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/index.ts

@@ -1,2 +1,6 @@
 export { LinkResolutionService } from "./link-resolution.service";
-export type { ResolvedEntry } from "./link-resolution.service";
+export type {
+  ResolvedEntry,
+  ResolvedLink,
+  Backlink,
+} from "./link-resolution.service";

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,
+          }),
+        })
+      );
+    });
+  });
 });

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

@@ -1,5 +1,6 @@
 import { Injectable } from "@nestjs/common";
 import { PrismaService } from "../../prisma/prisma.service";
+import { parseWikiLinks, WikiLink } from "../utils/wiki-link-parser";
 
 /**
  * Represents a knowledge entry that matches a link target
@@ -9,6 +10,32 @@ export interface ResolvedEntry {
   title: string;
 }
 
+/**
+ * Represents a resolved wiki link with entry information
+ */
+export interface ResolvedLink {
+  /** The parsed wiki link */
+  link: WikiLink;
+  /** The resolved entry ID, or null if not found */
+  entryId: string | null;
+}
+
+/**
+ * Represents a backlink - an entry that links to a target entry
+ */
+export interface Backlink {
+  /** The source entry ID */
+  sourceId: string;
+  /** The source entry title */
+  sourceTitle: string;
+  /** The source entry slug */
+  sourceSlug: string;
+  /** The link text used to reference the target */
+  linkText: string;
+  /** The display text shown for the link */
+  displayText: string;
+}
+
 /**
  * Service for resolving wiki-style links to knowledge entries
  *
@@ -165,4 +192,72 @@ export class LinkResolutionService {
 
     return matches;
   }
+
+  /**
+   * Parse wiki links from content and resolve them to knowledge entries
+   *
+   * @param content - The markdown content containing wiki links
+   * @param workspaceId - The workspace scope for resolution
+   * @returns Array of resolved links with entry IDs (or null if not found)
+   */
+  async resolveLinksFromContent(
+    content: string,
+    workspaceId: string
+  ): Promise<ResolvedLink[]> {
+    // Parse wiki links from content
+    const parsedLinks = parseWikiLinks(content);
+
+    if (parsedLinks.length === 0) {
+      return [];
+    }
+
+    // Resolve each link
+    const resolvedLinks: ResolvedLink[] = [];
+
+    for (const link of parsedLinks) {
+      const entryId = await this.resolveLink(workspaceId, link.target);
+      resolvedLinks.push({
+        link,
+        entryId,
+      });
+    }
+
+    return resolvedLinks;
+  }
+
+  /**
+   * Get all entries that link TO a specific entry (backlinks)
+   *
+   * @param entryId - The target entry ID
+   * @returns Array of backlinks with source entry information
+   */
+  async getBacklinks(entryId: string): Promise<Backlink[]> {
+    // Find all links where this entry is the target
+    const links = await this.prisma.knowledgeLink.findMany({
+      where: {
+        targetId: entryId,
+        resolved: true,
+      },
+      include: {
+        source: {
+          select: {
+            id: true,
+            title: true,
+            slug: true,
+          },
+        },
+      },
+      orderBy: {
+        createdAt: "desc",
+      },
+    });
+
+    return links.map((link) => ({
+      sourceId: link.source.id,
+      sourceTitle: link.source.title,
+      sourceSlug: link.source.slug,
+      linkText: link.linkText,
+      displayText: link.displayText,
+    }));
+  }
 }