diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5f071b7e2..fa7818137 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - MRF: fix use of unserializable keyword lists in describe() implementations
 
 ### Added
+- Conversations: Add Pleroma-specific conversation endpoints and status posting extensions. Run the `bump_all_conversations` task again to create the necessary data.
 - **Breaking:** MRF describe API, which adds support for exposing configuration information about MRF policies to NodeInfo.
   Custom modules will need to be updated by adding, at the very least, `def describe, do: {:ok, %{}}` to the MRF policy modules.
 - MRF: Support for priming the mediaproxy cache (`Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy`)
diff --git a/docs/api/differences_in_mastoapi_responses.md b/docs/api/differences_in_mastoapi_responses.md
index 1907d70c8..79ca531b8 100644
--- a/docs/api/differences_in_mastoapi_responses.md
+++ b/docs/api/differences_in_mastoapi_responses.md
@@ -59,12 +59,19 @@ Has these additional fields under the `pleroma` object:
 - `show_role`: boolean, nullable, true when the user wants his role (e.g admin, moderator) to be shown
 - `no_rich_text` - boolean, nullable, true when html tags are stripped from all statuses requested from the API
 
+## Conversations
+
+Has an additional field under the `pleroma` object:
+
+- `recipients`: The list of the recipients of this Conversation. These will be addressed when replying to this conversation.
+
 ## Account Search
 
 Behavior has changed:
 
 - `/api/v1/accounts/search`: Does not require authentication
 
+
 ## Notifications
 
 Has these additional fields under the `pleroma` object:
@@ -79,6 +86,7 @@ Additional parameters can be added to the JSON body/Form data:
 - `content_type`: string, contain the MIME type of the status, it is transformed into HTML by the backend. You can get the list of the supported MIME types with the nodeinfo endpoint.
 - `to`: A list of nicknames (like `lain@soykaf.club` or `lain` on the local server) that will be used to determine who is going to be addressed by this post. Using this will disable the implicit addressing by mentioned names in the `status` body, only the people in the `to` list will be addressed. The normal rules for for post visibility are not affected by this and will still apply.
 - `visibility`: string, besides standard MastoAPI values (`direct`, `private`, `unlisted` or `public`) it can be used to address a List by setting it to `list:LIST_ID`.
+- `in_reply_to_conversation_id`: Will reply to a given conversation, addressing only the people who are part of the recipient set of that conversation. Sets the visibility to `direct`.
 
 ## PATCH `/api/v1/update_credentials`
 
diff --git a/docs/api/pleroma_api.md b/docs/api/pleroma_api.md
index 5698e88ac..b134b31a8 100644
--- a/docs/api/pleroma_api.md
+++ b/docs/api/pleroma_api.md
@@ -319,3 +319,38 @@ See [Admin-API](Admin-API.md)
   "healthy": true # Instance state
 }
 ```
+
+# Pleroma Conversations
+
+Pleroma Conversations have the same general structure that Mastodon Conversations have. The behavior differs in the following ways when using these endpoints:
+
+1. Pleroma Conversations never add or remove recipients, unless explicitly changed by the user. 
+2. Pleroma Conversations statuses can be requested by Conversation id.
+3. Pleroma Conversations can be replied to.
+
+Conversations have the additional field "recipients" under the "pleroma" key. This holds a list of all the accounts that will receive a message in this conversation.
+
+The status posting endpoint takes an additional parameter, `in_reply_to_conversation_id`, which, when set, will set the visiblity to direct and address only the people who are the recipients of that Conversation.
+
+
+## `GET /api/v1/pleroma/conversations/:id/statuses`
+### Timeline for a given conversation
+* Method `GET`
+* Authentication: required
+* Params: Like other timelines
+* Response: JSON, statuses (200 - healthy, 503 unhealthy).
+
+## `GET /api/v1/pleroma/conversations/:id`
+### The conversation with the given ID.
+* Method `GET`
+* Authentication: required
+* Params: None
+* Response: JSON, statuses (200 - healthy, 503 unhealthy).
+
+## `PATCH /api/v1/pleroma/conversations/:id`
+### Update a conversation. Used to change the set of recipients.
+* Method `PATCH`
+* Authentication: required
+* Params:
+    * `recipients`: A list of ids of users that should receive posts to this conversation. This will replace the current list of recipients, so submit the full list. The owner of owner of the conversation will always be part of the set of recipients, though.
