Change followers page to relationships page in admin UI (#12927)

Allow browsing and filtering all relationships instead of just
followers, unify the codebase with the user-facing relationship
manager, add ability to see who the user invited

app/models/relationship_filter.rb

@@ -7,5 +7,114 @@ class RelationshipFilter
     by_domain
     activity
     order
+    location
   ).freeze
+
+  attr_reader :params, :account
+
+  def initialize(account, params)
+    @account = account
+    @params  = params
+
+    set_defaults!
+  end
+
+  def results
+    scope = scope_for('relationship', params['relationship'])
+
+    params.each do |key, value|
+      next if key.to_s == 'page'
+
+      scope.merge!(scope_for(key, value)) if value.present?
+    end
+
+    scope
+  end
+
+  private
+
+  def set_defaults!
+    params['relationship'] = 'following' if params['relationship'].blank?
+    params['order']        = 'recent' if params['order'].blank?
+  end
+
+  def scope_for(key, value)
+    case key.to_s
+    when 'relationship'
+      relationship_scope(value)
+    when 'by_domain'
+      by_domain_scope(value)
+    when 'location'
+      location_scope(value)
+    when 'status'
+      status_scope(value)
+    when 'order'
+      order_scope(value)
+    when 'activity'
+      activity_scope(value)
+    else
+      raise "Unknown filter: #{key}"
+    end
+  end
+
+  def relationship_scope(value)
+    case value.to_s
+    when 'following'
+      account.following.eager_load(:account_stat).reorder(nil)
+    when 'followed_by'
+      account.followers.eager_load(:account_stat).reorder(nil)
+    when 'mutual'
+      account.followers.eager_load(:account_stat).reorder(nil).merge(Account.where(id: account.following))
+    when 'invited'
+      Account.joins(user: :invite).merge(Invite.where(user: account.user)).eager_load(:account_stat).reorder(nil)
+    else
+      raise "Unknown relationship: #{value}"
+    end
+  end
+
+  def by_domain_scope(value)
+    Account.where(domain: value.to_s)
+  end
+
+  def location_scope(value)
+    case value.to_s
+    when 'local'
+      Account.local
+    when 'remote'
+      Account.remote
+    else
+      raise "Unknown location: #{value}"
+    end
+  end
+
+  def status_scope(value)
+    case value.to_s
+    when 'moved'
+      Account.where.not(moved_to_account_id: nil)
+    when 'primary'
+      Account.where(moved_to_account_id: nil)
+    else
+      raise "Unknown status: #{value}"
+    end
+  end
+
+  def order_scope(value)
+    case value.to_s
+    when 'active'
+      Account.by_recent_status
+    when 'recent'
+      Follow.recent
+    else
+      raise "Unknown order: #{value}"
+    end
+  end
+
+  def activity_scope(value)
+    case value.to_s
+    when 'dormant'
+      AccountStat.where(last_status_at: nil).or(AccountStat.where(AccountStat.arel_table[:last_status_at].lt(1.month.ago)))
+    else
+      raise "Unknown activity: #{value}"
+    end
+  end
 end