gotosocial/internal/timeline/postindex.go

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/*
GoToSocial
Copyright (C) 2021 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"
"errors"
)
type postIndex struct {
data *list.List
}
type postIndexEntry struct {
statusID string
boostOfID string
accountID string
boostOfAccountID string
}
func (p *postIndex) insertIndexed(i *postIndexEntry) (bool, error) {
if p.data == nil {
p.data = &list.List{}
}
// if we have no entries yet, this is both the newest and oldest entry, so just put it in the front
if p.data.Len() == 0 {
p.data.PushFront(i)
return true, nil
}
var insertMark *list.Element
var position int
// We need to iterate through the index to make sure we put this post in the appropriate place according to when it was created.
// We also need to make sure we're not inserting a duplicate post -- this can happen sometimes and it's not nice UX (*shudder*).
for e := p.data.Front(); e != nil; e = e.Next() {
position = position + 1
entry, ok := e.Value.(*postIndexEntry)
if !ok {
return false, errors.New("index: could not parse e as a postIndexEntry")
}
// don't insert this if it's a boost of a status we've seen recently
if i.boostOfID != "" {
if i.boostOfID == entry.boostOfID || i.boostOfID == entry.statusID {
if position < boostReinsertionDepth {
return false, nil
}
}
}
// if the post to index is newer than e, insert it before e in the list
if insertMark == nil {
if i.statusID > entry.statusID {
insertMark = e
}
}
// make sure we don't insert a duplicate
if entry.statusID == i.statusID {
return false, nil
}
}
if insertMark != nil {
p.data.InsertBefore(i, insertMark)
return true, nil
}
// if we reach this point it's the oldest post we've seen so put it at the back
p.data.PushBack(i)
return true, nil
}