defmodule FrenzyWeb.Fervor.FeedsController do
  use FrenzyWeb, :controller
  alias Frenzy.{Repo, Feed, Item}
  import Ecto.Query
  alias FrenzyWeb.Fervor.Paginator

  plug :get_specific_feed

  def get_specific_feed(%Plug.Conn{path_params: %{"id" => id}} = conn, _opts) do
    user = conn.assigns[:user] |> Repo.preload(groups: [:feeds])
    {id, _} = Integer.parse(id)

    feeds = Enum.flat_map(user.groups, fn g -> g.feeds end)

    case Enum.find(feeds, fn f -> f.id == id end) do
      nil ->
        conn
        |> put_status(404)
        |> json(%{error: "Unknown feed"})
        |> halt()

      feed ->
        assign(conn, :feed, feed)
    end
  end

  def get_specific_feed(conn, _opts), do: conn

  def feeds_list(conn, _params) do
    user = conn.assigns[:user] |> Repo.preload(groups: [:feeds])

    feeds =
      user.groups
      |> Enum.flat_map(fn g -> g.feeds end)
      |> Enum.map(&Feed.to_fervor/1)

    json(conn, feeds)
  end

  def specific_feed(conn, _params) do
    feed = conn.assigns[:feed]

    json(conn, Feed.to_fervor(feed))
  end

  def specific_feed_items(conn, params) do
    feed = conn.assigns[:feed]
    feed_id = feed.id

    query = from(i in Item, where: i.feed_id == ^feed_id)

    query =
      case Map.get(params, "only") do
        "read" -> from(i in query, where: i.read)
        "unread" -> from(i in query, where: not i.read)
        _ -> query
      end
      |> Paginator.paginate(params)
      |> Paginator.limit(params)

    items =
      query
      |> Repo.all()
      |> Enum.map(&Item.to_fervor/1)

    json(conn, items)
  end

  def create(conn, %{"feed_url" => feed_url, "group_ids" => group_ids}) do
    case Integer.parse(group_ids) do
      {_, rest} when rest != "" ->
        conn
        |> put_status(400)
        |> json(%{error: "Could not create feed. Exactly 1 group must be provided."})

      {group_id, _} ->
        user = conn.assigns[:user] |> Repo.preload(:groups)

        case Enum.find(user.groups, fn g -> g.id == group_id end) do
          nil ->
            conn
            |> put_status(400)
            |> json(%{error: "Could not create feed. Invalid group."})

          group ->
            changeset =
              Ecto.build_assoc(group, :feeds, %{
                feed_url: feed_url
              })

            {:ok, feed} = Repo.insert(changeset)

            feed = Frenzy.UpdateFeeds.refresh(Frenzy.UpdateFeeds, feed)

            json(conn, Feed.to_fervor(feed))
        end
    end
  end

  def create(conn, _params) do
    conn
    |> put_status(400)
    |> json(%{
      error: "Could not create feed",
      error_description: "feed URL and one group ID must be provided"
    })
  end

  def delete(conn, _params) do
    feed = conn.assigns[:feed]

    {:ok, _} = Repo.delete(feed)

    send_resp(conn, 204, "")
  end
end