[bugfix] Use better plaintext representation of status for filtering (#3301)

* [bugfix] Use better plaintext representation of status for filtering

* add new deps to readme

* lint

* update tests

* update regexes

* address review comments

* remove now unused xxhash

* whoops, wrong logger

* Merge branch 'main' into status_filtering_bugfix

* put cache in caches struct

* pain

6 files changed, 205 insertions, 61 deletions

diff --git a/internal/cache/cache.go b/internal/cache/cache.go
index 5554445b2..8291dec5a 100644
--- a/internal/cache/cache.go
+++ b/internal/cache/cache.go
@@ -47,6 +47,11 @@ type Caches struct {
 	// Webfinger provides access to the webfinger URL cache.
 	Webfinger *ttl.Cache[string, string] // TTL=24hr, sweep=5min
 
+	// TTL cache of statuses -> filterable text fields.
+	// To ensure up-to-date fields, cache is keyed as:
+	// `[status.ID][status.UpdatedAt.Unix()]`
+	StatusesFilterableFields *ttl.Cache[string, []string]
+
 	// prevent pass-by-value.
 	_ nocopy
 }
@@ -109,6 +114,7 @@ func (c *Caches) Init() {
 	c.initUserMuteIDs()
 	c.initWebfinger()
 	c.initVisibility()
+	c.initStatusesFilterableFields()
 }
 
 // Start will start any caches that require a background
@@ -119,6 +125,10 @@ func (c *Caches) Start() {
 	tryUntil("starting webfinger cache", 5, func() bool {
 		return c.Webfinger.Start(5 * time.Minute)
 	})
+
+	tryUntil("starting statusesFilterableFields cache", 5, func() bool {
+		return c.StatusesFilterableFields.Start(5 * time.Minute)
+	})
 }
 
 // Stop will stop any caches that require a background
@@ -127,6 +137,7 @@ func (c *Caches) Stop() {
 	log.Infof(nil, "stop: %p", c)
 
 	tryUntil("stopping webfinger cache", 5, c.Webfinger.Stop)
+	tryUntil("stopping statusesFilterableFields cache", 5, c.StatusesFilterableFields.Stop)
 }
 
 // Sweep will sweep all the available caches to ensure none
@@ -204,3 +215,12 @@ func (c *Caches) initWebfinger() {
 		24*time.Hour,
 	)
 }
+
+func (c *Caches) initStatusesFilterableFields() {
+	c.StatusesFilterableFields = new(ttl.Cache[string, []string])
+	c.StatusesFilterableFields.Init(
+		0,
+		512,
+		1*time.Hour,
+	)
+}
diff --git a/internal/gtsmodel/filter.go b/internal/gtsmodel/filter.go
index e670e6fc0..95047a44f 100644
--- a/internal/gtsmodel/filter.go
+++ b/internal/gtsmodel/filter.go
@@ -20,6 +20,8 @@ package gtsmodel
 import (
 	"regexp"
 	"time"
+
+	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
 
 // Filter stores a filter created by a local account.
@@ -61,14 +63,23 @@ type FilterKeyword struct {
 
 // Compile will compile this FilterKeyword as a prepared regular expression.
 func (k *FilterKeyword) Compile() (err error) {
-	var wordBreak string
-	if k.WholeWord != nil && *k.WholeWord {
-		wordBreak = `\b`
+	var (
+		wordBreakStart string
+		wordBreakEnd   string
+	)
+
+	if util.PtrOrZero(k.WholeWord) {
+		// Either word boundary or
+		// whitespace or start of line.
+		wordBreakStart = `(?:\b|\s|^)`
+		// Either word boundary or
+		// whitespace or end of line.
+		wordBreakEnd = `(?:\b|\s|$)`
 	}
 
 	// Compile keyword filter regexp.
 	quoted := regexp.QuoteMeta(k.Keyword)
-	k.Regexp, err = regexp.Compile(`(?i)` + wordBreak + quoted + wordBreak)
+	k.Regexp, err = regexp.Compile(`(?i)` + wordBreakStart + quoted + wordBreakEnd)
 	return // caller is expected to wrap this error
 }
 
diff --git a/internal/typeutils/internaltofrontend.go b/internal/typeutils/internaltofrontend.go
index 55af2c1f1..fe49766fa 100644
--- a/internal/typeutils/internaltofrontend.go
+++ b/internal/typeutils/internaltofrontend.go
@@ -21,6 +21,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"slices"
+	"strconv"
 	"strings"
 	"time"
 
