lecture 06

lectures/06/counter/.formatter.exs

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+[
+  import_deps: [:phoenix],
+  inputs: ["*.{ex,exs}", "{config,lib,test}/**/*.{ex,exs}"]
+]

lectures/06/counter/.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 3rd-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
+
+# Temporary files, for example, from tests.
+/tmp/
+
+# Ignore package tarball (built via "mix hex.build").
+counter-*.tar
+

lectures/06/counter/AGENTS.md

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+This is a web application written using the Phoenix web framework.
+
+## Project guidelines
+
+- Use `mix precommit` alias when you are done with all changes and fix any pending issues
+- Use the already included and available `:req` (`Req`) library for HTTP requests, **avoid** `:httpoison`, `:tesla`, and `:httpc`. Req is included by default and is the preferred HTTP client for Phoenix apps
+
+### Phoenix v1.8 guidelines
+
+- **Always** begin your LiveView templates with `<Layouts.app flash={@flash} ...>` which wraps all inner content
+- The `MyAppWeb.Layouts` module is aliased in the `my_app_web.ex` file, so you can use it without needing to alias it again
+- Anytime you run into errors with no `current_scope` assign:
+  - You failed to follow the Authenticated Routes guidelines, or you failed to pass `current_scope` to `<Layouts.app>`
+  - **Always** fix the `current_scope` error by moving your routes to the proper `live_session` and ensure you pass `current_scope` as needed
+- Phoenix v1.8 moved the `<.flash_group>` component to the `Layouts` module. You are **forbidden** from calling `<.flash_group>` outside of the `layouts.ex` module
+- Out of the box, `core_components.ex` imports an `<.icon name="hero-x-mark" class="w-5 h-5"/>` component for hero icons. **Always** use the `<.icon>` component for icons, **never** use `Heroicons` modules or similar
+- **Always** use the imported `<.input>` component for form inputs from `core_components.ex` when available. `<.input>` is imported and using it will save steps and prevent errors
+- If you override the default input classes (`<.input class="myclass px-2 py-1 rounded-lg">)`) class with your own values, no default classes are inherited, so your
+custom classes must fully style the input
+
+
+<!-- usage-rules-start -->
+
+<!-- phoenix:elixir-start -->
+## Elixir guidelines
+
+- Elixir lists **do not support index based access via the access syntax**
+
+  **Never do this (invalid)**:
+
+      i = 0
+      mylist = ["blue", "green"]
+      mylist[i]
+
+  Instead, **always** use `Enum.at`, pattern matching, or `List` for index based list access, ie:
+
+      i = 0
+      mylist = ["blue", "green"]
+      Enum.at(mylist, i)
+
+- Elixir variables are immutable, but can be rebound, so for block expressions like `if`, `case`, `cond`, etc
+  you *must* bind the result of the expression to a variable if you want to use it and you CANNOT rebind the result inside the expression, ie:
+
+      # INVALID: we are rebinding inside the `if` and the result never gets assigned
+      if connected?(socket) do
+        socket = assign(socket, :val, val)
+      end
+
+      # VALID: we rebind the result of the `if` to a new variable
+      socket =
+        if connected?(socket) do
+          assign(socket, :val, val)
+        end
+
+- **Never** nest multiple modules in the same file as it can cause cyclic dependencies and compilation errors
+- **Never** use map access syntax (`changeset[:field]`) on structs as they do not implement the Access behaviour by default. For regular structs, you **must** access the fields directly, such as `my_struct.field` or use higher level APIs that are available on the struct if they exist, `Ecto.Changeset.get_field/2` for changesets
+- Elixir's standard library has everything necessary for date and time manipulation. Familiarize yourself with the common `Time`, `Date`, `DateTime`, and `Calendar` interfaces by accessing their documentation as necessary. **Never** install additional dependencies unless asked or for date/time parsing (which you can use the `date_time_parser` package)
+- Don't use `String.to_atom/1` on user input (memory leak risk)
+- Predicate function names should not start with `is_` and should end in a question mark. Names like `is_thing` should be reserved for guards
+- Elixir's builtin OTP primitives like `DynamicSupervisor` and `Registry`, require names in the child spec, such as `{DynamicSupervisor, name: MyApp.MyDynamicSup}`, then you can use `DynamicSupervisor.start_child(MyApp.MyDynamicSup, child_spec)`
+- Use `Task.async_stream(collection, callback, options)` for concurrent enumeration with back-pressure. The majority of times you will want to pass `timeout: :infinity` as option
+
+## Mix guidelines
+
+- Read the docs and options before using tasks (by using `mix help task_name`)
+- To debug test failures, run tests in a specific file with `mix test test/my_test.exs` or run all previously failed tests with `mix test --failed`
+- `mix deps.clean --all` is **almost never needed**. **Avoid** using it unless you have good reason
+
+## Test guidelines
+
+- **Always use `start_supervised!/1`** to start processes in tests as it guarantees cleanup between tests
+- **Avoid** `Process.sleep/1` and `Process.alive?/1` in tests
+  - Instead of sleeping to wait for a process to finish, **always** use `Process.monitor/1` and assert on the DOWN message:
+
+      ref = Process.monitor(pid)
+      assert_receive {:DOWN, ^ref, :process, ^pid, :normal}
+
+   - Instead of sleeping to synchronize before the next call, **always** use `_ = :sys.get_state/1` to ensure the process has handled prior messages
+<!-- phoenix:elixir-end -->
+
+<!-- phoenix:phoenix-start -->
+## Phoenix guidelines
+
+- Remember Phoenix router `scope` blocks include an optional alias which is prefixed for all routes within the scope. **Always** be mindful of this when creating routes within a scope to avoid duplicate module prefixes.
+
+- You **never** need to create your own `alias` for route definitions! The `scope` provides the alias, ie:
+
+      scope "/admin", AppWeb.Admin do
+        pipe_through :browser
+
+        live "/users", UserLive, :index
+      end
+
+  the UserLive route would point to the `AppWeb.Admin.UserLive` module
+
+- `Phoenix.View` no longer is needed or included with Phoenix, don't use it
+<!-- phoenix:phoenix-end -->
+
+<!-- usage-rules-end -->

