# Pleroma: A lightweight social networking server
# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Web.Websub do
  alias Ecto.Changeset
  alias Pleroma.Activity
  alias Pleroma.HTTP
  alias Pleroma.Instances
  alias Pleroma.Repo
  alias Pleroma.User
  alias Pleroma.Web.ActivityPub.Visibility
  alias Pleroma.Web.Endpoint
  alias Pleroma.Web.Federator
  alias Pleroma.Web.Federator.Publisher
  alias Pleroma.Web.OStatus
  alias Pleroma.Web.OStatus.FeedRepresenter
  alias Pleroma.Web.Router.Helpers
  alias Pleroma.Web.Websub.WebsubClientSubscription
  alias Pleroma.Web.Websub.WebsubServerSubscription
  alias Pleroma.Web.XML
  require Logger

  import Ecto.Query

  @behaviour Pleroma.Web.Federator.Publisher

  def verify(subscription, getter \\ &HTTP.get/3) do
    challenge = Base.encode16(:crypto.strong_rand_bytes(8))
    lease_seconds = NaiveDateTime.diff(subscription.valid_until, subscription.updated_at)
    lease_seconds = lease_seconds |> to_string

    params = %{
      "hub.challenge": challenge,
      "hub.lease_seconds": lease_seconds,
      "hub.topic": subscription.topic,
      "hub.mode": "subscribe"
    }

    url = hd(String.split(subscription.callback, "?"))
    query = URI.parse(subscription.callback).query || ""
    params = Map.merge(params, URI.decode_query(query))

    with {:ok, response} <- getter.(url, [], params: params),
         ^challenge <- response.body do
      changeset = Changeset.change(subscription, %{state: "active"})
      Repo.update(changeset)
    else
      e ->
        Logger.debug("Couldn't verify subscription")
        Logger.debug(inspect(e))
        {:error, subscription}
    end
  end

  @supported_activities [
    "Create",
    "Follow",
    "Like",
    "Announce",
    "Undo",
    "Delete"
  ]

  def is_representable?(%Activity{data: %{"type" => type}} = activity)
      when type in @supported_activities,
      do: Visibility.is_public?(activity)

  def is_representable?(_), do: false

  def publish(topic, user, %{data: %{"type" => type}} = activity)
      when type in @supported_activities do
    response =
      user
      |> FeedRepresenter.to_simple_form([activity], [user])
      |> :xmerl.export_simple(:xmerl_xml)
      |> to_string

    query =
      from(
        sub in WebsubServerSubscription,
        where: sub.topic == ^topic and sub.state == "active",
        where: fragment("? > (NOW() at time zone 'UTC')", sub.valid_until)
      )

    subscriptions = Repo.all(query)

    callbacks = Enum.map(subscriptions, & &1.callback)
    reachable_callbacks_metadata = Instances.filter_reachable(callbacks)
    reachable_callbacks = Map.keys(reachable_callbacks_metadata)

    subscriptions
    |> Enum.filter(&(&1.callback in reachable_callbacks))
    |> Enum.each(fn sub ->
      data = %{
        xml: response,
        topic: topic,
        callback: sub.callback,
        secret: sub.secret,
        unreachable_since: reachable_callbacks_metadata[sub.callback]
      }

      Publisher.enqueue_one(__MODULE__, data)
    end)
  end

  def publish(_, _, _), do: ""

  def publish(actor, activity), do: publish(Pleroma.Web.OStatus.feed_path(actor), actor, activity)

  def sign(secret, doc) do
    :crypto.hmac(:sha, secret, to_string(doc)) |> Base.encode16() |> String.downcase()
  end

  def incoming_subscription_request(user, %{"hub.mode" => "subscribe"} = params) do
    with {:ok, topic} <- valid_topic(params, user),
         {:ok, lease_time} <- lease_time(params),
         secret <- params["hub.secret"],
         callback <- params["hub.callback"] do
      subscription = get_subscription(topic, callback)

      data = %{
        state: subscription.state || "requested",
        topic: topic,
        secret: secret,
        callback: callback
      }

      change = Changeset.change(subscription, data)
      websub = Repo.insert_or_update!(change)

      change =
        Changeset.change(websub, %{valid_until: NaiveDateTime.add(websub.updated_at, lease_time)})

      websub = Repo.update!(change)

      Federator.verify_websub(websub)

      {:ok, websub}
    else
      {:error, reason} ->
        Logger.debug("Couldn't create subscription")
        Logger.debug(inspect(reason))

        {:error, reason}
    end
  end

  def incoming_subscription_request(user, params) do
    Logger.info("Unhandled WebSub request for #{user.nickname}: #{inspect(params)}")

    {:error, "Invalid WebSub request"}
  end

  defp get_subscription(topic, callback) do
    Repo.get_by(WebsubServerSubscription, topic: topic, callback: callback) ||
      %WebsubServerSubscription{}
  end