@@ -35,7 +37,6 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/language"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/superseriousbusiness/gotosocial/internal/media"
-	"github.com/superseriousbusiness/gotosocial/internal/text"
 	"github.com/superseriousbusiness/gotosocial/internal/uris"
 	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
@@ -939,32 +940,48 @@ func (c *Converter) statusToAPIFilterResults(
 		return nil, nil
 	}
 
-	// Extract text fields from the status that we will match filters against.
-	fields := filterableTextFields(s)
+	// Key this status based on ID + last updated time,
+	// to ensure we always filter on latest version.
+	statusKey := s.ID + strconv.FormatInt(s.UpdatedAt.Unix(), 10)
+
+	// Check if we have filterable fields cached for this status.
+	cache := c.state.Caches.StatusesFilterableFields
+	fields, stored := cache.Get(statusKey)
+	if !stored {
+		// We don't have filterable fields
+		// cached, calculate + cache now.
+		fields = filterableFields(s)
+		cache.Set(statusKey, fields)
+	}
 
 	// Record all matching warn filters and the reasons they matched.
 	filterResults := make([]apimodel.FilterResult, 0, len(filters))
 	for _, filter := range filters {
 		if !filterAppliesInContext(filter, filterContext) {
-			// Filter doesn't apply to this context.
+			// Filter doesn't apply
+			// to this context.
 			continue
 		}
+
 		if filter.Expired(now) {
+			// Filter doesn't
+			// apply anymore.
 			continue
 		}
 
-		// List all matching keywords.
+		// Assemble matching keywords (if any) from this filter.
 		keywordMatches := make([]string, 0, len(filter.Keywords))
-		for _, filterKeyword := range filter.Keywords {
-			var isMatch bool
-			for _, field := range fields {
-				if filterKeyword.Regexp.MatchString(field) {
-					isMatch = true
-					break
-				}
-			}
-			if isMatch {
-				keywordMatches = append(keywordMatches, filterKeyword.Keyword)
+		for _, keyword := range filter.Keywords {
+			// Check if at least one filterable field
+			// in the status matches on this filter.
+			if slices.ContainsFunc(
+				fields,
+				func(field string) bool {
+					return keyword.Regexp.MatchString(field)
+				},
+			) {
+				// At least one field matched on this filter.
+				keywordMatches = append(keywordMatches, keyword.Keyword)
 			}
 		}
 
@@ -1001,40 +1018,6 @@ func (c *Converter) statusToAPIFilterResults(
 	return filterResults, nil
 }
 
-// filterableTextFields returns all text from a status that we might want to filter on:
-// - content
-// - content warning
-// - media descriptions
-// - poll options
-func filterableTextFields(s *gtsmodel.Status) []string {
-	fieldCount := 2 + len(s.Attachments)
-	if s.Poll != nil {
-		fieldCount += len(s.Poll.Options)
-	}
-	fields := make([]string, 0, fieldCount)
-
-	if s.Content != "" {
-		fields = append(fields, text.SanitizeToPlaintext(s.Content))
-	}
-	if s.ContentWarning != "" {
-		fields = append(fields, s.ContentWarning)
-	}
-	for _, attachment := range s.Attachments {
-		if attachment.Description != "" {
-			fields = append(fields, attachment.Description)
-		}
-	}
-	if s.Poll != nil {
-		for _, option := range s.Poll.Options {
-			if option != "" {
-				fields = append(fields, option)
-			}
-		}
-	}
-
-	return fields
-}
-
 // filterAppliesInContext returns whether a given filter applies in a given context.
 func filterAppliesInContext(filter *gtsmodel.Filter, filterContext statusfilter.FilterContext) bool {
 	switch filterContext {
diff --git a/internal/typeutils/internaltofrontend_test.go b/internal/typeutils/internaltofrontend_test.go
index 651ff867d..a44afe67e 100644
--- a/internal/typeutils/internaltofrontend_test.go
+++ b/internal/typeutils/internaltofrontend_test.go
@@ -1063,15 +1063,21 @@ func (suite *InternalToFrontendTestSuite) TestHideFilteredBoostToFrontend() {
 