lectures/06/counter/README.md

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+# Counter
+
+To start your Phoenix server:
+
+* Run `mix setup` to install and setup dependencies
+* Start Phoenix endpoint with `mix phx.server` or inside IEx with `iex -S mix phx.server`
+
+Now you can visit [`localhost:4000`](http://localhost:4000) from your browser.
+
+Ready to run in production? Please [check our deployment guides](https://phoenix.hexdocs.pm/deployment.html).
+
+## Learn more
+
+* Official website: https://www.phoenixframework.org/
+* Guides: https://phoenix.hexdocs.pm/overview.html
+* Docs: https://phoenix.hexdocs.pm
+* Forum: https://elixirforum.com/c/phoenix-forum
+* Source: https://github.com/phoenixframework/phoenix

lectures/06/counter/config/config.exs

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+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Config module.
+#
+# This configuration file is loaded before any dependency and
+# is restricted to this project.
+
+# General application configuration
+import Config
+
+config :counter,
+  generators: [timestamp_type: :utc_datetime]
+
+# Configure the endpoint
+config :counter, CounterWeb.Endpoint,
+  url: [host: "localhost"],
+  adapter: Bandit.PhoenixAdapter,
+  render_errors: [
+    formats: [json: CounterWeb.ErrorJSON],
+    layout: false
+  ],
+  pubsub_server: Counter.PubSub,
+  live_view: [signing_salt: "UG6iEmGW"]
+
+# Configure Elixir's Logger
+config :logger, :default_formatter,
+  format: "$time $metadata[$level] $message\n",
+  metadata: [:request_id]
+
+# Use Jason for JSON parsing in Phoenix
+config :phoenix, :json_library, Jason
+
+# Import environment specific config. This must remain at the bottom
+# of this file so it overrides the configuration defined above.
+import_config "#{config_env()}.exs"

lectures/06/counter/config/dev.exs

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+import Config
+
+# For development, we disable any cache and enable
+# debugging and code reloading.
+#
+# The watchers configuration can be used to run external
+# watchers to your application. For example, we can use it
+# to bundle .js and .css sources.
+config :counter, CounterWeb.Endpoint,
+  # Binding to loopback ipv4 address prevents access from other machines.
+  # Change to `ip: {0, 0, 0, 0}` to allow access from other machines.
+  http: [ip: {127, 0, 0, 1}],
+  check_origin: false,
+  code_reloader: true,
+  debug_errors: true,
+  secret_key_base: "Nm2C7L4YM6o1zK8UqGcMikP609+pl2WFHlZvyM70R/1Z/lKz3bTFGFjhT8Gs67aU",
+  watchers: []
+
+# ## SSL Support
+#
+# In order to use HTTPS in development, a self-signed
+# certificate can be generated by running the following
+# Mix task:
+#
+#     mix phx.gen.cert
+#
+# Run `mix help phx.gen.cert` for more information.
+#
+# The `http:` config above can be replaced with:
+#
+#     https: [
+#       port: 4001,
+#       cipher_suite: :strong,
+#       keyfile: "priv/cert/selfsigned_key.pem",
+#       certfile: "priv/cert/selfsigned.pem"
+#     ],
+#
+# If desired, both `http:` and `https:` keys can be
+# configured to run both http and https servers on
+# different ports.
+
+# Enable dev routes for dashboard and mailbox
+config :counter, dev_routes: true
+
+# Do not include metadata nor timestamps in development logs
+config :logger, :default_formatter, format: "[$level] $message\n"
+
+# Set a higher stacktrace during development. Avoid configuring such
+# in production as building large stacktraces may be expensive.
+config :phoenix, :stacktrace_depth, 20
+
+# Initialize plugs at runtime for faster development compilation
+config :phoenix, :plug_init_mode, :runtime

lectures/06/counter/config/prod.exs

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+import Config
+
+# Force using SSL in production. This also sets the "strict-security-transport" header,
+# known as HSTS. If you have a health check endpoint, you may want to exclude it below.
+# Note `:force_ssl` is required to be set at compile-time.
+config :counter, CounterWeb.Endpoint,
+  force_ssl: [
+    rewrite_on: [:x_forwarded_proto],
+    exclude: [
+      # paths: ["/health"],
+      hosts: ["localhost", "127.0.0.1"]
+    ]
+  ]
+
+# Do not print debug messages in production
+config :logger, level: :info
+
+# Runtime production configuration, including reading
+# of environment variables, is done on config/runtime.exs.

