From 31d3e55489653ca1ec28e2a09f20dc9db4dc8f04 Mon Sep 17 00:00:00 2001
From: Evgeniy Kulikov <kim@nspcc.ru>
Date: Fri, 27 Nov 2020 15:33:31 +0300
Subject: [PATCH] Add content detector

Signed-off-by: Evgeniy Kulikov <kim@nspcc.ru>
---
 api/layer/detector.go | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 api/layer/detector.go

diff --git a/api/layer/detector.go b/api/layer/detector.go
new file mode 100644
index 00000000..3a9b7d85
--- /dev/null
+++ b/api/layer/detector.go
@@ -0,0 +1,26 @@
+package layer
+
+import (
+	"io"
+	"net/http"
+	"sync"
+)
+
+type detector struct {
+	io.Reader
+	sync.Once
+
+	contentType string
+}
+
+func newDetector(r io.Reader) *detector {
+	return &detector{Reader: r}
+}
+
+func (d *detector) Read(data []byte) (int, error) {
+	d.Do(func() {
+		d.contentType = http.DetectContentType(data)
+	})
+
+	return d.Reader.Read(data)
+}