Added backend to retrive data based on page number and also to return…

… the total amount of histories for the page numbers

app/api/projects_api.rb

@@ -20,20 +20,69 @@ class ProjectsApi < Grape::API
     present projects, with: Entities::ProjectEntity, for_student: true, summary_only: true, user: current_user
   end
 
-  desc 'Get project with target grade history'
+  desc 'Get project with target grade history (unchanged route)'
   params do
     requires :id, type: Integer, desc: 'The id of the project to get'
   end
   get '/projects/:id' do
     project = Project.includes(:unit, :user, target_grade_histories: :changed_by).find(params[:id])
 
     if authorise? current_user, project, :get
-      present project, with: Entities::ProjectEntity, user: current_user, for_student: true, in_project: true
+      present project, with: Entities::ProjectEntity,
+                       user: current_user,
+                       for_student: true,
+                       in_project: true
     else
       error!({ error: "Couldn't find Project with id=#{params[:id]}" }, 403)
     end
   end
 
+
+  desc 'Get paginated target grade histories for a project (manual pagination)'
+  params do
+    requires :id, type: Integer, desc: 'The id of the project'
+    optional :page,  type: Integer, desc: 'Page number', default: 1
+    optional :limit, type: Integer, desc: 'Records per page', default: 10
+  end
+  get '/projects/:id/target_grade_histories' do
+    project = Project.find(params[:id])
+    unless authorise?(current_user, project, :get)
+      error!({ error: "You are not authorised to view this project" }, 403)
+    end
+
+    page  = params[:page]
+    limit = params[:limit]
+    offset = (page - 1) * limit
+
+    # Sort by changed_at DESC in DB, then limit/offset for pagination
+    total_histories = project.target_grade_histories.count
+    paged_histories = project.target_grade_histories
+                            .order(changed_at: :desc)
+                            .limit(limit)
+                            .offset(offset)
+                            .includes(:changed_by)
+
+    present({
+      target_grade_histories: paged_histories.map do |h|
+        {
+          id: h.id,
+          previous_grade:   h.previous_grade,
+          new_grade:        h.new_grade,
+          changed_at:       h.changed_at,
+          changed_by: {
+            id: h.changed_by_id,
+            email: h.changed_by&.email,
+            first_name: h.changed_by&.first_name,
+            last_name: h.changed_by&.last_name,
+            username: h.changed_by&.username,
+            nickname: h.changed_by&.nickname
+          }
+        }
+      end,
+      total_histories: total_histories
+    })
+  end
+
   desc 'Update a project'
   params do
     optional :trigger,            type: String,  desc: 'The update trigger'
@@ -67,7 +116,7 @@ class ProjectsApi < Grape::API
         error!({ error: "You cannot change the campus for this student" }, 403)
       end
       for_student = false
-      project.campus_id = params[:campus_id] == -1 ? nil : params[:campus_id]
+      project.campus_id = (params[:campus_id] == -1) ? nil : params[:campus_id]
       project.save!
     elsif !params[:enrolled].nil?
       unless authorise? current_user, project.unit, :change_project_enrolment
@@ -128,7 +177,6 @@ class ProjectsApi < Grape::API
       end
 
       for_student = false
-
       project.grade = params[:grade]
       project.grade_rationale = params[:grade_rationale]
       project.save!
@@ -140,13 +188,20 @@ class ProjectsApi < Grape::API
         error!({ error: "You do not have permissions to change this student" }, 403)
       end
 
-      # if someone changes this setting manually, clear the autogenerated status
       project.portfolio_auto_generated = false
       project.compile_portfolio = params[:compile_portfolio]
       project.save
     end
 
-    Entities::ProjectEntity.represent(project, only: [:campus_id, :enrolled, :target_grade, :submitted_grade, :compile_portfolio, :portfolio_available, :uses_draft_learning_summary, :stats], for_student: for_student)
+    Entities::ProjectEntity.represent(
+      project,
+      only: [
+        :campus_id, :enrolled, :target_grade, :submitted_grade,
+        :compile_portfolio, :portfolio_available, :uses_draft_learning_summary,
+        :stats
+      ],
+      for_student: for_student
+    )
   end # put
 
   desc 'Enrol a student in a unit, creating them a project'
@@ -199,4 +254,4 @@ class ProjectsApi < Grape::API
       error!({ error: "Couldn't find Unit with id=#{params[:unit_id]}" }, 403)
     end
   end
-end
+end