+* Response: JSON, statuses (200 - healthy, 503 unhealthy)
diff --git a/lib/pleroma/conversation.ex b/lib/pleroma/conversation.ex
index bc97b39ca..be5821ad7 100644
--- a/lib/pleroma/conversation.ex
+++ b/lib/pleroma/conversation.ex
@@ -4,6 +4,7 @@
 
 defmodule Pleroma.Conversation do
   alias Pleroma.Conversation.Participation
+  alias Pleroma.Conversation.Participation.RecipientShip
   alias Pleroma.Repo
   alias Pleroma.User
   use Ecto.Schema
@@ -39,6 +40,15 @@ defmodule Pleroma.Conversation do
     Repo.get_by(__MODULE__, ap_id: ap_id)
   end
 
+  def maybe_create_recipientships(participation, activity) do
+    participation = Repo.preload(participation, :recipients)
+
+    if participation.recipients |> Enum.empty?() do
+      recipients = User.get_all_by_ap_id(activity.recipients)
+      RecipientShip.create(recipients, participation)
+    end
+  end
+
   @doc """
   This will
   1. Create a conversation if there isn't one already
@@ -60,6 +70,7 @@ defmodule Pleroma.Conversation do
           {:ok, participation} =
             Participation.create_for_user_and_conversation(user, conversation, opts)
 
+          maybe_create_recipientships(participation, activity)
           participation
         end)
 
diff --git a/lib/pleroma/conversation/participation.ex b/lib/pleroma/conversation/participation.ex
index 5883e4183..ea5b9fe17 100644
--- a/lib/pleroma/conversation/participation.ex
+++ b/lib/pleroma/conversation/participation.ex
@@ -5,6 +5,7 @@
 defmodule Pleroma.Conversation.Participation do
   use Ecto.Schema
   alias Pleroma.Conversation
+  alias Pleroma.Conversation.Participation.RecipientShip
   alias Pleroma.Repo
   alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ActivityPub
@@ -17,6 +18,9 @@ defmodule Pleroma.Conversation.Participation do
     field(:read, :boolean, default: false)
     field(:last_activity_id, Pleroma.FlakeId, virtual: true)
 
+    has_many(:recipient_ships, RecipientShip)
+    has_many(:recipients, through: [:recipient_ships, :user])
+
     timestamps()
   end
 
@@ -65,6 +69,14 @@ defmodule Pleroma.Conversation.Participation do
     |> Pleroma.Pagination.fetch_paginated(params)
   end
 
+  def for_user_and_conversation(user, conversation) do
+    from(p in __MODULE__,
+      where: p.user_id == ^user.id,
+      where: p.conversation_id == ^conversation.id
+    )
+    |> Repo.one()
+  end
+
   def for_user_with_last_activity_id(user, params \\ %{}) do
     for_user(user, params)
     |> Enum.map(fn participation ->
@@ -81,4 +93,46 @@ defmodule Pleroma.Conversation.Participation do
     end)
     |> Enum.filter(& &1.last_activity_id)
   end
+
+  def get(_, _ \\ [])
+  def get(nil, _), do: nil
+
+  def get(id, params) do
+    query =
+      if preload = params[:preload] do
+        from(p in __MODULE__,
+          preload: ^preload
+        )
+      else
+        __MODULE__
+      end
+
+    Repo.get(query, id)
+  end
+
+  def set_recipients(participation, user_ids) do
+    user_ids =
+      [participation.user_id | user_ids]
+      |> Enum.uniq()
+
+    Repo.transaction(fn ->
+      query =
+        from(r in RecipientShip,
+          where: r.participation_id == ^participation.id
+        )
+
+      Repo.delete_all(query)
+
+      users =
+        from(u in User,
+          where: u.id in ^user_ids
+        )
+        |> Repo.all()
+
+      RecipientShip.create(users, participation)
+      :ok
+    end)
+
+    {:ok, Repo.preload(participation, :recipients, force: true)}
+  end
 end
diff --git a/lib/pleroma/conversation/participation_recipient_ship.ex b/lib/pleroma/conversation/participation_recipient_ship.ex
new file mode 100644
index 000000000..932cbd04c
--- /dev/null
+++ b/lib/pleroma/conversation/participation_recipient_ship.ex
@@ -0,0 +1,34 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Conversation.Participation.RecipientShip do
+  use Ecto.Schema
+
+  alias Pleroma.Conversation.Participation
+  alias Pleroma.Repo
+  alias Pleroma.User
+
+  import Ecto.Changeset
+
+  schema "conversation_participation_recipient_ships" do
+    belongs_to(:user, User, type: Pleroma.FlakeId)
+    belongs_to(:participation, Participation)
+  end
+
+  def creation_cng(struct, params) do
+    struct
+    |> cast(params, [:user_id, :participation_id])
+    |> validate_required([:user_id, :participation_id])
+  end
+
+  def create(%User{} = user, participation), do: create([user], participation)
+
+  def create(users, participation) do
+    Enum.each(users, fn user ->
+      %__MODULE__{}
+      |> creation_cng(%{user_id: user.id, participation_id: participation.id})
+      |> Repo.insert!()
+    end)
+  end
+end
diff --git a/lib/pleroma/user.ex b/lib/pleroma/user.ex
index a1040fe71..5c3c8a8a2 100644
--- a/lib/pleroma/user.ex
+++ b/lib/pleroma/user.ex
@@ -485,6 +485,13 @@ defmodule Pleroma.User do
     Repo.get_by(User, ap_id: ap_id)
   end
 
+  def get_all_by_ap_id(ap_ids) do
+    from(u in __MODULE__,
+      where: u.ap_id in ^ap_ids
+    )
+    |> Repo.all()
+  end
+
   # This is mostly an SPC migration fix. This guesses the user nickname by taking the last part
   # of the ap_id and the domain and tries to get that user
   def get_by_guessed_nickname(ap_id) do
diff --git a/lib/pleroma/web/common_api/common_api.ex b/lib/pleroma/web/common_api/common_api.ex
index 2db58324b..72da46263 100644
--- a/lib/pleroma/web/common_api/common_api.ex
+++ b/lib/pleroma/web/common_api/common_api.ex
@@ -4,6 +4,7 @@
 
 defmodule Pleroma.Web.CommonAPI do
   alias Pleroma.Activity
+  alias Pleroma.Conversation.Participation
   alias Pleroma.Formatter
   alias Pleroma.Object
   alias Pleroma.ThreadMute
@@ -171,21 +172,25 @@ defmodule Pleroma.Web.CommonAPI do
     end)
   end
 
-  def get_visibility(%{"visibility" => visibility}, in_reply_to)
+  def get_visibility(_, _, %Participation{}) do
+    {"direct", "direct"}
+  end
+
+  def get_visibility(%{"visibility" => visibility}, in_reply_to, _)
       when visibility in ~w{public unlisted private direct},