lectures/06/counter/config/runtime.exs

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+import Config
+
+# config/runtime.exs is executed for all environments, including
+# during releases. It is executed after compilation and before the
+# system starts, so it is typically used to load production configuration
+# and secrets from environment variables or elsewhere. Do not define
+# any compile-time configuration in here, as it won't be applied.
+# The block below contains prod specific runtime configuration.
+
+# ## Using releases
+#
+# If you use `mix release`, you need to explicitly enable the server
+# by passing the PHX_SERVER=true when you start it:
+#
+#     PHX_SERVER=true bin/counter start
+#
+# Alternatively, you can use `mix phx.gen.release` to generate a `bin/server`
+# script that automatically sets the env var above.
+if System.get_env("PHX_SERVER") do
+  config :counter, CounterWeb.Endpoint, server: true
+end
+
+config :counter, CounterWeb.Endpoint,
+  http: [port: String.to_integer(System.get_env("PORT", "4000"))]
+
+if config_env() == :prod do
+  # The secret key base is used to sign/encrypt cookies and other secrets.
+  # A default value is used in config/dev.exs and config/test.exs but you
+  # want to use a different value for prod and you most likely don't want
+  # to check this value into version control, so we use an environment
+  # variable instead.
+  secret_key_base =
+    System.get_env("SECRET_KEY_BASE") ||
+      raise """
+      environment variable SECRET_KEY_BASE is missing.
+      You can generate one by calling: mix phx.gen.secret
+      """
+
+  host = System.get_env("PHX_HOST") || "example.com"
+
+  config :counter, :dns_cluster_query, System.get_env("DNS_CLUSTER_QUERY")
+
+  config :counter, CounterWeb.Endpoint,
+    url: [host: host, port: 443, scheme: "https"],
+    http: [
+      # Enable IPv6 and bind on all interfaces.
+      # Set it to  {0, 0, 0, 0, 0, 0, 0, 1} for local network only access.
+      # See the documentation on https://bandit.hexdocs.pm/Bandit.html#t:options/0
+      # for details about using IPv6 vs IPv4 and loopback vs public addresses.
+      ip: {0, 0, 0, 0, 0, 0, 0, 0}
+    ],
+    secret_key_base: secret_key_base
+
+  # ## SSL Support
+  #
+  # To get SSL working, you will need to add the `https` key
+  # to your endpoint configuration:
+  #
+  #     config :counter, CounterWeb.Endpoint,
+  #       https: [
+  #         ...,
+  #         port: 443,
+  #         cipher_suite: :strong,
+  #         keyfile: System.get_env("SOME_APP_SSL_KEY_PATH"),
+  #         certfile: System.get_env("SOME_APP_SSL_CERT_PATH")
+  #       ]
+  #
+  # The `cipher_suite` is set to `:strong` to support only the
+  # latest and more secure SSL ciphers. This means old browsers
+  # and clients may not be supported. You can set it to
+  # `:compatible` for wider support.
+  #
+  # `:keyfile` and `:certfile` expect an absolute path to the key
+  # and cert in disk or a relative path inside priv, for example
+  # "priv/ssl/server.key". For all supported SSL configuration
+  # options, see https://plug.hexdocs.pm/Plug.SSL.html#configure/1
+  #
+  # We also recommend setting `force_ssl` in your config/prod.exs,
+  # ensuring no data is ever sent via http, always redirecting to https:
+  #
+  #     config :counter, CounterWeb.Endpoint,
+  #       force_ssl: [hsts: true]
+  #
+  # Check `Plug.SSL` for all available options in `force_ssl`.
+end

lectures/06/counter/config/test.exs

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+import Config
+
+# We don't run a server during test. If one is required,
+# you can enable the server option below.
+config :counter, CounterWeb.Endpoint,
+  http: [ip: {127, 0, 0, 1}, port: 4002],
+  secret_key_base: "uxfKXTx3MLHXTHnOIm1NBoAS8fGuPzG7fUrKS/fMB861UO9L31ewk4CQH5LhdHfb",
+  server: false
+
+# Print only warnings and errors during test
+config :logger, level: :warning
+
+# Initialize plugs at runtime for faster test compilation
+config :phoenix, :plug_init_mode, :runtime
+
+# Sort query params output of verified routes for robust url comparisons
+config :phoenix,
+  sort_verified_routes_query_params: true

lectures/06/counter/lib/counter.ex

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+defmodule Counter do
+  @moduledoc """
+  Counter keeps the contexts that define your domain
+  and business logic.
+
+  Contexts are also responsible for managing your data, regardless
+  if it comes from the database, an external API or others.
+  """
+end

