[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, 70 insertions, 132 deletions

diff --git a/internal/processing/timeline/list.go b/internal/processing/timeline/list.go
index 147f87ab4..10a7bb388 100644
--- a/internal/processing/timeline/list.go
+++ b/internal/processing/timeline/list.go
@@ -22,155 +22,93 @@ import (
 	"errors"
 
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
-	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
 	"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/filter/visibility"
 	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
-	"github.com/superseriousbusiness/gotosocial/internal/state"
-	"github.com/superseriousbusiness/gotosocial/internal/timeline"
-	"github.com/superseriousbusiness/gotosocial/internal/typeutils"
-	"github.com/superseriousbusiness/gotosocial/internal/util"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/paging"
 )
 
-// ListTimelineGrab returns a function that satisfies GrabFunction for list timelines.
-func ListTimelineGrab(state *state.State) timeline.GrabFunction {
-	return func(ctx context.Context, listID string, maxID string, sinceID string, minID string, limit int) ([]timeline.Timelineable, bool, error) {
-		statuses, err := state.DB.GetListTimeline(ctx, listID, maxID, sinceID, minID, limit)
-		if err != nil && !errors.Is(err, db.ErrNoEntries) {
-			err = gtserror.Newf("error getting statuses from db: %w", err)
-			return nil, false, err
-		}
-
-		count := len(statuses)
-		if count == 0 {
-			// We just don't have enough statuses
-			// left in the db so return stop = true.
-			return nil, true, nil
-		}
-
-		items := make([]timeline.Timelineable, count)
-		for i, s := range statuses {
-			items[i] = s
-		}
-
-		return items, false, nil
+// ListTimelineGet gets a pageable timeline of statuses
+// in the list timeline of ID by the requesting account.
+func (p *Processor) ListTimelineGet(
+	ctx context.Context,
+	requester *gtsmodel.Account,
+	listID string,
+	page *paging.Page,
+) (
+	*apimodel.PageableResponse,
+	gtserror.WithCode,
+) {
+	// Fetch the requested list with ID.
+	list, err := p.state.DB.GetListByID(
+		gtscontext.SetBarebones(ctx),
+		listID,
+	)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		return nil, gtserror.NewErrorInternalError(err)
 	}
-}
 
-// ListTimelineFilter returns a function that satisfies FilterFunction for list timelines.
-func ListTimelineFilter(state *state.State, visFilter *visibility.Filter) timeline.FilterFunction {
-	return func(ctx context.Context, listID string, item timeline.Timelineable) (shouldIndex bool, err error) {
-		status, ok := item.(*gtsmodel.Status)
-		if !ok {
-			err = gtserror.New("could not convert item to *gtsmodel.Status")
-			return false, err
-		}
-
-		list, err := state.DB.GetListByID(ctx, listID)
-		if err != nil {
-			err = gtserror.Newf("error getting list with id %s: %w", listID, err)
-			return false, err
-		}
-
-		requestingAccount, err := state.DB.GetAccountByID(ctx, list.AccountID)
-		if err != nil {
-			err = gtserror.Newf("error getting account with id %s: %w", list.AccountID, err)
-			return false, err
-		}
-
-		timelineable, err := visFilter.StatusHomeTimelineable(ctx, requestingAccount, status)
-		if err != nil {
-			err = gtserror.Newf("error checking hometimelineability of status %s for account %s: %w", status.ID, list.AccountID, err)
-			return false, err
-		}
-
-		return timelineable, nil
+	// Check exists.
+	if list == nil {
+		const text = "list not found"
+		return nil, gtserror.NewErrorNotFound(
+			errors.New(text),
+			text,
+		)
 	}
-}
 