       do: {visibility, get_replied_to_visibility(in_reply_to)}
 
-  def get_visibility(%{"visibility" => "list:" <> list_id}, in_reply_to) do
+  def get_visibility(%{"visibility" => "list:" <> list_id}, in_reply_to, _) do
     visibility = {:list, String.to_integer(list_id)}
     {visibility, get_replied_to_visibility(in_reply_to)}
   end
 
-  def get_visibility(_, in_reply_to) when not is_nil(in_reply_to) do
+  def get_visibility(_, in_reply_to, _) when not is_nil(in_reply_to) do
     visibility = get_replied_to_visibility(in_reply_to)
     {visibility, visibility}
   end
 
-  def get_visibility(_, in_reply_to), do: {"public", get_replied_to_visibility(in_reply_to)}
+  def get_visibility(_, in_reply_to, _), do: {"public", get_replied_to_visibility(in_reply_to)}
 
   def get_replied_to_visibility(nil), do: nil
 
@@ -201,7 +206,9 @@ defmodule Pleroma.Web.CommonAPI do
     with status <- String.trim(status),
          attachments <- attachments_from_ids(data),
          in_reply_to <- get_replied_to_activity(data["in_reply_to_status_id"]),
-         {visibility, in_reply_to_visibility} <- get_visibility(data, in_reply_to),
+         in_reply_to_conversation <- Participation.get(data["in_reply_to_conversation_id"]),
+         {visibility, in_reply_to_visibility} <-
+           get_visibility(data, in_reply_to, in_reply_to_conversation),
          {_, false} <-
            {:private_to_public, in_reply_to_visibility == "direct" && visibility != "direct"},
          {content_html, mentions, tags} <-
@@ -214,8 +221,9 @@ defmodule Pleroma.Web.CommonAPI do
          mentioned_users <- for({_, mentioned_user} <- mentions, do: mentioned_user.ap_id),
          addressed_users <- get_addressed_users(mentioned_users, data["to"]),
          {poll, poll_emoji} <- make_poll_data(data),
-         {to, cc} <- get_to_and_cc(user, addressed_users, in_reply_to, visibility),
-         context <- make_context(in_reply_to),
+         {to, cc} <-
+           get_to_and_cc(user, addressed_users, in_reply_to, visibility, in_reply_to_conversation),
+         context <- make_context(in_reply_to, in_reply_to_conversation),
          cw <- data["spoiler_text"] || "",
          sensitive <- data["sensitive"] || Enum.member?(tags, {"#nsfw", "nsfw"}),
          full_payload <- String.trim(status <> cw),
diff --git a/lib/pleroma/web/common_api/utils.ex b/lib/pleroma/web/common_api/utils.ex
index 22c44a0a3..61b96aba9 100644
--- a/lib/pleroma/web/common_api/utils.ex
+++ b/lib/pleroma/web/common_api/utils.ex
@@ -8,6 +8,7 @@ defmodule Pleroma.Web.CommonAPI.Utils do
   alias Calendar.Strftime
   alias Pleroma.Activity
   alias Pleroma.Config
+  alias Pleroma.Conversation.Participation
   alias Pleroma.Formatter
   alias Pleroma.Object
   alias Pleroma.Plugs.AuthenticationPlug
@@ -86,9 +87,21 @@ defmodule Pleroma.Web.CommonAPI.Utils do
     |> Enum.filter(& &1)
   end
 
-  @spec get_to_and_cc(User.t(), list(String.t()), Activity.t() | nil, String.t()) ::
+  @spec get_to_and_cc(
+          User.t(),
+          list(String.t()),
+          Activity.t() | nil,
+          String.t(),
+          Participation.t() | nil
+        ) ::
           {list(String.t()), list(String.t())}
-  def get_to_and_cc(user, mentioned_users, inReplyTo, "public") do
+
+  def get_to_and_cc(_, _, _, _, %Participation{} = participation) do
+    participation = Repo.preload(participation, :recipients)
+    {Enum.map(participation.recipients, & &1.ap_id), []}
+  end
+
+  def get_to_and_cc(user, mentioned_users, inReplyTo, "public", _) do
     to = [Pleroma.Constants.as_public() | mentioned_users]
     cc = [user.follower_address]
 
@@ -99,7 +112,7 @@ defmodule Pleroma.Web.CommonAPI.Utils do
     end
   end
 
-  def get_to_and_cc(user, mentioned_users, inReplyTo, "unlisted") do
+  def get_to_and_cc(user, mentioned_users, inReplyTo, "unlisted", _) do
     to = [user.follower_address | mentioned_users]
     cc = [Pleroma.Constants.as_public()]
 
@@ -110,12 +123,12 @@ defmodule Pleroma.Web.CommonAPI.Utils do
     end
   end
 
-  def get_to_and_cc(user, mentioned_users, inReplyTo, "private") do
-    {to, cc} = get_to_and_cc(user, mentioned_users, inReplyTo, "direct")
+  def get_to_and_cc(user, mentioned_users, inReplyTo, "private", _) do
+    {to, cc} = get_to_and_cc(user, mentioned_users, inReplyTo, "direct", nil)
     {[user.follower_address | to], cc}
   end
 
-  def get_to_and_cc(_user, mentioned_users, inReplyTo, "direct") do
+  def get_to_and_cc(_user, mentioned_users, inReplyTo, "direct", _) do
     if inReplyTo do
       {Enum.uniq([inReplyTo.data["actor"] | mentioned_users]), []}
     else
@@ -123,7 +136,7 @@ defmodule Pleroma.Web.CommonAPI.Utils do
     end
   end
 
-  def get_to_and_cc(_user, mentions, _inReplyTo, {:list, _}), do: {mentions, []}
+  def get_to_and_cc(_user, mentions, _inReplyTo, {:list, _}, _), do: {mentions, []}
 
   def get_addressed_users(_, to) when is_list(to) do
     User.get_ap_ids_by_nicknames(to)
@@ -253,8 +266,12 @@ defmodule Pleroma.Web.CommonAPI.Utils do
 
   defp maybe_add_nsfw_tag(data, _), do: data
 
-  def make_context(%Activity{data: %{"context" => context}}), do: context
-  def make_context(_), do: Utils.generate_context_id()
+  def make_context(_, %Participation{} = participation) do
+    Repo.preload(participation, :conversation).conversation.ap_id
+  end
+
+  def make_context(%Activity{data: %{"context" => context}}, _), do: context
+  def make_context(_, _), do: Utils.generate_context_id()
 
   def maybe_add_attachments(parsed, _attachments, true = _no_links), do: parsed
 
diff --git a/lib/pleroma/web/controller_helper.ex b/lib/pleroma/web/controller_helper.ex
index 8a753bb4f..eeac9f503 100644
--- a/lib/pleroma/web/controller_helper.ex
+++ b/lib/pleroma/web/controller_helper.ex
@@ -33,4 +33,80 @@ defmodule Pleroma.Web.ControllerHelper do
   end
 
   defp param_to_integer(_, default), do: default
+
+  def add_link_headers(
+        conn,
+        method,
