wiki/lib/wiki_web/controllers/page_controller.ex

defmodule WikiWeb.PageController do
  use WikiWeb, :controller

  alias Wiki.Repo
  alias Wiki.Content
  alias Wiki.Content.{Page, Upload}
  import Ecto.Query

  plug :get_page
       when action in [
              :show,
              :edit,
              :update,
              :delete,
              :create_upload,
              :get_upload,
              :delete_upload
            ]

  plug :get_upload_plug when action in [:get_upload, :delete_upload]

  defp get_page(%Plug.Conn{path_params: %{"id" => id}} = conn, _opts) do
    case Content.get_page(id) do
      nil ->
        conn
        |> send_resp(404, "Not found")
        |> halt()

      page ->
        key = get_session(conn, :content_encryption_key)

        page = %Page{page | content_encryption_key: key}

        page =
          if action_name(conn) in [:show, :edit] do
            Page.decrypt_content(page)
          else
            page
          end

        assign(conn, :page, page)
    end
  end

  defp get_upload_plug(%Plug.Conn{path_params: %{"upload_id" => id}} = conn, _opts) do
    page = conn.assigns.page

    case Content.get_upload(page, id) do
      nil ->
        conn
        |> send_resp(404, "Not found")
        |> halt()

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

  def index(conn, _params) do
    pages = Content.list_pages(conn.assigns.current_user)
    render(conn, "index.html", pages: pages)
  end

  def new(conn, params) do
    changeset = Content.change_page(%Page{}, params, encrypt: false)
    render(conn, "new.html", changeset: changeset, page_title: "New Page")
  end

  def create(conn, %{"page" => page_params} = params) do
    key = get_session(conn, :content_encryption_key)

    page_params =
      page_params
      |> Map.put("user_id", conn.assigns.current_user.id)
      |> Map.put("content_encryption_key", key)

    case Content.create_page(page_params) do
      {:ok, page} ->
        file = Map.get(params, "initial_file")

        unless is_nil(file) do
          decoded_key = Base.decode16!(key, case: :lower)

          changeset =
            Upload.create_from_plug(file, decoded_key)
            |> Upload.changeset(%{page_id: page.id})

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

        conn
        |> put_flash(:info, "Page created successfully.")
        |> redirect(to: Routes.page_path(conn, :show, page))

      {:error, %Ecto.Changeset{} = changeset} ->
        render(conn, "new.html", changeset: changeset)
    end
  end

  def show(conn, _params) do
    page = Repo.preload(conn.assigns.page, [:uploads, :pages_linked_from])
    render(conn, "show.html", page: page, page_title: page.title)
  end

  def edit(conn, _params) do
    page = conn.assigns.page |> Repo.preload(:uploads)
    changeset = Content.change_page(page)
    render(conn, "edit.html", page: page, changeset: changeset, page_title: "Edit #{page.title}")
  end

  def update(conn, %{"page" => page_params}) do
    page = conn.assigns.page

    case Content.update_page(page, page_params) do
      {:ok, page} ->
        conn
        |> put_flash(:info, "Page updated successfully.")
        |> redirect(to: Routes.page_path(conn, :show, page))

      {:error, %Ecto.Changeset{} = changeset} ->
        render(conn, "edit.html", page: page, changeset: changeset)
    end
  end

  def create_upload(conn, %{"file" => %Plug.Upload{} = file}) do
    page = conn.assigns.page
    key = get_session(conn, :content_encryption_key)
    key = Base.decode16!(key, case: :lower)

    changeset =
      Upload.create_from_plug(file, key)
      |> Upload.changeset(%{page_id: page.id})

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

    redirect(conn, to: Routes.page_path(conn, :edit, page.id))
  end

  def get_upload(conn, _params) do
    upload = conn.assigns.upload
    key = get_session(conn, :content_encryption_key)
    key = Base.decode16!(key, case: :lower)

    conn =
      conn
      |> put_resp_header("content-type", upload.content_type)
      |> send_chunked(200)

    upload
    |> Upload.decrypt_stream(key)
    |> Enum.reduce_while(conn, fn decrypted_chunk, conn ->
      case chunk(conn, decrypted_chunk) do
        {:ok, conn} ->
          {:cont, conn}

        {:error, :closed} ->
          {:halt, {:halt, conn}}
      end
    end)
  end

  def delete_upload(conn, _params) do
    page = conn.assigns.page
    upload = conn.assigns.upload
    Upload.delete_file(upload)
    Repo.delete(upload)
    redirect(conn, to: Routes.page_path(conn, :edit, page.id))
  end

  def delete(conn, _params) do
    page = conn.assigns.page
    {:ok, _page} = Content.delete_page(page)

    conn
    |> put_flash(:info, "Page deleted successfully.")
    |> redirect(to: Routes.page_path(conn, :index))
  end

  def random(conn, _params) do
    user = conn.assigns.current_user
    page_ids = Repo.all(from p in Page, where: p.user_id == ^user.id, select: p.id)
    random_page = Enum.random(page_ids)
    redirect(conn, to: Routes.page_path(conn, :show, random_page))
  end
end