feat: add GET /api/chats/[id]/segment endpoint

app/api/chats/[id]/segment/route.ts

@@ -0,0 +1,35 @@
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import { getCorsHeaders } from "@/lib/networking/getCorsHeaders";
+import { getChatSegmentHandler } from "@/lib/chats/getChatSegmentHandler";
+
+/**
+ * OPTIONS handler for CORS preflight requests.
+ *
+ * @returns A NextResponse with CORS headers.
+ */
+export async function OPTIONS() {
+  return new NextResponse(null, {
+    status: 200,
+    headers: getCorsHeaders(),
+  });
+}
+
+/**
+ * GET /api/chats/[id]/segment
+ *
+ * Retrieves the segment associated with a chat room.
+ * Returns 404 when the room does not exist or is not accessible by the caller.
+ *
+ * @param request - The incoming request object.
+ * @param root0 - The route context object.
+ * @param root0.params - The dynamic route params containing chat id.
+ * @returns A NextResponse with segment linkage data or an error.
+ */
+export async function GET(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string }> },
+): Promise<NextResponse> {
+  const { id } = await params;
+  return getChatSegmentHandler(request, id);
+}

lib/chats/__tests__/getChatSegmentHandler.test.ts

@@ -0,0 +1,96 @@
+import { describe, expect, it, vi, beforeEach } from "vitest";
+import { NextRequest, NextResponse } from "next/server";
+import { getChatSegmentHandler } from "@/lib/chats/getChatSegmentHandler";
+import { validateChatAccess } from "@/lib/chats/validateChatAccess";
+import { selectSegmentRoomByRoomId } from "@/lib/supabase/segment_rooms/selectSegmentRoomByRoomId";
+
+vi.mock("@/lib/chats/validateChatAccess", () => ({
+  validateChatAccess: vi.fn(),
+}));
+
+vi.mock("@/lib/supabase/segment_rooms/selectSegmentRoomByRoomId", () => ({
+  selectSegmentRoomByRoomId: vi.fn(),
+}));
+
+const createRequest = () => new NextRequest("http://localhost/api/chats/chat-id/segment");
+
+describe("getChatSegmentHandler", () => {
+  const roomId = "123e4567-e89b-42d3-a456-426614174000";
+  const segmentId = "123e4567-e89b-42d3-a456-426614174003";
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns validation/auth response from resolver", async () => {
+    vi.mocked(validateChatAccess).mockResolvedValue(
+      NextResponse.json({ status: "error", error: "Unauthorized" }, { status: 401 }),
+    );
+
+    const response = await getChatSegmentHandler(createRequest(), roomId);
+    const body = await response.json();
+
+    expect(response.status).toBe(401);
+    expect(body).toEqual({
+      status: "error",
+      error: "Unauthorized",
+    });
+    expect(selectSegmentRoomByRoomId).not.toHaveBeenCalled();
+  });
+
+  it("returns linked segment when segment_room exists", async () => {
+    vi.mocked(validateChatAccess).mockResolvedValue({
+      room: {
+        id: roomId,
+        account_id: "11111111-1111-1111-1111-111111111111",
+        artist_id: null,
+        topic: "Test",
+        updated_at: null,
+      },
+      accountId: "11111111-1111-1111-1111-111111111111",
+    });
+    vi.mocked(selectSegmentRoomByRoomId).mockResolvedValue({
+      room_id: roomId,
+      segment_id: segmentId,
+      id: "123e4567-e89b-42d3-a456-426614174004",
+      created_at: null,
+      updated_at: null,
+    });
+
+    const response = await getChatSegmentHandler(createRequest(), roomId);
+    const body = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(body).toEqual({
+      status: "success",
+      room_id: roomId,
+      segment_id: segmentId,
+      segment_exists: true,
+    });
+  });
+
+  it("returns null segment when no segment_room exists", async () => {
+    vi.mocked(validateChatAccess).mockResolvedValue({
+      room: {
+        id: roomId,
+        account_id: "11111111-1111-1111-1111-111111111111",
+        artist_id: null,
+        topic: "Test",
+        updated_at: null,
+      },
+      accountId: "11111111-1111-1111-1111-111111111111",
+    });
+    vi.mocked(selectSegmentRoomByRoomId).mockResolvedValue(null);
+
+    const response = await getChatSegmentHandler(createRequest(), roomId);
+    const body = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(body).toEqual({
+      status: "success",
+      room_id: roomId,
+      segment_id: null,
+      segment_exists: false,
+    });
+  });
+});

lib/chats/getChatSegmentHandler.ts

@@ -0,0 +1,36 @@
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import { getCorsHeaders } from "@/lib/networking/getCorsHeaders";
+import { validateChatAccess } from "@/lib/chats/validateChatAccess";
+import { selectSegmentRoomByRoomId } from "@/lib/supabase/segment_rooms/selectSegmentRoomByRoomId";
+
+/**
+ * Handles GET /api/chats/[id]/segment.
+ *
+ * Returns the segment associated with a chat room if one exists.
+ *
+ * @param request - The incoming request object for auth context.
+ * @param id - The chat room ID from route params.
+ * @returns A NextResponse with segment linkage data or an error.
+ */
+export async function getChatSegmentHandler(
+  request: NextRequest,
+  id: string,
+): Promise<NextResponse> {
+  const roomResult = await validateChatAccess(request, id);
+  if (roomResult instanceof NextResponse) {
+    return roomResult;
+  }
+
+  const segmentRoom = await selectSegmentRoomByRoomId(roomResult.room.id);
+
+  return NextResponse.json(
+    {
+      status: "success",
+      room_id: roomResult.room.id,
+      segment_id: segmentRoom?.segment_id || null,
+      segment_exists: Boolean(segmentRoom?.segment_id),
+    },
+    { status: 200, headers: getCorsHeaders() },
+  );
+}

lib/supabase/segment_rooms/selectSegmentRoomByRoomId.ts

@@ -0,0 +1,25 @@
+import supabase from "@/lib/supabase/serverClient";
+import type { Tables } from "@/types/database.types";
+
+/**
+ * Retrieves a segment_rooms row by room_id.
+ *
+ * @param roomId - The chat room ID.
+ * @returns The first matching segment_rooms row or null if none exists.
+ */
+export async function selectSegmentRoomByRoomId(
+  roomId: string,
+): Promise<Tables<"segment_rooms"> | null> {
+  const { data, error } = await supabase
+    .from("segment_rooms")
+    .select("*")
+    .eq("room_id", roomId)
+    .maybeSingle();
+
+  if (error) {
+    console.error("[ERROR] selectSegmentRoomByRoomId:", error);
+    throw error;
+  }
+
+  return data;
+}