2 files changed, 85 insertions, 10 deletions
diff --git a/lib/pleroma/hashtag.ex b/lib/pleroma/hashtag.ex
new file mode 100644
index 000000000..b05927563
--- /dev/null
+++ b/lib/pleroma/hashtag.ex
@@ -0,0 +1,58 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Hashtag do
+  use Ecto.Schema
+
+  import Ecto.Changeset
+
+  alias Pleroma.Hashtag
+  alias Pleroma.Repo
+
+  @derive {Jason.Encoder, only: [:data]}
+
+  schema "hashtags" do
+    field(:name, :string)
+    field(:data, :map, default: %{})
+
+    many_to_many(:objects, Pleroma.Object, join_through: "hashtags_objects", on_replace: :delete)
+
+    timestamps()
+  end
+
+  def get_by_name(name) do
+    Repo.get_by(Hashtag, name: name)
+  end
+
+  def get_or_create_by_name(name) when is_bitstring(name) do
+    with %Hashtag{} = hashtag <- get_by_name(name) do
+      {:ok, hashtag}
+    else
+      _ ->
+        %Hashtag{}
+        |> changeset(%{name: name})
+        |> Repo.insert()
+    end
+  end
+
+  def get_or_create_by_names(names) when is_list(names) do
+    Enum.reduce_while(names, {:ok, []}, fn name, {:ok, list} ->
+      case get_or_create_by_name(name) do
+        {:ok, %Hashtag{} = hashtag} ->
+          {:cont, {:ok, list ++ [hashtag]}}
+
+        error ->
+          {:halt, error}
+      end
+    end)
+  end
+
+  def changeset(%Hashtag{} = struct, params) do
+    struct
+    |> cast(params, [:name, :data])
+    |> update_change(:name, &String.downcase/1)
+    |> validate_required([:name])
+    |> unique_constraint(:name)
+  end
+end
diff --git a/lib/pleroma/object.ex b/lib/pleroma/object.ex
index 2088c7656..357a3b504 100644
--- a/lib/pleroma/object.ex
+++ b/lib/pleroma/object.ex
@@ -10,6 +10,7 @@ defmodule Pleroma.Object do
 
   alias Pleroma.Activity
   alias Pleroma.Config
+  alias Pleroma.Hashtag
   alias Pleroma.Object
   alias Pleroma.Object.Fetcher
   alias Pleroma.ObjectTombstone
@@ -26,6 +27,8 @@ defmodule Pleroma.Object do
   schema "objects" do
     field(:data, :map)
 
+    many_to_many(:hashtags, Hashtag, join_through: "hashtags_objects", on_replace: :delete)
+
     timestamps()
   end
 
@@ -53,17 +56,31 @@ defmodule Pleroma.Object do
   end
 
   def change(struct, params \\ %{}) do
-    changeset =
-      struct
-      |> cast(params, [:data])
-      |> validate_required([:data])
-      |> unique_constraint(:ap_id, name: :objects_unique_apid_index)
-
-    if hashtags_changed?(struct, get_change(changeset, :data)) do
-      # TODO: modify assoc once it's introduced
-      changeset
+    struct
+    |> cast(params, [:data])
+    |> validate_required([:data])
+    |> unique_constraint(:ap_id, name: :objects_unique_apid_index)
+    |> maybe_handle_hashtags_change(struct)
+  end
+
+  defp maybe_handle_hashtags_change(changeset, struct) do
+    with data_hashtags_change = get_change(changeset, :data),
+         true <- hashtags_changed?(struct, data_hashtags_change),
+         {:ok, hashtag_records} <-
+           data_hashtags_change
+           |> object_data_hashtags()
+           |> Hashtag.get_or_create_by_names() do
+      put_assoc(changeset, :hashtags, hashtag_records)
     else
-      changeset
+      false ->
+        changeset
+
+      {:error, hashtag_changeset} ->
+        failed_hashtag = get_field(hashtag_changeset, :name)
+
+        validate_change(changeset, :data, fn _, _ ->
+          [data: "error referencing hashtag: #{failed_hashtag}"]
+        end)
     end
   end