[performance] rewrite timelines to rely on new timeline cache type (#3941)

* start work rewriting timeline cache type

* further work rewriting timeline caching

* more work integration new timeline code

* remove old code

* add local timeline, fix up merge conflicts

* remove old use of go-bytes

* implement new timeline code into more areas of codebase, pull in latest go-mangler, go-mutexes, go-structr

* remove old timeline package, add local timeline cache

* remove references to old timeline types that needed starting up in tests

* start adding page validation

* fix test-identified timeline cache package issues

* fix up more tests, fix missing required changes, etc

* add exclusion for test.out in gitignore

* clarify some things better in code comments

* tweak cache size limits

* fix list timeline cache fetching

* further list timeline fixes

* linter, ssssssssshhhhhhhhhhhh please

* fix linter hints

* reslice the output if it's beyond length of 'lim'

* remove old timeline initialization code, bump go-structr to v0.9.4

* continued from previous commit

* improved code comments

* don't allow multiple entries for BoostOfID values to prevent repeated boosts of same boosts

* finish writing more code comments

* some variable renaming, for ease of following

* change the way we update lo,hi paging values during timeline load

* improved code comments for updated / returned lo , hi paging values

* finish writing code comments for the StatusTimeline{} type itself

* fill in more code comments

* update go-structr version to latest with changed timeline unique indexing logic

* have a local and public timeline *per user*

* rewrite calls to public / local timeline calls

* remove the zero length check, as lo, hi values might still be set

* simplify timeline cache loading, fix lo/hi returns, fix timeline invalidation side-effects missing for some federated actions

* swap the lo, hi values :facepalm:

* add (now) missing slice reverse of tag timeline statuses when paging ASC

* remove local / public caches (is out of scope for this work), share more timeline code

* remove unnecessary change

* again, remove more unused code

* remove unused function to appease the linter

* move boost checking to prepare function

* fix use of timeline.lastOrder, fix incorrect range functions used

* remove comments for repeat code

* remove the boost logic from prepare function

* do a maximum of 5 loads, not 10

* add repeat boost filtering logic, update go-structr, general improvements

* more code comments

* add important note

* fix timeline tests now that timelines are returned in page order

* remove unused field

* add StatusTimeline{} tests

* add more status timeline tests

* start adding preloading support

* ensure repeat boosts are marked in preloaded entries

* share a bunch of the database load code in timeline cache, don't clear timelines on relationship change

* add logic to allow dynamic clear / preloading of timelines

* comment-out unused functions, but leave in place as we might end-up using them

* fix timeline preload state check

* much improved status timeline code comments

* more code comments, don't bother inserting statuses if timeline not preloaded

* shift around some logic to make sure things aren't accidentally left set

* finish writing code comments

* remove trim-after-insert behaviour

* fix-up some comments referring to old logic

* remove unsetting of lo, hi

* fix preload repeatBoost checking logic

* don't return on status filter errors, these are usually transient

* better concurrency safety in Clear() and Done()

* fix test broken due to addition of preloader

* fix repeatBoost logic that doesn't account for already-hidden repeatBoosts

* ensure edit submodels are dropped on cache insertion

* update code-comment to expand CAS accronym

* use a plus1hULID() instead of 24h

* remove unused functions

* add note that public / local timeline requester can be nil

* fix incorrect visibility filtering of tag timeline statuses

* ensure we filter home timeline statuses on local only

* some small re-orderings to confirm query params in correct places

* fix the local only home timeline filter func

1 files changed, 56 insertions, 84 deletions

diff --git a/internal/processing/timeline/tag.go b/internal/processing/timeline/tag.go
index 811d0bb33..685bac376 100644
--- a/internal/processing/timeline/tag.go
+++ b/internal/processing/timeline/tag.go
@@ -20,18 +20,16 @@ package timeline
 import (
 	"context"
 	"errors"
-	"fmt"
+	"net/http"
 
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	statusfilter "github.com/superseriousbusiness/gotosocial/internal/filter/status"
-	"github.com/superseriousbusiness/gotosocial/internal/filter/usermute"
-	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/paging"
 	"github.com/superseriousbusiness/gotosocial/internal/text"
-	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
 
 // TagTimelineGet gets a pageable timeline for the given
@@ -40,37 +38,77 @@ import (
 // to requestingAcct before returning it.
 func (p *Processor) TagTimelineGet(
 	ctx context.Context,
-	requestingAcct *gtsmodel.Account,
+	requester *gtsmodel.Account,
 	tagName string,
 	maxID string,
 	sinceID string,
 	minID string,
 	limit int,
 ) (*apimodel.PageableResponse, gtserror.WithCode) {
+
+	// Fetch the requested tag with name.
 	tag, errWithCode := p.getTag(ctx, tagName)
 	if errWithCode != nil {
 		return nil, errWithCode
 	}
 
