PiedTeam · KietPham-VN · May 31, 2026 · May 31, 2026 · May 31, 2026 · May 31, 2026
diff --git a/backend/Src/PIED_LMS.Application/UserCases/Commands/Course/CreateCourseHandler.cs b/backend/Src/PIED_LMS.Application/UserCases/Commands/Course/CreateCourseHandler.cs
@@ -1,7 +1,7 @@
 using PIED_LMS.Contract.Abstractions.Storage;
 using PIED_LMS.Contract.Services.Course;
 using PIED_LMS.Contract.Services.Identity;
-using PIED_LMS.Application.UserCases;
+
 using PIED_LMS.Domain.Abstractions;
 
 namespace PIED_LMS.Application.UserCases.Commands.Course;
@@ -35,20 +35,7 @@
                 return new ServiceResponse<Guid>(false, errorMessage);
             }
 
-            var (curriculumJson, curriculumError) = CourseContentHelper.ValidateAndSerializeCurriculum(request.Curriculum);
-            if (curriculumError is not null)
-            {
-                logger.LogWarning("Course creation validation failed: {ValidationError}", curriculumError);
-                return new ServiceResponse<Guid>(false, curriculumError);
-            }
 
-            var insight = CourseContentHelper.ValidateAndNormalizeInsight(request.Insight);
-            if (insight is null)
-            {
-                const string errorMessage = "Insight is required and cannot be empty.";
-                logger.LogWarning("Course creation validation failed: {ValidationError}", errorMessage);
-                return new ServiceResponse<Guid>(false, errorMessage);
-            }
 
             // Subtask 5.4: Implement file upload and course creation
             string? thumbnailPath = null;
@@ -90,11 +77,39 @@
                 Seats = request.Seats,
                 Price = request.Price,
                 Value = request.Value,
-                Curriculum = curriculumJson,
-                Insight = insight,
                 CreatedAt = DateTime.UtcNow
             };
 
+            try
+            {
+                if (request.Curriculum != null)
+                {
+                    var domainCurriculum = request.Curriculum.Select(c => 
+                        new Domain.Entities.CurriculumSection(c.Title, c.Summary, c.Content)).ToList();
+                    course.SetCurriculum(domainCurriculum);
+                }
+                course.SetInsight(request.Insight);
+            }
+            catch (ArgumentException ex)
+            {
+                logger.LogWarning("Course creation validation failed: {ValidationError}", ex.Message);
+
+                if (!string.IsNullOrEmpty(thumbnailPath))
+                {
+                    try
+                    {
+                        await fileStorageService.DeleteFileAsync(thumbnailPath, cancellationToken);
+                        logger.LogInformation("Deleted orphaned thumbnail {ThumbnailPath} after validation failure", thumbnailPath);
+                    }
+                    catch (Exception deleteEx)
+                    {
+                        logger.LogError(deleteEx, "Failed to delete orphaned thumbnail {ThumbnailPath}", thumbnailPath);
+                    }
+                }
+
+                return new ServiceResponse<Guid>(false, ex.Message);
+            }
+
             // Add course to repository
             var repository = unitOfWork.Repository<Domain.Entities.Course>();
             await repository.AddAsync(course, cancellationToken);

diff --git a/backend/Src/PIED_LMS.Application/UserCases/Commands/Course/UpdateCourseHandler.cs b/backend/Src/PIED_LMS.Application/UserCases/Commands/Course/UpdateCourseHandler.cs
@@ -1,7 +1,7 @@
 using PIED_LMS.Contract.Abstractions.Storage;
 using PIED_LMS.Contract.Services.Course;
 using PIED_LMS.Contract.Services.Identity;
-using PIED_LMS.Application.UserCases;
+
 using PIED_LMS.Domain.Abstractions;
 
 namespace PIED_LMS.Application.UserCases.Commands.Course;
@@ -37,21 +37,43 @@ public async Task<ServiceResponse<string>> Handle(UpdateCourseCommand request, C
                 return new ServiceResponse<string>(false, validationError);
             }
 
