feat: add course approval history endpoint for instructors to view rejection reasons and approval timeline

Backend/src/services/CoursesInstructor.service.ts

@@ -32,6 +32,7 @@ import {
     GetQuizAttemptDetailResponse,
     GetEnrolledStudentDetailInput,
     GetEnrolledStudentDetailResponse,
+    GetCourseApprovalHistoryResponse,
 } from "../types/CoursesInstructor.types";
 import { auditService } from './audit.service';
 import { AuditAction } from '@prisma/client';
@@ -1103,4 +1104,60 @@ export class CoursesInstructorService {
             throw error;
         }
     }
+
+    /**
+     * ดึงประวัติการขออนุมัติคอร์ส
+     * Get course approval history for instructor to see rejection reasons
+     */
+    static async getCourseApprovalHistory(token: string, courseId: number): Promise<GetCourseApprovalHistoryResponse> {
+        try {
+            const decoded = jwt.verify(token, config.jwt.secret) as { id: number };
+
+            // Validate instructor access
+            await this.validateCourseInstructor(token, courseId);
+
+            // Get course with approval history
+            const course = await prisma.course.findUnique({
+                where: { id: courseId },
+                include: {
+                    courseApprovals: {
+                        orderBy: { created_at: 'desc' },
+                        include: {
+                            submitter: {
+                                select: { id: true, username: true, email: true }
+                            },
+                            reviewer: {
+                                select: { id: true, username: true, email: true }
+                            }
+                        }
+                    }
+                }
+            });
+
+            if (!course) {
+                throw new NotFoundError('Course not found');
+            }
+
+            return {
+                code: 200,
+                message: 'Course approval history retrieved successfully',
+                data: {
+                    course_id: course.id,
+                    course_title: course.title as { th: string; en: string },
+                    current_status: course.status,
+                    approval_history: course.courseApprovals.map(a => ({
+                        id: a.id,
+                        action: a.action,
+                        comment: a.comment,
+                        created_at: a.created_at,
+                        submitter: a.submitter,
+                        reviewer: a.reviewer
+                    }))
+                }
+            };
+        } catch (error) {
+            logger.error(`Error getting course approval history: ${error}`);
+            throw error;
+        }
+    }
 }