From d078e43325eb0b5c275ca3556fcbf2209be8dd8c Mon Sep 17 00:00:00 2001
From: Dan Fabulich <dan@fabulich.com>
Date: Thu, 23 Jan 2025 00:13:46 -0800
Subject: [PATCH] Add support for `engine_files` `lastmod` metadata

Apropos https://github.com/curiousdannii/parchment/issues/177
---
 src/common/file/browser.ts   | 4 ++++
 src/common/file/interface.ts | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/common/file/browser.ts b/src/common/file/browser.ts
index 529f7a3..f03ddbb 100644
--- a/src/common/file/browser.ts
+++ b/src/common/file/browser.ts
@@ -55,6 +55,10 @@ async function fetch_resource_inner(options: DownloadOptions, path: string, prog
     let url: URL | string
     try {
         url = new URL(path, lib_path)
+        const lastmod = options.engine_files?.[path]
+        if (lastmod) {
+            url.searchParams.set('lastmod', lastmod)
+        }
     }
     catch {
         url = lib_path + path
diff --git a/src/common/file/interface.ts b/src/common/file/interface.ts
index ea49e68..464e344 100644
--- a/src/common/file/interface.ts
+++ b/src/common/file/interface.ts
@@ -25,4 +25,5 @@ export interface DownloadOptions {
     /** Use the file proxy; if disabled may mean that some files can't be loaded */
     // We could just say to exclude proxy_url instead?
     use_proxy?: boolean | number,
-}
\ No newline at end of file
+    engine_files?: {[key: string]: string},
+}