From d34ab2abb2ed544433f7c359b70a3396a8f0bf08 Mon Sep 17 00:00:00 2001
From: Connor Rigby <connor@farmbot.io>
Date: Thu, 7 Nov 2019 09:00:48 -0800
Subject: [PATCH] Add new system to track dependency statuses globally

---
 farmbot_core/lib/farmbot_core.ex              |  1 +
 farmbot_core/lib/farmbot_core/dep_tracker.ex  | 81 +++++++++++++++++++
 .../lib/farmbot_core/dep_tracker/logger.ex    | 52 ++++++++++++
 .../farmbot_core/dep_tracker/supervisor.ex    | 29 +++++++
 .../lib/farmbot_core/dep_tracker/table.ex     | 69 ++++++++++++++++
 5 files changed, 232 insertions(+)
 create mode 100644 farmbot_core/lib/farmbot_core/dep_tracker.ex
 create mode 100644 farmbot_core/lib/farmbot_core/dep_tracker/logger.ex
 create mode 100644 farmbot_core/lib/farmbot_core/dep_tracker/supervisor.ex
 create mode 100644 farmbot_core/lib/farmbot_core/dep_tracker/table.ex

diff --git a/farmbot_core/lib/farmbot_core.ex b/farmbot_core/lib/farmbot_core.ex
index 769596e6..075bf929 100644
--- a/farmbot_core/lib/farmbot_core.ex
+++ b/farmbot_core/lib/farmbot_core.ex
@@ -16,6 +16,7 @@ defmodule FarmbotCore do
   def init([]) do
 