-            var (curriculumJson, curriculumError) = CourseContentHelper.ValidateAndSerializeCurriculum(request.Curriculum);
-            if (curriculumError is not null)
+
+
+            // Validate new slug uniqueness if slug changed
+            var newSlug = course.Slug;
+            if (!string.IsNullOrWhiteSpace(request.Slug) && request.Slug != course.Slug)
             {
-                logger.LogWarning("Course update validation failed for course {CourseId}: {ValidationError}",
-                    request.Id, curriculumError);
-                return new ServiceResponse<string>(false, curriculumError);
+                var slugToValidate = request.Slug.ToLowerInvariant().Trim();
+                var slugExists = await repository.AnyAsync(
+                    c => c.Slug == slugToValidate && c.Id != request.Id,
+                    cancellationToken);
+
+                if (slugExists)
+                {
+                    logger.LogWarning("Course update failed for course {CourseId}: Slug '{Slug}' already exists",
+                        request.Id, slugToValidate);
+                    return new ServiceResponse<string>(false, "Slug already exists. Please provide a unique slug.");
+                }
+
+                newSlug = slugToValidate;
             }
 
-            var insight = CourseContentHelper.ValidateAndNormalizeInsight(request.Insight);
-            if (insight is null)
+            // Validate Domain rules (Curriculum and Insight) before any side-effects
+            try
             {
-                const string errorMessage = "Insight is required and cannot be empty.";
-                logger.LogWarning("Course update validation failed for course {CourseId}: {ValidationError}",
-                    request.Id, errorMessage);
-                return new ServiceResponse<string>(false, errorMessage);
+                if (request.Curriculum != null)
+                {
+                    var domainCurriculum = request.Curriculum.Select(c => 
+                        new Domain.Entities.CurriculumSection(c.Title, c.Summary, c.Content)).ToList();
+                    course.SetCurriculum(domainCurriculum);
+                }
+
+                course.SetInsight(request.Insight);
+            }
+            catch (ArgumentException ex)
+            {
+                logger.LogWarning("Course update validation failed for course {CourseId}: {ValidationError}", request.Id, ex.Message);
+                return new ServiceResponse<string>(false, ex.Message);
             }
 
             // Subtask 6.3: Implement thumbnail update logic
@@ -85,25 +107,6 @@ public async Task<ServiceResponse<string>> Handle(UpdateCourseCommand request, C
                 }
 
             // Subtask 6.4: Implement course update and commit
-            // Validate new slug uniqueness if slug changed
-            var newSlug = course.Slug;
-            if (!string.IsNullOrWhiteSpace(request.Slug) && request.Slug != course.Slug)
-            {
-                var slugToValidate = request.Slug.ToLowerInvariant().Trim();
-                var slugExists = await repository.AnyAsync(
-                    c => c.Slug == slugToValidate && c.Id != request.Id,
-                    cancellationToken);
-
-                if (slugExists)
-                {
-                    logger.LogWarning("Course update failed for course {CourseId}: Slug '{Slug}' already exists",
-                        request.Id, slugToValidate);
-                    return new ServiceResponse<string>(false, "Slug already exists. Please provide a unique slug.");
-                }
-
-                newSlug = slugToValidate;
-            }
-
             // Track changed properties for logging
             var changedProperties = new List<string>();
             if (course.Title != request.Title) changedProperties.Add($"Title: '{course.Title}' -> '{request.Title}'");
@@ -113,8 +116,6 @@ public async Task<ServiceResponse<string>> Handle(UpdateCourseCommand request, C
             if (course.Status != request.Status) changedProperties.Add($"Status: {course.Status} -> {request.Status}");
             if (course.Slug != newSlug) changedProperties.Add($"Slug: '{course.Slug}' -> '{newSlug}'");
             if (course.ThumbnailPath != newThumbnailPath) changedProperties.Add("ThumbnailPath");
-            if (course.Curriculum != curriculumJson) changedProperties.Add("Curriculum");
-            if (course.Insight != insight) changedProperties.Add("Insight");
 
