[chore] Text formatting overhaul (#1406)

* Implement goldmark debug print for hashtags and mentions

* Minify HTML in FromPlain

* Convert plaintext status parser to goldmark

* Move mention/tag/emoji finding logic into formatter

* Combine mention and hashtag boundary characters

* Normalize unicode when rendering hashtags

internal/text/replace.go

@@ -0,0 +1,141 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2023 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 (
+	"errors"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
+	"golang.org/x/text/unicode/norm"
+	"strings"
+)
+
+const (
+	maximumHashtagLength = 30
+)
+
+// given a mention or a hashtag string, the methods in this file will attempt to parse it,
+// add it to the database, and render it as HTML. If any of these steps fails, the method
+// will just return the original string and log an error.
+
+// replaceMention takes a string in the form @username@domain.com or @localusername
+func (r *customRenderer) replaceMention(text string) string {
+	menchie, err := r.parseMention(r.ctx, text, r.accountID, r.statusID)
+	if err != nil {
+		log.Errorf("error parsing mention %s from status: %s", text, err)
+		return text
+	}
+
+	if r.statusID != "" {
+		if err := r.f.db.Put(r.ctx, menchie); err != nil {
+			log.Errorf("error putting mention in db: %s", err)
+			return text
+		}
+	}
+
+	// only append if it's not been listed yet
+	listed := false
+	for _, m := range r.result.Mentions {
+		if menchie.ID == m.ID {
+			listed = true
+			break
+		}
+	}
+	if !listed {
+		r.result.Mentions = append(r.result.Mentions, menchie)
+	}
+
+	// make sure we have an account attached to this mention
+	if menchie.TargetAccount == nil {
+		a, err := r.f.db.GetAccountByID(r.ctx, menchie.TargetAccountID)
+		if err != nil {
+			log.Errorf("error getting account with id %s from the db: %s", menchie.TargetAccountID, err)
+			return text
+		}
+		menchie.TargetAccount = a
+	}
+
+	// The mention's target is our target
+	targetAccount := menchie.TargetAccount
+
+	var b strings.Builder
+
+	// replace the mention with the formatted mention content
+	// <span class="h-card"><a href="targetAccount.URL" class="u-url mention">@<span>targetAccount.Username</span></a></span>
+	b.WriteString(`<span class="h-card"><a href="`)
+	b.WriteString(targetAccount.URL)
+	b.WriteString(`" class="u-url mention">@<span>`)
+	b.WriteString(targetAccount.Username)
+	b.WriteString(`</span></a></span>`)
+	return b.String()
+}
+
+// replaceMention takes a string in the form #HashedTag, and will normalize it before
+// adding it to the db and turning it into HTML.
+func (r *customRenderer) replaceHashtag(text string) string {
+	// this normalization is specifically to avoid cases where visually-identical
+	// hashtags are stored with different unicode representations (e.g. with combining
+	// diacritics). It allows a tasteful number of combining diacritics to be used,
+	// as long as they can be combined with parent characters to form regular letter
+	// symbols.
+	normalized := norm.NFC.String(text[1:])
+
+	for i, r := range normalized {
+		if i >= maximumHashtagLength || !util.IsPermittedInHashtag(r) {
+			return text
+		}
+	}
+
+	tag, err := r.f.db.TagStringToTag(r.ctx, normalized, r.accountID)
+	if err != nil {
+		log.Errorf("error generating hashtags from status: %s", err)
+		return text
+	}
+
+	// only append if it's not been listed yet
+	listed := false
+	for _, t := range r.result.Tags {
+		if tag.ID == t.ID {
+			listed = true
+			break
+		}
+	}
+	if !listed {
+		err = r.f.db.Put(r.ctx, tag)
+		if err != nil {
+			if !errors.Is(err, db.ErrAlreadyExists) {
+				log.Errorf("error putting tags in db: %s", err)
+				return text
+			}
+		}
+		r.result.Tags = append(r.result.Tags, tag)
+	}
+
+	var b strings.Builder
+	// replace the #tag with the formatted tag content
+	// `<a href="tag.URL" class="mention hashtag" rel="tag">#<span>tagAsEntered</span></a>
+	b.WriteString(`<a href="`)
+	b.WriteString(tag.URL)
+	b.WriteString(`" class="mention hashtag" rel="tag">#<span>`)
+	b.WriteString(normalized)
+	b.WriteString(`</span></a>`)
+
+	return b.String()
+}