1 files changed, 57 insertions, 0 deletions
diff --git a/internal/timeline/postindex.go b/internal/timeline/postindex.go
new file mode 100644
index 000000000..2ab65e087
--- /dev/null
+++ b/internal/timeline/postindex.go
@@ -0,0 +1,57 @@
+package timeline
+
+import (
+	"container/list"
+	"errors"
+)
+
+type postIndex struct {
+	data *list.List
+}
+
+type postIndexEntry struct {
+	statusID string
+}
+
+func (p *postIndex) insertIndexed(i *postIndexEntry) 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 nil
+	}
+
+	var insertMark *list.Element
+	// 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() {
+		entry, ok := e.Value.(*postIndexEntry)
+		if !ok {
+			return errors.New("index: could not parse e as a postIndexEntry")
+		}
+
+		// 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 nil
+		}
+	}
+
+	if insertMark != nil {
+		p.data.InsertBefore(i, insertMark)
+		return 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 nil
+}