-// ListTimelineStatusPrepare returns a function that satisfies PrepareFunction for list timelines.
-func ListTimelineStatusPrepare(state *state.State, converter *typeutils.Converter) timeline.PrepareFunction {
-	return func(ctx context.Context, listID string, itemID string) (timeline.Preparable, error) {
-		status, err := state.DB.GetStatusByID(ctx, itemID)
-		if err != nil {
-			err = gtserror.Newf("error getting status with id %s: %w", itemID, err)
-			return nil, err
-		}
-
-		list, err := state.DB.GetListByID(ctx, listID)
-		if err != nil {
-			err = gtserror.Newf("error getting list with id %s: %w", listID, err)
-			return nil, err
-		}
-
-		requestingAccount, err := state.DB.GetAccountByID(ctx, list.AccountID)
-		if err != nil {
-			err = gtserror.Newf("error getting account with id %s: %w", list.AccountID, err)
-			return nil, err
-		}
-
-		filters, err := state.DB.GetFiltersForAccountID(ctx, requestingAccount.ID)
-		if err != nil {
-			err = gtserror.Newf("couldn't retrieve filters for account %s: %w", requestingAccount.ID, err)
-			return nil, err
-		}
-
-		mutes, err := state.DB.GetAccountMutes(gtscontext.SetBarebones(ctx), requestingAccount.ID, nil)
-		if err != nil {
-			err = gtserror.Newf("couldn't retrieve mutes for account %s: %w", requestingAccount.ID, err)
-			return nil, err
-		}
-		compiledMutes := usermute.NewCompiledUserMuteList(mutes)
-
-		return converter.StatusToAPIStatus(ctx, status, requestingAccount, statusfilter.FilterContextHome, filters, compiledMutes)
+	// Check list owned by auth'd account.
+	if list.AccountID != requester.ID {
+		err := gtserror.New("list does not belong to account")
+		return nil, gtserror.NewErrorNotFound(err)
 	}
-}
 
-func (p *Processor) ListTimelineGet(ctx context.Context, authed *apiutil.Auth, listID string, maxID string, sinceID string, minID string, limit int) (*apimodel.PageableResponse, gtserror.WithCode) {
-	// Ensure list exists + is owned by this account.
-	list, err := p.state.DB.GetListByID(ctx, listID)
-	if err != nil {
-		if errors.Is(err, db.ErrNoEntries) {
-			return nil, gtserror.NewErrorNotFound(err)
-		}
-		return nil, gtserror.NewErrorInternalError(err)
-	}
+	// Fetch status timeline for list.
+	return p.getStatusTimeline(ctx,
 
-	if list.AccountID != authed.Account.ID {
-		err = gtserror.Newf("list with id %s does not belong to account %s", list.ID, authed.Account.ID)
-		return nil, gtserror.NewErrorNotFound(err)
-	}
+		// Auth'd
+		// account.
+		requester,
 
-	statuses, err := p.state.Timelines.List.GetTimeline(ctx, listID, maxID, sinceID, minID, limit, false)
-	if err != nil && !errors.Is(err, db.ErrNoEntries) {
-		err = gtserror.Newf("error getting statuses: %w", err)
-		return nil, gtserror.NewErrorInternalError(err)
-	}
+		// Keyed-by-list-ID, list timeline cache.
+		p.state.Caches.Timelines.List.MustGet(listID),
 
-	count := len(statuses)
-	if count == 0 {
-		return util.EmptyPageableResponse(), nil
-	}
+		// Current
+		// page.
+		page,
 
-	var (
-		items          = make([]interface{}, count)
-		nextMaxIDValue = statuses[count-1].GetID()
-		prevMinIDValue = statuses[0].GetID()
-	)
+		// List timeline ID's endpoint.
+		"/api/v1/timelines/list/"+listID,
 
-	for i := range statuses {
-		items[i] = statuses[i]
-	}
+		// No page
+		// query.
+		nil,
 
-	return util.PackagePageableResponse(util.PageableResponseParams{
-		Items:          items,
-		Path:           "/api/v1/timelines/list/" + listID,
-		NextMaxIDValue: nextMaxIDValue,
-		PrevMinIDValue: prevMinIDValue,
-		Limit:          limit,
-	})
+		// Status filter context.
+		statusfilter.FilterContextHome,
+
+		// Database load function.
+		func(pg *paging.Page) (statuses []*gtsmodel.Status, err error) {
+			return p.state.DB.GetListTimeline(ctx, listID, 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.StatusHomeTimelineable(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,
+	)
 }