Convert Documents module to MediatR commands/queries

Replaces IDocumentService/DocumentService. The permission-check and
descendant-deletion logic moves to a shared DocumentAccess static
helper used by all seven handlers.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

mws.application/Documents/Commands/CreateDocument.cs

@@ -0,0 +1,57 @@
+using AutoMapper;
+using MediatR;
+using Mws.Application.Common;
+using Mws.Application.Permissions;
+using Mws.Domain.Documents;
+
+namespace Mws.Application.Documents;
+
+public record CreateDocumentCommand(Guid UserId, Guid ProjectId, CreateDocumentRequest Request) : IRequest<DocumentDto>;
+
+public class CreateDocumentHandler(IUnitOfWork uow, IMapper mapper) : IRequestHandler<CreateDocumentCommand, DocumentDto>
+{
+    public async Task<DocumentDto> Handle(CreateDocumentCommand command, CancellationToken ct)
+    {
+        await DocumentAccess.EnsureDocumentPermissionAsync(uow, command.UserId, command.ProjectId, PermissionAction.Create, ct);
+
+        var request = command.Request;
+        if (string.IsNullOrWhiteSpace(request.Title))
+        {
+            throw new BadRequestException("Title is required");
+        }
+
+        if (request.ParentId is { } parentId)
+        {
+            var parent = await uow.Documents.GetInProjectAsync(parentId, command.ProjectId, ct)
+                ?? throw new BadRequestException("Parent document not found");
+            if (parent.Type != DocumentType.Folder)
+            {
+                throw new BadRequestException("Parent must be a folder");
+            }
+        }
+
+        if (request.Type == DocumentType.Folder && !string.IsNullOrWhiteSpace(request.Content))
+        {
+            throw new BadRequestException("Folders cannot have content");
+        }
+
+        var now = DateTime.UtcNow;
+        var doc = new Document
+        {
+            Id = Guid.NewGuid(),
+            ProjectId = command.ProjectId,
+            ParentId = request.ParentId,
+            Title = request.Title.Trim(),
+            Type = request.Type,
+            Content = request.Type == DocumentType.Document ? request.Content : null,
+            CreatedBy = command.UserId,
+            CreatedAt = now,
+            UpdatedBy = command.UserId,
+            UpdatedAt = now,
+        };
+
+        uow.Documents.Add(doc);
+        await uow.SaveChangesAsync(ct);
+        return mapper.Map<DocumentDto>(doc);
+    }
+}

mws.application/Documents/Commands/DeleteDocument.cs

@@ -0,0 +1,20 @@
+using MediatR;
+using Mws.Application.Common;
+using Mws.Application.Permissions;
+
+namespace Mws.Application.Documents;
+
+public record DeleteDocumentCommand(Guid UserId, Guid DocumentId) : IRequest;
+
+public class DeleteDocumentHandler(IUnitOfWork uow) : IRequestHandler<DeleteDocumentCommand>
+{
+    public async Task Handle(DeleteDocumentCommand command, CancellationToken ct)
+    {
+        var doc = await DocumentAccess.GetDocumentForUserAsync(uow, command.UserId, command.DocumentId, ct);
+        await DocumentAccess.EnsureDocumentPermissionAsync(uow, command.UserId, doc.ProjectId, PermissionAction.Delete, ct);
+
+        await DocumentAccess.DeleteDescendantsAsync(uow, command.DocumentId, ct);
+        uow.Documents.Remove(doc);
+        await uow.SaveChangesAsync(ct);
+    }
+}

mws.application/Documents/Commands/MoveDocument.cs

@@ -0,0 +1,51 @@
+using MediatR;
+using Mws.Application.Common;
+using Mws.Application.Permissions;
+using Mws.Domain.Documents;
+
+namespace Mws.Application.Documents;
+
+public record MoveDocumentCommand(Guid UserId, Guid DocumentId, Guid? NewParentId) : IRequest;
+
+public class MoveDocumentHandler(IUnitOfWork uow) : IRequestHandler<MoveDocumentCommand>
+{
+    public async Task Handle(MoveDocumentCommand command, CancellationToken ct)
+    {
+        var doc = await DocumentAccess.GetDocumentForUserAsync(uow, command.UserId, command.DocumentId, ct);
+        await DocumentAccess.EnsureDocumentPermissionAsync(uow, command.UserId, doc.ProjectId, PermissionAction.Edit, ct);
+
+        if (command.NewParentId == command.DocumentId)
+        {
+            throw new BadRequestException("A document cannot be moved into itself");
+        }
+
+        if (command.NewParentId is { } parentId)
+        {
+            var parent = await uow.Documents.GetByIdAsync(parentId, ct)
+                ?? throw new NotFoundException("Parent folder not found");
+            if (parent.ProjectId != doc.ProjectId)
+            {
+                throw new BadRequestException("Parent must belong to the same project");
+            }
+            if (parent.Type != DocumentType.Folder)
+            {
+                throw new BadRequestException("Parent must be a folder");
+            }
+
+            var cursor = parent.ParentId;
+            while (cursor is not null)
+            {
+                if (cursor == command.DocumentId)
+                {
+                    throw new BadRequestException("A folder cannot be moved into its own descendant");
+                }
+                cursor = await uow.Documents.GetParentIdAsync(cursor.Value, ct);
+            }
+        }
+
+        doc.ParentId = command.NewParentId;
+        doc.UpdatedAt = DateTime.UtcNow;
+        doc.UpdatedBy = command.UserId;
+        await uow.SaveChangesAsync(ct);
+    }
+}

mws.application/Documents/Commands/UpdateDocument.cs

@@ -0,0 +1,40 @@
+using AutoMapper;
+using MediatR;
+using Mws.Application.Common;
+using Mws.Application.Permissions;
+using Mws.Domain.Documents;
+
+namespace Mws.Application.Documents;
+
+public record UpdateDocumentCommand(Guid UserId, Guid DocumentId, UpdateDocumentRequest Request) : IRequest<DocumentDto>;
+
+public class UpdateDocumentHandler(IUnitOfWork uow, IMapper mapper) : IRequestHandler<UpdateDocumentCommand, DocumentDto>
+{
+    public async Task<DocumentDto> Handle(UpdateDocumentCommand command, CancellationToken ct)
+    {
+        var doc = await DocumentAccess.GetDocumentForUserAsync(uow, command.UserId, command.DocumentId, ct);
+        await DocumentAccess.EnsureDocumentPermissionAsync(uow, command.UserId, doc.ProjectId, PermissionAction.Edit, ct);
+
+        var request = command.Request;
+        if (string.IsNullOrWhiteSpace(request.Title))
+        {
+            throw new BadRequestException("Title is required");
+        }
+
+        doc.Title = request.Title.Trim();
+        if (doc.Type == DocumentType.Document)
+        {
+            doc.Content = request.Content;
+            doc.UpdatedAt = DateTime.UtcNow;
+            doc.UpdatedBy = command.UserId;
+        }
+        else
+        {
+            doc.UpdatedAt = DateTime.UtcNow;
+            doc.UpdatedBy = command.UserId;
+        }
+
+        await uow.SaveChangesAsync(ct);
+        return mapper.Map<DocumentDto>(doc);
+    }
+}