GoToSocial/internal/timeline/get.go

360 lines
10 KiB
Go

/*
GoToSocial
Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
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"
"github.com/sirupsen/logrus"
)
const retries = 5
func (t *timeline) Get(ctx context.Context, amount int, maxID string, sinceID string, minID string, prepareNext bool) ([]Preparable, error) {
l := logrus.WithFields(logrus.Fields{
"func": "Get",
"accountID": t.accountID,
"amount": amount,
"maxID": maxID,
"sinceID": sinceID,
"minID": minID,
})
l.Debug("entering get")
var items []Preparable
var err error
// no params are defined to just fetch from the top
// this is equivalent to a user asking for the top x items from their timeline
if maxID == "" && sinceID == "" && minID == "" {
items, err = t.GetXFromTop(ctx, amount)
// aysnchronously prepare the next predicted query so it's ready when the user asks for it
if len(items) != 0 {
nextMaxID := items[len(items)-1].GetID()
if prepareNext {
// already cache the next query to speed up scrolling
go func() {
// use context.Background() because we don't want the query to abort when the request finishes
if err := t.prepareNextQuery(context.Background(), amount, nextMaxID, "", ""); err != nil {
l.Errorf("error preparing next query: %s", err)
}
}()
}
}
}
// maxID is defined but sinceID isn't so take from behind
// this is equivalent to a user asking for the next x items from their timeline, starting from maxID
if maxID != "" && sinceID == "" {
attempts := 0
items, err = t.GetXBehindID(ctx, amount, maxID, &attempts)
// aysnchronously prepare the next predicted query so it's ready when the user asks for it
if len(items) != 0 {
nextMaxID := items[len(items)-1].GetID()
if prepareNext {
// already cache the next query to speed up scrolling
go func() {
// use context.Background() because we don't want the query to abort when the request finishes
if err := t.prepareNextQuery(context.Background(), amount, nextMaxID, "", ""); err != nil {
l.Errorf("error preparing next query: %s", err)
}
}()
}
}
}
// maxID is defined and sinceID || minID are as well, so take a slice between them
// this is equivalent to a user asking for items older than x but newer than y
if maxID != "" && sinceID != "" {
items, err = t.GetXBetweenID(ctx, amount, maxID, minID)
}
if maxID != "" && minID != "" {
items, err = t.GetXBetweenID(ctx, amount, maxID, minID)
}
// maxID isn't defined, but sinceID || minID are, so take x before
// this is equivalent to a user asking for items newer than x (eg., refreshing the top of their timeline)
if maxID == "" && sinceID != "" {
items, err = t.GetXBeforeID(ctx, amount, sinceID, true)
}
if maxID == "" && minID != "" {
items, err = t.GetXBeforeID(ctx, amount, minID, true)
}
return items, err
}
func (t *timeline) GetXFromTop(ctx context.Context, amount int) ([]Preparable, error) {
// make a slice of preparedItems with the length we need to return
preparedItems := make([]Preparable, 0, amount)
if t.preparedItems.data == nil {
t.preparedItems.data = &list.List{}
}
// make sure we have enough items prepared to return
if t.preparedItems.data.Len() < amount {
if err := t.PrepareFromTop(ctx, amount); err != nil {
return nil, err
}
}
// work through the prepared items from the top and return
var served int
for e := t.preparedItems.data.Front(); e != nil; e = e.Next() {
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXFromTop: could not parse e as a preparedItemsEntry")
}
preparedItems = append(preparedItems, entry.prepared)
served++
if served >= amount {
break
}
}
return preparedItems, nil
}
func (t *timeline) GetXBehindID(ctx context.Context, amount int, behindID string, attempts *int) ([]Preparable, error) {
l := logrus.WithFields(logrus.Fields{
"func": "GetXBehindID",
"amount": amount,
"behindID": behindID,
"attempts": *attempts,
})
newAttempts := *attempts
newAttempts++
attempts = &newAttempts
// make a slice of items with the length we need to return
items := make([]Preparable, 0, amount)
if t.preparedItems.data == nil {
t.preparedItems.data = &list.List{}
}
// iterate through the modified list until we hit the mark we're looking for
var position int
var behindIDMark *list.Element
findMarkLoop:
for e := t.preparedItems.data.Front(); e != nil; e = e.Next() {
position++
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBehindID: could not parse e as a preparedPostsEntry")
}
if entry.itemID <= behindID {
l.Trace("found behindID mark")
behindIDMark = e
break findMarkLoop
}
}
// we didn't find it, so we need to make sure it's indexed and prepared and then try again
