add updateHTTPPage function

fetch/http.go

@@ -76,24 +76,35 @@ func newHTTPFeed(remoteURL *url.URL, title string) (*core.Feed, error) {
 
 // newHTTPPage will create a new core.Page given an http url
 func newHTTPPage(remoteURL *url.URL, title string) (*core.Page, error) {
-	resp, err := fetchHTTP(remoteURL)
+	var page core.Page
+	page.Title = title
+	page.Link = remoteURL
+
+	err := updateHTTPPage(&page)
 	if err != nil {
 		return nil, err
 	}
+	return &page, nil
+}
+
+// updateHTTPPage will check an existing core.Page for changes
+func updateHTTPPage(p *core.Page) error {
+	resp, err := fetchHTTP(p.Link)
+	if err != nil {
+		return err
+	}
 	defer resp.Body.Close()
 
 	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB
 
-	var page core.Page
-	page.Title = title
-	page.Link = remoteURL
-	page.Updated = time.Now()
-
 	h := sha256.New()
 	if _, err := io.Copy(h, reader); err != nil {
-		return nil, err
+		return err
 	}
-	page.Hash = fmt.Sprintf("%x", h.Sum(nil))
-
-	return &page, nil
+	newHash := fmt.Sprintf("%x", h.Sum(nil))
+	if newHash != p.Hash {
+		p.Hash = newHash
+		p.Updated = time.Now()
+	}
+	return nil
 }