+        activities,
+        param \\ nil,
+        params \\ %{},
+        func3 \\ nil,
+        func4 \\ nil
+      ) do
+    params =
+      conn.params
+      |> Map.drop(["since_id", "max_id", "min_id"])
+      |> Map.merge(params)
+
+    last = List.last(activities)
+
+    func3 = func3 || (&mastodon_api_url/3)
+    func4 = func4 || (&mastodon_api_url/4)
+
+    if last do
+      max_id = last.id
+
+      limit =
+        params
+        |> Map.get("limit", "20")
+        |> String.to_integer()
+
+      min_id =
+        if length(activities) <= limit do
+          activities
+          |> List.first()
+          |> Map.get(:id)
+        else
+          activities
+          |> Enum.at(limit * -1)
+          |> Map.get(:id)
+        end
+
+      {next_url, prev_url} =
+        if param do
+          {
+            func4.(
+              Pleroma.Web.Endpoint,
+              method,
+              param,
+              Map.merge(params, %{max_id: max_id})
+            ),
+            func4.(
+              Pleroma.Web.Endpoint,
+              method,
+              param,
+              Map.merge(params, %{min_id: min_id})
+            )
+          }
+        else
+          {
+            func3.(
+              Pleroma.Web.Endpoint,
+              method,
+              Map.merge(params, %{max_id: max_id})
+            ),
+            func3.(
+              Pleroma.Web.Endpoint,
+              method,
+              Map.merge(params, %{min_id: min_id})
+            )
+          }
+        end
+
+      conn
+      |> put_resp_header("link", "<#{next_url}>; rel=\"next\", <#{prev_url}>; rel=\"prev\"")
+    else
+      conn
+    end
+  end
 end
diff --git a/lib/pleroma/web/mastodon_api/mastodon_api_controller.ex b/lib/pleroma/web/mastodon_api/mastodon_api_controller.ex
index 7ce2b5b06..8fe7be8be 100644
--- a/lib/pleroma/web/mastodon_api/mastodon_api_controller.ex
+++ b/lib/pleroma/web/mastodon_api/mastodon_api_controller.ex
@@ -5,7 +5,8 @@
 defmodule Pleroma.Web.MastodonAPI.MastodonAPIController do
   use Pleroma.Web, :controller
 
-  import Pleroma.Web.ControllerHelper, only: [json_response: 3]
+  import Pleroma.Web.ControllerHelper,
+    only: [json_response: 3, add_link_headers: 5, add_link_headers: 4, add_link_headers: 3]
 
   alias Ecto.Changeset
   alias Pleroma.Activity
@@ -342,71 +343,6 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPIController do
     json(conn, mastodon_emoji)
   end
 
-  defp add_link_headers(conn, method, activities, param \\ nil, params \\ %{}) do
-    params =
-      conn.params
-      |> Map.drop(["since_id", "max_id", "min_id"])
-      |> Map.merge(params)
-
-    last = List.last(activities)
-
-    if last do
-      max_id = last.id
-
-      limit =
-        params
-        |> Map.get("limit", "20")
-        |> String.to_integer()
-
-      min_id =
-        if length(activities) <= limit do
-          activities
-          |> List.first()
-          |> Map.get(:id)
-        else
-          activities
-          |> Enum.at(limit * -1)
-          |> Map.get(:id)
-        end
-
-      {next_url, prev_url} =
-        if param do
-          {
-            mastodon_api_url(
-              Pleroma.Web.Endpoint,
-              method,
-              param,
-              Map.merge(params, %{max_id: max_id})
-            ),
-            mastodon_api_url(
-              Pleroma.Web.Endpoint,
-              method,
-              param,
-              Map.merge(params, %{min_id: min_id})
-            )
-          }
-        else
-          {
-            mastodon_api_url(
-              Pleroma.Web.Endpoint,
-              method,
-              Map.merge(params, %{max_id: max_id})
-            ),
-            mastodon_api_url(
-              Pleroma.Web.Endpoint,
-              method,
-              Map.merge(params, %{min_id: min_id})
-            )
-          }
-        end
-
-      conn
-      |> put_resp_header("link", "<#{next_url}>; rel=\"next\", <#{prev_url}>; rel=\"prev\"")
-    else
-      conn
-    end
-  end
-
   def home_timeline(%{assigns: %{user: user}} = conn, params) do
     params =
       params
@@ -1797,7 +1733,7 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPIController do
 
     conversations =
       Enum.map(participations, fn participation ->
-        ConversationView.render("participation.json", %{participation: participation, user: user})
+        ConversationView.render("participation.json", %{participation: participation, for: user})
       end)
 
     conn
@@ -1810,7 +1746,7 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPIController do
            Repo.get_by(Participation, id: participation_id, user_id: user.id),
          {:ok, participation} <- Participation.mark_as_read(participation) do
       participation_view =
-        ConversationView.render("participation.json", %{participation: participation, user: user})
+        ConversationView.render("participation.json", %{participation: participation, for: user})
 
       conn
       |> json(participation_view)
diff --git a/lib/pleroma/web/mastodon_api/views/conversation_view.ex b/lib/pleroma/web/mastodon_api/views/conversation_view.ex
index 38bdec737..40acc07b3 100644
--- a/lib/pleroma/web/mastodon_api/views/conversation_view.ex
+++ b/lib/pleroma/web/mastodon_api/views/conversation_view.ex
@@ -11,8 +11,8 @@ defmodule Pleroma.Web.MastodonAPI.ConversationView do
   alias Pleroma.Web.MastodonAPI.AccountView
   alias Pleroma.Web.MastodonAPI.StatusView
 
-  def render("participation.json", %{participation: participation, user: user}) do
-    participation = Repo.preload(participation, conversation: :users)
+  def render("participation.json", %{participation: participation, for: user}) do
+    participation = Repo.preload(participation, conversation: [], recipients: [])
 
     last_activity_id =
       with nil <- participation.last_activity_id do
@@ -28,7 +28,7 @@ defmodule Pleroma.Web.MastodonAPI.ConversationView do
 
