take proper RSS/Atom Content-Type headers into account

.gitignore

@@ -16,3 +16,4 @@ go-jamming
 vangen
 
 *.sublime-workspace
+.idea/*

.idea/go-jamming.iml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <module type="WEB_MODULE" version="4">
+  <component name="Go" enabled="true" />
   <component name="NewModuleRootManager">
     <content url="file://$MODULE_DIR$" />
     <orderEntry type="inheritedJdk" />

app/webmention/send/discoverer.go

@@ -4,6 +4,7 @@ import (
 	"brainbaking.com/go-jamming/rest"
 	"fmt"
 	"github.com/rs/zerolog/log"
+	"net/http"
 	"net/url"
 	"regexp"
 	"strings"
@@ -25,14 +26,32 @@ var (
 		"feed",
 		"feed/index.xml",
 	}
+
+	possibleContentTypes = []string{
+		"application/rss+xml",
+		"application/atom+xml",
+		"application/xml",
+		"text/xml",
+		"application/rdf+xml",
+	}
 )
 
+func isContentTypeFeedCompatible(header http.Header) bool {
+	cType := header.Get("Content-Type")
+	for _, possibleType := range possibleContentTypes {
+		if strings.Contains(cType, possibleType) {
+			return true
+		}
+	}
+	return false
+}
+
 func (sndr *Sender) discoverRssFeed(domain string) (string, error) {
 	for _, endpt := range possibleFeedEndpoints {
 		feedUrl := fmt.Sprintf("https://%s/%s", domain, endpt)
 		resp, err := sndr.RestClient.Head(feedUrl)
 
-		if err != nil || !rest.IsStatusOk(resp) || resp.Header.Get("Content-Type") != "text/xml" {
+		if err != nil || !rest.IsStatusOk(resp) || !isContentTypeFeedCompatible(resp.Header) {
 			continue
 		}
 

app/webmention/send/discoverer_test.go

@@ -10,6 +10,17 @@ import (
 	"testing"
 )
 
+func TestDiscoverRssFeedE2EBrainbaking(t *testing.T) {
+	var sender = &Sender{
+		RestClient: &rest.HttpClient{},
+	}
+
+	link, err := sender.discoverRssFeed("brainbaking.com")
+	expectedUrl := "https://brainbaking.com/index.xml"
+	assert.Nil(t, err)
+	assert.Truef(t, strings.HasPrefix(link, expectedUrl), "should start with %s, but was %s", expectedUrl, link)
+}
+
 func TestDiscoverMentionEndpointE2EWithRedirect(t *testing.T) {
 	t.Skip("Skipping TestDiscoverE2EWithRedirect, webmention.rocks is slow.")
 	var sender = &Sender{