Implement soft-delete for clients, projects, and time entries

Replace hard deletes with deletedAt timestamp flags on all three entities.
Deleting a client or project only sets its own deletedAt; child records are
excluded implicitly by filtering on parent deletedAt in every read query.
Raw SQL statistics queries also filter out soft-deleted parents.
FK ON DELETE CASCADE removed from Project→Client and TimeEntry→Project.

backend/prisma/migrations/20260223200000_add_soft_delete/migration.sql

@@ -0,0 +1,20 @@
+-- AlterTable: add deleted_at column to clients
+ALTER TABLE "clients" ADD COLUMN "deleted_at" TIMESTAMP(3);
+
+-- AlterTable: add deleted_at column to projects
+ALTER TABLE "projects" ADD COLUMN "deleted_at" TIMESTAMP(3);
+
+-- AlterTable: add deleted_at column to time_entries
+ALTER TABLE "time_entries" ADD COLUMN "deleted_at" TIMESTAMP(3);
+
+-- DropForeignKey: remove cascade from projects -> clients
+ALTER TABLE "projects" DROP CONSTRAINT "projects_client_id_fkey";
+
+-- DropForeignKey: remove cascade from time_entries -> projects
+ALTER TABLE "time_entries" DROP CONSTRAINT "time_entries_project_id_fkey";
+
+-- AddForeignKey: re-add without onDelete cascade
+ALTER TABLE "projects" ADD CONSTRAINT "projects_client_id_fkey" FOREIGN KEY ("client_id") REFERENCES "clients"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+
+-- AddForeignKey: re-add without onDelete cascade
+ALTER TABLE "time_entries" ADD CONSTRAINT "time_entries_project_id_fkey" FOREIGN KEY ("project_id") REFERENCES "projects"("id") ON DELETE RESTRICT ON UPDATE CASCADE;

backend/prisma/schema.prisma

@@ -30,6 +30,7 @@ model Client {
   description String?   @db.Text
   createdAt   DateTime  @default(now()) @map("created_at")
   updatedAt   DateTime  @updatedAt @map("updated_at")
+  deletedAt   DateTime? @map("deleted_at")
 
   userId        String         @map("user_id") @db.VarChar(255)
   user          User           @relation(fields: [userId], references: [id], onDelete: Cascade)
@@ -47,11 +48,12 @@ model Project {
   color       String?   @db.VarChar(7) // Hex color code
   createdAt   DateTime  @default(now()) @map("created_at")
   updatedAt   DateTime  @updatedAt @map("updated_at")
+  deletedAt   DateTime? @map("deleted_at")
 
   userId   String @map("user_id") @db.VarChar(255)
   user     User   @relation(fields: [userId], references: [id], onDelete: Cascade)
   clientId String @map("client_id")
-  client   Client @relation(fields: [clientId], references: [id], onDelete: Cascade)
+  client   Client @relation(fields: [clientId], references: [id])
 
   timeEntries   TimeEntry[]
   ongoingTimers OngoingTimer[]
@@ -69,11 +71,12 @@ model TimeEntry {
   description  String?   @db.Text
   createdAt    DateTime  @default(now()) @map("created_at")
   updatedAt    DateTime  @updatedAt @map("updated_at")
+  deletedAt    DateTime? @map("deleted_at")
 
   userId    String  @map("user_id") @db.VarChar(255)
   user      User    @relation(fields: [userId], references: [id], onDelete: Cascade)
   projectId String  @map("project_id")
-  project   Project @relation(fields: [projectId], references: [id], onDelete: Cascade)
+  project   Project @relation(fields: [projectId], references: [id])
 
   @@index([userId])
   @@index([userId, startTime])

backend/src/services/client.service.ts

@@ -5,14 +5,14 @@ import type { CreateClientInput, UpdateClientInput } from "../types";
 export class ClientService {
   async findAll(userId: string) {
     return prisma.client.findMany({
-      where: { userId },
+      where: { userId, deletedAt: null },
       orderBy: { name: "asc" },
     });
   }
 
   async findById(id: string, userId: string) {
     return prisma.client.findFirst({
-      where: { id, userId },
+      where: { id, userId, deletedAt: null },
     });
   }
 
@@ -43,8 +43,9 @@ export class ClientService {
       throw new NotFoundError("Client not found");
     }
 
-    await prisma.client.delete({
+    await prisma.client.update({
       where: { id },
+      data: { deletedAt: new Date() },
     });
   }
 }

backend/src/services/project.service.ts

@@ -7,6 +7,8 @@ export class ProjectService {
     return prisma.project.findMany({
       where: {
         userId,
+        deletedAt: null,
+        client: { deletedAt: null },
         ...(clientId && { clientId }),
       },
       orderBy: { name: "asc" },
@@ -23,7 +25,12 @@ export class ProjectService {
 
   async findById(id: string, userId: string) {
     return prisma.project.findFirst({
-      where: { id, userId },
+      where: {
+        id,
+        userId,
+        deletedAt: null,
+        client: { deletedAt: null },
+      },
       include: {
         client: {
           select: {
@@ -36,9 +43,9 @@ export class ProjectService {
   }
 
   async create(userId: string, data: CreateProjectInput) {
-    // Verify the client belongs to the user
+    // Verify the client belongs to the user and is not soft-deleted
     const client = await prisma.client.findFirst({
-      where: { id: data.clientId, userId },
+      where: { id: data.clientId, userId, deletedAt: null },
     });
 
     if (!client) {
@@ -70,10 +77,10 @@ export class ProjectService {
       throw new NotFoundError("Project not found");
     }
 
