lib/pleroma/hashtag.ex

@@ -31,6 +31,10 @@ def get_by_id(id) do
     Repo.get(Hashtag, id)
   end
 
+  def get_by_name(name) do
+    Repo.get_by(Hashtag, name: normalize_name(name))
+  end
+
   def get_or_create_by_name(name) do
     changeset = changeset(%Hashtag{}, %{name: name})
 

lib/pleroma/web/api_spec/operations/tag_operation.ex

@@ -0,0 +1,65 @@
+defmodule Pleroma.Web.ApiSpec.TagOperation do
+  alias OpenApiSpex.Operation
+  alias OpenApiSpex.Schema
+  alias Pleroma.Web.ApiSpec.Schemas.ApiError
+  alias  Pleroma.Web.ApiSpec.Schemas.Tag
+
+  def open_api_operation(action) do
+    operation = String.to_existing_atom("#{action}_operation")
+    apply(__MODULE__, operation, [])
+  end
+
+  def show_operation do
+    %Operation{
+      tags: ["Tags"],
+      summary: "Hashtag",
+      description: "View a hashtag",
+      security: [%{"oAuth" => ["read"]}],
+      parameters: [id_param()],
+      operationId: "TagController.show",
+      responses: %{
+        200 => Operation.response("Hashtag", "application/json", Tag),
+        404 => Operation.response("Not Found", "application/json", ApiError)
+      }
+    }
+  end
+
+  def follow_operation do
+    %Operation{
+      tags: ["Tags"],
+      summary: "Follow a hashtag",
+      description: "Follow a hashtag",
+      security: [%{"oAuth" => ["write:follow"]}],
+      parameters: [id_param()],
+      operationId: "TagController.follow",
+      responses: %{
+        200 => Operation.response("Hashtag", "application/json", Tag),
+        404 => Operation.response("Not Found", "application/json", ApiError)
+      }
+    }
+  end
+
+  def unfollow_operation do
+    %Operation{
+      tags: ["Tags"],
+      summary: "Unfollow a hashtag",
+      description: "Unfollow a hashtag",
+      security: [%{"oAuth" => ["write:follow"]}],
+      parameters: [id_param()],
+      operationId: "TagController.unfollow",
+      responses: %{
+        200 => Operation.response("Hashtag", "application/json", Tag),
+        404 => Operation.response("Not Found", "application/json", ApiError)
+      }
+    }
+  end
+
+  defp id_param do
+    Operation.parameter(
+      :id,
+      :path,
+      %Schema{type: :string},
+      "Name of the hashtag"
+    )
+  end
+end

lib/pleroma/web/api_spec/schemas/tag.ex

@@ -17,11 +17,16 @@ defmodule Pleroma.Web.ApiSpec.Schemas.Tag do
         type: :string,
         format: :uri,
         description: "A link to the hashtag on the instance"
+      },
+      following: %Schema{
+        type: :boolean,
+        description: "Whether the authenticated user is following the hashtag"
       }
     },
     example: %{
       name: "cofe",
-      url: "https://lain.com/tag/cofe"
+      url: "https://lain.com/tag/cofe",
+      following: false
     }
   })
 end

lib/pleroma/web/mastodon_api/controllers/tag_controller.ex

@@ -0,0 +1,47 @@
+defmodule Pleroma.Web.MastodonAPI.TagController do
+  @moduledoc "Hashtag routes for mastodon API"
+  use Pleroma.Web, :controller
+
+  alias Pleroma.User
+  alias Pleroma.Hashtag
+
+  plug(Pleroma.Web.ApiSpec.CastAndValidate)
+  plug(Pleroma.Web.Plugs.OAuthScopesPlug, %{scopes: ["read"]} when action in [:show])
+
+  plug(
+    Pleroma.Web.Plugs.OAuthScopesPlug,
+    %{scopes: ["write:follows"]} when action in [:follow, :unfollow]
+  )
+
+  defdelegate open_api_operation(action), to: Pleroma.Web.ApiSpec.TagOperation
+
+  def show(conn, %{id: id} = params) do
+    with %Hashtag{} = hashtag <- Hashtag.get_by_name(id) do
+      render(conn, "show.json", tag: hashtag, for_user: conn.assigns.user)
+    else
+      _ -> conn |> render_error(:not_found, "Hashtag not found")
+    end
+  end
+
+  def follow(conn, %{id: id} = params) do
+    with %Hashtag{} = hashtag <- Hashtag.get_by_name(id),
+         %User{} = user <- conn.assigns.user,
+         {:ok, _} <-
+           User.follow_hashtag(user, hashtag) do
+      render(conn, "show.json", tag: params["tag"], for_user: user)
+    else
+      _ -> render_error(conn, :not_found, "Hashtag not found")
+    end
+  end
+
+  def unfollow(conn, %{id: id} = params) do
+    with %Hashtag{} = hashtag <- Hashtag.get_by_name(id),
+         %User{} = user <- conn.assigns.user,
+         {:ok, _} <-
+           User.unfollow_hashtag(user, hashtag) do
+      render(conn, "show.json", tag: params["tag"], for_user: user)
+    else
+      _ -> render_error(conn, :not_found, "Hashtag not found")
+    end
+  end
+end

lib/pleroma/web/mastodon_api/views/tag_view.ex

@@ -0,0 +1,21 @@
+defmodule Pleroma.Web.MastodonAPI.TagView do
+  use Pleroma.Web, :view
+  alias Pleroma.User
+  alias Pleroma.Web.Router.Helpers
+
+  def render("show.json", %{tag: tag, for_user: user}) do
+    following =
+      with %User{} <- user do
+        User.following_hashtag?(user, tag)
+      else
+        _ -> false
+      end
+
+    %{
+      name: tag.name,
+      url: Helpers.tag_url(Pleroma.Web.Endpoint, :show, tag),
+      history: [],
+      following: following
+    }
+  end
+end

lib/pleroma/web/router.ex

@@ -598,6 +598,10 @@ defmodule Pleroma.Web.Router do
 
     get("/announcements", AnnouncementController, :index)
     post("/announcements/:id/dismiss", AnnouncementController, :mark_read)
+
+    get("/tags/:id", TagController, :show)
+    post("/tags/:id/follow", TagController, :follow)
+    post("/tags/:id/unfollow", TagController, :unfollow)
   end
 
   scope "/api/web", Pleroma.Web do