adds append only functions, #1

.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

@@ -7,3 +7,4 @@ erl_crash.dump
 *.ez
 *.beam
 /config/*.secret.exs
+.elixir_ls

config/config.exs

@@ -0,0 +1,30 @@
+# 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
+# 3rd-party users, it should be done in your "mix.exs" file.
+
+# You can configure your application as:
+#
+#     config :alog, key: :value
+#
+# and access this configuration in your application as:
+#
+#     Application.get_env(:alog, :key)
+#
+# You can also configure a 3rd-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"

lib/alog.ex

@@ -0,0 +1,105 @@
+defmodule Alog do
+  @moduledoc """
+  Behaviour that defines functions for accessing and inserting data in an
+  Append-Only database
+  """
+
+  @callback insert(struct) :: {:ok, Ecto.Schema.t()} | {:error, Ecto.Changeset.t()}
+  @callback get(integer) :: Ecto.Schema.t() | nil | no_return()
+  @callback get_by(Keyword.t() | map) :: Ecto.Schema.t() | nil | no_return()
+  @callback update(Ecto.Schema.t(), struct) ::
+              {:ok, Ecto.Schema.t()} | {:error, Ecto.Changeset.t()}
+  @callback get_history(Ecto.Schema.t()) :: [Ecto.Schema.t()] | no_return()
+
+  defmacro __using__(_opts) do
+    quote location: :keep do
+      @behaviour Alog
+      @before_compile unquote(__MODULE__)
+    end
+  end
+
+  defmacro __before_compile__(_env) do
+    quote generated: true do
+      import Ecto.Query, only: [from: 2, subquery: 1]
+
+      @repo __MODULE__ |> Module.split() |> List.first() |> Module.concat("Repo")
+
+      def insert(attrs) do
+        %__MODULE__{}
+        |> __MODULE__.changeset(attrs)
+        |> @repo.insert()
+      end
+
+      def get(entry_id) do
+        sub =
+          from(
+            m in __MODULE__,
+            where: m.entry_id == ^entry_id,
+            order_by: [desc: :inserted_at],
+            limit: 1,
+            select: m
+          )
+
+        query = from(m in subquery(sub), where: not m.deleted, select: m)
+
+        item = @repo.one(query)
+      end
+
+      def get_by(clauses) do
+        @repo.get_by(__MODULE__, clauses)
+      end
+
+      def update(%__MODULE__{} = item, attrs) do
+        item
+        |> @repo.preload(__MODULE__.__schema__(:associations))
+        |> Map.put(:id, nil)
+        |> Map.put(:inserted_at, nil)
+        |> Map.put(:updated_at, nil)
+        |> __MODULE__.changeset(attrs)
+        |> @repo.insert()
+      end
+
+      def get_history(%__MODULE__{} = item) do
+        query =
+          from(m in __MODULE__,
+            where: m.entry_id == ^item.entry_id,
+            select: m
+          )
+
+        @repo.all(query)
+      end
+
+      def all do
+        sub =
+          from(m in __MODULE__,
+            distinct: m.entry_id,
+            order_by: [desc: :inserted_at],
+            select: m
+          )
+
+        query = from(m in subquery(sub), where: not m.deleted, select: m)
+
+        @repo.all(query)
+      end
+
+      def insert_entry_id(entry) do
+        case Map.fetch(entry, :entry_id) do
+          {:ok, nil} -> %{entry | entry_id: Ecto.UUID.generate()}
+          _ -> entry
+        end
+      end
+
+      def delete(item) do
+        item
+        |> @repo.preload(__MODULE__.__schema__(:associations))
+        |> Map.put(:id, nil)
+        |> Map.put(:inserted_at, nil)
+        |> Map.put(:updated_at, nil)
+        |> __MODULE__.changeset(%{deleted: true})
+        |> @repo.insert()
+      end
+
+      defoverridable Alog
+    end
+  end
+end

mix.exs

@@ -0,0 +1,27 @@
+defmodule Alog.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :alog,
+      version: "0.1.0",
+      elixir: "~> 1.7",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:ecto, "~> 2.2.10"}
+    ]
+  end
+end

mix.lock

@@ -0,0 +1,5 @@
+%{
+  "decimal": {:hex, :decimal, "1.5.0", "b0433a36d0e2430e3d50291b1c65f53c37d56f83665b43d79963684865beab68", [:mix], [], "hexpm"},
+  "ecto": {:hex, :ecto, "2.2.11", "4bb8f11718b72ba97a2696f65d247a379e739a0ecabf6a13ad1face79844791c", [:mix], [{:db_connection, "~> 1.1", [hex: :db_connection, repo: "hexpm", optional: true]}, {:decimal, "~> 1.2", [hex: :decimal, repo: "hexpm", optional: false]}, {:mariaex, "~> 0.8.0", [hex: :mariaex, repo: "hexpm", optional: true]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: true]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: false]}, {:postgrex, "~> 0.13.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
+  "poolboy": {:hex, :poolboy, "1.5.1", "6b46163901cfd0a1b43d692657ed9d7e599853b3b21b95ae5ae0a777cf9b6ca8", [:rebar], [], "hexpm"},
+}

test/alog_test.exs

@@ -0,0 +1,8 @@
+defmodule AlogTest do
+  use ExUnit.Case
+  doctest Alog
+
+  test "greets the world" do
+    assert Alog.hello() == :world
+  end
+end

test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()