mentionutil: Add a mentions extractor

mentionnutil/extractor.go

@@ -0,0 +1,30 @@
+package mentionnutil
+
+import (
+	"regexp"
+	"strings"
+
+	"github.com/upfluence/pkg/slices"
+	"github.com/upfluence/pkg/stringutil"
+)
+
+var mentionRegex = regexp.MustCompile(`\B@[\w\.]+[\w]+`)
+
+func ExtractMentions(s string) []string {
+	mentions := slices.Map(
+		mentionRegex.FindAllString(s, -1),
+		func(v string) string {
+			return strings.TrimPrefix(v, "@")
+		},
+	)
+
+	if len(mentions) == 0 {
+		return nil
+	}
+
+	var set stringutil.Set
+
+	set.Add(mentions...)
+
+	return set.Strings()
+}

mentionnutil/extractor_test.go

@@ -0,0 +1,37 @@
+package mentionnutil
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExtractMentions(t *testing.T) {
+	for _, tt := range []struct {
+		name   string
+		input  string
+		expect []string
+	}{
+		{
+			name: "empty",
+		},
+		{
+			name:  "no mentions",
+			input: "foo bar",
+		},
+		{
+			name:   "multi mentions",
+			input:  "foo bar @buz. @taz_ @dot.name hello @buz @with_1",
+			expect: []string{"buz", "taz_", "dot.name", "with_1"},
+		},
+		{
+			name:   "youtube url",
+			input:  "foo bar @buz. https://www.youtube.com/@SalonViking test",
+			expect: []string{"buz", "SalonViking"},
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.ElementsMatch(t, tt.expect, ExtractMentions(tt.input))
+		})
+	}
+}