     # Conversations return all users except the current user.
     users =
-      participation.conversation.users
+      participation.recipients
       |> Enum.reject(&(&1.id == user.id))
 
     accounts =
diff --git a/lib/pleroma/web/mastodon_api/views/status_view.ex b/lib/pleroma/web/mastodon_api/views/status_view.ex
index 7e4e99280..42fbdf51b 100644
--- a/lib/pleroma/web/mastodon_api/views/status_view.ex
+++ b/lib/pleroma/web/mastodon_api/views/status_view.ex
@@ -8,6 +8,8 @@ defmodule Pleroma.Web.MastodonAPI.StatusView do
   require Pleroma.Constants
 
   alias Pleroma.Activity
+  alias Pleroma.Conversation
+  alias Pleroma.Conversation.Participation
   alias Pleroma.HTML
   alias Pleroma.Object
   alias Pleroma.Repo
@@ -235,6 +237,19 @@ defmodule Pleroma.Web.MastodonAPI.StatusView do
         object.data["url"] || object.data["external_url"] || object.data["id"]
       end
 
+    direct_conversation_id =
+      with {_, true} <- {:include_id, opts[:with_direct_conversation_id]},
+           {_, %User{} = for_user} <- {:for_user, opts[:for]},
+           %{data: %{"context" => context}} when is_binary(context) <- activity,
+           %Conversation{} = conversation <- Conversation.get_for_ap_id(context),
+           %Participation{id: participation_id} <-
+             Participation.for_user_and_conversation(for_user, conversation) do
+        participation_id
+      else
+        _e ->
+          nil
+      end
+
     %{
       id: to_string(activity.id),
       uri: object.data["id"],
@@ -272,7 +287,8 @@ defmodule Pleroma.Web.MastodonAPI.StatusView do
         conversation_id: get_context_id(activity),
         in_reply_to_account_acct: reply_to_user && reply_to_user.nickname,
         content: %{"text/plain" => content_plaintext},
-        spoiler_text: %{"text/plain" => summary_plaintext}
+        spoiler_text: %{"text/plain" => summary_plaintext},
+        direct_conversation_id: direct_conversation_id
       }
     }
   end
diff --git a/lib/pleroma/web/pleroma_api/pleroma_api_controller.ex b/lib/pleroma/web/pleroma_api/pleroma_api_controller.ex
new file mode 100644
index 000000000..b6d2bf86b
--- /dev/null
+++ b/lib/pleroma/web/pleroma_api/pleroma_api_controller.ex
@@ -0,0 +1,73 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.PleromaAPI.PleromaAPIController do
+  use Pleroma.Web, :controller
+
+  import Pleroma.Web.ControllerHelper, only: [add_link_headers: 7]
+
+  alias Pleroma.Conversation.Participation
+  alias Pleroma.Web.ActivityPub.ActivityPub
+  alias Pleroma.Web.MastodonAPI.ConversationView
+  alias Pleroma.Web.MastodonAPI.StatusView
+
+  def conversation(%{assigns: %{user: user}} = conn, %{"id" => participation_id}) do
+    with %Participation{} = participation <- Participation.get(participation_id),
+         true <- user.id == participation.user_id do
+      conn
+      |> put_view(ConversationView)
+      |> render("participation.json", %{participation: participation, for: user})
+    end
+  end
+
+  def conversation_statuses(
+        %{assigns: %{user: user}} = conn,
+        %{"id" => participation_id} = params
+      ) do
+    params =
+      params
+      |> Map.put("blocking_user", user)
+      |> Map.put("muting_user", user)
+      |> Map.put("user", user)
+
+    participation =
+      participation_id
+      |> Participation.get(preload: [:conversation])
+
+    if user.id == participation.user_id do
+      activities =
+        participation.conversation.ap_id
+        |> ActivityPub.fetch_activities_for_context(params)
+        |> Enum.reverse()
+
+      conn
+      |> add_link_headers(
+        :conversation_statuses,
+        activities,
+        participation_id,
+        params,
+        nil,
+        &pleroma_api_url/4
+      )
+      |> put_view(StatusView)
+      |> render("index.json", %{activities: activities, for: user, as: :activity})
+    end
+  end
+
+  def update_conversation(
+        %{assigns: %{user: user}} = conn,
+        %{"id" => participation_id, "recipients" => recipients}
+      ) do
+    participation =
+      participation_id
+      |> Participation.get()
+
+    with true <- user.id == participation.user_id,
+         {:ok, participation} <- Participation.set_recipients(participation, recipients) do
+      conn
+      |> put_view(ConversationView)
+      |> render("participation.json", %{participation: participation, for: user})