+	// Check for a useable returned tag for endpoint.
 	if tag == nil || !*tag.Useable || !*tag.Listable {
+
 		// Obey mastodon API by returning 404 for this.
-		err := fmt.Errorf("tag was not found, or not useable/listable on this instance")
-		return nil, gtserror.NewErrorNotFound(err, err.Error())
+		const text = "tag was not found, or not useable/listable on this instance"
+		return nil, gtserror.NewWithCode(http.StatusNotFound, text)
 	}
 
-	statuses, err := p.state.DB.GetTagTimeline(ctx, tag.ID, maxID, sinceID, minID, limit)
-	if err != nil && !errors.Is(err, db.ErrNoEntries) {
-		err = gtserror.Newf("db error getting statuses: %w", err)
-		return nil, gtserror.NewErrorInternalError(err)
-	}
+	// Fetch status timeline for tag.
+	return p.getStatusTimeline(ctx,
+
+		// Auth'd
+		// account.
+		requester,
+
+		// No
+		// cache.
+		nil,
 
-	return p.packageTagResponse(
-		ctx,
-		requestingAcct,
-		statuses,
-		limit,
-		// Use API URL for tag.
+		// Current
+		// page.
+		&paging.Page{
+			Min:   paging.EitherMinID(minID, sinceID),
+			Max:   paging.MaxID(maxID),
+			Limit: limit,
+		},
+
+		// Tag timeline name's endpoint.
 		"/api/v1/timelines/tag/"+tagName,
+
+		// No page
+		// query.
+		nil,
+
+		// Status filter context.
+		statusfilter.FilterContextPublic,
+
+		// Database load function.
+		func(pg *paging.Page) (statuses []*gtsmodel.Status, err error) {
+			return p.state.DB.GetTagTimeline(ctx, tag.ID, pg)
+		},
+
+		// Filtering function,
+		// i.e. filter before caching.
+		func(s *gtsmodel.Status) bool {
+
+			// Check the visibility of passed status to requesting user.
+			ok, err := p.visFilter.StatusPublicTimelineable(ctx, requester, s)
+			if err != nil {
+				log.Errorf(ctx, "error filtering status %s: %v", s.URI, err)
+			}
+			return !ok
+		},
+
+		// Post filtering funtion,
+		// i.e. filter after caching.
+		nil,
 	)
 }
 
@@ -92,69 +130,3 @@ func (p *Processor) getTag(ctx context.Context, tagName string) (*gtsmodel.Tag,
 
 	return tag, nil
 }
-
-func (p *Processor) packageTagResponse(
-	ctx context.Context,
-	requestingAcct *gtsmodel.Account,
-	statuses []*gtsmodel.Status,
-	limit int,
-	requestPath string,
-) (*apimodel.PageableResponse, gtserror.WithCode) {
-	count := len(statuses)
-	if count == 0 {
-		return util.EmptyPageableResponse(), nil
-	}
-
-	var (
-		items = make([]interface{}, 0, count)
-
-		// Set next + prev values before filtering and API
-		// converting, so caller can still page properly.
-		nextMaxIDValue = statuses[count-1].ID
-		prevMinIDValue = statuses[0].ID
-	)
-
-	filters, err := p.state.DB.GetFiltersForAccountID(ctx, requestingAcct.ID)
-	if err != nil {
-		err = gtserror.Newf("couldn't retrieve filters for account %s: %w", requestingAcct.ID, err)
-		return nil, gtserror.NewErrorInternalError(err)
-	}
-
-	mutes, err := p.state.DB.GetAccountMutes(gtscontext.SetBarebones(ctx), requestingAcct.ID, nil)
-	if err != nil {
-		err = gtserror.Newf("couldn't retrieve mutes for account %s: %w", requestingAcct.ID, err)
-		return nil, gtserror.NewErrorInternalError(err)
-	}
-	compiledMutes := usermute.NewCompiledUserMuteList(mutes)
-
-	for _, s := range statuses {
-		timelineable, err := p.visFilter.StatusTagTimelineable(ctx, requestingAcct, s)
-		if err != nil {
-			log.Errorf(ctx, "error checking status visibility: %v", err)
-			continue
-		}
-
-		if !timelineable {
-			continue
-		}
-
-		apiStatus, err := p.converter.StatusToAPIStatus(ctx, s, requestingAcct, statusfilter.FilterContextPublic, filters, compiledMutes)
-		if errors.Is(err, statusfilter.ErrHideStatus) {
-			continue
-		}
-		if err != nil {
-			log.Errorf(ctx, "error converting to api status: %v", err)
-			continue
-		}
-
-		items = append(items, apiStatus)
-	}
-
-	return util.PackagePageableResponse(util.PageableResponseParams{
-		Items:          items,
-		Path:           requestPath,
-		NextMaxIDValue: nextMaxIDValue,
-		PrevMinIDValue: prevMinIDValue,
-		Limit:          limit,
-	})
-}