lectures/06/counter/lib/counter/application.ex

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+defmodule Counter.Application do
+  # See https://elixir.hexdocs.pm/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+  @table Counter.Table
+  @registry Counter.Registry
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+	:ets.new(@table, [:set, :public, :named_table])
+
+	children = [
+	  CounterWeb.Telemetry,
+	  {DNSCluster, query: Application.get_env(:counter, :dns_cluster_query) || :ignore},
+	  {Phoenix.PubSub, name: Counter.PubSub},
+	  {Registry, name: @registry, keys: :unique},
+	  # Starts workers on demand by calling: Counter.DynamicSupervisor.start_worker(name)
+	  Counter.DynamicSupervisor,
+	  # Start to serve requests, typically the last entry
+	  CounterWeb.Endpoint
+	]
+
+	# See https://elixir.hexdocs.pm/Supervisor.html
+	# for other strategies and supported options
+	opts = [strategy: :one_for_one, name: Counter.Supervisor]
+	Supervisor.start_link(children, opts)
+  end
+
+  # Tell Phoenix to update the endpoint configuration
+  # whenever the application is updated.
+  @impl true
+  def config_change(changed, _new, removed) do
+	CounterWeb.Endpoint.config_change(changed, removed)
+	:ok
+  end
+end

lectures/06/counter/lib/counter/dynamic_supervisor.ex

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

lectures/06/counter/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/06/counter/lib/counter_web.ex

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+defmodule CounterWeb do
+  @moduledoc """
+  The entrypoint for defining your web interface, such
+  as controllers, components, channels, and so on.
+
+  This can be used in your application as:
+
+      use CounterWeb, :controller
+      use CounterWeb, :html
+
+  The definitions below will be executed for every controller,
+  component, etc, so keep them short and clean, focused
+  on imports, uses and aliases.
+
+  Do NOT define functions inside the quoted expressions
+  below. Instead, define additional modules and import
+  those modules here.
+  """
+
+  def static_paths, do: ~w(assets fonts images favicon.ico robots.txt)
+
+  def router do
+    quote do
+      use Phoenix.Router, helpers: false
+
+      # Import common connection and controller functions to use in pipelines
+      import Plug.Conn
+      import Phoenix.Controller
+    end
+  end
+
+  def channel do
+    quote do
+      use Phoenix.Channel
+    end
+  end
+
+  def controller do
+    quote do
+      use Phoenix.Controller, formats: [:html, :json]
+
+      use Gettext, backend: CounterWeb.Gettext
+
+      import Plug.Conn
+
+      unquote(verified_routes())
+    end
+  end
+
+  def verified_routes do
+    quote do
+      use Phoenix.VerifiedRoutes,
+        endpoint: CounterWeb.Endpoint,
+        router: CounterWeb.Router,
+        statics: CounterWeb.static_paths()
+    end
+  end
+
+  @doc """
+  When used, dispatch to the appropriate controller/live_view/etc.
+  """
+  defmacro __using__(which) when is_atom(which) do
+    apply(__MODULE__, which, [])
+  end
+end

lectures/06/counter/lib/counter_web/controllers/counter_controller.ex

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+defmodule CounterWeb.CounterController do
+  use CounterWeb, :controller
+
+  def new(conn, %{"name" => name}) do
+	Counter.DynamicSupervisor.start_worker(name)
+	render(conn, :new)
+  end
+
+  def value(conn, %{"name" => name}) do
+	value = Counter.Worker.value(name)
+	render(conn, :value, value: value)
+  end
+
+  def inc(conn, %{"name" => name, "amt" => amt}) when is_integer(amt) do
+	Counter.Worker.inc(name, amt)
+	render(conn, :inc)
+  end
+end

lectures/06/counter/lib/counter_web/controllers/counter_json.ex

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+defmodule CounterWeb.CounterJSON do
+  def value(assigns) do
+	%{value: assigns.value}
+  end
+
+  def new(_assigns) do
+	%{status: "ok"}
+  end
+
+  def inc(_assigns) do
+	%{status: "ok"}
+  end
+end

lectures/06/counter/lib/counter_web/controllers/error_json.ex

@@ -0,0 +1,21 @@
+defmodule CounterWeb.ErrorJSON do
+  @moduledoc """
+  This module is invoked by your endpoint in case of errors on JSON requests.
+
+  See config/config.exs.
+  """
+
+  # If you want to customize a particular status code,
+  # you may add your own clauses, such as:
+  #
+  # def render("500.json", _assigns) do
+  #   %{errors: %{detail: "Internal Server Error"}}
+  # end
+
+  # By default, Phoenix returns the status message from
+  # the template name. For example, "404.json" becomes
+  # "Not Found".
+  def render(template, _assigns) do
+    %{errors: %{detail: Phoenix.Controller.status_message_from_template(template)}}
+  end
+end