+    end
+  end
+end
diff --git a/lib/pleroma/web/router.ex b/lib/pleroma/web/router.ex
index c8c1c22dd..1eb6f7b9d 100644
--- a/lib/pleroma/web/router.ex
+++ b/lib/pleroma/web/router.ex
@@ -259,6 +259,21 @@ defmodule Pleroma.Web.Router do
     end
   end
 
+  scope "/api/v1/pleroma", Pleroma.Web.PleromaAPI do
+    pipe_through(:authenticated_api)
+
+    scope [] do
+      pipe_through(:oauth_read)
+      get("/conversations/:id/statuses", PleromaAPIController, :conversation_statuses)
+      get("/conversations/:id", PleromaAPIController, :conversation)
+    end
+
+    scope [] do
+      pipe_through(:oauth_write)
+      patch("/conversations/:id", PleromaAPIController, :update_conversation)
+    end
+  end
+
   scope "/api/v1", Pleroma.Web.MastodonAPI do
     pipe_through(:authenticated_api)
 
diff --git a/lib/pleroma/web/streamer.ex b/lib/pleroma/web/streamer.ex
index bbaddd852..66c8cd2c4 100644
--- a/lib/pleroma/web/streamer.ex
+++ b/lib/pleroma/web/streamer.ex
@@ -202,7 +202,7 @@ defmodule Pleroma.Web.Streamer do
       payload:
         Pleroma.Web.MastodonAPI.ConversationView.render("participation.json", %{
           participation: participation,
-          user: participation.user
+          for: participation.user
         })
         |> Jason.encode!()
     }
diff --git a/priv/repo/migrations/20190205114625_create_thread_mutes.exs b/priv/repo/migrations/20190205114625_create_thread_mutes.exs
index 7e44db121..baaf07253 100644
--- a/priv/repo/migrations/20190205114625_create_thread_mutes.exs
+++ b/priv/repo/migrations/20190205114625_create_thread_mutes.exs
@@ -6,7 +6,7 @@ defmodule Pleroma.Repo.Migrations.CreateThreadMutes do
       add :user_id, references(:users, type: :uuid, on_delete: :delete_all)
       add :context, :string
     end
-    
+
     create_if_not_exists unique_index(:thread_mutes, [:user_id, :context], name: :unique_index)
   end
 end
diff --git a/priv/repo/migrations/20190801154554_create_conversation_participation_recipient_ships.exs b/priv/repo/migrations/20190801154554_create_conversation_participation_recipient_ships.exs
new file mode 100644
index 000000000..c6e3469d5
--- /dev/null
+++ b/priv/repo/migrations/20190801154554_create_conversation_participation_recipient_ships.exs
@@ -0,0 +1,13 @@
+defmodule Pleroma.Repo.Migrations.CreateConversationParticipationRecipientShips do
+  use Ecto.Migration
+
+  def change do
+    create_if_not_exists table(:conversation_participation_recipient_ships) do
+      add(:user_id, references(:users, type: :uuid, on_delete: :delete_all))
+      add(:participation_id, references(:conversation_participations, on_delete: :delete_all))
+    end
+
+    create_if_not_exists index(:conversation_participation_recipient_ships, [:user_id])
+    create_if_not_exists index(:conversation_participation_recipient_ships, [:participation_id])
+  end
+end
diff --git a/test/conversation/participation_test.exs b/test/conversation/participation_test.exs
index 2a03e5d67..a27167d42 100644
--- a/test/conversation/participation_test.exs
+++ b/test/conversation/participation_test.exs
@@ -8,6 +8,50 @@ defmodule Pleroma.Conversation.ParticipationTest do
   alias Pleroma.Conversation.Participation
   alias Pleroma.Web.CommonAPI
 
+  test "getting a participation will also preload things" do
+    user = insert(:user)
+    other_user = insert(:user)
+
+    {:ok, _activity} =
+      CommonAPI.post(user, %{"status" => "Hey @#{other_user.nickname}.", "visibility" => "direct"})
+
+    [participation] = Participation.for_user(user)
+
+    participation = Participation.get(participation.id, preload: [:conversation])
+
+    assert %Pleroma.Conversation{} = participation.conversation
+  end
+
+  test "for a new conversation, it sets the recipents of the participation" do
+    user = insert(:user)
+    other_user = insert(:user)
+    third_user = insert(:user)
+
+    {:ok, activity} =
+      CommonAPI.post(user, %{"status" => "Hey @#{other_user.nickname}.", "visibility" => "direct"})
+
+    [participation] = Participation.for_user(user)
+    participation = Pleroma.Repo.preload(participation, :recipients)
+
+    assert length(participation.recipients) == 2
+    assert user in participation.recipients
+    assert other_user in participation.recipients
+
+    # Mentioning another user in the same conversation will not add a new recipients.
