First working version

[nsscash/nsscash.git] / fetch.go

diff --git a/fetch.go b/fetch.go
new file mode 100644 (file)
index 0000000..9834f3e
--- /dev/null
+++ b/fetch.go
@@ -0,0 +1,60 @@
+// Download files via HTTP with support for If-Modified-Since
+
+// Copyright (C) 2019  Simon Ruderich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package main
+
+import (
+       "io/ioutil"
+       "net/http"
+       "time"
+)
+
+// Global variable to permit reuse of connections (keep-alive)
+var client *http.Client
+
+func init() {
+       client = &http.Client{}
+}
+
+func fetchIfModified(url string, lastModified *time.Time) (int, []byte, error) {
+       req, err := http.NewRequest("GET", url, nil)
+       if err != nil {
+               return 0, nil, err
+       }
+       if !lastModified.IsZero() {
+               req.Header.Add("If-Modified-Since",
+                       lastModified.Format(http.TimeFormat))
+       }
+
+       resp, err := client.Do(req)
+       if err != nil {
+               return 0, nil, err
+       }
+       defer resp.Body.Close()
+
+       body, err := ioutil.ReadAll(resp.Body)
+       if err != nil {
+               return 0, nil, err
+       }
+
+       modified, err := http.ParseTime(resp.Header.Get("Last-Modified"))
+       if err == nil {
+               *lastModified = modified
+       }
+
+       return resp.StatusCode, body, nil
+}