From 2615a8f217796caa3a0572c25574f63055247edf Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Thu, 24 Feb 2022 01:01:24 -0500
Subject: nvdmirror/sync.go: compact source, improve documentation

---
 nvdmirror/sync.go | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/nvdmirror/sync.go b/nvdmirror/sync.go
index 8cdd4c7..dcbf6a9 100644
--- a/nvdmirror/sync.go
+++ b/nvdmirror/sync.go
@@ -1,7 +1,10 @@
 package nvdmirror
 
-// Sync to destination directory based on given sync configuration and
-// cache.  Returns an array of file names which have been updated in the
+//
+// Sync NVD data files to destination directory based on given sync
+// configuration and cache.
+//
+// Returns an array of file names which have been updated in the
 // destination directory.
 //
 // This function does the following:
@@ -16,24 +19,25 @@ package nvdmirror
 // 3. Fetch the contents of the changed CVE feeds, CPE match files, and
 //    the CPE dictionary.
 //
-// All HTTP requests are made with the following request headers:
+// All HTTP requests are sent with the following headers:
+//
+// * if-modified-since: The last-modified header from the previous
+//   successful response, if it was set.
 //
-// * if-modified-since (if the URL was queried previously and the
-//   previous successful response had a "last-modified" header).
-// * if-none-match (if the URL was queried previously and the
-//   previous successful response had an "etag" header).
-// * user-agent
+// * if-none-match: The etag header from the last successful response,
+//   if it was set.
+//
+// * user-agent: User agent from config, or the default user agent if
+//   the config value is unspecified.
 //
 func Sync(config SyncConfig, cache Cache, dstDir string) []string {
   // build sync context
   ctx := newSyncContext(config, cache, dstDir)
 
-  // fetch updated meta files
-  checks := ctx.fetchMetas()
-
-  // get syncable URLs
-  urls := append(ctx.checkMetas(checks), config.GetCpeDictUrl())
-
-  // sync urls and return changed files
-  return ctx.syncUrls(urls)
+  // fetch meta files, check for updates, append cpe dictionary URL,
+  // fetch updated files, and then return a list of changed files
+  return ctx.syncUrls(append(
+    ctx.checkMetas(ctx.fetchMetas()),
+    config.GetCpeDictUrl(),
+  ))
 }
-- 
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