From eb26d597c6d526f84077afdc141b0a5d585c7da3 Mon Sep 17 00:00:00 2001
From: NeonXP <i@neonxp.dev>
Date: Wed, 16 Nov 2022 21:35:48 +0300
Subject: [PATCH] Utility methods

---
 README.md          | 15 +++++++++++++
 model/array.go     | 10 +++++++++
 model/condition.go | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 model/map.go       |  9 ++++++++
 model/node.go      | 30 +++++++++++++++++++++++++
 5 files changed, 119 insertions(+)
 create mode 100644 model/condition.go

diff --git a/README.md b/README.md
index fb99e4b..72d4d2b 100644
--- a/README.md
+++ b/README.md
@@ -62,4 +62,19 @@ func (n *Node) Value() any
 
 // MarshalJSON to []byte
 func (n *Node) MarshalJSON() ([]byte, error)
+
+// Merge two object or array nodes
+func (n *Node) Merge(node *Node) error
+
+// Len returns length of object or array nodes
+func (n *Node) Len() (int, error)
+
+// Compare current node with another node
+func (n *Node) Compare(op Operand, node *Node) bool
+
+// Remove by key from object
+func (n *Node) Remove(key string) error 
+
+// RemoveIndex from array
+func (n *Node) RemoveIndex(idx int) error
 ```
diff --git a/model/array.go b/model/array.go
index b3d2586..5d64209 100644
--- a/model/array.go
+++ b/model/array.go
@@ -30,3 +30,13 @@ func (n *Node) Each(cb func(idx int, value *Node) error) error {
 	}
 	return nil
 }
+
+// RemoveIndex from array
+func (n *Node) RemoveIndex(idx int) error {
+	arrlen := len(n.arrayValue)
+	if idx >= arrlen {
+		return fmt.Errorf("index %d out of range (len=%d)", idx, arrlen)
+	}
+	n.arrayValue = append(n.arrayValue[:idx], n.arrayValue[idx:]...)
+	return nil
+}
diff --git a/model/condition.go b/model/condition.go
new file mode 100644
index 0000000..0b558b4
--- /dev/null
+++ b/model/condition.go
@@ -0,0 +1,55 @@
+package model
+
+// Compare current node with another node
+func (n *Node) Compare(op Operand, node *Node) bool {
+	switch op {
+	case OpEq:
+		return n.Value() == node.Value()
+	case OpNeq:
+		return n.Value() != node.Value()
+	case OpLess:
+		return less(n, node)
+	case OpGt:
+		return less(node, n)
+	case OpLessEq:
+		return less(n, node) || n.Value() == node.Value()
+	case OpGtEq:
+		return less(node, n) || n.Value() == node.Value()
+	case OpIn:
+		if n.Type != ArrayNode {
+			return false
+		}
+		for _, v := range n.arrayValue {
+			if v.Value() == node.Value() {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func less(n1 *Node, n2 *Node) bool {
+	if n1.Type != n2.Type {
+		return false
+	}
+	switch n1.Type {
+	case NumberNode:
+		return n1.numberValue < n2.numberValue
+	case StringNode:
+		return n1.stringValue < n2.stringValue
+	default:
+		return false
+	}
+}
+
+type Operand int
+
+const (
+	OpEq Operand = iota
+	OpNeq
+	OpLess
+	OpLessEq
+	OpGt
+	OpGtEq
+	OpIn
+)
diff --git a/model/map.go b/model/map.go
index 59ba2d8..7bfdaa3 100644
--- a/model/map.go
+++ b/model/map.go
@@ -41,3 +41,12 @@ func (n *Node) Map(cb func(key string, value *Node) (*Node, error)) error {
 	}
 	return nil
 }
+
+// Remove by key from object
+func (n *Node) Remove(key string) error {
+	if n.Type != ObjectNode {
+		return fmt.Errorf("node must be object, got %s", n.Type)
+	}
+	delete(n.objectValue, key)
+	return nil
+}
diff --git a/model/node.go b/model/node.go
index 1483eaf..fea8fcd 100644
--- a/model/node.go
+++ b/model/node.go
@@ -113,3 +113,33 @@ func (n *Node) MarshalJSON() ([]byte, error) {
 		return []byte("null"), nil
 	}
 }
+
+// Merge two object or array nodes
+func (n *Node) Merge(node *Node) error {
+	if n.Type != node.Type {
+		return fmt.Errorf("can't merge nodes of different types")
+	}
+	switch n.Type {
+	case ObjectNode:
+		for k, v := range node.objectValue {
+			n.objectValue[k] = v
+		}
+	case ArrayNode:
+		n.arrayValue = append(n.arrayValue, node.arrayValue...)
+	default:
+		return fmt.Errorf("merge not implemented for type %s", n.Type)
+	}
+	return nil
+}
+
+// Len returns length of object or array nodes
+func (n *Node) Len() (int, error) {
+	switch n.Type {
+	case ObjectNode:
+		return len(n.objectValue), nil
+	case ArrayNode:
+		return len(n.arrayValue), nil
+	default:
+		return 0, fmt.Errorf("merge not implemented for type %s", n.Type)
+	}
+}