gotosocial/internal/timeline/get.go
tobi 3510454768
[bugfix/chore] Refactor timeline code (#1656)
* start poking timelines

* OK yes we're refactoring, but it's nothing like the last time so don't worry

* more fiddling

* update tests, simplify Get

* thanks linter, you're the best, mwah mwah kisses

* do a bit more tidying up

* start buggering about with the prepare function

* fix little oopsie

* start merging lists into 1

* ik heb een heel zwaar leven
nee nee echt waar

* hey it works we did it reddit

* regenerate swagger docs

* tidy up a wee bit

* adjust paging

* fix little error, remove unused functions
2023-04-06 12:43:13 +01:00

414 lines
13 KiB
Go

// 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 timeline
import (
"container/list"
"context"
"errors"
"fmt"
"time"
"codeberg.org/gruf/go-kv"
"github.com/superseriousbusiness/gotosocial/internal/db"
"github.com/superseriousbusiness/gotosocial/internal/id"
"github.com/superseriousbusiness/gotosocial/internal/log"
)
func (t *timeline) LastGot() time.Time {
t.Lock()
defer t.Unlock()
return t.lastGot
}
func (t *timeline) Get(ctx context.Context, amount int, maxID string, sinceID string, minID string, prepareNext bool) ([]Preparable, error) {
l := log.WithContext(ctx).
WithFields(kv.Fields{
{"accountID", t.accountID},
{"amount", amount},
{"maxID", maxID},
{"sinceID", sinceID},
{"minID", minID},
}...)
l.Trace("entering get and updating t.lastGot")
// Regardless of what happens below, update the
// last time Get was called for this timeline.
t.Lock()
t.lastGot = time.Now()
t.Unlock()
var (
items []Preparable
err error
)
switch {
case maxID == "" && sinceID == "" && minID == "":
// No params are defined so just fetch from the top.
// This is equivalent to a user starting to view
// their timeline from newest -> older posts.
items, err = t.getXBetweenIDs(ctx, amount, id.Highest, id.Lowest, true)
// Cache expected next query to speed up scrolling.
// Assume the user will be scrolling downwards from
// the final ID in items.
if prepareNext && err == nil && len(items) != 0 {
nextMaxID := items[len(items)-1].GetID()
t.prepareNextQuery(amount, nextMaxID, "", "")
}
case maxID != "" && sinceID == "" && minID == "":
// Only maxID is defined, so fetch from maxID onwards.
// This is equivalent to a user paging further down
// their timeline from newer -> older posts.
items, err = t.getXBetweenIDs(ctx, amount, maxID, id.Lowest, true)
// Cache expected next query to speed up scrolling.
// Assume the user will be scrolling downwards from
// the final ID in items.
if prepareNext && err == nil && len(items) != 0 {
nextMaxID := items[len(items)-1].GetID()
t.prepareNextQuery(amount, nextMaxID, "", "")
}
// In the next cases, maxID is defined, and so are
// either sinceID or minID. This is equivalent to
// a user opening an in-progress timeline and asking
// for a slice of posts somewhere in the middle, or
// trying to "fill in the blanks" between two points,
// paging either up or down.
case maxID != "" && sinceID != "":
items, err = t.getXBetweenIDs(ctx, amount, maxID, sinceID, true)
// Cache expected next query to speed up scrolling.
// We can assume the caller is scrolling downwards.
// Guess id.Lowest as sinceID, since we don't actually
// know what the next sinceID would be.
if prepareNext && err == nil && len(items) != 0 {
nextMaxID := items[len(items)-1].GetID()
t.prepareNextQuery(amount, nextMaxID, id.Lowest, "")
}
case maxID != "" && minID != "":
items, err = t.getXBetweenIDs(ctx, amount, maxID, minID, false)
// Cache expected next query to speed up scrolling.
// We can assume the caller is scrolling upwards.
// Guess id.Highest as maxID, since we don't actually
// know what the next maxID would be.
if prepareNext && err == nil && len(items) != 0 {
prevMinID := items[0].GetID()
t.prepareNextQuery(amount, id.Highest, "", prevMinID)
}
// In the final cases, maxID is not defined, but
// either sinceID or minID are. This is equivalent to
// a user either "pulling up" at the top of their timeline
// to refresh it and check if newer posts have come in, or
// trying to scroll upwards from an old post to see what
// they missed since then.
//
// In these calls, we use the highest possible ulid as