 // Test that a hashtag filter for a hashtag in Mastodon HTML content works the way most users would expect.
 func (suite *InternalToFrontendTestSuite) testHashtagFilteredStatusToFrontend(wholeWord bool, boost bool) {
-	testStatus := suite.testStatuses["admin_account_status_1"]
+	testStatus := new(gtsmodel.Status)
+	*testStatus = *suite.testStatuses["admin_account_status_1"]
 	testStatus.Content = `<p>doggo doggin' it</p><p><a href="https://example.test/tags/dogsofmastodon" class="mention hashtag" rel="tag nofollow noreferrer noopener" target="_blank">#<span>dogsofmastodon</span></a></p>`
 
 	if boost {
-		// Modify a fixture boost into a boost of the above status.
-		boostStatus := suite.testStatuses["admin_account_status_4"]
-		boostStatus.BoostOf = testStatus
-		boostStatus.BoostOfID = testStatus.ID
-		testStatus = boostStatus
+		boost, err := suite.typeconverter.StatusToBoost(
+			context.Background(),
+			testStatus,
+			suite.testAccounts["admin_account"],
+			"",
+		)
+		if err != nil {
+			suite.FailNow(err.Error())
+		}
+		testStatus = boost
 	}
 
 	requestingAccount := suite.testAccounts["local_account_1"]
@@ -1103,9 +1109,11 @@ func (suite *InternalToFrontendTestSuite) testHashtagFilteredStatusToFrontend(wh
 		[]*gtsmodel.Filter{filter},
 		nil,
 	)
-	if suite.NoError(err) {
-		suite.NotEmpty(apiStatus.Filtered)
+	if err != nil {
+		suite.FailNow(err.Error())
 	}
+
+	suite.NotEmpty(apiStatus.Filtered)
 }
 
 func (suite *InternalToFrontendTestSuite) TestHashtagWholeWordFilteredStatusToFrontend() {
diff --git a/internal/typeutils/util.go b/internal/typeutils/util.go
index 3441e89a9..3a867ba35 100644
--- a/internal/typeutils/util.go
+++ b/internal/typeutils/util.go
@@ -27,6 +27,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/k3a/html2text"
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
@@ -284,3 +285,64 @@ func ContentToContentLanguage(
 
