Add EventSource support (#11235)

If the browser supports EventSource switch to use this instead of
polling notifications.

Signed-off-by: Andrew Thornton art27@cantab.net

modules/eventsource/event_test.go

@@ -0,0 +1,54 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package eventsource
+
+import (
+	"bytes"
+	"testing"
+)
+
+func Test_wrapNewlines(t *testing.T) {
+	tests := []struct {
+		name   string
+		prefix string
+		value  string
+		output string
+	}{
+		{
+			"check no new lines",
+			"prefix: ",
+			"value",
+			"prefix: value\n",
+		},
+		{
+			"check simple newline",
+			"prefix: ",
+			"value1\nvalue2",
+			"prefix: value1\nprefix: value2\n",
+		},
+		{
+			"check pathological newlines",
+			"p: ",
+			"\n1\n\n2\n3\n",
+			"p: \np: 1\np: \np: 2\np: 3\np: \n",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			w := &bytes.Buffer{}
+			gotSum, err := wrapNewlines(w, []byte(tt.prefix), []byte(tt.value))
+			if err != nil {
+				t.Errorf("wrapNewlines() error = %v", err)
+				return
+			}
+			if gotSum != int64(len(tt.output)) {
+				t.Errorf("wrapNewlines() = %v, want %v", gotSum, int64(len(tt.output)))
+			}
+			if gotW := w.String(); gotW != tt.output {
+				t.Errorf("wrapNewlines() = %v, want %v", gotW, tt.output)
+			}
+		})
+	}
+}