// this can happen when a user asks for really old items
if behindIDMark == nil {
if err := t.PrepareBehind(ctx, behindID, amount); err != nil {
return nil, fmt.Errorf("GetXBehindID: error preparing behind and including ID %s", behindID)
}
oldestID, err := t.OldestPreparedItemID(ctx)
if err != nil {
return nil, err
}
if oldestID == "" {
l.Tracef("oldestID is empty so we can't return behindID %s", behindID)
return items, nil
}
if oldestID == behindID {
l.Tracef("given behindID %s is the same as oldestID %s so there's nothing to return behind it", behindID, oldestID)
return items, nil
}
if *attempts > retries {
l.Tracef("exceeded retries looking for behindID %s", behindID)
return items, nil
}
l.Trace("trying GetXBehindID again")
return t.GetXBehindID(ctx, amount, behindID, attempts)
}
// make sure we have enough items prepared behind it to return what we're being asked for
if t.preparedItems.data.Len() < amount+position {
if err := t.PrepareBehind(ctx, behindID, amount); err != nil {
return nil, err
}
}
// start serving from the entry right after the mark
var served int
serveloop:
for e := behindIDMark.Next(); e != nil; e = e.Next() {
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBehindID: could not parse e as a preparedPostsEntry")
}
// serve up to the amount requested
items = append(items, entry.prepared)
served++
if served >= amount {
break serveloop
}
}
return items, nil
}
func (t *timeline) GetXBeforeID(ctx context.Context, amount int, beforeID string, startFromTop bool) ([]Preparable, error) {
// make a slice of items with the length we need to return
items := make([]Preparable, 0, amount)
if t.preparedItems.data == nil {
t.preparedItems.data = &list.List{}
}
// iterate through the modified list until we hit the mark we're looking for, or as close as possible to it
var beforeIDMark *list.Element
findMarkLoop:
for e := t.preparedItems.data.Front(); e != nil; e = e.Next() {
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBeforeID: could not parse e as a preparedPostsEntry")
}
if entry.itemID >= beforeID {
beforeIDMark = e
} else {
break findMarkLoop
}
}
if beforeIDMark == nil {
return items, nil
}
var served int
if startFromTop {
// start serving from the front/top and keep going until we hit mark or get x amount items
serveloopFromTop:
for e := t.preparedItems.data.Front(); e != nil; e = e.Next() {
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBeforeID: could not parse e as a preparedPostsEntry")
}
if entry.itemID == beforeID {
break serveloopFromTop
}
// serve up to the amount requested
items = append(items, entry.prepared)
served++
if served >= amount {
break serveloopFromTop
}
}
} else if !startFromTop {
// start serving from the entry right before the mark
serveloopFromBottom:
for e := beforeIDMark.Prev(); e != nil; e = e.Prev() {
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBeforeID: could not parse e as a preparedPostsEntry")
}
// serve up to the amount requested
items = append(items, entry.prepared)
served++
if served >= amount {
break serveloopFromBottom
}
}
}
return items, nil
}
func (t *timeline) GetXBetweenID(ctx context.Context, amount int, behindID string, beforeID string) ([]Preparable, error) {
// make a slice of items with the length we need to return
items := make([]Preparable, 0, amount)
if t.preparedItems.data == nil {
t.preparedItems.data = &list.List{}
}
// iterate through the modified list until we hit the mark we're looking for
var position int
var behindIDMark *list.Element
findMarkLoop:
for e := t.preparedItems.data.Front(); e != nil; e = e.Next() {
position++
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBetweenID: could not parse e as a preparedPostsEntry")
}
if entry.itemID == behindID {
behindIDMark = e
break findMarkLoop
}
}
// we didn't find it
if behindIDMark == nil {
return nil, fmt.Errorf("GetXBetweenID: couldn't find item with ID %s", behindID)
}
// make sure we have enough items prepared behind it to return what we're being asked for
if t.preparedItems.data.Len() < amount+position {
if err := t.PrepareBehind(ctx, behindID, amount); err != nil {
return nil, err
}
}
// start serving from the entry right after the mark
var served int
serveloop:
for e := behindIDMark.Next(); e != nil; e = e.Next() {
entry, ok := e.Value.(*preparedItemsEntry)
if !ok {
return nil, errors.New("GetXBetweenID: could not parse e as a preparedPostsEntry")
}
if entry.itemID == beforeID {
break serveloop
}
// serve up to the amount requested
items = append(items, entry.prepared)
served++
if served >= amount {
break serveloop
}
}
return items, nil
}