lectures/06/counter/lib/counter_web/endpoint.ex

@@ -0,0 +1,52 @@
+defmodule CounterWeb.Endpoint do
+  use Phoenix.Endpoint, otp_app: :counter
+
+  # The session will be stored in the cookie and signed,
+  # this means its contents can be read but not tampered with.
+  # Set :encryption_salt if you would also like to encrypt it.
+  @session_options [
+    store: :cookie,
+    key: "_counter_key",
+    signing_salt: "u8wt1XSs",
+    same_site: "Lax"
+  ]
+
+  socket "/live", Phoenix.LiveView.Socket,
+    websocket: [connect_info: [session: @session_options]],
+    longpoll: [connect_info: [session: @session_options]]
+
+  # Serve at "/" the static files from "priv/static" directory.
+  #
+  # When code reloading is disabled (e.g., in production),
+  # the `gzip` option is enabled to serve compressed
+  # static files generated by running `phx.digest`.
+  plug Plug.Static,
+    at: "/",
+    from: :counter,
+    gzip: not code_reloading?,
+    only: CounterWeb.static_paths(),
+    raise_on_missing_only: code_reloading?
+
+  # Code reloading can be explicitly enabled under the
+  # :code_reloader configuration of your endpoint.
+  if code_reloading? do
+    plug Phoenix.CodeReloader
+  end
+
+  plug Phoenix.LiveDashboard.RequestLogger,
+    param_key: "request_logger",
+    cookie_key: "request_logger"
+
+  plug Plug.RequestId
+  plug Plug.Telemetry, event_prefix: [:phoenix, :endpoint]
+
+  plug Plug.Parsers,
+    parsers: [:urlencoded, :multipart, :json],
+    pass: ["*/*"],
+    json_decoder: Phoenix.json_library()
+
+  plug Plug.MethodOverride
+  plug Plug.Head
+  plug Plug.Session, @session_options
+  plug CounterWeb.Router
+end

lectures/06/counter/lib/counter_web/gettext.ex

@@ -0,0 +1,25 @@
+defmodule CounterWeb.Gettext do
+  @moduledoc """
+  A module providing Internationalization with a gettext-based API.
+
+  By using [Gettext](https://gettext.hexdocs.pm), your module compiles translations
+  that you can use in your application. To use this Gettext backend module,
+  call `use Gettext` and pass it as an option:
+
+      use Gettext, backend: CounterWeb.Gettext
+
+      # Simple translation
+      gettext("Here is the string to translate")
+
+      # Plural translation
+      ngettext("Here is the string to translate",
+               "Here are the strings to translate",
+               3)
+
+      # Domain-based translation
+      dgettext("errors", "Here is the error message to translate")
+
+  See the [Gettext Docs](https://gettext.hexdocs.pm) for detailed usage.
+  """
+  use Gettext.Backend, otp_app: :counter
+end

lectures/06/counter/lib/counter_web/router.ex

@@ -0,0 +1,31 @@
+defmodule CounterWeb.Router do
+  use CounterWeb, :router
+
+  pipeline :api do
+	plug :accepts, ["json"]
+  end
+
+  scope "/api", CounterWeb do
+	pipe_through :api
+
+	post "/counter/new/:name", CounterController, :new
+	get "/counter/value/:name", CounterController, :value
+	post "/counter/inc/:name", CounterController, :inc
+  end
+
+  # Enable LiveDashboard in development
+  if Application.compile_env(:counter, :dev_routes) do
+	# If you want to use the LiveDashboard in production, you should put
+	# it behind authentication and allow only admins to access it.
+	# If your application does not have an admins-only section yet,
+	# you can use Plug.BasicAuth to set up some basic authentication
+	# as long as you are also using SSL (which you should anyway).
+	import Phoenix.LiveDashboard.Router
+
+	scope "/dev" do
+	  pipe_through [:fetch_session, :protect_from_forgery]
+
+	  live_dashboard "/dashboard", metrics: CounterWeb.Telemetry
+	end
+  end
+end

lectures/06/counter/lib/counter_web/telemetry.ex

@@ -0,0 +1,70 @@
+defmodule CounterWeb.Telemetry do
+  use Supervisor
+  import Telemetry.Metrics
+
+  def start_link(arg) do
+    Supervisor.start_link(__MODULE__, arg, name: __MODULE__)
+  end
+
+  @impl true
+  def init(_arg) do
+    children = [
+      # Telemetry poller will execute the given period measurements
+      # every 10_000ms. Learn more here: https://telemetry-metrics.hexdocs.pm
+      {:telemetry_poller, measurements: periodic_measurements(), period: 10_000}
+      # Add reporters as children of your supervision tree.
+      # {Telemetry.Metrics.ConsoleReporter, metrics: metrics()}
+    ]
+
+    Supervisor.init(children, strategy: :one_for_one)
+  end
+
+  def metrics do
+    [
+      # Phoenix Metrics
+      summary("phoenix.endpoint.start.system_time",
+        unit: {:native, :millisecond}
+      ),
+      summary("phoenix.endpoint.stop.duration",
+        unit: {:native, :millisecond}
+      ),
+      summary("phoenix.router_dispatch.start.system_time",
+        tags: [:route],
+        unit: {:native, :millisecond}
+      ),
+      summary("phoenix.router_dispatch.exception.duration",
+        tags: [:route],
+        unit: {:native, :millisecond}
+      ),
+      summary("phoenix.router_dispatch.stop.duration",
+        tags: [:route],
+        unit: {:native, :millisecond}
+      ),
+      summary("phoenix.socket_connected.duration",
+        unit: {:native, :millisecond}
+      ),
+      sum("phoenix.socket_drain.count"),
+      summary("phoenix.channel_joined.duration",
+        unit: {:native, :millisecond}
+      ),
+      summary("phoenix.channel_handled_in.duration",
+        tags: [:event],
+        unit: {:native, :millisecond}
+      ),
+
+      # VM Metrics
+      summary("vm.memory.total", unit: {:byte, :kilobyte}),
+      summary("vm.total_run_queue_lengths.total"),
+      summary("vm.total_run_queue_lengths.cpu"),
+      summary("vm.total_run_queue_lengths.io")
+    ]
+  end
+
+  defp periodic_measurements do
+    [
+      # A module, function and arguments to be invoked periodically.
+      # This function must call :telemetry.execute/3 and a metric must be added above.
+      # {CounterWeb, :count_users, []}
+    ]
+  end
+end