// behindID because we don't have a cap for newest that
// we're interested in.
case maxID == "" && sinceID != "":
items, err = t.getXBetweenIDs(ctx, amount, id.Highest, sinceID, true)
// We can't cache an expected next query for this one,
// since presumably the caller is at the top of their
// timeline already.
case maxID == "" && minID != "":
items, err = t.getXBetweenIDs(ctx, amount, id.Highest, minID, false)
// Cache expected next query to speed up scrolling.
// We can assume the caller is scrolling upwards.
// Guess id.Highest as maxID, since we don't actually
// know what the next maxID would be.
if prepareNext && err == nil && len(items) != 0 {
prevMinID := items[0].GetID()
t.prepareNextQuery(amount, id.Highest, "", prevMinID)
}
default:
err = errors.New("Get: switch statement exhausted with no results")
}
return items, err
}
// getXBetweenIDs returns x amount of items somewhere between (not including) the given IDs.
//
// If frontToBack is true, items will be served paging down from behindID.
// This corresponds to an api call to /timelines/home?max_id=WHATEVER&since_id=WHATEVER
//
// If frontToBack is false, items will be served paging up from beforeID.
// This corresponds to an api call to /timelines/home?max_id=WHATEVER&min_id=WHATEVER
func (t *timeline) getXBetweenIDs(ctx context.Context, amount int, behindID string, beforeID string, frontToBack bool) ([]Preparable, error) {
l := log.
WithContext(ctx).
WithFields(kv.Fields{
{"amount", amount},
{"behindID", behindID},
{"beforeID", beforeID},
{"frontToBack", frontToBack},
}...)
l.Trace("entering getXBetweenID")
// Assume length we need to return.
items := make([]Preparable, 0, amount)
if beforeID >= behindID {
// This is an impossible situation, we
// can't serve anything between these.
return items, nil
}
// Try to ensure we have enough items prepared.
if err := t.prepareXBetweenIDs(ctx, amount, behindID, beforeID, frontToBack); err != nil {
// An error here doesn't necessarily mean we
// can't serve anything, so log + keep going.
l.Debugf("error calling prepareXBetweenIDs: %s", err)
}
var (
beforeIDMark *list.Element
served int
// Our behavior while ranging through the
// list changes depending on if we're
// going front-to-back or back-to-front.
//
// To avoid checking which one we're doing
// in each loop iteration, define our range
// function here outside the loop.
//
// The bool indicates to the caller whether
// iteration should continue (true) or stop
// (false).
rangeF func(e *list.Element) (bool, error)
// If we get certain errors on entries as we're
// looking through, we might want to cheekily
// remove their elements from the timeline.
// Everything added to this slice will be removed.
removeElements = []*list.Element{}
)
defer func() {
for _, e := range removeElements {
t.items.data.Remove(e)
}
}()
if frontToBack {
// We're going front-to-back, which means we
// don't need to look for a mark per se, we
// just keep serving items until we've reached
// a point where the items are out of the range
// we're interested in.
rangeF = func(e *list.Element) (bool, error) {
entry := e.Value.(*indexedItemsEntry) //nolint:forcetypeassert
if entry.itemID >= behindID {
// ID of this item is too high,
// just keep iterating.
l.Trace("item is too new, continuing")
return true, nil
}
if entry.itemID <= beforeID {
// We've gone as far as we can through
// the list and reached entries that are
// now too old for us, stop here.
l.Trace("reached older items, breaking")
return false, nil
}
l.Trace("entry is just right")
if entry.prepared == nil {
// Whoops, this entry isn't prepared yet; some
// race condition? That's OK, we can do it now.
prepared, err := t.prepareFunction(ctx, t.accountID, entry.itemID)
if err != nil {
if errors.Is(err, db.ErrNoEntries) {
// ErrNoEntries means something has been deleted,
// so we'll likely not be able to ever prepare this.
// This means we can remove it and skip past it.
l.Debugf("db.ErrNoEntries while trying to prepare %s; will remove from timeline", entry.itemID)
removeElements = append(removeElements, e)
return true, nil
}
// We've got a proper db error.
return false, fmt.Errorf("getXBetweenIDs: db error while trying to prepare %s: %w", entry.itemID, err)