  # Temp hack for mastodon.
  defp lease_time(%{"hub.lease_seconds" => ""}) do
    # three days
    {:ok, 60 * 60 * 24 * 3}
  end

  defp lease_time(%{"hub.lease_seconds" => lease_seconds}) do
    {:ok, String.to_integer(lease_seconds)}
  end

  defp lease_time(_) do
    # three days
    {:ok, 60 * 60 * 24 * 3}
  end

  defp valid_topic(%{"hub.topic" => topic}, user) do
    if topic == OStatus.feed_path(user) do
      {:ok, OStatus.feed_path(user)}
    else
      {:error, "Wrong topic requested, expected #{OStatus.feed_path(user)}, got #{topic}"}
    end
  end

  def subscribe(subscriber, subscribed, requester \\ &request_subscription/1) do
    topic = subscribed.topic
    # FIXME: Race condition, use transactions
    {:ok, subscription} =
      with subscription when not is_nil(subscription) <-
             Repo.get_by(WebsubClientSubscription, topic: topic) do
        subscribers = [subscriber.ap_id | subscription.subscribers] |> Enum.uniq()
        change = Ecto.Changeset.change(subscription, %{subscribers: subscribers})
        Repo.update(change)
      else
        _e ->
          subscription = %WebsubClientSubscription{
            topic: topic,
            hub: subscribed.hub,
            subscribers: [subscriber.ap_id],
            state: "requested",
            secret: :crypto.strong_rand_bytes(8) |> Base.url_encode64(),
            user: subscribed
          }

          Repo.insert(subscription)
      end

    requester.(subscription)
  end

  def gather_feed_data(topic, getter \\ &HTTP.get/1) do
    with {:ok, response} <- getter.(topic),
         status when status in 200..299 <- response.status,
         body <- response.body,
         doc <- XML.parse_document(body),
         uri when not is_nil(uri) <- XML.string_from_xpath("/feed/author[1]/uri", doc),
         hub when not is_nil(hub) <- XML.string_from_xpath(~S{/feed/link[@rel="hub"]/@href}, doc) do
      name = XML.string_from_xpath("/feed/author[1]/name", doc)
      preferred_username = XML.string_from_xpath("/feed/author[1]/poco:preferredUsername", doc)
      display_name = XML.string_from_xpath("/feed/author[1]/poco:displayName", doc)
      avatar = OStatus.make_avatar_object(doc)
      bio = XML.string_from_xpath("/feed/author[1]/summary", doc)

      {:ok,
       %{
         "uri" => uri,
         "hub" => hub,
         "nickname" => preferred_username || name,
         "name" => display_name || name,
         "host" => URI.parse(uri).host,
         "avatar" => avatar,
         "bio" => bio
       }}
    else
      e ->
        {:error, e}
    end
  end

  def request_subscription(websub, poster \\ &HTTP.post/3, timeout \\ 10_000) do
    data = [
      "hub.mode": "subscribe",
      "hub.topic": websub.topic,
      "hub.secret": websub.secret,
      "hub.callback": Helpers.websub_url(Endpoint, :websub_subscription_confirmation, websub.id)
    ]

    # This checks once a second if we are confirmed yet
    websub_checker = fn ->
      helper = fn helper ->
        :timer.sleep(1000)
        websub = Repo.get_by(WebsubClientSubscription, id: websub.id, state: "accepted")
        if websub, do: websub, else: helper.(helper)
      end

      helper.(helper)
    end

    task = Task.async(websub_checker)

    with {:ok, %{status: 202}} <-
           poster.(websub.hub, {:form, data}, "Content-type": "application/x-www-form-urlencoded"),
         {:ok, websub} <- Task.yield(task, timeout) do
      {:ok, websub}
    else
      e ->
        Task.shutdown(task)

        change = Ecto.Changeset.change(websub, %{state: "rejected"})
        {:ok, websub} = Repo.update(change)

        Logger.debug(fn -> "Couldn't confirm subscription: #{inspect(websub)}" end)
        Logger.debug(fn -> "error: #{inspect(e)}" end)

        {:error, websub}
    end
  end

  def refresh_subscriptions(delta \\ 60 * 60 * 24) do
    Logger.debug("Refreshing subscriptions")

    cut_off = NaiveDateTime.add(NaiveDateTime.utc_now(), delta)

    query = from(sub in WebsubClientSubscription, where: sub.valid_until < ^cut_off)

    subs = Repo.all(query)

    Enum.each(subs, fn sub ->
      Federator.request_subscription(sub)
    end)
  end

  def publish_one(%{xml: xml, topic: topic, callback: callback, secret: secret} = params) do
    signature = sign(secret || "", xml)
    Logger.info(fn -> "Pushing #{topic} to #{callback}" end)

    with {:ok, %{status: code}} when code in 200..299 <-
           HTTP.post(
             callback,
             xml,
             [
               {"Content-Type", "application/atom+xml"},
               {"X-Hub-Signature", "sha1=#{signature}"}
             ]
           ) do
      if !Map.has_key?(params, :unreachable_since) || params[:unreachable_since],
        do: Instances.set_reachable(callback)

      Logger.info(fn -> "Pushed to #{callback}, code #{code}" end)
      {:ok, code}
    else
      {_post_result, response} ->
        unless params[:unreachable_since], do: Instances.set_reachable(callback)
        Logger.debug(fn -> "Couldn't push to #{callback}, #{inspect(response)}" end)
        {:error, response}
    end
  end

  def gather_webfinger_links(%User{} = user) do
    [
      %{
        "rel" => "http://schemas.google.com/g/2010#updates-from",
        "type" => "application/atom+xml",
        "href" => OStatus.feed_path(user)
      },
      %{
        "rel" => "http://ostatus.org/schema/1.0/subscribe",
        "template" => OStatus.remote_follow_path()
      }
    ]
  end

  def gather_nodeinfo_protocol_names, do: ["ostatus"]
end