feat(project-chat): add task detail chat with @mentions and full backend integration

apps/api/prisma/migrations/20260304053000_project_chat/migration.sql

@@ -0,0 +1,41 @@
+-- CreateTable
+CREATE TABLE "ProjectChatMessage" (
+    "id" TEXT NOT NULL,
+    "content" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+    "projectId" TEXT NOT NULL,
+    "authorId" TEXT NOT NULL,
+
+    CONSTRAINT "ProjectChatMessage_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "ProjectChatMention" (
+    "id" TEXT NOT NULL,
+    "messageId" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+
+    CONSTRAINT "ProjectChatMention_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "ProjectChatMessage_projectId_createdAt_idx" ON "ProjectChatMessage"("projectId", "createdAt");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "ProjectChatMention_messageId_userId_key" ON "ProjectChatMention"("messageId", "userId");
+
+-- CreateIndex
+CREATE INDEX "ProjectChatMention_userId_idx" ON "ProjectChatMention"("userId");
+
+-- AddForeignKey
+ALTER TABLE "ProjectChatMessage" ADD CONSTRAINT "ProjectChatMessage_projectId_fkey" FOREIGN KEY ("projectId") REFERENCES "Project"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ProjectChatMessage" ADD CONSTRAINT "ProjectChatMessage_authorId_fkey" FOREIGN KEY ("authorId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ProjectChatMention" ADD CONSTRAINT "ProjectChatMention_messageId_fkey" FOREIGN KEY ("messageId") REFERENCES "ProjectChatMessage"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ProjectChatMention" ADD CONSTRAINT "ProjectChatMention_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;

apps/api/prisma/schema.prisma

@@ -16,10 +16,12 @@ model User {
   providerId    String
   createdAt     DateTime  @default(now())
 
-  ownedTeams    Team[]     @relation("TeamOwner")
-  memberships   TeamMember[]
-  assignedTasks Task[]     @relation("TaskAssignee")
-  createdTasks  Task[]     @relation("TaskCreator")
+  ownedTeams      Team[]               @relation("TeamOwner")
+  memberships     TeamMember[]
+  assignedTasks   Task[]               @relation("TaskAssignee")
+  createdTasks    Task[]               @relation("TaskCreator")
+  projectMessages ProjectChatMessage[] @relation("ProjectChatAuthor")
+  chatMentions    ProjectChatMention[] @relation("ProjectChatMentionedUser")
 
   @@unique([provider, providerId])
 }
@@ -63,9 +65,10 @@ model Project {
   status      ProjectStatus @default(ACTIVE)
   createdAt   DateTime      @default(now())
 
-  teamId String
-  team   Team   @relation(fields: [teamId], references: [id], onDelete: Cascade)
-  tasks  Task[]
+  teamId       String
+  team         Team                @relation(fields: [teamId], references: [id], onDelete: Cascade)
+  tasks        Task[]
+  chatMessages ProjectChatMessage[]
 }
 
 enum ProjectStatus {
@@ -94,6 +97,36 @@ model Task {
   creator   User    @relation("TaskCreator", fields: [creatorId], references: [id])
 }
 
+model ProjectChatMessage {
+  id        String   @id @default(cuid())
+  content   String
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  projectId String
+  project   Project @relation(fields: [projectId], references: [id], onDelete: Cascade)
+
+  authorId String
+  author   User    @relation("ProjectChatAuthor", fields: [authorId], references: [id], onDelete: Cascade)
+
+  mentions ProjectChatMention[]
+
+  @@index([projectId, createdAt])
+}
+
+model ProjectChatMention {
+  id String @id @default(cuid())
+
+  messageId String
+  message   ProjectChatMessage @relation(fields: [messageId], references: [id], onDelete: Cascade)
+
+  userId String
+  user   User @relation("ProjectChatMentionedUser", fields: [userId], references: [id], onDelete: Cascade)
+
+  @@unique([messageId, userId])
+  @@index([userId])
+}
+
 enum TaskStatus {
   TODO
   IN_PROGRESS

apps/api/src/app.module.ts

@@ -5,6 +5,7 @@ import { AuthModule } from "./auth/auth.module";
 import { JwtAuthGuard } from "./auth/guards/jwt-auth.guard";
 import { MailModule } from "./mail/mail.module";
 import { PrismaModule } from "./prisma/prisma.module";
+import { ProjectChatModule } from "./project-chat/project-chat.module";
 import { ProjectsModule } from "./projects/projects.module";
 import { TasksModule } from "./tasks/tasks.module";
 import { TeamsModule } from "./teams/teams.module";
@@ -17,6 +18,7 @@ import { UsersModule } from "./users/users.module";
     AuthModule,
     TeamsModule,
     ProjectsModule,
+    ProjectChatModule,
     TasksModule,
     UsersModule,
   ],

apps/api/src/project-chat/dto/create-project-chat-message.dto.ts

@@ -0,0 +1,14 @@
+import { ArrayMaxSize, IsArray, IsOptional, IsString, MaxLength, MinLength } from "class-validator";
+
+export class CreateProjectChatMessageDto {
+  @IsString()
+  @MinLength(1)
+  @MaxLength(2000)
+  content!: string;
+
+  @IsOptional()
+  @IsArray()
+  @ArrayMaxSize(20)
+  @IsString({ each: true })
+  mentionUserIds?: string[];
+}

