[performance] add statusfilter cache to cache calculated status filtering results (#4303)

this adds another 'filter' type cache, similar to the visibility and mute caches, to cache the results of status filtering checks. for the moment this keeps all the check calls themselves within the frontend typeconversion code, but i may move this out of the typeconverter in a future PR (also removing the ErrHideStatus means of propagating a hidden status).

also tweaks some of the cache invalidation hooks to not make unnecessary calls.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4303
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/internal/filter/status/text.go b/internal/filter/status/text.go
new file mode 100644
index 000000000..347e1193c
--- /dev/null
+++ b/internal/filter/status/text.go
@@ -0,0 +1,80 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// 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 status
+
+import (
+	"code.superseriousbusiness.org/gotosocial/internal/gtsmodel"
+	"code.superseriousbusiness.org/gotosocial/internal/text"
+)
+
+// getFilterableFields returns text fields from
+// a status that we might want to filter on:
+//
+//   - content warning
+//   - content (converted to plaintext from HTML)
+//   - media descriptions
+//   - poll options
+//
+// Each field should be filtered separately. This avoids
+// scenarios where false-positive multiple-word matches
+// can be made by matching the last word of one field
+// combined with the first word of the next field together.
+func getFilterableFields(status *gtsmodel.Status) []string {
+
+	// Estimate expected no of status fields.
+	fieldCount := 2 + len(status.Attachments)
+	if status.Poll != nil {
+		fieldCount += len(status.Poll.Options)
+	}
+	fields := make([]string, 0, fieldCount)
+
+	// Append content warning / title.
+	if status.ContentWarning != "" {
+		fields = append(fields, status.ContentWarning)
+	}
+
+	// Status content. Though we have raw text
+	// available for statuses created on our
+	// instance, use the plaintext version to
+	// remove markdown-formatting characters
+	// and ensure more consistent filtering.
+	if status.Content != "" {
+		text := text.ParseHTMLToPlain(status.Content)
+		if text != "" {
+			fields = append(fields, text)
+		}
+	}
+
+	// Media descriptions, only where they are set.
+	for _, attachment := range status.Attachments {
+		if attachment.Description != "" {
+			fields = append(fields, attachment.Description)
+		}
+	}
+
+	// Non-empty poll options.
+	if status.Poll != nil {
+		for _, opt := range status.Poll.Options {
+			if opt != "" {
+				fields = append(fields, opt)
+			}
+		}
+	}
+
+	return fields
+}