lecture 05

lectures/05/partition_counters/.formatter.exs

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

lectures/05/partition_counters/.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").
+partition_counters-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

lectures/05/partition_counters/README.md

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+# Counter
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `partition_counters` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:partition_counters, "~> 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/partition_counters>.
+

lectures/05/partition_counters/lib/counter/application.ex

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+defmodule Counter.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  @registry Counter.Registry
+  @table	Counter.Table
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+	children = [
+	  {Registry, name: @registry, keys: :unique}, # recall same as {Registry, [name: @registry, keys: :unique]}
+	  # Starts a worker by calling: Counter.Worker.start_link(arg)
+	  # {DynamicSupervisor, name: Counter.DynamicSupervisor, strategy: :one_for_one}
+		{PartitionSupervisor, name: Counter.DynamicSupervisors, child_spec: Counter.DynamicSupervisor}
+	]
+
+	:ets.new(@table, [:named_table, :public])
+	# See https://hexdocs.pm/elixir/Supervisor.html
+	# for other strategies and supported options
+	opts = [strategy: :one_for_one, name: Counter.Supervisor]
+	Supervisor.start_link(children, opts)
+  end
+end

lectures/05/partition_counters/lib/counter/dynamic_supervisor.ex

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+defmodule Counter.DynamicSupervisor do
+  use DynamicSupervisor
+
+  def start_link(_) do
+	DynamicSupervisor.start_link(__MODULE__, nil)
+  end
+
+  def start_worker(name) do
+	DynamicSupervisor.start_child(
+		{:via, PartitionSupervisor, {Counter.DynamicSupervisors, self()}},
+		{Counter.Worker, name})
+  end
+
+  @impl true
+  def init(_) do
+	DynamicSupervisor.init(strategy: :one_for_one)
+  end
+end

lectures/05/partition_counters/lib/counter/worker.ex

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+defmodule Counter.Worker do
+  use GenServer
+
+  @registry Counter.Registry
+  @table Counter.Table
+
+  ### Client API ###
+  def start_link(name) do
+	GenServer.start_link(__MODULE__, name, name: via(name))
+  end
+
+  def value(name) do
+	GenServer.call(via(name), :value)
+  end
+
+  def inc(name, amt \\ 1) do
+	GenServer.cast(via(name), {:inc, amt})
+  end
+
+  # wrap the name in a triple to use the Registry to get the
+  # process ID by name
+  defp via(name) do
+	{:via, Registry, {@registry, {__MODULE__, name}}}
+  end
+
+  ### Server Impl ###
+  @impl true
+  def init(arg) do
+	name = {__MODULE__, arg}
+	value = case :ets.lookup(@table, name) do
+		[] -> 0
+		[{_, v}] -> v
+	end
+   {:ok, {name, value}}
+  end
+
+  @impl true
+  def handle_call(:value, _from, {_, value} = state) do
+	{:reply, value, state}
+  end
+
+  @impl true
+  def handle_cast({:inc, amt}, {name, value}) do
+	{:noreply, {name, value + amt}}
+  end
+
+  # save state to term table when process terminates
+  @impl true
+  def terminate(_, state) do
+	:ets.insert(@table, state)
+  end
+end

lectures/05/partition_counters/mix.exs

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+defmodule Counter.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :partition_counters,
+      version: "0.1.0",
+      elixir: "~> 1.17",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {Counter.Application, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

lectures/05/partition_counters/test/counter_test.exs

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+defmodule CounterTest do
+  use ExUnit.Case
+  doctest Counter
+
+  test "greets the world" do
+    assert Counter.hello() == :world
+  end
+end

lectures/05/partition_counters/test/test_helper.exs

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+ExUnit.start()