}
entry.prepared = prepared
}
items = append(items, entry.prepared)
served++
return served < amount, nil
}
} else {
// Iterate through the list from the top, until
// we reach an item with id smaller than beforeID;
// ie., an item OLDER than beforeID. At that point,
// we can stop looking because we're not interested
// in older entries.
rangeF = func(e *list.Element) (bool, error) {
// Move the mark back one place each loop.
beforeIDMark = e
//nolint:forcetypeassert
if entry := e.Value.(*indexedItemsEntry); entry.itemID <= beforeID {
// We've gone as far as we can through
// the list and reached entries that are
// now too old for us, stop here.
l.Trace("reached older items, breaking")
return false, nil
}
return true, nil
}
}
// Iterate through the list until the function
// we defined above instructs us to stop.
for e := t.items.data.Front(); e != nil; e = e.Next() {
keepGoing, err := rangeF(e)
if err != nil {
return nil, err
}
if !keepGoing {
break
}
}
if frontToBack || beforeIDMark == nil {
// If we're serving front to back, then
// items should be populated by now. If
// we're serving back to front but didn't
// find any items newer than beforeID,
// we can just return empty items.
return items, nil
}
// We're serving back to front, so iterate upwards
// towards the front of the list from the mark we found,
// until we either get to the front, serve enough
// items, or reach behindID.
//
// To preserve ordering, we need to reverse the slice
// when we're finished.
for e := beforeIDMark; e != nil; e = e.Prev() {
entry := e.Value.(*indexedItemsEntry) //nolint:forcetypeassert
if entry.itemID == beforeID {
// Don't include the beforeID
// entry itself, just continue.
l.Trace("entry item ID is equal to beforeID, skipping")
continue
}
if entry.itemID >= behindID {
// We've reached items that are
// newer than what we're looking
// for, just stop here.
l.Trace("reached newer items, breaking")
break
}
if entry.prepared == nil {
// Whoops, this entry isn't prepared yet; some
// race condition? That's OK, we can do it now.
prepared, err := t.prepareFunction(ctx, t.accountID, entry.itemID)
if err != nil {
if errors.Is(err, db.ErrNoEntries) {
// ErrNoEntries means something has been deleted,
// so we'll likely not be able to ever prepare this.
// This means we can remove it and skip past it.
l.Debugf("db.ErrNoEntries while trying to prepare %s; will remove from timeline", entry.itemID)
removeElements = append(removeElements, e)
continue
}
// We've got a proper db error.
return nil, fmt.Errorf("getXBetweenIDs: db error while trying to prepare %s: %w", entry.itemID, err)
}
entry.prepared = prepared
}
items = append(items, entry.prepared)
served++
if served >= amount {
break
}
}
// Reverse order of items.
// https://zchee.github.io/golang-wiki/SliceTricks/#reversing
for l, r := 0, len(items)-1; l < r; l, r = l+1, r-1 {
items[l], items[r] = items[r], items[l]
}
return items, nil
}
func (t *timeline) prepareNextQuery(amount int, maxID string, sinceID string, minID string) {
var (
// We explicitly use context.Background() rather than
// accepting a context param because we don't want this
// to stop/break when the calling context finishes.
ctx = context.Background()
err error
)
// Always perform this async so caller doesn't have to wait.
go func() {
switch {
case maxID == "" && sinceID == "" && minID == "":
err = t.prepareXBetweenIDs(ctx, amount, id.Highest, id.Lowest, true)
case maxID != "" && sinceID == "" && minID == "":
err = t.prepareXBetweenIDs(ctx, amount, maxID, id.Lowest, true)
case maxID != "" && sinceID != "":
err = t.prepareXBetweenIDs(ctx, amount, maxID, sinceID, true)
case maxID != "" && minID != "":
err = t.prepareXBetweenIDs(ctx, amount, maxID, minID, false)
case maxID == "" && sinceID != "":
err = t.prepareXBetweenIDs(ctx, amount, id.Highest, sinceID, true)
case maxID == "" && minID != "":
err = t.prepareXBetweenIDs(ctx, amount, id.Highest, minID, false)
default:
err = errors.New("Get: switch statement exhausted with no results")
}
if err != nil {
log.
WithContext(ctx).
WithFields(kv.Fields{
{"amount", amount},
{"maxID", maxID},
{"sinceID", sinceID},
{"minID", minID},
}...).
Warnf("error preparing next query: %s", err)
}
}()
}