Refactor student removal and project user fetching logic

Co-authored-by: adrian.lansdown <adrian.lansdown@raspberrypi.org>

Author: cursoragent

app/models/project.rb

@@ -43,8 +43,30 @@ module Types
   )
 
   def self.users(current_user)
-    school = School.find_by(id: pluck(:school_id))
-    SchoolStudent::List.call(school:, token: current_user.token, student_ids: pluck(:user_id).uniq)[:school_students] || []
+    return [] unless current_user&.token
+
+    projects_scope = all
+    school_user_pairs = projects_scope.pluck(:school_id, :user_id)
+    user_ids_by_school = school_user_pairs.each_with_object(Hash.new { |h, k| h[k] = [] }) do |(school_id, user_id), memo|
+      next if user_id.blank?
+
+      memo[school_id] << user_id
+    end
+
+    school_lookup = School.where(id: user_ids_by_school.keys.compact).index_by(&:id)
+
+    user_ids_by_school.each_with_object([]) do |(school_id, user_ids), users|
+      school = school_lookup[school_id]
+      next unless school
+
+      response = SchoolStudent::List.call(
+        school:,
+        token: current_user.token,
+        student_ids: user_ids.uniq
+      )
+
+      users.concat(response.fetch(:school_students, []))
+    end
   end
 
   def self.with_users(current_user)

app/models/school_class.rb

@@ -7,7 +7,7 @@ class SchoolClass < ApplicationRecord
   has_many :lessons, dependent: :nullify
   accepts_nested_attributes_for :teachers
 
-  scope :with_teachers, ->(user_id) { joins(:teachers).where(teachers: { id: user_id }) }
+  scope :with_teachers, ->(user_id) { joins(:teachers).where(class_teachers: { teacher_id: user_id }) }
 
   before_validation :assign_class_code, on: %i[create import]
 

app/services/student_removal_service.rb

@@ -14,23 +14,25 @@ def remove_students
     @students.each do |user_id|
       result = { user_id: }
       begin
-        # Skip if student has projects
-        projects = Project.where(user_id: user_id)
-        result[:skipped] = true if projects.length.positive?
+        projects_scope = Project.where(user_id:, school_id: @school.id)
+        result[:skipped] = true if projects_scope.exists?
 
         unless result[:skipped]
           ActiveRecord::Base.transaction do
-            # Remove from classes
             class_assignments = ClassStudent.where(student_id: user_id)
             class_assignments.destroy_all
 
-            # Remove roles
             roles = Role.student.where(user_id: user_id)
             roles.destroy_all
           end
 
-          # Remove from profile if requested
-          ProfileApiClient.delete_school_student(token: @token, school_id: @school.id, student_id: user_id) if @remove_from_profile && @token.present?
+          if @remove_from_profile && @token.present?
+            ProfileApiClient.delete_school_student(
+              token: @token,
+              school_id: @school.id,
+              student_id: user_id
+            )
+          end
         end
       rescue StandardError => e
         result[:error] = "#{e.class}: #{e.message}"