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gotosocial/internal/text/link.go

116 lines
3.3 KiB
Go

/*
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 text
import (
"fmt"
"net/url"
"mvdan.cc/xurls/v2"
)
// schemes is the regex for schemes we accept when looking for links.
// Basically, we accept https or http.
var schemes = `(((http|https))://)`
// FindLinks parses the given string looking for recognizable URLs (including scheme).
// It returns a list of those URLs, without changing the string, or an error if something goes wrong.
// If no URLs are found within the given string, an empty slice and nil will be returned.
func FindLinks(in string) ([]*url.URL, error) {
rxStrict, err := xurls.StrictMatchingScheme(schemes)
if err != nil {
return nil, err
}
urls := []*url.URL{}
// bail already if we don't find anything
found := rxStrict.FindAllString(in, -1)
if len(found) == 0 {
return urls, nil
}
// for each string we find, we want to parse it into a URL if we can
// if we fail to parse it, just ignore this match and continue
for _, f := range found {
u, err := url.Parse(f)
if err != nil {
continue
}
urls = append(urls, u)
}
// deduplicate the URLs
urlsDeduped := []*url.URL{}
for _, u := range urls {
if !contains(urlsDeduped, u) {
urlsDeduped = append(urlsDeduped, u)
}
}
return urlsDeduped, nil
}
// contains checks if the given url is already within a slice of URLs
func contains(urls []*url.URL, url *url.URL) bool {
for _, u := range urls {
if u.String() == url.String() {
return true
}
}
return false
}
// ReplaceLinks replaces all detected links in a piece of text with their HTML (href) equivalents.
// Note: because Go doesn't allow negative lookbehinds in regex, it's possible that an already-formatted
// href will end up double-formatted, if the text you pass here contains one or more hrefs already.
// To avoid this, you should sanitize any HTML out of text before you pass it into this function.
func (f *formatter) ReplaceLinks(in string) string {
rxStrict, err := xurls.StrictMatchingScheme(schemes)
if err != nil {
panic(err)
}
replaced := rxStrict.ReplaceAllStringFunc(in, func(urlString string) string {
thisURL, err := url.Parse(urlString)
if err != nil {
return urlString // we can't parse it as a URL so don't replace it
}
shortString := thisURL.Hostname()
if thisURL.Path != "" {
shortString = shortString + thisURL.Path
}
if thisURL.Fragment != "" {
shortString = shortString + "#" + thisURL.Fragment
}
if thisURL.RawQuery != "" {
shortString = shortString + "?" + thisURL.RawQuery
}
replacement := fmt.Sprintf(`<a href="%s" rel="noopener">%s</a>`, urlString, shortString)
return replacement
})
return replaced
}