it's coming along

internal/processing/timeline/preparedposts.go

@@ -0,0 +1,49 @@
+package timeline
+
+import (
+	"container/list"
+	"errors"
+	"time"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+)
+
+type preparedPosts struct {
+	data *list.List
+}
+
+type preparedPostsEntry struct {
+	createdAt time.Time
+	statusID  string
+	prepared  *apimodel.Status
+}
+
+func (p *preparedPosts) insertPrepared(i *preparedPostsEntry) 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
+	}
+
+	// we need to iterate through the index to make sure we put this post in the appropriate place according to when it was created
+	for e := p.data.Front(); e != nil; e = e.Next() {
+		entry, ok := e.Value.(*preparedPostsEntry)
+		if !ok {
+			return errors.New("index: could not parse e as a preparedPostsEntry")
+		}
+
+		// if the post to index is newer than e, insert it before e in the list
+		if i.createdAt.After(entry.createdAt) {
+			p.data.InsertBefore(i, e)
+			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
+}