perf(producer): cache local font compression (#2397)

packages/producer/src/services/fontCompression.test.ts

@@ -1,5 +1,7 @@
 import { describe, expect, it } from "bun:test";
-import { existsSync, readFileSync } from "node:fs";
+import { existsSync, mkdtempSync, readFileSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import { compressToWoff2, fontToDataUri } from "./fontCompression.js";
 
 /**
@@ -41,6 +43,26 @@ describe("compressToWoff2", () => {
 });
 
 describe("fontToDataUri", () => {
+  it("reuses cached compression across calls", async () => {
+    const cacheDir = mkdtempSync(join(tmpdir(), "hf-local-font-cache-"));
+    const raw = Buffer.from("stable-font-content");
+    let compressionCalls = 0;
+    const compressImpl = async () => {
+      compressionCalls += 1;
+      return Buffer.from("compressed-font-content");
+    };
+
+    try {
+      const first = await fontToDataUri(raw, "ttf", { cacheDir, compressImpl });
+      const second = await fontToDataUri(raw, "ttf", { cacheDir, compressImpl });
+
+      expect(second).toBe(first);
+      expect(compressionCalls).toBe(1);
+    } finally {
+      rmSync(cacheDir, { recursive: true, force: true });
+    }
+  });
+
   it("skips compression for woff2 input and returns a data URI", async () => {
     const raw = Buffer.from("fake-woff2-bytes");
     const uri = await fontToDataUri(raw, "woff2");

packages/producer/src/services/fontCompression.ts

@@ -1,5 +1,9 @@
 // @ts-expect-error -- wawoff2 ships no type declarations; ambient .d.ts only visible to producer's own tsconfig
 import wawoff2 from "wawoff2";
+import { createHash } from "node:crypto";
+import { existsSync, mkdirSync, readFileSync, renameSync, rmSync, writeFileSync } from "node:fs";
+import { homedir, tmpdir } from "node:os";
+import { dirname, join } from "node:path";
 
 const { compress } = wawoff2 as {
   compress: (input: Buffer | Uint8Array) => Promise<Uint8Array>;
@@ -18,12 +22,77 @@ function rawMimeType(format: string): string {
   return RAW_MIME_TYPES[format] ?? "font/ttf";
 }
 
-export async function fontToDataUri(input: Buffer, originalFormat: string): Promise<string> {
+type FontCompressionOptions = {
+  cacheDir?: string;
+  compressImpl?: (input: Buffer) => Promise<Buffer>;
+};
+
+function defaultCacheDir(): string {
+  const root =
+    process.env.HYPERFRAMES_FONT_CACHE_DIR ??
+    (process.env.AWS_LAMBDA_FUNCTION_NAME
+      ? join(tmpdir(), "hyperframes", "fonts")
+      : join(homedir(), ".cache", "hyperframes", "fonts"));
+  return join(root, "local-compression-v1");
+}
+
+function cachedCompressionPath(input: Buffer, originalFormat: string, cacheDir: string): string {
+  const digest = createHash("sha256")
+    .update("hyperframes-local-font-compression-v1\0")
+    .update(originalFormat)
+    .update("\0")
+    .update(input)
+    .digest("hex");
+  return join(cacheDir, `${digest}.woff2`);
+}
+
+function readCachedCompression(path: string): Buffer | null {
+  try {
+    if (!existsSync(path)) return null;
+    const cached = readFileSync(path);
+    return cached.length > 0 ? cached : null;
+  } catch {
+    return null;
+  }
+}
+
+function cacheCompression(path: string, compressed: Buffer): void {
+  const tmpPath = `${path}.tmp-${process.pid}-${Date.now()}`;
+  try {
+    mkdirSync(dirname(path), { recursive: true });
+    writeFileSync(tmpPath, compressed, { flag: "wx", mode: 0o644 });
+    renameSync(tmpPath, path);
+  } catch {
+    // A concurrent process may have populated the cache, or the cache may be
+    // read-only. Compression still succeeded, so rendering can continue.
+  } finally {
+    try {
+      rmSync(tmpPath, { force: true });
+    } catch {
+      // Best-effort cleanup only.
+    }
+  }
+}
+
+export async function fontToDataUri(
+  input: Buffer,
+  originalFormat: string,
+  options: FontCompressionOptions = {},
+): Promise<string> {
   if (originalFormat === "woff2") {
     return `data:font/woff2;base64,${input.toString("base64")}`;
   }
   try {
-    const compressed = await compressToWoff2(input);
+    const cachePath = cachedCompressionPath(
+      input,
+      originalFormat,
+      options.cacheDir ?? defaultCacheDir(),
+    );
+    const cached = readCachedCompression(cachePath);
+    if (cached) return `data:font/woff2;base64,${cached.toString("base64")}`;
+
+    const compressed = await (options.compressImpl ?? compressToWoff2)(input);
+    cacheCompression(cachePath, compressed);
     return `data:font/woff2;base64,${compressed.toString("base64")}`;
   } catch {
     console.warn(