From 0bd47d31ad77db4c41336f02928b7cb47274b2ab Mon Sep 17 00:00:00 2001
From: Alex Gaetano Padula <apadula@cursusdb.com>
Date: Tue, 24 Sep 2024 07:36:34 -0400
Subject: [PATCH] NRange() function implementation and tests

---
 btree.go      | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++
 btree_test.go | 32 ++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)

diff --git a/btree.go b/btree.go
index 93f084c..81255d8 100644
--- a/btree.go
+++ b/btree.go
@@ -939,6 +939,64 @@ func (k *Key) Iterator() func() ([]byte, bool) {
 	}
 }
 
+// NRange returns all keys not within the range [start, end]
+func (b *BTree) NRange(start, end []byte) ([]*Key, error) {
+	root, err := b.getRoot()
+	if err != nil {
+		return nil, err
+	}
+
+	return b.nrange(root, start, end)
+}
+
+// nrange returns all keys not within the range [start, end]
+// nrange returns all keys not within the range [start, end]
+func (b *BTree) nrange(x *Node, start, end []byte) ([]*Key, error) {
+	keys := make([]*Key, 0)
+	if x != nil {
+		for i := 0; i < len(x.Keys); i++ {
+			if !x.Leaf {
+				childBytes, err := b.Pager.GetPage(x.Children[i])
+				if err != nil {
+					return nil, err
+				}
+
+				child, err := decodeNode(childBytes)
+				if err != nil {
+					return nil, err
+				}
+
+				childKeys, err := b.nrange(child, start, end)
+				if err != nil {
+					return nil, err
+				}
+				keys = append(keys, childKeys...)
+			}
+			if lessThan(x.Keys[i].K, start) || greaterThan(x.Keys[i].K, end) {
+				keys = append(keys, x.Keys[i])
+			}
+		}
+		if !x.Leaf {
+			childBytes, err := b.Pager.GetPage(x.Children[len(x.Children)-1])
+			if err != nil {
+				return nil, err
+			}
+
+			child, err := decodeNode(childBytes)
+			if err != nil {
+				return nil, err
+			}
+
+			childKeys, err := b.nrange(child, start, end)
+			if err != nil {
+				return nil, err
+			}
+			keys = append(keys, childKeys...)
+		}
+	}
+	return keys, nil
+}
+
 // Range returns all keys in the BTree that are within the range [start, end]
 func (b *BTree) Range(start, end []byte) ([]interface{}, error) {
 	root, err := b.getRoot()
diff --git a/btree_test.go b/btree_test.go
index c3ef713..42ceeaa 100644
--- a/btree_test.go
+++ b/btree_test.go
@@ -299,6 +299,38 @@ func TestBTree_GreaterThan(t *testing.T) {
 	}
 }
 
+func TestBTree_NRange(t *testing.T) {
+
+	defer os.Remove("btree.db")
+	defer os.Remove("btree.db.del")
+
+	btree, err := Open("btree.db", os.O_CREATE|os.O_RDWR, 0644, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer btree.Close()
+
+	for i := 0; i < 500; i++ {
+		key := fmt.Sprintf("%03d", i) // pad the key with leading zeros
+		err := btree.Put([]byte(key), []byte(key))
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	keys, err := btree.NRange([]byte("010"), []byte("020")) // use padded keys
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Expect 489 keys
+	if len(keys) != 489 {
+		t.Fatalf("expected 489 keys, got %d", len(keys))
+
+	}
+}
+
 func TestBTree_LessThan(t *testing.T) {
 	defer os.Remove("btree.db")
 	defer os.Remove("btree.db.del")