-    // If clientId is being updated, verify it belongs to the user
+    // If clientId is being updated, verify it belongs to the user and is not soft-deleted
     if (data.clientId) {
       const client = await prisma.client.findFirst({
-        where: { id: data.clientId, userId },
+        where: { id: data.clientId, userId, deletedAt: null },
       });
 
       if (!client) {
@@ -108,8 +115,9 @@ export class ProjectService {
       throw new NotFoundError("Project not found");
     }
 
-    await prisma.project.delete({
+    await prisma.project.update({
       where: { id },
+      data: { deletedAt: new Date() },
     });
   }
 }

backend/src/services/timeEntry.service.ts

@@ -46,7 +46,11 @@ export class TimeEntryService {
           COUNT(te.id)::bigint AS entry_count
         FROM time_entries te
         JOIN projects p ON p.id = te.project_id
+        JOIN clients  c ON c.id = p.client_id
         WHERE te.user_id = ${userId}
+          AND te.deleted_at IS NULL
+          AND p.deleted_at IS NULL
+          AND c.deleted_at IS NULL
         ${filterClause}
         GROUP BY p.id, p.name, p.color
         ORDER BY total_seconds DESC
@@ -69,6 +73,9 @@ export class TimeEntryService {
         JOIN projects p ON p.id = te.project_id
         JOIN clients  c ON c.id = p.client_id
         WHERE te.user_id = ${userId}
+          AND te.deleted_at IS NULL
+          AND p.deleted_at IS NULL
+          AND c.deleted_at IS NULL
         ${filterClause}
         GROUP BY c.id, c.name
         ORDER BY total_seconds DESC
@@ -81,7 +88,11 @@ export class TimeEntryService {
             COUNT(te.id)::bigint AS entry_count
           FROM time_entries te
           JOIN projects p ON p.id = te.project_id
+          JOIN clients  c ON c.id = p.client_id
           WHERE te.user_id = ${userId}
+            AND te.deleted_at IS NULL
+            AND p.deleted_at IS NULL
+            AND c.deleted_at IS NULL
           ${filterClause}
         `,
       ),
@@ -125,10 +136,11 @@ export class TimeEntryService {
 
     const where: {
       userId: string;
+      deletedAt: null;
       startTime?: { gte?: Date; lte?: Date };
       projectId?: string;
-      project?: { clientId?: string };
+      project?: { deletedAt: null; clientId?: string; client: { deletedAt: null } };
-    } = { userId };
+    } = { userId, deletedAt: null };
 
     if (startDate || endDate) {
       where.startTime = {};
@@ -140,9 +152,13 @@ export class TimeEntryService {
       where.projectId = projectId;
     }
 
-    if (clientId) {
+    // Always filter out entries whose project or client is soft-deleted,
-      where.project = { clientId };
+    // merging the optional clientId filter into the project relation filter.
-    }
+    where.project = {
+      deletedAt: null,
+      client: { deletedAt: null },
+      ...(clientId && { clientId }),
+    };
 
     const [entries, total] = await Promise.all([
       prisma.timeEntry.findMany({
@@ -182,7 +198,12 @@ export class TimeEntryService {
 
   async findById(id: string, userId: string) {
     return prisma.timeEntry.findFirst({
-      where: { id, userId },
+      where: {
+        id,
+        userId,
+        deletedAt: null,
+        project: { deletedAt: null, client: { deletedAt: null } },
+      },
       include: {
         project: {
           select: {
@@ -217,9 +238,9 @@ export class TimeEntryService {
       throw new BadRequestError("Break time cannot exceed total duration");
     }
 
-    // Verify the project belongs to the user
+    // Verify the project belongs to the user and is not soft-deleted (nor its client)
     const project = await prisma.project.findFirst({
-      where: { id: data.projectId, userId },
+      where: { id: data.projectId, userId, deletedAt: null, client: { deletedAt: null } },
     });
 
     if (!project) {
@@ -288,10 +309,10 @@ export class TimeEntryService {
       throw new BadRequestError("Break time cannot exceed total duration");
     }
 
-    // If project changed, verify it belongs to the user
+    // If project changed, verify it belongs to the user and is not soft-deleted
     if (data.projectId && data.projectId !== entry.projectId) {
       const project = await prisma.project.findFirst({
-        where: { id: data.projectId, userId },
+        where: { id: data.projectId, userId, deletedAt: null, client: { deletedAt: null } },
       });
 
       if (!project) {
@@ -345,8 +366,9 @@ export class TimeEntryService {
       throw new NotFoundError("Time entry not found");
     }
 
-    await prisma.timeEntry.delete({
+    await prisma.timeEntry.update({
       where: { id },
+      data: { deletedAt: new Date() },
     });
   }
 }

frontend/src/types/index.ts

@@ -11,6 +11,7 @@ export interface Client {
   description: string | null;
   createdAt: string;
   updatedAt: string;
+  deletedAt: string | null;
 }
 
 export interface Project {
@@ -22,6 +23,7 @@ export interface Project {
   client: Pick<Client, 'id' | 'name'>;
   createdAt: string;
   updatedAt: string;
+  deletedAt: string | null;
 }
 
 export interface TimeEntry {
@@ -36,6 +38,7 @@ export interface TimeEntry {
   };
   createdAt: string;
   updatedAt: string;
+  deletedAt: string | null;
 }
 
 export interface OngoingTimer {