lectures/06/counter/mix.exs

@@ -0,0 +1,65 @@
+defmodule Counter.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :counter,
+      version: "0.1.0",
+      elixir: "~> 1.17",
+      elixirc_paths: elixirc_paths(Mix.env()),
+      start_permanent: Mix.env() == :prod,
+      aliases: aliases(),
+      deps: deps(),
+      listeners: [Phoenix.CodeReloader]
+    ]
+  end
+
+  # Configuration for the OTP application.
+  #
+  # Type `mix help compile.app` for more information.
+  def application do
+    [
+      mod: {Counter.Application, []},
+      extra_applications: [:logger, :runtime_tools]
+    ]
+  end
+
+  def cli do
+    [
+      preferred_envs: [precommit: :test]
+    ]
+  end
+
+  # Specifies which paths to compile per environment.
+  defp elixirc_paths(:test), do: ["lib", "test/support"]
+  defp elixirc_paths(_), do: ["lib"]
+
+  # Specifies your project dependencies.
+  #
+  # Type `mix help deps` for examples and options.
+  defp deps do
+    [
+      {:phoenix, "~> 1.8.15"},
+      {:phoenix_live_dashboard, "~> 0.8.3"},
+      {:telemetry_metrics, "~> 1.0"},
+      {:telemetry_poller, "~> 1.0"},
+      {:gettext, "~> 1.0"},
+      {:jason, "~> 1.2"},
+      {:dns_cluster, "~> 0.2.0"},
+      {:bandit, "~> 1.5"}
+    ]
+  end
+
+  # Aliases are shortcuts or tasks specific to the current project.
+  # For example, to install project dependencies and perform other setup tasks, run:
+  #
+  #     $ mix setup
+  #
+  # See the documentation for `Mix` for more info on aliases.
+  defp aliases do
+    [
+      setup: ["deps.get"],
+      precommit: ["compile --warnings-as-errors", "deps.unlock --unused", "format", "test"]
+    ]
+  end
+end

