From e6c5ff85cbb003fa06e19dc98ff8f2c2186b4314 Mon Sep 17 00:00:00 2001
From: Brian Woods <me@brian.biz>
Date: Sun, 31 Mar 2019 08:17:09 -0700
Subject: [PATCH] Adds gzip to json responses

---
 commons/services/http_service.go |  2 +-
 commons/utils/gzip.go            | 50 ++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 commons/utils/gzip.go

diff --git a/commons/services/http_service.go b/commons/services/http_service.go
index dbd4643..51dc14b 100644
--- a/commons/services/http_service.go
+++ b/commons/services/http_service.go
@@ -79,7 +79,7 @@ func (this *HttpService) Go() {
 		})
 		handler := cors.Handler(this.router)
 
-		err := http.ListenAndServe(listen, handler)
+		err := http.ListenAndServe(listen, utils.Gzip(handler))
 
 		// QUESTION: this line is never reached
 		utils.Error("unable to listen/serve HTTP [error=" + err.Error() + "]")
diff --git a/commons/utils/gzip.go b/commons/utils/gzip.go
new file mode 100644
index 0000000..77a8b13
--- /dev/null
+++ b/commons/utils/gzip.go
@@ -0,0 +1,50 @@
+package utils
+
+import (
+	"compress/gzip"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"strings"
+	"sync"
+)
+
+var gzPool = sync.Pool{
+	New: func() interface{} {
+		w := gzip.NewWriter(ioutil.Discard)
+		return w
+	},
+}
+
+type gzipResponseWriter struct {
+	io.Writer
+	http.ResponseWriter
+}
+
+func (w *gzipResponseWriter) WriteHeader(status int) {
+	w.Header().Del("Content-Length")
+	w.ResponseWriter.WriteHeader(status)
+}
+
+func (w *gzipResponseWriter) Write(b []byte) (int, error) {
+	return w.Writer.Write(b)
+}
+
+func Gzip(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+			next.ServeHTTP(w, r)
+			return
+		}
+
+		w.Header().Set("Content-Encoding", "gzip")
+
+		gz := gzPool.Get().(*gzip.Writer)
+		defer gzPool.Put(gz)
+
+		gz.Reset(w)
+		defer gz.Close()
+
+		next.ServeHTTP(&gzipResponseWriter{ResponseWriter: w, Writer: gz}, r)
+	})
+}