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

  plug :get_specific_item

  def get_specific_item(%Plug.Conn{path_params: %{"id" => id}} = conn, _opts) when id != "sync" do
    user = conn.assigns[:user] |> Repo.preload(:feeds)

    item = Repo.get(Item, id)

    if Enum.any?(user.feeds, fn f -> f.id == item.feed_id end) do
      assign(conn, :item, item)
    else
      conn
      |> put_status(404)
      |> json(%{error: "Unknown item"})
      |> halt()
    end
  end

  def get_specific_item(conn, _opts), do: conn

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

    feed_ids =
      user.groups
      |> Enum.flat_map(fn g -> g.feeds end)
      |> Enum.map(fn f -> f.id end)

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

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

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

    json(conn, items)
  end

  def specific_item(conn, _params) do
    item = conn.assigns[:item]

    json(conn, Item.to_fervor(item))
  end

  defp mark_item(conn, changes) do
    item = conn.assigns[:item] |> Repo.preload(:feed)

    changeset = Item.changeset(item, changes)

    if changeset.valid? do
      {:ok, item} = Repo.update(changeset)

      json(conn, Item.to_fervor(item))
    else
      json(conn, Item.to_fervor(item))
    end
  end

  def read_specific_item(conn, _params) do
    mark_item(conn, %{read: true})
  end

  def unread_specific_item(conn, _params) do
    mark_item(conn, %{read: false})
  end

  defp mark_multiple_items(conn, %{"ids" => ids}, changes) do
    user = conn.assigns[:user] |> Repo.preload(groups: [:feeds])
    feeds = Enum.flat_map(user.groups, fn g -> g.feeds end)

    read_ids =
      ids
      |> String.split(",")
      |> Enum.map(fn s ->
        {id, _} =
          s
          |> String.trim()
          |> Integer.parse()

        Repo.get(Item, id)
      end)
      |> Enum.filter(fn item ->
        Enum.any?(feeds, fn f -> f.id == item.feed_id end) && !item.tombstone
      end)
      |> Enum.map(fn item ->
        item = Repo.preload(item, :feed)
        changeset = Item.changeset(item, changes)

        case Repo.update(changeset) do
          {:ok, item} -> to_string(item.id)
          _ -> nil
        end
      end)
      |> Enum.reject(&is_nil/1)

    json(conn, read_ids)
  end

  defp mark_multiple_items(conn, _params, _changes) do
    conn
    |> put_status(400)
    |> json(%{error: "No items provided."})
  end

  def read_multiple(conn, params) do
    mark_multiple_items(conn, params, %{read: true})
  end

  def unread_multiple(conn, params) do
    mark_multiple_items(conn, params, %{read: false})
  end

  def sync(conn, params) do
    sync_timestamp = Timex.now()

    feed_ids =
      Group
      |> where([g], g.user_id == ^conn.assigns.user.id)
      |> join(:inner, [g], f in Feed, on: f.group_id == g.id)
      |> select([g, f], f.id)
      |> Repo.all()

    last_sync =
      with s when is_binary(s) <- Map.get(params, "last_sync"),
           {:ok, datetime} <- Timex.parse(s, "{ISO:Extended:Z}") do
        datetime
      else
        _ ->
          nil
      end

    {deleted_ids, upserted} =
      case last_sync do
        nil ->
          items =
            Item
            |> where([i], not i.tombstone and i.feed_id in ^feed_ids)
            |> order_by([i], desc: i.inserted_at)
            |> limit(1000)
            |> Repo.all()

          {[], items}

        _ ->
          all_items =
            Repo.all(from i in Item, where: i.feed_id in ^feed_ids and i.updated_at >= ^last_sync)

          {tombstones, rest} = Enum.split_with(all_items, & &1.tombstone)
          {Enum.map(tombstones, & &1.id), rest}
      end

    json(conn, %{
      sync_timestamp: Timex.format!(sync_timestamp, "{ISO:Extended:Z}"),
      delete: Enum.map(deleted_ids, &to_string/1),
      upsert: Enum.map(upserted, &Item.to_fervor/1)
    })
  end
end