Add API router, index

.env

@@ -1,2 +0,0 @@
-DATABASE_URL='postgres://chris:DB_d3v%24pw@localhost:5432/booktest'
-PORT=8300

api/src/category.router.test.ts

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+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { buildCategoryTree, CategoryNode } from './tree.utility.ts';
+
+describe('Tree Utility - buildCategoryTree()', () => {
+    it('should transform a flat list of ltree rows into a nested JSON structure', () => {
+        const flatNodes: CategoryNode[] = [
+            { id: 1, name: 'Root', path: 'Top' },
+            { id: 3, name: 'Astronomy', path: 'Top.Science.Astronomy' },
+            { id: 2, name: 'Science', path: 'Top.Science' },
+            { id: 4, name: 'Gardening', path: 'Top.Hobbies.Gardening' },
+            { id: 5, name: 'Hobbies', path: 'Top.Hobbies' }
+        ];
+
+        const tree = buildCategoryTree(flatNodes);
+
+        // Verify root nodes count
+        assert.equal(tree.length, 1);
+        assert.equal(tree[0].name, 'Root');
+
+        // Verify second level ("Science" and "Hobbies")
+        const rootChildren = tree[0].children;
+        assert.equal(rootChildren.length, 2);
+
+        const scienceNode = rootChildren.find(c => c.name === 'Science');
+        const hobbiesNode = rootChildren.find(c => c.name === 'Hobbies');
+
+        assert.ok(scienceNode);
+        assert.ok(hobbiesNode);
+
+        // Verify third level deeply nested child ("Astronomy")
+        assert.equal(scienceNode.children.length, 1);
+        assert.equal(scienceNode.children[0].name, 'Astronomy');
+    });
+});

api/src/category.router.ts

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+import { Router, Request, Response } from 'express';
+import { CategoryRepository } from './category.repository.ts';
+import { buildCategoryTree } from './tree.utility.ts';
+
+export function createCategoryRouter(repository: CategoryRepository): Router {
+    const router = Router();
+
+    /**
+     * GET /api/categories/tree/:path?
+     * Fetches all descendants of a path and returns them formatted as a tree.
+     * If no path parameter is provided, it defaults to the root level.
+     */
+    router.get('/tree/:path?', async (req: Request, params: Response): Promise<void> => {
+        try {
+            const rawPath = req.params.path;
+
+            const parentPath = Array.isArray(rawPath)
+                ? rawPath[0]
+                : (rawPath || 'Top');  // default fallback root value in the database
+
+            // Fetch flat database rows from our repository
+            const flatRows = await repository.findAllDescendants(parentPath);
+
+            // Format data into nested layout
+            const nestedTree = buildCategoryTree(flatRows);
+
+            params.json({ success: true, data: nestedTree });
+        } catch (error) {
+            console.error('Failed to resolve category tree:', error);
+            params.status(500).json({ success: false, error: 'Internal Server Error' });
+        }
+    });
+
+    return router;
+}

api/src/index.ts

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+import express from 'express';
+import { Pool } from 'pg';
+import { CategoryRepository } from './category.repository.ts';
+import { createCategoryRouter } from './category.router.ts';
+
+const app = express();
+const port = process.env.API_PORT || 8300;
+
+// Initialize your database pool
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL
+});
+
+app.use(express.json());
+
+// Inject the database pool into the repository layer
+const categoryRepository = new CategoryRepository(pool);
+
+// Attach your category endpoints to the Express app
+app.use('/api/categories', createCategoryRouter(categoryRepository));
+
+app.listen(port, () => {
+  console.log(`🚀 API workspace server running smoothly on http://localhost:${port}`);
+});