From 466731e2cfa9973f38865cf2e80fcb91aab4eedd Mon Sep 17 00:00:00 2001
From: Amolith <amolith@secluded.site>
Date: Tue, 6 Sep 2022 11:44:11 -0400
Subject: [PATCH] finish up pagination support in API and backend

---
 helperfuncs.go | 44 ++++++++++++++++++++++++++++++++------------
 1 file changed, 32 insertions(+), 12 deletions(-)

diff --git a/helperfuncs.go b/helperfuncs.go
index 2c94a061b8e28d37954b18cca7bac9b40e3e0356..0696847ad34dc8837cd7d93f93c5efa522228c29 100644
--- a/helperfuncs.go
+++ b/helperfuncs.go
@@ -22,6 +22,7 @@ func (m model) create(name string, url string) string {
 		return txn.Set([]byte(name), []byte(url))
 	})
 	if err != nil {
+		// TODO: return an error instead so it can be handled like an error
 		return fmt.Sprint(err)
 	}
 
@@ -42,24 +43,43 @@ func (m model) read(start string, end string, count int) (map[string]string, err
 
 	err := m.database.View(func(txn *badger.Txn) error {
 		opts := badger.DefaultIteratorOptions
-		opts.PrefetchSize = 10
+		opts.PrefetchSize = 20
 		if start != "" && end == "" {
+			// Start value provided, iterate backwards
 			opts.Reverse = true
 		}
 		iterator := txn.NewIterator(opts)
-		if start != "" && end == "" {
-			iterator.Seek([]byte(end))
-		} else if start == "" && end != "" {
+		defer iterator.Close()
+		if start == "" && end == "" {
+			iterator.Rewind()
+		} else if start != "" && end == "" {
+			// Set position to "start"
 			iterator.Seek([]byte(start))
+			// If "start" exists, move to next value
+			if iterator.Valid() {
+				iterator.Next()
+			}
+		} else if start == "" && end != "" {
+			// Start value provided, iterate forwards
+			// Set position to "end"
+			iterator.Seek([]byte(end))
+			// If "end" exists, move to next value
+			if iterator.Valid() {
+				iterator.Next()
+			}
+		} else {
+			return errors.New("Only provide start OR end parameters, not both")
 		}
-		defer iterator.Close()
-		for iterator.Rewind(); iterator.Valid(); iterator.Next() {
-			err := iterator.Item().Value(func(v []byte) error {
-				links[string(iterator.Item().Key())] = string(v)
-				return nil
-			})
-			if err != nil {
-				return err
+		for i := 0; i < count; i++ {
+			if iterator.Valid() {
+				err := iterator.Item().Value(func(v []byte) error {
+					links[string(iterator.Item().Key())] = string(v)
+					return nil
+				})
+				if err != nil {
+					return err
+				}
+				iterator.Next()
 			}
 		}
 		return nil