lectures/06/counter/mix.lock

@@ -0,0 +1,23 @@
+%{
+  "bandit": {:hex, :bandit, "1.13.1", "1ce25a7beb750ed3fa2e905962f1f9a679cb585f1da0ae45637d06e385ce2eae", [:mix], [{:hpax, "~> 1.1", [hex: :hpax, repo: "hexpm", optional: false]}, {:plug, "~> 1.18", [hex: :plug, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}, {:thousand_island, "~> 1.6", [hex: :thousand_island, repo: "hexpm", optional: false]}, {:websock, "~> 0.5", [hex: :websock, repo: "hexpm", optional: false]}], "hexpm", "39028f0b5a21404661410a6c19275060a9822c9dcca70b7c3e4e4fa50b11da58"},
+  "dns_cluster": {:hex, :dns_cluster, "0.2.0", "aa8eb46e3bd0326bd67b84790c561733b25c5ba2fe3c7e36f28e88f384ebcb33", [:mix], [], "hexpm", "ba6f1893411c69c01b9e8e8f772062535a4cf70f3f35bcc964a324078d8c8240"},
+  "expo": {:hex, :expo, "1.1.1", "4202e1d2ca6e2b3b63e02f69cfe0a404f77702b041d02b58597c00992b601db5", [:mix], [], "hexpm", "5fb308b9cb359ae200b7e23d37c76978673aa1b06e2b3075d814ce12c5811640"},
+  "gettext": {:hex, :gettext, "1.0.2", "5457e1fd3f4abe47b0e13ff85086aabae760497a3497909b8473e0acee57673b", [:mix], [{:expo, "~> 0.5.1 or ~> 1.0", [hex: :expo, repo: "hexpm", optional: false]}], "hexpm", "eab805501886802071ad290714515c8c4a17196ea76e5afc9d06ca85fb1bfeb3"},
+  "hpax": {:hex, :hpax, "1.1.0", "782931867cc23217c68fb5f68fe1a11f5e7544c7fda82c8a7019a5df5a4a1cdf", [:mix], [], "hexpm", "0b8d0f05832f55571d65ac720f79bf8994138ffbb133209dc4685eae0ad456a8"},
+  "jason": {:hex, :jason, "1.4.5", "2e3a008590b0b8d7388c20293e9dcc9cf3e5d642fd2a114e4cbbb52e595d940a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0 or ~> 3.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "b0c823996102bcd0239b3c2444eb00409b72f6a140c1950bc8b457d836b30684"},
+  "mime": {:hex, :mime, "2.0.7", "b8d739037be7cd402aee1ba0306edfdef982687ee7e9859bee6198c1e7e2f128", [:mix], [], "hexpm", "6171188e399ee16023ffc5b76ce445eb6d9672e2e241d2df6050f3c771e80ccd"},
+  "phoenix": {:hex, :phoenix, "1.8.15", "dcdb304113660ec97e1579458824d3c34b5d2eed07a0fdf25a836a9515b63146", [:mix], [{:bandit, "~> 1.0", [hex: :bandit, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 2.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:phoenix_template, "~> 1.0", [hex: :phoenix_template, repo: "hexpm", optional: false]}, {:phoenix_view, "~> 2.0", [hex: :phoenix_view, repo: "hexpm", optional: true]}, {:plug, "~> 1.14", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.7", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:plug_crypto, "~> 2.2", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}, {:websock_adapter, "~> 0.5", [hex: :websock_adapter, repo: "hexpm", optional: false]}], "hexpm", "7b83ed6b3d544f24a29277eab7f051be38b76f390bb511bb6ddb7ec6e8e05b95"},
+  "phoenix_html": {:hex, :phoenix_html, "4.3.0", "d3577a5df4b6954cd7890c84d955c470b5310bb49647f0a114a6eeecc850f7ad", [:mix], [], "hexpm", "3eaa290a78bab0f075f791a46a981bbe769d94bc776869f4f3063a14f30497ad"},
+  "phoenix_live_dashboard": {:hex, :phoenix_live_dashboard, "0.8.7", "405880012cb4b706f26dd1c6349125bfc903fb9e44d1ea668adaf4e04d4884b7", [:mix], [{:ecto, "~> 3.6.2 or ~> 3.7", [hex: :ecto, repo: "hexpm", optional: true]}, {:ecto_mysql_extras, "~> 0.5", [hex: :ecto_mysql_extras, repo: "hexpm", optional: true]}, {:ecto_psql_extras, "~> 0.7", [hex: :ecto_psql_extras, repo: "hexpm", optional: true]}, {:ecto_sqlite3_extras, "~> 1.1.7 or ~> 1.2.0", [hex: :ecto_sqlite3_extras, repo: "hexpm", optional: true]}, {:mime, "~> 1.6 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:phoenix_live_view, "~> 0.19 or ~> 1.0", [hex: :phoenix_live_view, repo: "hexpm", optional: false]}, {:telemetry_metrics, "~> 0.6 or ~> 1.0", [hex: :telemetry_metrics, repo: "hexpm", optional: false]}], "hexpm", "3a8625cab39ec261d48a13b7468dc619c0ede099601b084e343968309bd4d7d7"},
+  "phoenix_live_view": {:hex, :phoenix_live_view, "1.2.12", "35848150bbab579e9d0aff79525269d7c0801a4f61232b84f635c11222cee88f", [:mix], [{:igniter, ">= 0.6.16 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:lazy_html, "~> 0.1.0", [hex: :lazy_html, repo: "hexpm", optional: true]}, {:phoenix, "~> 1.6.15 or ~> 1.7.0 or ~> 1.8.0", [hex: :phoenix, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 3.3 or ~> 4.0", [hex: :phoenix_html, repo: "hexpm", optional: false]}, {:phoenix_template, "~> 1.0", [hex: :phoenix_template, repo: "hexpm", optional: false]}, {:phoenix_view, "~> 2.0", [hex: :phoenix_view, repo: "hexpm", optional: true]}, {:plug, "~> 1.15", [hex: :plug, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.2 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "656810d716e3369545dd63981196a5d68b77fdb253afe02ef0c6fa14cfd8dc2b"},
+  "phoenix_pubsub": {:hex, :phoenix_pubsub, "2.4.1", "2ff3e7ba8b432120989870997b9adaefb76e1f63805554ab0b9e948987981f4b", [:mix], [], "hexpm", "352fba7a87bf61395b6e97da66944ad9b1bfe5459e5981039f60d68270bd9700"},
+  "phoenix_template": {:hex, :phoenix_template, "1.1.0", "b329582281b1e00e4dc664afd60ef5b489cbb356923caa3b1e00abe8651b9a18", [:mix], [{:phoenix_html, "~> 2.14.2 or ~> 3.0 or ~> 4.0", [hex: :phoenix_html, repo: "hexpm", optional: true]}], "hexpm", "eba70070de79b2c3501ef205a74a69f98ab352f3785aa15da9ed161f9fe0fd5d"},
+  "plug": {:hex, :plug, "1.20.3", "56c480c633ec2ce10140e236e15233bf576e1d323887d7c96711bd02ab5160db", [:mix], [{:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.1.1 or ~> 1.2 or ~> 2.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.3 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "be266aee1b8536ef6409d58cf39a3121319f0ec47cfa1b24024485aa0e76ad76"},
+  "plug_crypto": {:hex, :plug_crypto, "2.2.0", "144014737daaf485407f5ed77daeaad74d651b216a28c87543f8cc7043f8efc8", [:mix], [], "hexpm", "83a95744ab1c75876542b6fab135fcc176280e0f301a111c1f757fddcec95d2c"},
+  "telemetry": {:hex, :telemetry, "1.4.2", "a0cb522801dffb1c49fe6e30561badffc7b6d0e180db1300df759faa22062855", [:rebar3], [], "hexpm", "928f6495066506077862c0d1646609eed891a4326bee3126ba54b60af61febb1"},
+  "telemetry_metrics": {:hex, :telemetry_metrics, "1.2.0", "7632c19c01d88d8aaca5da1a0e8912f5af39b79e7c08a2c253aeb3c14c2c957e", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "71dde12fc29b58b9c77ec17ec319109e5ca848d010fc1965ed4463bba1837c07"},
+  "telemetry_poller": {:hex, :telemetry_poller, "1.3.0", "d5c46420126b5ac2d72bc6580fb4f537d35e851cc0f8dbd571acf6d6e10f5ec7", [:rebar3], [{:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "51f18bed7128544a50f75897db9974436ea9bfba560420b646af27a9a9b35211"},
+  "thousand_island": {:hex, :thousand_island, "1.6.0", "d6ad7c2220c96a270cc8ca1586ec4d8bde648a4a3a53f003ce093f41beec0288", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "4d4720470f091fc21a1311777c2ac66916c43621bffc068590c9f9bb3cd057a3"},
+  "websock": {:hex, :websock, "0.5.3", "2f69a6ebe810328555b6fe5c831a851f485e303a7c8ce6c5f675abeb20ebdadc", [:mix], [], "hexpm", "6105453d7fac22c712ad66fab1d45abdf049868f253cf719b625151460b8b453"},
+  "websock_adapter": {:hex, :websock_adapter, "0.6.0", "73db5ab8aaefd1a876a97ce3e6afc96562625de69ef17a4e04426e034849d0b8", [:mix], [{:bandit, ">= 0.6.0", [hex: :bandit, repo: "hexpm", optional: true]}, {:plug, "~> 1.14", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.6", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:websock, "~> 0.5", [hex: :websock, repo: "hexpm", optional: false]}], "hexpm", "50021a85bce8f203b086705d9e0c5415e2c7eb05d319111b0428fe71f9934617"},
+}

