feat(knowledge): add link resolution service

- Add resolveLinksFromContent() to parse wiki links from content and resolve them
- Add getBacklinks() to find all entries that link to a target entry
- Import parseWikiLinks from utils for content parsing
- Export new types: ResolvedLink, Backlink
- Add comprehensive tests for new functionality (27 tests total)

apps/api/src/knowledge/services/link-resolution.service.spec.ts

@@ -63,6 +63,9 @@ describe("LinkResolutionService", () => {
       findFirst: vi.fn(),
       findMany: vi.fn(),
     },
+    knowledgeLink: {
+      findMany: vi.fn(),
+    },
   };
 
   beforeEach(async () => {
@@ -403,4 +406,186 @@ describe("LinkResolutionService", () => {
       expect(result).toHaveLength(1);
     });
   });
+
+  describe("resolveLinksFromContent", () => {
+    it("should parse and resolve wiki links from content", async () => {
+      const content =
+        "Check out [[TypeScript Guide]] and [[React Hooks]] for more info.";
+
+      // Mock resolveLink for each target
+      mockPrismaService.knowledgeEntry.findFirst
+        .mockResolvedValueOnce({ id: "entry-1" }) // TypeScript Guide
+        .mockResolvedValueOnce({ id: "entry-2" }); // React Hooks
+
+      const result = await service.resolveLinksFromContent(content, workspaceId);
+
+      expect(result).toHaveLength(2);
+      expect(result[0].link.target).toBe("TypeScript Guide");
+      expect(result[0].entryId).toBe("entry-1");
+      expect(result[1].link.target).toBe("React Hooks");
+      expect(result[1].entryId).toBe("entry-2");
+    });
+
+    it("should return null entryId for unresolved links", async () => {
+      const content = "See [[Non-existent Page]] for details.";
+
+      mockPrismaService.knowledgeEntry.findFirst.mockResolvedValueOnce(null);
+      mockPrismaService.knowledgeEntry.findUnique.mockResolvedValueOnce(null);
+      mockPrismaService.knowledgeEntry.findMany.mockResolvedValueOnce([]);
+
+      const result = await service.resolveLinksFromContent(content, workspaceId);
+
+      expect(result).toHaveLength(1);
+      expect(result[0].link.target).toBe("Non-existent Page");
+      expect(result[0].entryId).toBeNull();
+    });
+
+    it("should return empty array for content with no wiki links", async () => {
+      const content = "This content has no wiki links.";
+
+      const result = await service.resolveLinksFromContent(content, workspaceId);
+
+      expect(result).toEqual([]);
+      expect(mockPrismaService.knowledgeEntry.findFirst).not.toHaveBeenCalled();
+    });
+
+    it("should handle content with display text syntax", async () => {
+      const content = "Read the [[typescript-guide|TS Guide]] first.";
+
+      mockPrismaService.knowledgeEntry.findFirst.mockResolvedValueOnce(null);
+      mockPrismaService.knowledgeEntry.findUnique.mockResolvedValueOnce({
+        id: "entry-1",
+      });
+
+      const result = await service.resolveLinksFromContent(content, workspaceId);
+
+      expect(result).toHaveLength(1);
+      expect(result[0].link.target).toBe("typescript-guide");
+      expect(result[0].link.displayText).toBe("TS Guide");
+      expect(result[0].entryId).toBe("entry-1");
+    });
+
+    it("should preserve link position information", async () => {
+      const content = "Start [[Page One]] middle [[Page Two]] end.";
+
+      mockPrismaService.knowledgeEntry.findFirst
+        .mockResolvedValueOnce({ id: "entry-1" })
+        .mockResolvedValueOnce({ id: "entry-2" });
+
+      const result = await service.resolveLinksFromContent(content, workspaceId);
+
+      expect(result).toHaveLength(2);
+      expect(result[0].link.start).toBe(6);
+      expect(result[0].link.end).toBe(18);
+      expect(result[1].link.start).toBe(26);
+      expect(result[1].link.end).toBe(38);
+    });
+  });
+
+  describe("getBacklinks", () => {
+    it("should return all entries that link to the target entry", async () => {
+      const targetEntryId = "entry-target";
+      const mockBacklinks = [
+        {
+          id: "link-1",
+          sourceId: "entry-1",
+          targetId: targetEntryId,
+          linkText: "Target Page",
+          displayText: "Target Page",
+          positionStart: 10,
+          positionEnd: 25,
+          resolved: true,
+          context: null,
+          createdAt: new Date(),
+          source: {
+            id: "entry-1",
+            title: "TypeScript Guide",
+            slug: "typescript-guide",
+          },
+        },
+        {
+          id: "link-2",
+          sourceId: "entry-2",
+          targetId: targetEntryId,
+          linkText: "Target Page",
+          displayText: "See Target",
+          positionStart: 50,
+          positionEnd: 70,
+          resolved: true,
+          context: null,
+          createdAt: new Date(),
+          source: {
+            id: "entry-2",
+            title: "React Hooks",
+            slug: "react-hooks",
+          },
+        },
+      ];
+
+      mockPrismaService.knowledgeLink.findMany.mockResolvedValueOnce(
+        mockBacklinks
+      );
+
+      const result = await service.getBacklinks(targetEntryId);
+
+      expect(result).toHaveLength(2);
+      expect(result[0]).toEqual({
+        sourceId: "entry-1",
+        sourceTitle: "TypeScript Guide",
+        sourceSlug: "typescript-guide",
+        linkText: "Target Page",
+        displayText: "Target Page",
+      });
+      expect(result[1]).toEqual({
+        sourceId: "entry-2",
+        sourceTitle: "React Hooks",
+        sourceSlug: "react-hooks",
+        linkText: "Target Page",
+        displayText: "See Target",
+      });
+
+      expect(mockPrismaService.knowledgeLink.findMany).toHaveBeenCalledWith({
+        where: {
+          targetId: targetEntryId,
+          resolved: true,
+        },
+        include: {
+          source: {
+            select: {
+              id: true,
+              title: true,
+              slug: true,
+            },
+          },
+        },
+        orderBy: {
+          createdAt: "desc",
+        },
+      });
+    });
+
+    it("should return empty array when no backlinks exist", async () => {
+      mockPrismaService.knowledgeLink.findMany.mockResolvedValueOnce([]);
+
+      const result = await service.getBacklinks("entry-with-no-backlinks");
+
+      expect(result).toEqual([]);
+    });
+
+    it("should only return resolved backlinks", async () => {
+      const targetEntryId = "entry-target";
+
+      mockPrismaService.knowledgeLink.findMany.mockResolvedValueOnce([]);
+
+      await service.getBacklinks(targetEntryId);
+
+      expect(mockPrismaService.knowledgeLink.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          where: expect.objectContaining({
+            resolved: true,
+          }),
+        })
+      );
+    });
+  });
 });