Project architecture boilerplate

.gitignore

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+# 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").
+service-*.tar
+
+# Ignore elixir-ls artifacts
+/.elixir_ls/

Dockerfile

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+FROM elixir:1.9-slim as build
+
+WORKDIR /root/shortnr/service
+COPY . .
+
+RUN mix local.hex --force
+RUN mix local.rebar --force
+
+RUN env MIX_ENV=prod mix release
+
+FROM debian:buster-20191014-slim
+
+WORKDIR /home/shortnr
+COPY --from=build /root/shortnr/service/_build/prod/rel/service/ .
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libtinfo5=6.1+20181013-2+deb10u2 \
+    openssl=1.1.1d-0+deb10u2 \
+    locales=2.28-10 \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN sed -i -e 's/# en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/' /etc/locale.gen && \
+    locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
+RUN groupadd -r shortnr && useradd --no-log-init -r -g shortnr shortnr
+RUN chown -R shortnr:shortnr /home/shortnr
+USER shortnr
+
+ENTRYPOINT ["bin/service", "start"]
+EXPOSE 8080

Makefile

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+.PHONY: all build clean install start test
+
+build: install test clean
+	docker build -t shortnr:latest .
+
+clean:
+	mix clean --deps
+
+install:
+	mix deps.get
+
+install-prod:
+	mix deps.get --only prod
+
+start:
+	iex -S mix run --no-halt
+
+test:
+	mix test

config/config.exs

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+import Config
+
+config :service,
+  port: 8080
+
+config :logger, :console,
+  format: "date=$date time=$time level=$level$levelpad message=\"$message\" $metadata\n",
+  metadata: [:port, :file, :line, :crash_reason, :stack]

lib/router.ex

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+defmodule Shortnr.Router do
+  use Plug.ErrorHandler
+  use Plug.Router
+
+  require Logger
+
+  alias Shortnr.Transport.{Json, Http}
+  alias Shortnr.Url
+
+  plug(Plug.Logger, log: :debug)
+  plug(:match)
+  plug(:dispatch)
+
+  post "/urls" do
+    conn
+    |> Json.decode_request(Url.CreateRequest)
+    |> Http.handle(&Url.create(&1, Url.Repo.DETS))
+    |> Json.encode_response()
+    |> Http.send(:created, conn)
+  end
+
+  match _ do
+    {:error, {:not_found, "route not found"}, conn}
+    |> Json.encode_response()
+    |> Http.send(:ignore, conn)
+  end
+
+  def handle_errors(conn, %{kind: _kind, reason: reason, stack: stack}) do
+    Logger.error(inspect(reason), stack: stack)
+
+    {:error, {:internal_server_error, "internal server error"}, conn}
+    |> Json.encode_response()
+    |> Http.send(:ignore, conn)
+  end
+end

lib/shortnr.ex

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+defmodule Shortnr do
+  @moduledoc """
+  Documentation for Shortnr.
+  """
+
+  use Application
+  require Logger
+
+  @impl true
+  def start(_type, _args) do
+    port = port()
+
+    children = [
+      {Plug.Cowboy, scheme: :http, plug: Shortnr.Router, options: [port: port]}
+    ]
+
+    Logger.info("server starting", port: port)
+    Supervisor.start_link(children, strategy: :one_for_one)
+  end
+
+  @spec port() :: integer()
+  defp port do
+    case Application.fetch_env(:service, :port) do
+      {:ok, port} -> port
+      _ -> 4000
+    end
+  end
+end

lib/transport/http.ex

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+defmodule Shortnr.Transport.Http do
+  import Plug.Conn
+
+  @type ok_error :: {:ok, term(), Plug.Conn.t()} | error()
+  @type error :: {:error, {atom(), String.t()}, Plug.Conn.t()}
+
+  @spec handle(ok_error(), (term() -> ok_error())) :: ok_error()
+  def handle(error = {:error, _sub_error, _conn}, _func), do: error
+
+  def handle({:ok, request, conn}, func) do
+    case func.(request) do
+      {:ok, response} -> {:ok, response, conn}
+      {:error, error_value} -> convert_error(error_value, conn)
+    end
+  end
+
+  defp convert_error({:invalid_argument, message}, conn),
+    do: {:error, {:bad_request, message}, conn}
+
+  defp convert_error(_, conn), do: {:error, {:internal_server_error, "unknown error"}, conn}
+
+  @spec send(ok_error(), atom(), Plug.Conn.t()) :: Plug.Conn.t()
+  def send({:error, {status, body}, _conn}, _success_status, original_conn) do
+    send_resp(original_conn, status_to_code(status), body)
+  end
+
+  def send({:ok, body, conn}, success_status, _original_conn) do
+    send_resp(conn, status_to_code(success_status), body)
+  end
+
+  defp status_to_code(:ok), do: 200
+  defp status_to_code(:created), do: 201
+  defp status_to_code(:bad_request), do: 400
+  defp status_to_code(:not_found), do: 404
+  defp status_to_code(:internal_server_error), do: 500
+end

