i have no idea what i'm doing

internal/processing/timeline/timeline.go

@@ -21,6 +21,7 @@ package timeline
 import (
 	"container/list"
 	"errors"
+	"fmt"
 	"sync"
 	"time"
 
@@ -28,33 +29,96 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 )
 
+const fromLatest = "FROM_LATEST"
+
 type timeline struct {
-	index     *list.List
-	readyToGo []*apimodel.Status
-	sharedCache *list.List
-	accountID string
-	db        db.DB
+	postIndex     *list.List
+	preparedPosts *list.List
+	sharedCache   *list.List
+	accountID     string
+	db            db.DB
 	*sync.Mutex
 }
 
-func newTimeline(accountID string, db db.DB) *timeline {
+func newTimeline(accountID string, db db.DB, sharedCache *list.List) *timeline {
 	return &timeline{
-		index:     list.New(),
-		readyToGo: []*apimodel.Status{},
-		accountID: accountID,
+		postIndex:     list.New(),
+		preparedPosts: list.New(),
+		sharedCache:   sharedCache,
+		accountID:     accountID,
 	}
 }
 
-func (t *timeline) prepareXFromID(limit int, statusID string) error {
+func (t *timeline) prepareNextXFromID(amount int, fromID string) error {
 	t.Lock()
 	defer t.Unlock()
 
+	prepared := make([]*post, 0, amount)
+
+	// find the mark in the index -- we want x statuses after this
+	var fromMark *list.Element
+	for e := t.postIndex.Front(); e != nil; e = e.Next() {
+		p, ok := e.Value.(*post)
+		if !ok {
+			return errors.New("could not convert interface to post")
+		}
+
+		if p.statusID == fromID {
+			fromMark = e
+			break
+		}
+	}
+
+	if fromMark == nil {
+		// we can't find the given id in the index -_-
+		return fmt.Errorf("prepareNextXFromID: fromID %s not found in index", fromID)
+	}
+
+	for e := fromMark.Next(); e != nil; e = e.Next() {
+
+	}
+
 	return nil
 }
 
-func (t *timeline) getX(limit int) (*apimodel.Status, error) {
-	t.Lock()
-	defer t.Unlock()
+func (t *timeline) getXFromTop(amount int) ([]*apimodel.Status, error) {
+	statuses := []*apimodel.Status{}
+	if amount == 0 {
+		return statuses, nil
+	}
+
+	if len(t.readyToGo) < amount {
+		if err := t.prepareNextXFromID(amount, fromLatest); err != nil {
+			return nil, err
+		}
+	}
+
+	return t.readyToGo[:amount], nil
+}
+
+// getXFromID gets x amount of posts in chronological order from the given ID onwards, NOT including the given id.
+// The posts will be taken from the readyToGo pile, unless nothing is ready to go.
+func (t *timeline) getXFromID(amount int, fromID string) ([]*apimodel.Status, error) {
+	statuses := []*apimodel.Status{}
+	if amount == 0 || fromID == "" {
+		return statuses, nil
+	}
+
+	// get the position of the given id in the ready to go pile
+	var indexOfID *int
+	for i, s := range t.readyToGo {
+		if s.ID == fromID {
+			indexOfID = &i
+		}
+	}
+
+	// the status isn't in the ready to go pile so prepare it
+	if indexOfID == nil {
+		if err := t.prepareNextXFromID(amount, fromID); err != nil {
+			return nil, err
+		}
+	}
+
 	return nil, nil
 }
 
@@ -62,7 +126,16 @@ func (t *timeline) insert(status *apimodel.Status) error {
 	t.Lock()
 	defer t.Unlock()
 
-	newPost := &post{}
+	createdAt, err := time.Parse(time.RFC3339, status.CreatedAt)
+	if err != nil {
+		return fmt.Errorf("insert: could not parse time %s: %s", status.CreatedAt, err)
+	}
+
+	newPost := &post{
+		createdAt:  createdAt,
+		statusID:   status.ID,
+		serialized: status,
+	}
 
 	if t.index == nil {
 		t.index.PushFront(newPost)
@@ -73,15 +146,21 @@ func (t *timeline) insert(status *apimodel.Status) error {
 		if !ok {
 			return errors.New("could not convert interface to post")
 		}
-		if p.createdAt.Before(newPost.createdAt) {
 
+		if newPost.createdAt.After(p.createdAt) {
+			// this is a newer post so insert it just before the post it's newer than
+			t.index.InsertBefore(newPost, e)
+			return nil
 		}
 	}
+
+	// if we haven't returned yet it's the oldest post we've seen so shove it at the back
+	t.index.PushBack(newPost)
 	return nil
 }
 
 type post struct {
-	createdAt time.Time
-	statusID  string
+	createdAt  time.Time
+	statusID   string
 	serialized *apimodel.Status
 }