 	return contentStr, langTagStr
 }
+
+// filterableFields 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 + the first word
+// of the next field together.
+func filterableFields(s *gtsmodel.Status) []string {
+	// Estimate length of fields.
+	fieldCount := 2 + len(s.Attachments)
+	if s.Poll != nil {
+		fieldCount += len(s.Poll.Options)
+	}
+	fields := make([]string, 0, fieldCount)
+
+	// Content warning / title.
+	if s.ContentWarning != "" {
+		fields = append(fields, s.ContentWarning)
+	}
+
+	// Status content. Though we have raw text
+	// available for statuses created on our
+	// instance, use the html2text version to
+	// remove markdown-formatting characters
+	// and ensure more consistent filtering.
+	if s.Content != "" {
+		text := html2text.HTML2TextWithOptions(
+			s.Content,
+			html2text.WithLinksInnerText(),
+			html2text.WithUnixLineBreaks(),
+		)
+		if text != "" {
+			fields = append(fields, text)
+		}
+	}
+
+	// Media descriptions.
+	for _, attachment := range s.Attachments {
+		if attachment.Description != "" {
+			fields = append(fields, attachment.Description)
+		}
+	}
+
+	// Poll options.
+	if s.Poll != nil {
+		for _, opt := range s.Poll.Options {
+			if opt != "" {
+				fields = append(fields, opt)
+			}
+		}
+	}
+
+	return fields
+}
diff --git a/internal/typeutils/util_test.go b/internal/typeutils/util_test.go
index 0f852d399..ea6667519 100644
--- a/internal/typeutils/util_test.go
+++ b/internal/typeutils/util_test.go
@@ -21,6 +21,7 @@ import (
 	"context"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/language"
@@ -158,3 +159,62 @@ func TestContentToContentLanguage(t *testing.T) {
 		}
 	}
 }
+
+func TestFilterableText(t *testing.T) {
+	type testcase struct {
+		status         *gtsmodel.Status
+		expectedFields []string
+	}
+
+	for _, testcase := range []testcase{
+		{
+			status: &gtsmodel.Status{
+				ContentWarning: "This is a test status",
+				Content:        `<p>Import / export of account data via CSV files will be coming in 0.17.0 :) No more having to run scripts + CLI tools to import a list of accounts you follow, after doing a migration to a <a href="https://gts.superseriousbusiness.org/tags/gotosocial" class="mention hashtag" rel="tag nofollow noreferrer noopener" target="_blank">#<span>GoToSocial</span></a> instance.</p>`,
+			},
+			expectedFields: []string{
+				"This is a test status",
+				"Import / export of account data via CSV files will be coming in 0.17.0 :) No more having to run scripts + CLI tools to import a list of accounts you follow, after doing a migration to a #GoToSocial <https://gts.superseriousbusiness.org/tags/gotosocial> instance.",
+			},
+		},
+		{
+			status: &gtsmodel.Status{
+				Content: `<p><span class="h-card"><a href="https://example.org/@zlatko" class="u-url mention" rel="nofollow noreferrer noopener" target="_blank">@<span>zlatko</span></a></span> currently we used modernc/sqlite3 for our sqlite driver, but we've been experimenting with wasm sqlite, and will likely move to that permanently in future; in the meantime, both options are available (the latter with a build tag)</p><p><a href="https://github.com/superseriousbusiness/gotosocial/pull/2863" rel="nofollow noreferrer noopener" target="_blank">https://github.com/superseriousbusiness/gotosocial/pull/2863</a></p>`,
+			},
+			expectedFields: []string{
+				"@zlatko <https://example.org/@zlatko> currently we used modernc/sqlite3 for our sqlite driver, but we've been experimenting with wasm sqlite, and will likely move to that permanently in future; in the meantime, both options are available (the latter with a build tag)\n\nhttps://github.com/superseriousbusiness/gotosocial/pull/2863 <https://github.com/superseriousbusiness/gotosocial/pull/2863>",
+			},
+		},
+		{
+			status: &gtsmodel.Status{
+				ContentWarning: "Nerd stuff",
+				Content:        `<p>Latest graphs for <a href="https://gts.superseriousbusiness.org/tags/gotosocial" class="mention hashtag" rel="tag nofollow noreferrer noopener" target="_blank">#<span>GoToSocial</span></a> on <a href="https://github.com/ncruces/go-sqlite3" rel="nofollow noreferrer noopener" target="_blank">Wasm sqlite3</a> with <a href="https://codeberg.org/gruf/go-ffmpreg" rel="nofollow noreferrer noopener" target="_blank">embedded Wasm ffmpeg</a>, both running on <a href="https://wazero.io/" rel="nofollow noreferrer noopener" target="_blank">Wazero</a>, and configured with a <a href="https://github.com/superseriousbusiness/gotosocial/blob/20fe430ef9ff3012a7a4dc2d01b68020c20e13bb/example/config.yaml#L259-L266" rel="nofollow noreferrer noopener" target="_blank">50MiB db cache target</a>. This is the version we'll be releasing soonish, now we're happy with how we've tamed everything.</p>`,
+				Attachments: []*gtsmodel.MediaAttachment{
+					{
+						Description: `Graph showing GtS using between 150-300 MiB of memory, steadily, over a few days.`,
+					},
+					{
+						Description: `Another media attachment`,
+					},
+				},
+				Poll: &gtsmodel.Poll{
+					Options: []string{
+						"Poll option 1",
+						"Poll option 2",
+					},
+				},
+			},
+			expectedFields: []string{
+				"Nerd stuff",
+				"Latest graphs for #GoToSocial <https://gts.superseriousbusiness.org/tags/gotosocial> on Wasm sqlite3 <https://github.com/ncruces/go-sqlite3> with embedded Wasm ffmpeg <https://codeberg.org/gruf/go-ffmpreg>, both running on Wazero <https://wazero.io/>, and configured with a 50MiB db cache target <https://github.com/superseriousbusiness/gotosocial/blob/20fe430ef9ff3012a7a4dc2d01b68020c20e13bb/example/config.yaml#L259-L266>. This is the version we'll be releasing soonish, now we're happy with how we've tamed everything.",
+				"Graph showing GtS using between 150-300 MiB of memory, steadily, over a few days.",
+				"Another media attachment",
+				"Poll option 1",
+				"Poll option 2",
+			},
+		},
+	} {
+		fields := filterableFields(testcase.status)
+		assert.Equal(t, testcase.expectedFields, fields)
+	}
+}