use consistent cache control

src/serve_font.js

@@ -42,6 +42,7 @@ export async function serve_font(options, allowedFonts, programOpts) {
     if (sanitizedFontStack.length == 0) {
       return res.status(400).send('Invalid font stack format');
     }
+
     fontstack = decodeURI(sanitizedFontStack);
     let range = req.params.range;
     const rangeMatch = range?.match(/^[\d-]+$/);
@@ -54,6 +55,16 @@ export async function serve_font(options, allowedFonts, programOpts) {
       );
     }
 
+    const modifiedSince = req.get('if-modified-since');
+    const cc = req.get('cache-control');
+    if (modifiedSince && (!cc || cc.indexOf('no-cache') === -1)) {
+      const lastDate = new Date(lastModified).getTime();
+      const modDate = new Date(modifiedSince).getTime();
+      if (lastDate === modDate) {
+        return res.sendStatus(304);
+      }
+    }
+
     try {
       const concatenated = await getFontsPbf(
         options.serveAllFonts ? null : allowedFonts,

src/serve_rendered.js

@@ -665,7 +665,9 @@ async function handleTileRequest(
   const modifiedSince = req.get('if-modified-since');
   const cc = req.get('cache-control');
   if (modifiedSince && (!cc || cc.indexOf('no-cache') === -1)) {
-    if (new Date(item.lastModified) <= new Date(modifiedSince)) {
+    const lastDate = new Date(item.lastModified).getTime();
+    const modDate = new Date(modifiedSince).getTime();
+    if (lastDate === modDate) {
       return res.sendStatus(304);
     }
   }

src/serve_style.js

@@ -143,7 +143,9 @@ export const serve_style = {
       const modifiedSince = req.get('if-modified-since');
       const cc = req.get('cache-control');
       if (modifiedSince && (!cc || cc.indexOf('no-cache') === -1)) {
-        if (new Date(item.lastModified) <= new Date(modifiedSince)) {
+        const lastDate = new Date(item.lastModified).getTime();
+        const modDate = new Date(modifiedSince).getTime();
+        if (lastDate === modDate) {
           return res.sendStatus(304);
         }
       }
@@ -327,6 +329,7 @@ export const serve_style = {
       spritePaths,
       publicUrl,
       name: styleJSON.name,
+      lastModified: new Date().toUTCString(),
     };
 
     return true;