+
+    {:ok, _activity} =
+      CommonAPI.post(user, %{
+        "in_reply_to_status_id" => activity.id,
+        "status" => "Hey @#{third_user.nickname}.",
+        "visibility" => "direct"
+      })
+
+    [participation] = Participation.for_user(user)
+    participation = Pleroma.Repo.preload(participation, :recipients)
+
+    assert length(participation.recipients) == 2
+  end
+
   test "it creates a participation for a conversation and a user" do
     user = insert(:user)
     conversation = insert(:conversation)
@@ -102,4 +146,23 @@ defmodule Pleroma.Conversation.ParticipationTest do
 
     [] = Participation.for_user_with_last_activity_id(user)
   end
+
+  test "it sets recipients, always keeping the owner of the participation even when not explicitly set" do
+    user = insert(:user)
+    other_user = insert(:user)
+
+    {:ok, _activity} = CommonAPI.post(user, %{"status" => ".", "visibility" => "direct"})
+    [participation] = Participation.for_user_with_last_activity_id(user)
+
+    participation = Repo.preload(participation, :recipients)
+
+    assert participation.recipients |> length() == 1
+    assert user in participation.recipients
+
+    {:ok, participation} = Participation.set_recipients(participation, [other_user.id])
+
+    assert participation.recipients |> length() == 2
+    assert user in participation.recipients
+    assert other_user in participation.recipients
+  end
 end
diff --git a/test/web/common_api/common_api_test.exs b/test/web/common_api/common_api_test.exs
index 16b3f121d..454523349 100644
--- a/test/web/common_api/common_api_test.exs
+++ b/test/web/common_api/common_api_test.exs
@@ -5,13 +5,58 @@
 defmodule Pleroma.Web.CommonAPITest do
   use Pleroma.DataCase
   alias Pleroma.Activity
+  alias Pleroma.Conversation.Participation
   alias Pleroma.Object
   alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ActivityPub
+  alias Pleroma.Web.ActivityPub.Visibility
   alias Pleroma.Web.CommonAPI
 
   import Pleroma.Factory
 
+  test "when replying to a conversation / participation, it will set the correct context id even if no explicit reply_to is given" do
+    user = insert(:user)
+    {:ok, activity} = CommonAPI.post(user, %{"status" => ".", "visibility" => "direct"})
+
+    [participation] = Participation.for_user(user)
+
+    {:ok, convo_reply} =
+      CommonAPI.post(user, %{"status" => ".", "in_reply_to_conversation_id" => participation.id})
+
+    assert Visibility.is_direct?(convo_reply)
+
+    assert activity.data["context"] == convo_reply.data["context"]
+  end
+
+  test "when replying to a conversation / participation, it only mentions the recipients explicitly declared in the participation" do
+    har = insert(:user)
+    jafnhar = insert(:user)
+    tridi = insert(:user)
+
+    {:ok, activity} =
+      CommonAPI.post(har, %{
+        "status" => "@#{jafnhar.nickname} hey",
+        "visibility" => "direct"
+      })
+
+    assert har.ap_id in activity.recipients
+    assert jafnhar.ap_id in activity.recipients
+
+    [participation] = Participation.for_user(har)
+
+    {:ok, activity} =
+      CommonAPI.post(har, %{
+        "status" => "I don't really like @#{tridi.nickname}",
+        "visibility" => "direct",
+        "in_reply_to_status_id" => activity.id,
+        "in_reply_to_conversation_id" => participation.id
+      })
+
+    assert har.ap_id in activity.recipients
+    assert jafnhar.ap_id in activity.recipients
+    refute tridi.ap_id in activity.recipients
+  end
+
   test "with the safe_dm_mention option set, it does not mention people beyond the initial tags" do
     har = insert(:user)
     jafnhar = insert(:user)
diff --git a/test/web/common_api/common_api_utils_test.exs b/test/web/common_api/common_api_utils_test.exs
index 5989d7d29..c281dd1f1 100644
--- a/test/web/common_api/common_api_utils_test.exs
+++ b/test/web/common_api/common_api_utils_test.exs
@@ -239,7 +239,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       mentioned_user = insert(:user)
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "public")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "public", nil)
 
       assert length(to) == 2
       assert length(cc) == 1
@@ -256,7 +256,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       {:ok, activity} = CommonAPI.post(third_user, %{"status" => "uguu"})
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "public")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "public", nil)
 
       assert length(to) == 3
       assert length(cc) == 1
@@ -272,7 +272,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       mentioned_user = insert(:user)
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "unlisted")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "unlisted", nil)
 
       assert length(to) == 2
       assert length(cc) == 1
@@ -289,7 +289,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       {:ok, activity} = CommonAPI.post(third_user, %{"status" => "uguu"})
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "unlisted")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "unlisted", nil)
 
       assert length(to) == 3
       assert length(cc) == 1
@@ -305,7 +305,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       mentioned_user = insert(:user)
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "private")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "private", nil)
       assert length(to) == 2
       assert length(cc) == 0
 
@@ -320,7 +320,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       {:ok, activity} = CommonAPI.post(third_user, %{"status" => "uguu"})
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "private")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "private", nil)
 
       assert length(to) == 3
       assert length(cc) == 0
@@ -335,7 +335,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       mentioned_user = insert(:user)
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "direct")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, nil, "direct", nil)
 
