Optimize Status#permitted_for 24x (#3069)

* Build query with arel node

* Add spec for current Status#permitted_for implementation

* Refactor status.rb

* Order by visibility to optimize query

app/models/status.rb

@@ -55,7 +55,7 @@ class Status < ApplicationRecord
   validates_with StatusLengthValidator
   validates :reblog, uniqueness: { scope: :account }, if: 'reblog?'
 
-  default_scope { order('id desc') }
+  default_scope { order(id: :desc) }
 
   scope :remote, -> { where.not(uri: nil) }
   scope :local, -> { where(uri: nil) }
@@ -202,18 +202,22 @@ class Status < ApplicationRecord
     end
 
     def permitted_for(target_account, account)
-      return where.not(visibility: [:private, :direct]) if account.nil?
+      visibility = [:public, :unlisted]
 
-      if target_account.blocking?(account) # get rid of blocked peeps
+      if account.nil?
+        where(visibility: visibility)
+      elsif target_account.blocking?(account) # get rid of blocked peeps
         none
       elsif account.id == target_account.id # author can see own stuff
         all
-      elsif account.following?(target_account) # followers can see followers-only stuff, but also things they are mentioned in
-        joins('LEFT OUTER JOIN mentions ON statuses.id = mentions.status_id AND mentions.account_id = ' + account.id.to_s)
-          .where('statuses.visibility != ? OR mentions.id IS NOT NULL', Status.visibilities[:direct])
-      else # non-followers can see everything that isn't private/direct, but can see stuff they are mentioned in
-        joins('LEFT OUTER JOIN mentions ON statuses.id = mentions.status_id AND mentions.account_id = ' + account.id.to_s)
-          .where('statuses.visibility NOT IN (?) OR mentions.id IS NOT NULL', [Status.visibilities[:direct], Status.visibilities[:private]])
+      else
+        # followers can see followers-only stuff, but also things they are mentioned in.
+        # non-followers can see everything that isn't private/direct, but can see stuff they are mentioned in.
+        visibility.push(:private) if account.following?(target_account)
+
+        joins("LEFT OUTER JOIN mentions ON statuses.id = mentions.status_id AND mentions.account_id = #{account.id}")
+          .where(arel_table[:visibility].in(visibility).or(Mention.arel_table[:id].not_eq(nil)))
+          .order(visibility: :desc)
       end
     end
 

spec/models/status_spec.rb

@@ -439,6 +439,59 @@ RSpec.describe Status, type: :model do
     end
   end
 
+  describe '.permitted_for' do
+    subject { described_class.permitted_for(target_account, account).pluck(:visibility) }
+
+    let(:target_account) { alice }
+    let(:account) { bob }
+    let!(:public_status) { Fabricate(:status, account: target_account, visibility: 'public') }
+    let!(:unlisted_status) { Fabricate(:status, account: target_account, visibility: 'unlisted') }
+    let!(:private_status) { Fabricate(:status, account: target_account, visibility: 'private') }
+
+    let!(:direct_status) do
+      Fabricate(:status, account: target_account, visibility: 'direct').tap do |status|
+        Fabricate(:mention, status: status, account: account)
+      end
+    end
+
+    let!(:other_direct_status) do
+      Fabricate(:status, account: target_account, visibility: 'direct').tap do |status|
+        Fabricate(:mention, status: status)
+      end
+    end
+
+    context 'given nil' do
+      let(:account) { nil }
+      let(:direct_status) { nil }
+      it { is_expected.to eq(%w(unlisted public)) }
+    end
+
+    context 'given blocked account' do
+      before do
+        target_account.block!(account)
+      end
+
+      it { is_expected.to be_empty }
+    end
+
+    context 'given same account' do
+      let(:account) { target_account }
+      it { is_expected.to eq(%w(direct direct private unlisted public)) }
+    end
+
+    context 'given followed account' do
+      before do
+        account.follow!(target_account)
+      end
+
+      it { is_expected.to eq(%w(direct private unlisted public)) }
+    end
+
+    context 'given unfollowed account' do
+      it { is_expected.to eq(%w(direct unlisted public)) }
+    end
+  end
+
   describe 'before_create' do
     it 'sets account being replied to correctly over intermediary nodes' do
       first_status = Fabricate(:status, account: bob)