From 036b879c53b182d8220b45ca19e2eb37f8c33260 Mon Sep 17 00:00:00 2001
From: Oscar Otero <oom@oscarotero.com>
Date: Sat, 26 Oct 2024 12:17:19 +0200
Subject: [PATCH] precompress middleware. close #664

---
 CHANGELOG.md               |  4 ++-
 middlewares/precompress.ts | 69 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 middlewares/precompress.ts

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48081997..918113a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ Go to the `v1` branch to see the changelog of Lume 1.
 - New plugin: `google_fonts` to download and self-host automatically fonts from Google Fonts.
 - New plugin: `brotli` to compress files. [#681]
 - New plugin: `gzip` to compress files. [#680]
+- New `precompress` middleware, to serve precompressed files. [#664]
 
 ### Fixed
 - Nav plugin: Breadcrumb with urls with CJK characters.
@@ -558,6 +559,7 @@ Go to the `v1` branch to see the changelog of Lume 1.
 [#652]: https://github.com/lumeland/lume/issues/652
 [#655]: https://github.com/lumeland/lume/issues/655
 [#662]: https://github.com/lumeland/lume/issues/662
+[#664]: https://github.com/lumeland/lume/issues/664
 [#667]: https://github.com/lumeland/lume/issues/667
 [#668]: https://github.com/lumeland/lume/issues/668
 [#671]: https://github.com/lumeland/lume/issues/671
@@ -566,8 +568,8 @@ Go to the `v1` branch to see the changelog of Lume 1.
 [#677]: https://github.com/lumeland/lume/issues/677
 [#678]: https://github.com/lumeland/lume/issues/678
 [#679]: https://github.com/lumeland/lume/issues/679
-[#681]: https://github.com/lumeland/lume/issues/681
 [#680]: https://github.com/lumeland/lume/issues/680
+[#681]: https://github.com/lumeland/lume/issues/681
 
 [Unreleased]: https://github.com/lumeland/lume/compare/v2.3.3...HEAD
 [2.3.3]: https://github.com/lumeland/lume/compare/v2.3.2...v2.3.3
diff --git a/middlewares/precompress.ts b/middlewares/precompress.ts
new file mode 100644
index 00000000..50bdc1c7
--- /dev/null
+++ b/middlewares/precompress.ts
@@ -0,0 +1,69 @@
+import { merge } from "../core/utils/object.ts";
+import { contentType } from "../deps/media_types.ts";
+import { extname } from "../deps/path.ts";
+
+import type { Middleware, RequestHandler } from "../core/server.ts";
+
+/** The options to configure the middleware server */
+export interface Options {
+  encodings: Record<string, string>;
+}
+
+export const defaults: Options = {
+  encodings: {
+    br: ".br",
+    gzip: ".gz",
+  },
+};
+
+export function preCompress(userOptions?: Options): Middleware {
+  const options = merge(defaults, userOptions);
+
+  return async function (
+    request: Request,
+    next: RequestHandler,
+  ): Promise<Response> {
+    const accepted = new Set(
+      request.headers.get("Accept-Encoding")
+        ?.split(",")
+        .map((encoding) => encoding.split(";").shift()?.trim())
+        .filter((encoding) => encoding),
+    );
+
+    if (!accepted.size) {
+      return next(request);
+    }
+
+    for (const [encoding, ext] of Object.entries(options.encodings)) {
+      if (!accepted.has(encoding)) {
+        continue;
+      }
+
+      const newUrl = new URL(request.url);
+      const initialExtension = newUrl.pathname.endsWith("/")
+        ? ".html"
+        : extname(newUrl.pathname);
+      newUrl.pathname += newUrl.pathname.endsWith("/")
+        ? `index.html${ext}`
+        : ext;
+      const compressedRequest = new Request(newUrl, request);
+      const response = await next(compressedRequest);
+
+      if (response.status >= 400) {
+        continue;
+      }
+
+      response.headers.set(
+        "Content-Type",
+        contentType(initialExtension) || "application/octet-stream",
+      );
+      response.headers.set("Content-Encoding", encoding);
+      response.headers.append("Vary", "Accept-Encoding");
+      return response;
+    }
+
+    return next(request);
+  };
+}
+
+export default preCompress;