Add following and followers

lib/nulla/activitypub.ex

@@ -139,4 +139,90 @@ defmodule Nulla.ActivityPub do
       to: activity.to
     )
   end
+
+  @spec following(String.t(), Nulla.Models.User.t(), Integer.t()) :: Jason.OrderedObject.t()
+  def following(domain, user, total) do
+    Jason.OrderedObject.new(
+      "@context": "https://www.w3.org/ns/activitystreams",
+      id: "https://#{domain}/@#{user.username}/following",
+      type: "OrderedCollection",
+      totalItems: total,
+      first: "https://#{domain}/@#{user.username}/following?page=1"
+    )
+  end
+
+  @spec following(String.t(), Nulla.Models.User.t(), Integer.t(), List.t(), Integer.t(), Integer.t()) :: Jason.OrderedObject.t()
+  def following(domain, user, total, following_list, page, offset) when is_integer(page) and page > 0 do
+    data = [
+      "@context": "https://www.w3.org/ns/activitystreams",
+      id: "https://#{domain}/@#{user.username}/following?page=#{page}",
+      type: "OrderedCollectionPage",
+      totalItems: total,
+      next: "https://#{domain}/@#{user.username}/following?page=#{page + 1}",
+      prev: "https://#{domain}/@#{user.username}/following?page=#{page - 1}",
+      partOf: "https://#{domain}/@#{user.username}/following",
+      orderedItems: following_list
+    ]
+
+    data =
+      if page <= 1 do
+        Keyword.delete(data, :prev)
+      else
+        data
+      end
+
+    data =
+      if page * offset > total do
+        data
+        |> Keyword.delete(:next)
+        |> Keyword.delete(:prev)
+      else
+        data
+      end
+
+    Jason.OrderedObject.new(data)
+  end
+
+  @spec followers(String.t(), Nulla.Models.User.t(), Integer.t()) :: Jason.OrderedObject.t()
+  def followers(domain, user, total) do
+    Jason.OrderedObject.new(
+      "@context": "https://www.w3.org/ns/activitystreams",
+      id: "https://#{domain}/@#{user.username}/followers",
+      type: "OrderedCollection",
+      totalItems: total,
+      first: "https://#{domain}/@#{user.username}/followers?page=1"
+    )
+  end
+
+  @spec followers(String.t(), Nulla.Models.User.t(), Integer.t(), List.t(), Integer.t(), Integer.t()) :: Jason.OrderedObject.t()
+  def followers(domain, user, total, followers_list, page, offset) when is_integer(page) and page > 0 do
+    data = [
+      "@context": "https://www.w3.org/ns/activitystreams",
+      id: "https://#{domain}/@#{user.username}/followers?page=#{page}",
+      type: "OrderedCollectionPage",
+      totalItems: total,
+      next: "https://#{domain}/@#{user.username}/followers?page=#{page + 1}",
+      prev: "https://#{domain}/@#{user.username}/followers?page=#{page - 1}",
+      partOf: "https://#{domain}/@#{user.username}/followers",
+      orderedItems: followers_list
+    ]
+
+    data =
+      if page <= 1 do
+        Keyword.delete(data, :prev)
+      else
+        data
+      end
+
+    data =
+      if page * offset > total do
+        data
+        |> Keyword.delete(:next)
+        |> Keyword.delete(:prev)
+      else
+        data
+      end
+
+    Jason.OrderedObject.new(data)
+  end
 end

lib/nulla/models/instance_settings.ex

@@ -11,6 +11,7 @@ defmodule Nulla.Models.InstanceSettings do
     field :registration, :boolean, default: false
     field :max_characters, :integer, default: 5000
     field :max_upload_size, :integer, default: 50
+    field :offset, :integer, default: 100
     field :public_key, :string
     field :private_key, :string
   end
@@ -25,6 +26,7 @@ defmodule Nulla.Models.InstanceSettings do
       :registration,
       :max_characters,
       :max_upload_size,
+      :offset,
       :public_key,
       :private_key
     ])
@@ -35,6 +37,7 @@ defmodule Nulla.Models.InstanceSettings do
       :registration,
       :max_characters,
       :max_upload_size,
+      :offset,
       :public_key,
       :private_key
     ])

lib/nulla/utils.ex

@@ -0,0 +1,87 @@
+defmodule Nulla.Utils do
+  import Ecto.Query
+  alias Nulla.Repo
+  alias Nulla.Models.User
+  alias Nulla.Models.Follow
+  alias Nulla.Models.InstanceSettings
+
+  def count_following_by_username!(username) do
+    case Repo.get_by(User, username: username) do
+      nil ->
+        {:error, :user_not_found}
+
+      %User{id: user_id} ->
+        count =
+          Follow
+          |> where([f], f.user_id == ^user_id)
+          |> select([f], count(f.id))
+          |> Repo.one()
+
+        count
+    end
+  end
+
+  def get_following_users_by_username!(username, page) when is_integer(page) and page > 0 do
+    case Repo.get_by(User, username: username) do
+      nil ->
+        {:error, :user_not_found}
+
+      %User{id: user_id} ->
+        instance_settings = InstanceSettings.get_instance_settings!()
+        per_page = instance_settings.offset
+        offset = (page - 1) * per_page
+
+        query =
+          from [f, u] in
+            from(f in Follow,
+              join: u in User, on: u.id == f.target_id,
+              where: f.user_id == ^user_id,
+              order_by: [asc: u.inserted_at],
+              offset: ^offset,
+              limit: ^per_page,
+              select: u
+            )
+
+        users = Repo.all(query)
+
+        users
+    end
+  end
+
+  def count_followers_by_username!(username) do
+    case Repo.get_by(User, username: username) do
+      nil ->
+        0
+
+      %User{id: user_id} ->
+        from(f in Follow, where: f.target_id == ^user_id)
+        |> select([f], count(f.id))
+        |> Repo.one()
+    end
+  end
+
+  def get_followers_by_username!(username, page) when is_integer(page) and page > 0 do
+    case Repo.get_by(User, username: username) do
+      nil ->
+        {:error, :user_not_found}
+
+      %User{id: user_id} ->
+        instance_settings = InstanceSettings.get_instance_settings!()
+        per_page = instance_settings.offset
+        offset = (page - 1) * per_page
+
+        query =
+          from f in Follow,
+            where: f.target_id == ^user_id,
+            join: u in User, on: u.id == f.user_id,
+            order_by: [asc: u.inserted_at],
+            offset: ^offset,
+            limit: ^per_page,
+            select: u
+
+        users = Repo.all(query)
+
+        users
+    end
+  end
+end