From 9323ccdfd14e7885b42dab9bac2b789308ac4566 Mon Sep 17 00:00:00 2001
From: Hans-Christoph Steiner <hans@eds.org>
Date: Mon, 18 Feb 2019 22:08:59 +0100
Subject: [PATCH] add HTTP Last-Modified header to nearby/swap webserver

This should support the new cache check scheme when using swap repos.
---
 .../java/org/fdroid/fdroid/net/LocalHTTPD.java    | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/app/src/full/java/org/fdroid/fdroid/net/LocalHTTPD.java b/app/src/full/java/org/fdroid/fdroid/net/LocalHTTPD.java
index b7a522261..8315909ee 100644
--- a/app/src/full/java/org/fdroid/fdroid/net/LocalHTTPD.java
+++ b/app/src/full/java/org/fdroid/fdroid/net/LocalHTTPD.java
@@ -50,13 +50,18 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Date;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.StringTokenizer;
+import java.util.TimeZone;
 
 /**
  * A HTTP server for serving the files that are being swapped via WiFi, etc.
@@ -79,6 +84,14 @@ public class LocalHTTPD extends NanoHTTPD {
 
     protected List<File> rootDirs;
 
+    // Date format specified by RFC 7231 section 7.1.1.1.
+    private static final DateFormat RFC_1123 = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss 'GMT'", Locale.US);
+
+    static {
+        RFC_1123.setLenient(false);
+        RFC_1123.setTimeZone(TimeZone.getTimeZone("GMT"));
+    }
+
     /**
      * Configure and start the webserver.  This also sets the MIME Types only
      * for files that should be downloadable when a browser is used to display
@@ -430,6 +443,7 @@ public class LocalHTTPD extends NanoHTTPD {
                     res.addHeader("Content-Length", "" + newLen);
                     res.addHeader("Content-Range", "bytes " + startFrom + "-" + endAt + "/" + fileLen);
                     res.addHeader("ETag", etag);
+                    res.addHeader("Last-Modified", RFC_1123.format(new Date(file.lastModified())));
                 }
             } else {
 
@@ -457,6 +471,7 @@ public class LocalHTTPD extends NanoHTTPD {
                     res = newFixedFileResponse(file, mime);
                     res.addHeader("Content-Length", "" + fileLen);
                     res.addHeader("ETag", etag);
+                    res.addHeader("Last-Modified", RFC_1123.format(new Date(file.lastModified())));
                 }
             }
         } catch (IOException ioe) {