apps/api/src/project-chat/project-chat.controller.ts

@@ -0,0 +1,29 @@
+import { Body, Controller, Get, Param, Post, UseGuards } from "@nestjs/common";
+import type { ProjectChatMessage } from "@repo/types";
+
+import { CurrentUser } from "../auth/decorators/current-user.decorator";
+import type { AuthUser } from "../auth/interfaces/auth-user.interface";
+import { ProjectMemberGuard } from "../tasks/guards/project-member.guard";
+
+import { CreateProjectChatMessageDto } from "./dto/create-project-chat-message.dto";
+import { ProjectChatService } from "./project-chat.service";
+
+@UseGuards(ProjectMemberGuard)
+@Controller("projects/:projectId/chat/messages")
+export class ProjectChatController {
+  constructor(private readonly projectChatService: ProjectChatService) {}
+
+  @Get()
+  listMessages(@Param("projectId") projectId: string): Promise<ProjectChatMessage[]> {
+    return this.projectChatService.listMessages(projectId);
+  }
+
+  @Post()
+  createMessage(
+    @Param("projectId") projectId: string,
+    @Body() dto: CreateProjectChatMessageDto,
+    @CurrentUser() user: AuthUser,
+  ): Promise<ProjectChatMessage> {
+    return this.projectChatService.createMessage(projectId, dto, user);
+  }
+}

apps/api/src/project-chat/project-chat.module.ts

@@ -0,0 +1,15 @@
+import { Module } from "@nestjs/common";
+
+import { PrismaModule } from "../prisma/prisma.module";
+import { ProjectMemberGuard } from "../tasks/guards/project-member.guard";
+
+import { ProjectChatController } from "./project-chat.controller";
+import { ProjectChatService } from "./project-chat.service";
+
+@Module({
+  imports: [PrismaModule],
+  controllers: [ProjectChatController],
+  providers: [ProjectChatService, ProjectMemberGuard],
+  exports: [ProjectChatService],
+})
+export class ProjectChatModule {}

apps/api/src/project-chat/project-chat.service.spec.ts

@@ -0,0 +1,123 @@
+import { NotFoundException } from "@nestjs/common";
+
+import { ProjectChatService } from "./project-chat.service";
+
+describe("ProjectChatService", () => {
+  it("creates a message and resolves mentions from content and explicit ids", async () => {
+    const create = jest.fn().mockResolvedValue({ id: "msg_1" });
+    const service = new ProjectChatService({
+      project: {
+        findUnique: jest.fn().mockResolvedValue({ teamId: "team_1" }),
+      },
+      teamMember: {
+        findMany: jest.fn().mockResolvedValue([
+          {
+            userId: "user_1",
+            user: {
+              id: "user_1",
+              email: "owner@example.com",
+              name: "Owner",
+              avatarUrl: null,
+            },
+          },
+          {
+            userId: "user_2",
+            user: {
+              id: "user_2",
+              email: "alice@example.com",
+              name: "Alice Johnson",
+              avatarUrl: null,
+            },
+          },
+        ]),
+      },
+      projectChatMessage: { create },
+    } as never);
+
+    await service.createMessage(
+      "project_1",
+      {
+        content: "Hello @alice and @alice.johnson",
+        mentionUserIds: ["user_2"],
+      },
+      {
+        sub: "user_1",
+        email: "owner@example.com",
+        provider: "github",
+      },
+    );
+
+    expect(create).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          projectId: "project_1",
+          authorId: "user_1",
+          content: "Hello @alice and @alice.johnson",
+          mentions: {
+            create: [{ userId: "user_2" }],
+          },
+        }),
+      }),
+    );
+  });
+
+  it("does not create mentions for users outside project team", async () => {
+    const create = jest.fn().mockResolvedValue({ id: "msg_1" });
+    const service = new ProjectChatService({
+      project: {
+        findUnique: jest.fn().mockResolvedValue({ teamId: "team_1" }),
+      },
+      teamMember: {
+        findMany: jest.fn().mockResolvedValue([
+          {
+            userId: "user_1",
+            user: {
+              id: "user_1",
+              email: "owner@example.com",
+              name: "Owner",
+              avatarUrl: null,
+            },
+          },
+        ]),
+      },
+      projectChatMessage: { create },
+    } as never);
+
+    await service.createMessage(
+      "project_1",
+      {
+        content: "Hey @external",
+        mentionUserIds: ["user_999"],
+      },
+      {
+        sub: "user_1",
+        email: "owner@example.com",
+        provider: "github",
+      },
+    );
+
+    expect(create).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          mentions: undefined,
+        }),
+      }),
+    );
+  });
+
+  it("throws when project does not exist", async () => {
+    const service = new ProjectChatService({
+      project: {
+        findUnique: jest.fn().mockResolvedValue(null),
+      },
+    } as never);
+
+    await expect(
+      service.createMessage(
+        "missing_project",
+        { content: "Message" },
+        { sub: "user_1", email: "user@example.com", provider: "github" },
+      ),
+    ).rejects.toBeInstanceOf(NotFoundException);
+  });
+});