Add list of reactions to API

app/controllers/api/v1/statuses/reactions_controller.rb

@@ -1,8 +1,18 @@
 # frozen_string_literal: true
 
 class Api::V1::Statuses::ReactionsController < Api::V1::Statuses::BaseController
-  before_action -> { doorkeeper_authorize! :write, :'write:favourites' }
-  before_action :require_user!
+  REACTIONS_LIMIT = 30
+
+  before_action -> { doorkeeper_authorize! :write, :'write:favourites' }, only: [:create, :destroy]
+  before_action -> { authorize_if_got_token! :read, :'read:accounts' }, only: [:index]
+  before_action :require_user!, only: [:create, :destroy]
+  before_action :set_reactions, only: [:index]
+  after_action :insert_pagination_headers, only: [:index]
+
+  def index
+    cache_if_unauthenticated!
+    render json: @reactions, each_serializer: REST::StatusReactionSerializer
+  end
 
   def create
     ReactService.new.call(current_account, @status, params[:id])
@@ -16,4 +26,73 @@ class Api::V1::Statuses::ReactionsController < Api::V1::Statuses::BaseController
   rescue Mastodon::NotPermittedError
     not_found
   end
+
+  private
+
+  def set_reactions
+    @reactions = ordered_reactions.select(
+      [:id, :account_id, :name, :custom_emoji_id].tap do |values|
+        values << value_for_reaction_me_column(current_account)
+      end
+    ).to_a_paginated_by_id(
+      limit_param(REACTIONS_LIMIT),
+      params_slice(:max_id, :since_id, :min_id)
+    )
+  end
+
+  def ordered_reactions
+    StatusReaction.where(status: @status)
+                  .group(:status_id, :id, :account_id, :name, :custom_emoji_id).order(
+                    Arel.sql('MIN(created_at)').asc
+                  )
+  end
+
+  def value_for_reaction_me_column(account)
+    if account.nil?
+      'FALSE AS me'
+    else
+      <<~SQL.squish
+        EXISTS(
+          SELECT 1
+          FROM status_reactions inner_reactions
+          WHERE inner_reactions.account_id = #{account.id}
+            AND inner_reactions.status_id = status_reactions.status_id
+            AND inner_reactions.name = status_reactions.name
+            AND (
+              inner_reactions.custom_emoji_id = status_reactions.custom_emoji_id
+              OR inner_reactions.custom_emoji_id IS NULL
+                AND status_reactions.custom_emoji_id IS NULL
+            )
+        ) AS me
+      SQL
+    end
+  end
+
+  def insert_pagination_headers
+    set_pagination_headers(next_path, prev_path)
+  end
+
+  def next_path
+    api_v1_status_reactions_url pagination_params(max_id: pagination_max_id) if records_continue?
+  end
+
+  def prev_path
+    api_v1_status_reactions_url pagination_params(since_id: pagination_since_id) unless @reactions.empty?
+  end
+
+  def pagination_max_id
+    @reactions.last.id
+  end
+
+  def pagination_since_id
+    @reactions.first.id
+  end
+
+  def records_continue?
+    @reactions.size == limit_param(REACTIONS_LIMIT)
+  end
+
+  def pagination_params(core_params)
+    params.slice(:limit).permit(:limit).merge(core_params)
+  end
 end

app/models/status_reaction.rb

@@ -13,6 +13,8 @@
 #  updated_at      :datetime         not null
 #
 class StatusReaction < ApplicationRecord
+  include Paginable
+
   belongs_to :account
   belongs_to :status, inverse_of: :status_reactions
   belongs_to :custom_emoji, optional: true

app/serializers/rest/reaction_serializer.rb

@@ -21,14 +21,6 @@ class REST::ReactionSerializer < ActiveModel::Serializer
     object.custom_emoji.present?
   end
 
-  def name
-    if extern?
-      [object.name, '@', object.custom_emoji.domain].join
-    else
-      object.name
-    end
-  end
-
   def url
     full_asset_url(object.custom_emoji.image.url)
   end
@@ -36,10 +28,4 @@ class REST::ReactionSerializer < ActiveModel::Serializer
   def static_url
     full_asset_url(object.custom_emoji.image.url(:static))
   end
-
-  private
-
-  def extern?
-    custom_emoji? && object.custom_emoji.domain.present?
-  end
 end

app/serializers/rest/status_reaction_serializer.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+class REST::StatusReactionSerializer < ActiveModel::Serializer
+  include RoutingHelper
+
+  attributes :name
+
+  attribute :me, if: :current_user?
+  attribute :url, if: :custom_emoji?
+  attribute :static_url, if: :custom_emoji?
+  attribute :count, if: :respond_to_count?
+
+  belongs_to :account, serializer: REST::AccountSerializer, unless: :respond_to_count?
+
+  delegate :count, to: :object
+
+  def respond_to_count?
+    object.respond_to?(:count)
+  end
+
+  def current_user?
+    !current_user.nil?
+  end
+
+  def custom_emoji?
+    object.custom_emoji.present?
+  end
+
+  def name
+    if extern?
+      [object.name, '@', object.custom_emoji.domain].join
+    else
+      object.name
+    end
+  end
+
+  def url
+    full_asset_url(object.custom_emoji.image.url)
+  end
+
+  def static_url
+    full_asset_url(object.custom_emoji.image.url(:static))
+  end
+
+  private
+
+  def extern?
+    custom_emoji? && object.custom_emoji.domain.present?
+  end
+end

app/serializers/rest/status_serializer.rb

@@ -28,7 +28,7 @@ class REST::StatusSerializer < ActiveModel::Serializer
   has_many :ordered_mentions, key: :mentions
   has_many :tags
   has_many :emojis, serializer: REST::CustomEmojiSerializer
-  has_many :reactions, serializer: REST::ReactionSerializer
+  has_many :reactions, serializer: REST::StatusReactionSerializer
 
   has_one :preview_card, key: :card, serializer: REST::PreviewCardSerializer
   has_one :preloadable_poll, key: :poll, serializer: REST::PollSerializer

config/routes/api.rb

@@ -10,6 +10,7 @@ namespace :api, format: false do
       scope module: :statuses do
         resources :reblogged_by, controller: :reblogged_by_accounts, only: :index
         resources :favourited_by, controller: :favourited_by_accounts, only: :index
+        resources :reactions, controller: :reactions, only: :index
         resource :reblog, only: :create
         post :unreblog, to: 'reblogs#destroy'