refactor(api): unify extension handling via shared service

Linked extension_comments_api (student-requested extensions) to use the
shared ExtensionService, previously set up for staff-granted extensions.

This refactor ensures both student and staff extension flows use the
same logic, improving consistency and reducing duplication.

Author: SahiruWithanage

app/api/extension_comments_api.rb

@@ -10,25 +10,21 @@ class ExtensionCommentsApi < Grape::API
     requires :weeks_requested, type: Integer, desc: 'The details of the request'
   end
   post '/projects/:project_id/task_def_id/:task_definition_id/request_extension' do
-    project = Project.find(params[:project_id])
-    task_definition = project.unit.task_definitions.find(params[:task_definition_id])
-    task = project.task_for_task_definition(task_definition)
-
-    # check permissions using specific permission has with addition of request extension if allowed in unit
-    unless authorise? current_user, task, :request_extension, ->(role, perm_hash, other) { task.specific_permission_hash(role, perm_hash, other) }
-      error!({ error: 'Not authorised to request an extension for this task' }, 403)
+    # Use the ExtensionService to handle the extension request
+    result = ExtensionService.grant_extension(
+      params[:project_id],
+      params[:task_definition_id],
+      current_user,
+      params[:weeks_requested],
+      params[:comment]
+    )
+
+    # Handle the service response
+    if result[:success]
+      present result[:result].serialize(current_user), Grape::Presenters::Presenter
+    else
+      error!({ error: result[:error] }, result[:status])
     end
-
-    error!({ error: 'Extension weeks can not be 0.' }, 403) if params[:weeks_requested] == 0
-
-    max_duration = task.weeks_can_extend
-    duration = params[:weeks_requested]
-    duration = max_duration unless params[:weeks_requested] <= max_duration
-
-    error!({ error: 'Extensions cannot be granted beyond task deadline.' }, 403) if duration <= 0
-
-    result = task.apply_for_extension(current_user, params[:comment], duration)
-    present result.serialize(current_user), Grape::Presenters::Presenter
   end
 
   desc 'Assess an extension for a task'

app/services/extension_service.rb

@@ -19,8 +19,8 @@ def self.grant_extension(project_id, task_definition_id, user, weeks_requested,
 
     # ===== Student Request Logic (current endpoint) =====
     unless is_staff_grant
-      # Check task-level authorization for student requests
-      unless AuthorisationHelpers.authorise?(user, task, :request_extension)
+      # Check task-level authorization for student requests with specific permission hash
+      unless AuthorisationHelpers.authorise?(user, task, :request_extension, ->(role, perm_hash, other) { task.specific_permission_hash(role, perm_hash, other) })
         return { success: false, error: 'Not authorised to request an extension for this task', status: 403 }
       end
     end