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

  plug :user_owns_group

  defp user_owns_group(%Plug.Conn{path_params: %{"id" => id}} = conn, _opts) do
    user = conn.assigns[:user]

    group = Repo.get(Group, id)

    if Enum.any?(user.groups, fn g -> g.id == group.id end) do
      conn
      |> assign(:group, group)
    else
      conn
      |> put_flash(:error, "You do not have permission to acess that resource.")
      |> redirect(to: Routes.group_path(Endpoint, :index))
      |> halt()
    end
  end

  defp user_owns_group(conn, _opts), do: conn

  def index(conn, _params) do
    groups = conn.assigns[:user].groups
    render(conn, "index.html", groups: groups)
  end

  def show(conn, _params) do
    group = conn.assigns[:group] |> Repo.preload(:feeds)

    create_feed_changeset =
      Feed.changeset(
        %Feed{
          group_id: group.id
        },
        %{}
      )

    render(conn, "show.html", %{
      group: group,
      create_feed_changeset: create_feed_changeset
    })
  end

  def new(conn, _params) do
    changeset = Group.changeset(%Group{}, %{})

    render(conn, "new.html", changeset: changeset)
  end

  def create(conn, %{"group" => %{"title" => title}}) do
    user = conn.assigns[:user]
    title = title |> String.trim()

    if String.length(title) > 0 do
      changeset =
        Ecto.build_assoc(user, :groups, %{
          title: title
        })

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

      redirect(conn, to: Routes.group_path(Endpoint, :show, group.id))
    else
      conn
      |> put_flash(:error, "Group title must not be empty")
      |> redirect(to: Routes.group_path(Endpoint, :new))
    end
  end

  def edit(conn, _params) do
    group = conn.assigns[:group]
    edit_changeset = Group.changeset(group, %{})

    render(conn, "edit.html", %{
      group: group,
      changeset: edit_changeset
    })
  end

  def update(conn, %{"group" => group_params}) do
    group = conn.assigns[:group]
    changeset = Group.changeset(group, group_params)
    {:ok, group} = Repo.update(changeset)
    redirect(conn, to: Routes.group_path(Endpoint, :show, group.id))
  end

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

    {:ok, _} = Repo.delete(group)
    redirect(conn, to: Routes.group_path(Endpoint, :index))
  end

  def read(conn, params) do
    group = conn.assigns[:group] |> Repo.preload(:feeds)
    feed_ids = Enum.map(group.feeds, fn feed -> feed.id end)

    items =
      Item
      |> where([i], not i.tombstone and i.feed_id in ^feed_ids)
      |> Paginator.paginate(params)
      |> limit(50)
      |> preload(:feed)
      |> Repo.all()
      |> Enum.sort_by(fn item -> item.date end, fn a, b ->
        DateTime.compare(a, b) == :gt
      end)

    first_item = List.first(items)
    last_item = List.last(items)

    prev_page_path =
      if !is_nil(first_item) &&
           Repo.exists?(
             from i in Item,
               where: not i.tombstone and i.date > ^first_item.date and i.feed_id in ^feed_ids
           ) do
        current_path(conn, %{after: first_item.id})
      else
        nil
      end

    next_page_path =
      if !is_nil(last_item) &&
           Repo.exists?(
             from i in Item,
               where: not i.tombstone and i.date < ^last_item.date and i.feed_id in ^feed_ids
           ) do
        current_path(conn, %{before: last_item.id})
      else
        nil
      end

    render(conn, "read.html", %{
      group: group,
      items: items,
      prev_page_path: prev_page_path,
      next_page_path: next_page_path
    })
  end
end