extract mentions from status

internal/util/status.go

@@ -0,0 +1,73 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package util
+
+import (
+	"fmt"
+	"regexp"
+)
+
+// To play around with these regexes, see: https://regex101.com/r/2km2EK/1
+var (
+	hostnameRegexString = `(?:(?:[a-zA-Z]{1})|(?:[a-zA-Z]{1}[a-zA-Z]{1})|(?:[a-zA-Z]{1}[0-9]{1})|(?:[0-9]{1}[a-zA-Z]{1})|(?:[a-zA-Z0-9][a-zA-Z0-9-_]{1,61}[a-zA-Z0-9]))\.(?:[a-zA-Z]{2,6}|[a-zA-Z0-9-]{2,30}\.[a-zA-Z]{2,5}))`
+	mentionRegexString  = fmt.Sprintf(`(?: |^|\W)(@[a-zA-Z0-9_]+@%s(?: |\n)`, hostnameRegexString)
+	mentionRegex        = regexp.MustCompile(mentionRegexString)
+)
+
+// DeriveMentions takes a plaintext (ie., not html-formatted) status,
+// and applies a regex to it to return a deduplicated list of accounts
+// mentioned in that status.
+//
+// It will look for fully-qualified account names in the form "@user@example.org".
+// Mentions that are just in the form "@username" will not be detected.
+func DeriveMentions(status string) []string {
+	menchies := []string{}
+	for _, match := range mentionRegex.FindAllStringSubmatch(status, -1) {
+		menchies = append(menchies, match[1])
+	}
+	return Unique(menchies)
+}
+
+// Unique returns a deduplicated version of a given string slice.
+func Unique(s []string) []string {
+    keys := make(map[string]bool)
+    list := []string{}
+    for _, entry := range s {
+        if _, value := keys[entry]; !value {
+            keys[entry] = true
+            list = append(list, entry)
+        }
+    }
+    return list
+}
+
+// HTMLFormat takes a plaintext formatted status string, and converts it into
+// a nice HTML-formatted string.
+//
+// This includes:
+//
+// - Replacing line-breaks with <p>
+//
+// - Replacing URLs with hrefs.
+//
+// - Replacing mentions with links to that account's URL as stored in the database.
+func HTMLFormat(status string) string {
+	// TODO: write proper HTML formatting logic for a status
+	return status
+}