Refactor modules into contexts (#78)

* [WIP] break out a few contexts, start refactoring fast index modules

* [WIP] more contexts, this time around slow indexing and downloads

* [WIP] got all tests passing

* [WIP] Added moduledocs

* Built a genserver to rename old jobs on boot

* Added a module naming check; moved things around

* Fixed specs

lib/pinchflat/downloading/downloading_helpers.ex

@@ -0,0 +1,50 @@
+defmodule Pinchflat.Downloading.DownloadingHelpers do
+  @moduledoc """
+  Methods for helping download media
+
+  Many of these methods are made to be kickoff or be consumed by workers.
+  """
+
+  require Logger
+
+  alias Pinchflat.Media
+  alias Pinchflat.Tasks
+  alias Pinchflat.Sources.Source
+  alias Pinchflat.Downloading.MediaDownloadWorker
+
+  @doc """
+  Starts tasks for downloading media for any of a sources _pending_ media items.
+  Jobs are not enqueued if the source is set to not download media. This will return :ok.
+
+  NOTE: this starts a download for each media item that is pending,
+  not just the ones that were indexed in this job run. This should ensure
+  that any stragglers are caught if, for some reason, they weren't enqueued
+  or somehow got de-queued.
+
+  Returns :ok
+  """
+  def enqueue_pending_download_tasks(%Source{download_media: true} = source) do
+    source
+    |> Media.list_pending_media_items_for()
+    |> Enum.each(fn media_item ->
+      %{id: media_item.id}
+      |> MediaDownloadWorker.new()
+      |> Tasks.create_job_with_task(media_item)
+    end)
+  end
+
+  def enqueue_pending_download_tasks(%Source{download_media: false}) do
+    :ok
+  end
+
+  @doc """
+  Deletes ALL pending tasks for a source's media items.
+
+  Returns :ok
+  """
+  def dequeue_pending_download_tasks(%Source{} = source) do
+    source
+    |> Media.list_pending_media_items_for()
+    |> Enum.each(&Tasks.delete_pending_tasks_for/1)
+  end
+end