lectures/06/counter/priv/gettext/en/LC_MESSAGES/errors.po

@@ -0,0 +1,11 @@
+## `msgid`s in this file come from POT (.pot) files.
+##
+## Do not add, change, or remove `msgid`s manually here as
+## they're tied to the ones in the corresponding POT file
+## (with the same domain).
+##
+## Use `mix gettext.extract --merge` or `mix gettext.merge`
+## to merge POT files into PO files.
+msgid ""
+msgstr ""
+"Language: en\n"

lectures/06/counter/priv/gettext/errors.pot

@@ -0,0 +1,10 @@
+## This is a PO Template file.
+##
+## `msgid`s here are often extracted from source code.
+## Add new translations manually only if they're dynamic
+## translations that can't be statically extracted.
+##
+## Run `mix gettext.extract` to bring this file up to
+## date. Leave `msgstr`s empty as changing them here has no
+## effect: edit them in PO (`.po`) files instead.
+

lectures/06/counter/priv/static/robots.txt

@@ -0,0 +1,5 @@
+# See https://www.robotstxt.org/robotstxt.html for documentation on how to use the robots.txt file
+#
+# To ban all spiders from the entire site uncomment the next two lines:
+# User-agent: *
+# Disallow: /

lectures/06/counter/test/counter_web/controllers/error_json_test.exs

@@ -0,0 +1,12 @@
+defmodule CounterWeb.ErrorJSONTest do
+  use CounterWeb.ConnCase, async: true
+
+  test "renders 404" do
+    assert CounterWeb.ErrorJSON.render("404.json", %{}) == %{errors: %{detail: "Not Found"}}
+  end
+
+  test "renders 500" do
+    assert CounterWeb.ErrorJSON.render("500.json", %{}) ==
+             %{errors: %{detail: "Internal Server Error"}}
+  end
+end

lectures/06/counter/test/support/conn_case.ex

@@ -0,0 +1,37 @@
+defmodule CounterWeb.ConnCase do
+  @moduledoc """
+  This module defines the test case to be used by
+  tests that require setting up a connection.
+
+  Such tests rely on `Phoenix.ConnTest` and also
+  import other functionality to make it easier
+  to build common data structures and query the data layer.
+
+  Finally, if the test case interacts with the database,
+  we enable the SQL sandbox, so changes done to the database
+  are reverted at the end of every test. If you are using
+  PostgreSQL, you can even run database tests asynchronously
+  by setting `use CounterWeb.ConnCase, async: true`, although
+  this option is not recommended for other databases.
+  """
+
+  use ExUnit.CaseTemplate
+
+  using do
+    quote do
+      # The default endpoint for testing
+      @endpoint CounterWeb.Endpoint
+
+      use CounterWeb, :verified_routes
+
+      # Import conveniences for testing with connections
+      import Plug.Conn
+      import Phoenix.ConnTest
+      import CounterWeb.ConnCase
+    end
+  end
+
+  setup _tags do
+    {:ok, conn: Phoenix.ConnTest.build_conn()}
+  end
+end

lectures/06/counter/test/test_helper.exs

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