -0,0 +1,7 @@
+defmodule WeekBudget.DB.Repo.Migrations.BudgetFkeyName do
+  use Ecto.Migration
+
+  def change do
+    rename(table("events"), :budget, to: :budget_id)
+  end
+end
diff --git a/backend/test/test_helper.exs b/backend/test/test_helper.exs
new file mode 100644
index 0000000..869559e
--- /dev/null
+++ b/backend/test/test_helper.exs
@@ -0,0 +1 @@
+ExUnit.start()
diff --git a/backend/test/week_budget_test.exs b/backend/test/week_budget_test.exs
new file mode 100644
index 0000000..eba3ede
--- /dev/null
+++ b/backend/test/week_budget_test.exs
@@ -0,0 +1,8 @@
+defmodule WeekBudgetTest do
+  use ExUnit.Case
+  doctest WeekBudget
+
+  test "greets the world" do
+    assert WeekBudget.hello() == :world
+  end
+end