Оптимизация проверки каналов (#5)

- теперь проверяется только первый 1 Кб контента
- скорректирована проверка mpd-контента

app/checker/checker.go

@@ -217,7 +217,6 @@ func CheckChannels(pls playlist.Playlist) playlist.Playlist {
 
 			http.DefaultTransport.(*http.Transport).TLSClientConfig = &tls.Config{InsecureSkipVerify: true}
 			req, err := http.NewRequest("GET", tvChannel.URL, nil)
-			tvChannel.CheckedAt = time.Now().Unix()
 			if err != nil {
 				data := errorData{tvChannel: tvChannel, err: err}
 				chError <- data
@@ -226,7 +225,9 @@ func CheckChannels(pls playlist.Playlist) playlist.Playlist {
 
 			//TODO user-agent
 			req.Header.Set("User-Agent", "Mozilla/5.0 WINK/1.31.1 (AndroidTV/9) HlsWinkPlayer")
+			req.Header.Add("Range", "bytes=0-1023") // 1 Kb, but sometimes servers ignore it
 			resp, err := httpClient.Do(req)
+			tvChannel.CheckedAt = time.Now().Unix()
 			if err != nil {
 				data := errorData{tvChannel: tvChannel, err: err}
 				chError <- data
@@ -236,7 +237,8 @@ func CheckChannels(pls playlist.Playlist) playlist.Playlist {
 			tvChannel.Status = resp.StatusCode
 			tvChannel.IsOnline = tvChannel.Status < http.StatusBadRequest
 			tvChannel.ContentType = resp.Header.Get("Content-Type")
-			bodyBytes, _ := io.ReadAll(resp.Body)
+			chunk := io.LimitReader(resp.Body, 1024) // just for sure
+			bodyBytes, _ := io.ReadAll(chunk)
 			bodyString := string(bodyBytes)
 			_ = resp.Body.Close()
 			contentType := http.DetectContentType(bodyBytes)
@@ -246,7 +248,9 @@ func CheckChannels(pls playlist.Playlist) playlist.Playlist {
 
 			isContentCorrect := isContentBinary ||
 				strings.Contains(bodyString, "#EXTM3U") ||
-				strings.Contains(bodyString, "<SegmentTemplate")
+				strings.Contains(bodyString, "<MPD ") ||
+				strings.Contains(bodyString, "<SegmentTemplate ") ||
+				strings.Contains(bodyString, "<AdaptationSet ")
 
 			if tvChannel.Status >= http.StatusBadRequest || !isContentCorrect {
 				tvChannel.Error = bodyString
@@ -254,12 +258,6 @@ func CheckChannels(pls playlist.Playlist) playlist.Playlist {
 				return
 			}
 
-			if isContentBinary {
-				tvChannel.Content = "binary"
-			} else {
-				tvChannel.Content = bodyString
-			}
-
 			chOnline <- tvChannel
 			return
 		}(tvChannel)