     children = [
+      FarmbotCore.DepTracker,
       FarmbotCore.Leds,
       FarmbotCore.EctoMigrator,
       FarmbotCore.BotState.Supervisor,
diff --git a/farmbot_core/lib/farmbot_core/dep_tracker.ex b/farmbot_core/lib/farmbot_core/dep_tracker.ex
new file mode 100644
index 00000000..1bff024c
--- /dev/null
+++ b/farmbot_core/lib/farmbot_core/dep_tracker.ex
@@ -0,0 +1,81 @@
+defmodule FarmbotCore.DepTracker do
+  @moduledoc """
+  Subscribe to internal dependency and service status events.
+  """
+  alias FarmbotCore.{DepTracker, DepTracker.Table}
+
+  @doc "Start a dep tracker instance"
+  def start_link(options) do
+    name = Keyword.get(options, :name, DepTracker)
+
+    unless !is_nil(name) and is_atom(name) do
+      raise ArgumentError, "expected :name to be given and to be an atom, got: #{inspect(name)}"
+    end
+    DepTracker.Supervisor.start_link(name)
+  end
+
+  @doc false
+  def child_spec(opts) do
+    %{
+      id: Keyword.get(opts, :name, DepTracker),
+      start: {DepTracker, :start_link, [opts]},
+      type: :supervisor
+    }
+  end
+
+  @doc "register an asset in the tracker"
+  def register_asset(table \\ DepTracker, %kind{local_id: local_id}, status) do
+    Table.put(table, {{kind, local_id}, status})
+  end
+
+  @doc "register a service in the tracker"
+  def register_service(table \\ DepTracker, service_name, status) do
+    Table.put(table, {service_name, status})
+  end
+
+  @doc """
+  subscribe to asset changes from the tracker
+  messages are dispatched in the shape of
+
+      {table_name, {kind, local_id}, status}
+  """
+  def subscribe_asset(table \\ DepTracker, kind) do
+    :ok = do_subscribe(table, kind)
+    initial = get_asset(table, kind)
+    for {{kind, local_id}, status} <- initial do
+      send self(), {table, {kind, local_id}, nil, status}
+    end
+    :ok
+  end
+
+  @doc "get all current assets by kind"
+  def get_asset(table \\ DepTracker, kind) do
+    Table.get(table, {kind, :"$1"})
+  end
+
+  @doc """
+  subscribe to service changes from the tracker
+  messages are dispatched in the shape of
+
+      {table_name, service_name, status}
+  """
+  def subscribe_service(table \\ DepTracker, service_name) do
+    :ok = do_subscribe(table, service_name)
+    initial = get_service(table, service_name)
+    for {^service_name, status} <- initial do
+      send self(), {table, {service_name, nil, status}}
+    end
+    :ok
+  end
+
+  @doc "get all current services by name"
+  def get_service(table \\ DepTracker, service_name) do
+    Table.get(table, service_name)
+  end
+
+  defp do_subscribe(table, name) do
+    registry = DepTracker.Supervisor.registry_name(table)
+    {:ok, _} = Registry.register(registry, name, nil)
+    :ok
+  end
+end
\ No newline at end of file
diff --git a/farmbot_core/lib/farmbot_core/dep_tracker/logger.ex b/farmbot_core/lib/farmbot_core/dep_tracker/logger.ex
new file mode 100644
index 00000000..f5a41db0
--- /dev/null
+++ b/farmbot_core/lib/farmbot_core/dep_tracker/logger.ex
@@ -0,0 +1,52 @@
+defmodule FarmbotCore.DepTracker.Logger do
+  alias FarmbotCore.DepTracker
+  require Logger
+  use GenServer
+
+  @doc false
+  def child_spec(args) do
+    %{
+      id: name(args),
+      start: {FarmbotCore.DepTracker.Logger, :start_link, [args]},
+    }
+  end
+
+  def start_link(args) do
+    GenServer.start_link(__MODULE__, args, [name: name(args)])
+  end
+
+  defp name({table, [service: service_name]}) do
+    Module.concat([__MODULE__, table, service_name])
+  end
+
+  defp name({table, [asset: kind]}) do
+    Module.concat([__MODULE__, table, kind])
+  end
+
+  def init({table, [service: service_name]}) do
+    :ok = DepTracker.subscribe_service(table, service_name)
+    {:ok, %{service: service_name, table: table}}
+  end
+
+  def init({table, [asset: kind]}) do
+    :ok = DepTracker.subscribe_asset(table, kind)
+    {:ok, %{asset: kind, table: table}}
+  end
+
+  def handle_info({table, {kind, local_id}, old_status, new_status}, %{asset: kind, table: table} = state) do
+    Logger.info """
+    #{inspect(table)} asset status change:
+    #{kind} local_id = #{local_id}
+    #{kind} #{inspect(old_status)} => #{inspect(new_status)}
+    """
+    {:noreply, state}
+  end
+
+  def handle_info({table, service, old_status, new_status}, %{service: service, table: table} = state) do
+    Logger.info """
+    #{inspect(table)} service status change:
+    #{service} #{inspect(old_status)} => #{inspect(new_status)}
+    """
+    {:noreply, state}
+  end
+end
\ No newline at end of file
diff --git a/farmbot_core/lib/farmbot_core/dep_tracker/supervisor.ex b/farmbot_core/lib/farmbot_core/dep_tracker/supervisor.ex
new file mode 100644
index 00000000..0691c410
--- /dev/null
+++ b/farmbot_core/lib/farmbot_core/dep_tracker/supervisor.ex
@@ -0,0 +1,29 @@
+defmodule FarmbotCore.DepTracker.Supervisor do
+  use Supervisor
+
+  alias FarmbotCore.DepTracker
+
+  @moduledoc false
+
+  def start_link(name) do
+    Supervisor.start_link(__MODULE__, name)
+  end
+
+  @impl true
+  def init(name) do
+    registry_name = registry_name(name)
+
+    children = [
+      {DepTracker.Table, {name, registry_name}},
+      {Registry, [keys: :duplicate, name: registry_name]},
+      # {DepTracker.Logger, {name, service: :firmware}},
+      {DepTracker.Logger, {name, asset: FarmbotCore.Asset.FbosConfig}},
+    ]
+
+    Supervisor.init(children, strategy: :one_for_one)
+  end
+
+  def registry_name(name) do
+    Module.concat(DepTracker.Registry, name)
+  end
+end
\ No newline at end of file
diff --git a/farmbot_core/lib/farmbot_core/dep_tracker/table.ex b/farmbot_core/lib/farmbot_core/dep_tracker/table.ex
new file mode 100644
index 00000000..c2a61fed
--- /dev/null
+++ b/farmbot_core/lib/farmbot_core/dep_tracker/table.ex
@@ -0,0 +1,69 @@
+defmodule FarmbotCore.DepTracker.Table do
+  use GenServer
+
+  @doc false
+  def start_link({table, _registry_name} = args) do
+    GenServer.start_link(__MODULE__, args, name: table)
+  end
+
+  @doc "put data"
+  def put(table, {identifier, status}) do
+    GenServer.call(table, {:put, identifier, status})
+  end
+
+  @doc "get data"
+  def get(table, {kind, _} = identifier) do
+    :ets.match(table, {identifier, :"$2"})
+    |> Enum.map(fn
+      [local_id, status] -> {{kind, local_id}, status}
+      other -> raise("unknown data in ets table: #{table} data: #{inspect(other)}")
+    end)
+  end
+
+  def get(table, service_name) do
+    :ets.match(table, {service_name, :"$2"})
+    |> Enum.map(fn
+      [status] -> {service_name, status}
+      other -> raise("unknown data in ets table: #{table} data: #{inspect(other)}")
+    end)
+  end
+
+  @impl GenServer
+  def init({table, registry_name}) do
+    ^table = :ets.new(table, [:named_table, read_concurrency: true])
+
+    state = %{table: table, registry: registry_name}
+    {:ok, state}
+  end
+
+  @impl GenServer
+  def handle_call({:put, identifier, status}, _from, state) do
+    case :ets.lookup(state.table, identifier) do
+      [{^identifier, ^status}] ->
+        # No change, so no notifications
+        :ok
+
+      [{^identifier, old_status}] ->
+        :ets.insert(state.table, {identifier, status})
+        dispatch(state, identifier, old_status, status)
+
+      [] ->
+        :ets.insert(state.table, {identifier, status})
+        dispatch(state, identifier, nil, status)
+    end
+
+    {:reply, :ok, state}
+  end
+
+  defp dispatch(state, identifier, old, new) do
+    kind = case identifier do
+      {kind, _} -> kind
+      kind -> kind
+    end
+    Registry.dispatch(state.registry, kind, fn entries ->
+      message = {state.table, identifier, old, new}
+      for {pid, _} <- entries, do: send(pid, message)
+    end)
+    :ok
+  end
+end
\ No newline at end of file