             // Update course properties
             course.Title = request.Title;
@@ -131,8 +132,6 @@ public async Task<ServiceResponse<string>> Handle(UpdateCourseCommand request, C
             course.Seats = request.Seats;
             course.Price = request.Price;
             course.Value = request.Value;
-            course.Curriculum = curriculumJson;
-            course.Insight = insight;
             course.UpdatedAt = DateTime.UtcNow;
 
             // Update course in repository

diff --git a/backend/Src/PIED_LMS.Application/UserCases/CourseContentHelper.cs b/backend/Src/PIED_LMS.Application/UserCases/CourseContentHelper.cs
diff --git a/backend/Src/PIED_LMS.Application/UserCases/Queries/Course/GetCourseByIdHandler.cs b/backend/Src/PIED_LMS.Application/UserCases/Queries/Course/GetCourseByIdHandler.cs
@@ -2,7 +2,7 @@
 using PIED_LMS.Contract.Abstractions.Storage;
 using PIED_LMS.Contract.Services.Course;
 using PIED_LMS.Contract.Services.Identity;
-using PIED_LMS.Application.UserCases;
+
 using PIED_LMS.Domain.Abstractions;
 
 namespace PIED_LMS.Application.UserCases.Queries.Course;
@@ -108,7 +108,8 @@ private async Task<CourseDto> MapToCourseDto(Domain.Entities.Course course, Canc
             t.ProfilePictureUrl
         )).ToList();
 
-        var curriculum = CourseContentHelper.DeserializeCurriculum(course.Curriculum, logger, course.Id);
+        var curriculumDto = course.Curriculum?.Select(c => 
+            new CurriculumSectionDto(c.Title, c.Summary, c.Content.ToList())).ToList() ?? new List<CurriculumSectionDto>();
 
         return new CourseDto(
             course.Id,
@@ -127,7 +128,7 @@ private async Task<CourseDto> MapToCourseDto(Domain.Entities.Course course, Canc
             course.CreatedAt,
             course.UpdatedAt,
             course.Value,
-            curriculum,
+            curriculumDto,
             course.Insight ?? string.Empty
         );
     }

diff --git a/backend/Src/PIED_LMS.Application/UserCases/Queries/Course/GetCourseCurriculumHandler.cs b/backend/Src/PIED_LMS.Application/UserCases/Queries/Course/GetCourseCurriculumHandler.cs
@@ -1,6 +1,6 @@
 using PIED_LMS.Contract.Services.Course;
 using PIED_LMS.Contract.Services.Identity;
-using PIED_LMS.Application.UserCases;
+
 using PIED_LMS.Domain.Abstractions;
 
 namespace PIED_LMS.Application.UserCases.Queries.Course;
@@ -28,12 +28,13 @@ public async Task<ServiceResponse<List<CurriculumSectionDto>>> Handle(
                 );
             }
 
-            var curriculum = CourseContentHelper.DeserializeCurriculum(course.Curriculum, logger, course.Id);
+            var curriculumDto = course.Curriculum?.Select(c => 
+                new CurriculumSectionDto(c.Title, c.Summary, c.Content.ToList())).ToList() ?? new List<CurriculumSectionDto>();
 
             return new ServiceResponse<List<CurriculumSectionDto>>(
                 true,
                 "Curriculum retrieved successfully",
-                curriculum
+                curriculumDto
             );
         }
         catch (Exception ex)

diff --git a/backend/Src/PIED_LMS.Application/UserCases/Queries/Course/GetCoursesHandler.cs b/backend/Src/PIED_LMS.Application/UserCases/Queries/Course/GetCoursesHandler.cs
@@ -2,7 +2,7 @@
 using PIED_LMS.Contract.Abstractions.Storage;
 using PIED_LMS.Contract.Services.Course;
 using PIED_LMS.Contract.Services.Identity;
-using PIED_LMS.Application.UserCases;
+
 using PIED_LMS.Domain.Abstractions;
 
 namespace PIED_LMS.Application.UserCases.Queries.Course;
@@ -119,7 +119,8 @@ private async Task<CourseDto> MapToCourseDto(Domain.Entities.Course course, Canc
                 t.ProfilePictureUrl
             )).ToList();
 