lib/transport/json.ex

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+defmodule Shortnr.Transport.Json do
+  import Plug.Conn
+  alias Shortnr.Transport.Http
+
+  @spec decode_request(Plug.Conn.t(), module()) :: Http.ok_error()
+  def decode_request(conn, struct_module) do
+    {:ok, body, conn} = read_body(conn)
+    {:ok, params} = Jason.decode(body)
+
+    params_list =
+      params
+      |> Map.to_list()
+      |> Enum.map(fn {key, value} -> {String.to_atom(key), value} end)
+
+    {:ok, struct(struct_module, params_list), conn}
+  end
+
+  @spec encode_response(Http.ok_error()) :: Http.ok_error()
+  def encode_response({:error, {status, response}, conn}) do
+    {:ok, json_body} = Jason.encode(%{data: response})
+    {:error, {status, json_body}, conn}
+  end
+
+  def encode_response({:ok, response, conn}) do
+    {:ok, json_body} = Jason.encode(%{data: response})
+    {:ok, json_body, conn}
+  end
+end

lib/transport/transport.ex

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+defmodule Shortnr.Transport do
+  @type error :: {:error, {atom(), String.t()}}
+  @type ok_error :: {:ok, term()} | error()
+end

mix.exs

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+defmodule Shortnr.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :service,
+      version: "0.1.0",
+      elixir: "~> 1.9",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      mod: {Shortnr, []},
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:plug_cowboy, "~> 2.0"},
+      {:elixir_uuid, "~> 1.2"},
+      {:jason, "~> 1.1"}
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

mix.lock

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+%{
+  "cowboy": {:hex, :cowboy, "2.7.0", "91ed100138a764355f43316b1d23d7ff6bdb0de4ea618cb5d8677c93a7a2f115", [:rebar3], [{:cowlib, "~> 2.8.0", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "~> 1.7.1", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm"},
+  "cowlib": {:hex, :cowlib, "2.8.0", "fd0ff1787db84ac415b8211573e9a30a3ebe71b5cbff7f720089972b2319c8a4", [:rebar3], [], "hexpm"},
+  "elixir_uuid": {:hex, :elixir_uuid, "1.2.1", "dce506597acb7e6b0daeaff52ff6a9043f5919a4c3315abb4143f0b00378c097", [:mix], [], "hexpm"},
+  "jason": {:hex, :jason, "1.1.2", "b03dedea67a99223a2eaf9f1264ce37154564de899fd3d8b9a21b1a6fd64afe7", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm"},
+  "mime": {:hex, :mime, "1.3.1", "30ce04ab3175b6ad0bdce0035cba77bba68b813d523d1aac73d9781b4d193cf8", [:mix], [], "hexpm"},
+  "plug": {:hex, :plug, "1.8.3", "12d5f9796dc72e8ac9614e94bda5e51c4c028d0d428e9297650d09e15a684478", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: true]}], "hexpm"},
+  "plug_cowboy": {:hex, :plug_cowboy, "2.1.0", "b75768153c3a8a9e8039d4b25bb9b14efbc58e9c4a6e6a270abff1cd30cbe320", [:mix], [{:cowboy, "~> 2.5", [hex: :cowboy, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
+  "plug_crypto": {:hex, :plug_crypto, "1.0.0", "18e49317d3fa343f24620ed22795ec29d4a5e602d52d1513ccea0b07d8ea7d4d", [:mix], [], "hexpm"},
+  "ranch": {:hex, :ranch, "1.7.1", "6b1fab51b49196860b733a49c07604465a47bdb78aa10c1c16a3d199f7f8c881", [:rebar3], [], "hexpm"},
+}

test/test_helper.exs

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+ExUnit.start()