chore: import upstream snapshot with attribution

tests/unit/api/compression-preview-engine.test.ts

@@ -0,0 +1,168 @@
+/**
+ * TDD: per-engine compression preview via engineId param.
+ *
+ * Auth pattern mirrors tests/unit/compression/compression-preview-auth.test.ts:
+ * - Use makeManagementSessionRequest to create a JWT-auth'd Request.
+ * - Set DATA_DIR to a temp dir and run the DB setup before importing the route.
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+import { makeManagementSessionRequest } from "../../helpers/managementSession.ts";
+
+// ─── temp DB isolation ────────────────────────────────────────────────────────
+
+const TEST_DATA_DIR = fs.mkdtempSync(
+  path.join(os.tmpdir(), "omniroute-compression-preview-engine-")
+);
+const originalDataDir = process.env.DATA_DIR;
+const originalJwtSecret = process.env.JWT_SECRET;
+
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const core = await import("../../../src/lib/db/core.ts");
+const settingsDb = await import("../../../src/lib/db/settings.ts");
+const previewRoute = await import("../../../src/app/api/compression/preview/route.ts");
+
+// ─── helpers ──────────────────────────────────────────────────────────────────
+
+async function setupAuth(): Promise<void> {
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+  fs.mkdirSync(TEST_DATA_DIR, { recursive: true });
+  await settingsDb.updateSettings({
+    requireLogin: true,
+    setupComplete: true,
+    password: "test-password-hash",
+  });
+}
+
+/**
+ * Build a message array whose content is a pretty-printed JSON string of a homogeneous
+ * array of ≥8 rows. headroom's crushText() tries the whole string as a JSON array when
+ * it starts with "[", so passing JSON.stringify(rows, null, 2) as content triggers
+ * compaction. Pretty-printed JSON has whitespace so countTokens() also gives a
+ * meaningful baseline to compare against the compact tabular output.
+ */
+function buildHeadroomMessages(): Array<{ role: string; content: string }> {
+  const rows = Array.from({ length: 10 }, (_, i) => ({
+    id: i + 1,
+    name: `item-${i + 1}`,
+    value: (i + 1) * 100,
+    active: true,
+  }));
+  // Pretty-print so word-split countTokens() produces a non-trivial baseline count
+  return [{ role: "user", content: JSON.stringify(rows, null, 2) }];
+}
+
+// ─── lifecycle ────────────────────────────────────────────────────────────────
+
+test.beforeEach(async () => {
+  process.env.DATA_DIR = TEST_DATA_DIR;
+  await setupAuth();
+});
+
+test.after(() => {
+  if (originalDataDir === undefined) delete process.env.DATA_DIR;
+  else process.env.DATA_DIR = originalDataDir;
+  if (originalJwtSecret === undefined) delete process.env.JWT_SECRET;
+  else process.env.JWT_SECRET = originalJwtSecret;
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+// ─── tests ────────────────────────────────────────────────────────────────────
+
+test("POST /api/compression/preview with engineId=headroom returns 200 with token savings", async () => {
+  const messages = buildHeadroomMessages();
+
+  const request = await makeManagementSessionRequest("http://localhost/api/compression/preview", {
+    method: "POST",
+    body: {
+      engineId: "headroom",
+      messages,
+      mode: "stacked",
+    },
+  });
+
+  const response = await previewRoute.POST(request);
+  assert.equal(response.status, 200, `Expected 200, got ${response.status}`);
+
+  const body = (await response.json()) as {
+    originalTokens: number;
+    compressedTokens: number;
+    tokensSaved: number;
+    savingsPct: number;
+    techniquesUsed: string[];
+    original: string;
+    compressed: string;
+    mode: string;
+  };
+
+  assert.ok(
+    typeof body.originalTokens === "number" && body.originalTokens > 0,
+    `originalTokens should be > 0, got: ${body.originalTokens}`
+  );
+  assert.ok(
+    typeof body.compressedTokens === "number",
+    `compressedTokens should be a number, got: ${body.compressedTokens}`
+  );
+  assert.ok(
+    body.compressedTokens < body.originalTokens,
+    `compressedTokens (${body.compressedTokens}) should be < originalTokens (${body.originalTokens}) — headroom should compact a 10-row homogeneous JSON array`
+  );
+  assert.ok(body.tokensSaved > 0, `tokensSaved should be > 0, got: ${body.tokensSaved}`);
+  assert.ok(body.savingsPct > 0, `savingsPct should be > 0, got: ${body.savingsPct}`);
+
+  // Response shape completeness checks
+  assert.ok(typeof body.original === "string", "should have original field");
+  assert.ok(typeof body.compressed === "string", "should have compressed field");
+  assert.ok(Array.isArray(body.techniquesUsed), "techniquesUsed should be an array");
+});
+
+test("POST /api/compression/preview with engineId but no mode still works (mode defaults to stacked)", async () => {
+  const messages = buildHeadroomMessages();
+
+  const request = await makeManagementSessionRequest("http://localhost/api/compression/preview", {
+    method: "POST",
+    body: {
+      engineId: "headroom",
+      messages,
+      // mode intentionally omitted — should default to "stacked" when engineId present
+    },
+  });
+
+  const response = await previewRoute.POST(request);
+  assert.equal(
+    response.status,
+    200,
+    `Expected 200 when mode omitted with engineId, got ${response.status}`
+  );
+
+  const body = (await response.json()) as { tokensSaved: number };
+  assert.ok(body.tokensSaved > 0, `tokensSaved should be > 0 even without explicit mode`);
+});
+
+test("POST /api/compression/preview without engineId still works (existing path untouched)", async () => {
+  const request = await makeManagementSessionRequest("http://localhost/api/compression/preview", {
+    method: "POST",
+    body: {
+      messages: [{ role: "user", content: "Hello world" }],
+      mode: "standard",
+    },
+  });
+
+  const response = await previewRoute.POST(request);
+  assert.equal(
+    response.status,
+    200,
+    `Existing path should still return 200, got ${response.status}`
+  );
+
+  const body = (await response.json()) as { original: string; mode: string };
+  assert.ok(typeof body.original === "string", "should have original field");
+  assert.equal(body.mode, "standard", "mode field should reflect the requested mode");
+});