-        var curriculum = CourseContentHelper.DeserializeCurriculum(course.Curriculum, logger, course.Id);
+        var curriculumDto = course.Curriculum?.Select(c => 
+            new CurriculumSectionDto(c.Title, c.Summary, c.Content.ToList())).ToList() ?? new List<CurriculumSectionDto>();
 
         return new CourseDto(
             course.Id,
@@ -138,7 +139,7 @@ private async Task<CourseDto> MapToCourseDto(Domain.Entities.Course course, Canc
             course.CreatedAt,
             course.UpdatedAt,
             course.Value,
-            curriculum,
+            curriculumDto,
             course.Insight ?? string.Empty
         );
     }

diff --git a/backend/Src/PIED_LMS.Application/UserCases/Queries/GetUserByIdHandler.cs b/backend/Src/PIED_LMS.Application/UserCases/Queries/GetUserByIdHandler.cs
@@ -1,6 +1,6 @@
 using PIED_LMS.Contract.Abstractions.Storage;
-using PIED_LMS.Contract.Abstractions.Storage;
 using PIED_LMS.Contract.Services.Identity;
+using PIED_LMS.Domain.Abstractions;
 using PIED_LMS.Domain.Entities;
 
 namespace PIED_LMS.Application.UserCases.Queries;

diff --git a/backend/Src/PIED_LMS.Contract/Services/Course/Command.cs b/backend/Src/PIED_LMS.Contract/Services/Course/Command.cs
@@ -19,8 +19,8 @@ public record CreateCourseCommand(
     string? Seats,
     string? Price,
     int Value,
-    string? Curriculum,
-    string? Insight
+    List<CurriculumSectionDto>? Curriculum,
+    string Insight
 ) : IRequest<ServiceResponse<Guid>>;
 
 // Update Course Command
@@ -38,8 +38,8 @@ public record UpdateCourseCommand(
     string? Seats,
     string? Price,
     int Value,
-    string? Curriculum,
-    string? Insight
+    List<CurriculumSectionDto>? Curriculum,
+    string Insight
 ) : IRequest<ServiceResponse<string>>;
 
 // Delete Course Command

diff --git a/backend/Src/PIED_LMS.Contract/Services/Course/Request.cs b/backend/Src/PIED_LMS.Contract/Services/Course/Request.cs
@@ -18,7 +18,7 @@ public sealed record CreateCourseRequest(
     [FromForm(Name = "seats")] string? Seats,
     [FromForm(Name = "price")] string? Price,
     [FromForm(Name = "value")] int Value,
-    [FromForm(Name = "curriculum")] string? Curriculum,
+    [FromForm(Name = "curriculum")] List<CurriculumSectionDto>? Curriculum,
     [FromForm(Name = "insight")]
     [Required(ErrorMessage = "Insight is required and cannot be empty.")]
     string Insight
@@ -37,7 +37,7 @@ public sealed record UpdateCourseRequest(
     [FromForm(Name = "seats")] string? Seats,
     [FromForm(Name = "price")] string? Price,
     [FromForm(Name = "value")] int Value,
-    [FromForm(Name = "curriculum")] string? Curriculum,
+    [FromForm(Name = "curriculum")] List<CurriculumSectionDto>? Curriculum,
     [FromForm(Name = "insight")]
     [Required(ErrorMessage = "Insight is required and cannot be empty.")]
     string Insight