       assert length(to) == 1
       assert length(cc) == 0
@@ -350,7 +350,7 @@ defmodule Pleroma.Web.CommonAPI.UtilsTest do
       {:ok, activity} = CommonAPI.post(third_user, %{"status" => "uguu"})
       mentions = [mentioned_user.ap_id]
 
-      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "direct")
+      {to, cc} = Utils.get_to_and_cc(user, mentions, activity, "direct", nil)
 
       assert length(to) == 2
       assert length(cc) == 0
diff --git a/test/web/mastodon_api/conversation_view_test.exs b/test/web/mastodon_api/conversation_view_test.exs
new file mode 100644
index 000000000..a2a880705
--- /dev/null
+++ b/test/web/mastodon_api/conversation_view_test.exs
@@ -0,0 +1,34 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.MastodonAPI.ConversationViewTest do
+  use Pleroma.DataCase
+
+  alias Pleroma.Conversation.Participation
+  alias Pleroma.Web.CommonAPI
+  alias Pleroma.Web.MastodonAPI.ConversationView
+
+  import Pleroma.Factory
+
+  test "represents a Mastodon Conversation entity" do
+    user = insert(:user)
+    other_user = insert(:user)
+
+    {:ok, activity} =
+      CommonAPI.post(user, %{"status" => "hey @#{other_user.nickname}", "visibility" => "direct"})
+
+    [participation] = Participation.for_user_with_last_activity_id(user)
+
+    assert participation
+
+    conversation =
+      ConversationView.render("participation.json", %{participation: participation, for: user})
+
+    assert conversation.id == participation.id |> to_string()
+    assert conversation.last_status.id == activity.id
+
+    assert [account] = conversation.accounts
+    assert account.id == other_user.id
+  end
+end
diff --git a/test/web/mastodon_api/status_view_test.exs b/test/web/mastodon_api/status_view_test.exs
index 0b167f839..c983b494f 100644
--- a/test/web/mastodon_api/status_view_test.exs
+++ b/test/web/mastodon_api/status_view_test.exs
@@ -23,6 +23,21 @@ defmodule Pleroma.Web.MastodonAPI.StatusViewTest do
     :ok
   end
 
+  test "returns the direct conversation id when given the `with_conversation_id` option" do
+    user = insert(:user)
+
+    {:ok, activity} = CommonAPI.post(user, %{"status" => "Hey @shp!", "visibility" => "direct"})
+
+    status =
+      StatusView.render("status.json",
+        activity: activity,
+        with_direct_conversation_id: true,
+        for: user
+      )
+
+    assert status[:pleroma][:direct_conversation_id]
+  end
+
   test "returns a temporary ap_id based user for activities missing db users" do
     user = insert(:user)
 
@@ -133,7 +148,8 @@ defmodule Pleroma.Web.MastodonAPI.StatusViewTest do
         conversation_id: convo_id,
         in_reply_to_account_acct: nil,
         content: %{"text/plain" => HtmlSanitizeEx.strip_tags(object_data["content"])},
-        spoiler_text: %{"text/plain" => HtmlSanitizeEx.strip_tags(object_data["summary"])}
+        spoiler_text: %{"text/plain" => HtmlSanitizeEx.strip_tags(object_data["summary"])},
+        direct_conversation_id: nil
       }
     }
 
diff --git a/test/web/pleroma_api/pleroma_api_controller_test.exs b/test/web/pleroma_api/pleroma_api_controller_test.exs
new file mode 100644
index 000000000..ed6b79727
--- /dev/null
+++ b/test/web/pleroma_api/pleroma_api_controller_test.exs
@@ -0,0 +1,94 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.PleromaAPI.PleromaAPIControllerTest do
+  use Pleroma.Web.ConnCase
+
+  alias Pleroma.Conversation.Participation
+  alias Pleroma.Repo
+  alias Pleroma.Web.CommonAPI
+
+  import Pleroma.Factory
+
+  test "/api/v1/pleroma/conversations/:id", %{conn: conn} do
+    user = insert(:user)
+    other_user = insert(:user)
+
+    {:ok, _activity} =
+      CommonAPI.post(user, %{"status" => "Hi @#{other_user.nickname}!", "visibility" => "direct"})
+
+    [participation] = Participation.for_user(other_user)
+
+    result =
+      conn
+      |> assign(:user, other_user)
+      |> get("/api/v1/pleroma/conversations/#{participation.id}")
+      |> json_response(200)
+
+    assert result["id"] == participation.id |> to_string()
+  end
+
+  test "/api/v1/pleroma/conversations/:id/statuses", %{conn: conn} do
+    user = insert(:user)
+    other_user = insert(:user)
+    third_user = insert(:user)
+
+    {:ok, _activity} =
+      CommonAPI.post(user, %{"status" => "Hi @#{third_user.nickname}!", "visibility" => "direct"})
+
+    {:ok, activity} =
+      CommonAPI.post(user, %{"status" => "Hi @#{other_user.nickname}!", "visibility" => "direct"})
+
+    [participation] = Participation.for_user(other_user)
+
+    {:ok, activity_two} =
+      CommonAPI.post(other_user, %{
+        "status" => "Hi!",
+        "in_reply_to_status_id" => activity.id,
+        "in_reply_to_conversation_id" => participation.id
+      })
+
+    result =
+      conn
+      |> assign(:user, other_user)
+      |> get("/api/v1/pleroma/conversations/#{participation.id}/statuses")
+      |> json_response(200)
+
+    assert length(result) == 2
+
+    id_one = activity.id
+    id_two = activity_two.id
+    assert [%{"id" => ^id_one}, %{"id" => ^id_two}] = result
+  end
+
+  test "PATCH /api/v1/pleroma/conversations/:id", %{conn: conn} do
+    user = insert(:user)
+    other_user = insert(:user)
+
+    {:ok, _activity} = CommonAPI.post(user, %{"status" => "Hi", "visibility" => "direct"})
+
+    [participation] = Participation.for_user(user)
+
+    participation = Repo.preload(participation, :recipients)
+
+    assert [user] == participation.recipients
+    assert other_user not in participation.recipients
+
+    result =
+      conn
+      |> assign(:user, user)
+      |> patch("/api/v1/pleroma/conversations/#{participation.id}", %{
+        "recipients" => [user.id, other_user.id]
+      })
+      |> json_response(200)
+
+    assert result["id"] == participation.id |> to_string
+
+    [participation] = Participation.for_user(user)
+    participation = Repo.preload(participation, :recipients)
+
+    assert user in participation.recipients
+    assert other_user in participation.recipients
+  end
+end