Add API for modify Node (#99)

* Add API for modify Node

yaml/shared/src/main/scala/org/virtuslab/yaml/Node.scala

@@ -2,6 +2,7 @@ package org.virtuslab.yaml
 
 import org.virtuslab.yaml.Range
 import org.virtuslab.yaml.Tag
+import org.virtuslab.yaml.syntax.NodeSelector
 import org.virtuslab.yaml.syntax.YamlPrimitive
 
 /**
@@ -16,6 +17,10 @@ sealed trait Node:
   ): Either[YamlError, T] =
     c.construct(this)
 
+  def modify(index: Int): NodeVisitor = NodeVisitor(this, List(NodeSelector.IntSelector(index)))
+  def modify(field: String): NodeVisitor =
+    NodeVisitor(this, List(NodeSelector.StringSelector(field)))
+
 object Node:
   final case class ScalarNode private[yaml] (value: String, tag: Tag, pos: Option[Range] = None)
       extends Node
@@ -55,4 +60,11 @@ object Node:
       new MappingNode(mappings, Tag.map, None)
     def unapply(node: MappingNode): Option[(Map[Node, Node], Tag)] = Some((node.mappings, node.tag))
   end MappingNode
+
+  extension (either: Either[TraverseError, Node])
+    def modify(index: Int): Either[TraverseError, NodeVisitor] = either.map(_.modify(index))
+
+  extension (either: Either[TraverseError, Node])
+    def modify(field: String): Either[TraverseError, NodeVisitor] = either.map(_.modify(field))
+
 end Node

yaml/shared/src/main/scala/org/virtuslab/yaml/NodeVisitor.scala

@@ -0,0 +1,103 @@
+package org.virtuslab.yaml
+
+import org.virtuslab.yaml.Node
+import org.virtuslab.yaml.Node.*
+import org.virtuslab.yaml.Range
+import org.virtuslab.yaml.TraverseError
+import org.virtuslab.yaml.YamlError
+import org.virtuslab.yaml.syntax.NodeSelector
+import org.virtuslab.yaml.syntax.NodeSelector.*
+
+class NodeVisitor(node: Node, selectors: List[NodeSelector]):
+  def apply(index: Int): NodeVisitor =
+    NodeVisitor(node, selectors :+ NodeSelector.IntSelector(index))
+  def apply(field: String): NodeVisitor =
+    NodeVisitor(node, selectors :+ NodeSelector.StringSelector(field))
+
+  private def updateScalarNode(
+      value: String,
+      scalar: ScalarNode
+  ): Either[TraverseError, ScalarNode] =
+    selectors match {
+      case Nil =>
+        Right(
+          scalar.copy(
+            value = value
+          )
+        )
+      case _ =>
+        Left(
+          TraverseError(
+            s"Expected end of scalar path, instead found path ${selectors.map(_.show).mkString(".")}"
+          )
+        )
+    }
+
+  private def updateSequenceNode(
+      value: String,
+      sequence: SequenceNode
+  ): Either[TraverseError, SequenceNode] =
+    selectors match {
+      case IntSelector(index) :: rest =>
+        val nodes      = sequence.nodes
+        val updateNode = NodeVisitor(nodes(index), rest).setValue(value)
+        updateNode.map(node => sequence.copy(nodes = nodes.updated(index, node)))
+
+      case StringSelector(field) :: rest =>
+        Left(
+          TraverseError(
+            s"Expeceted index of sequence, insted found string path: ${field}"
+          )
+        )
+      case _ => Left(TraverseError(s"Expeceted index of sequence, insted found end of path"))
+    }
+
+  private def updateMappingNode(value: String, mapping: MappingNode) =
+    selectors match
+      case StringSelector(field) :: rest =>
+        val mappings = mapping.mappings
+        val entryToUpdateOpt = mappings.find {
+          case (ScalarNode(keyName, _), _) => keyName == field
+          case _                           => false
+        }
+
+        entryToUpdateOpt match
+          case Some(entryToUpdate) =>
+            val updatedValueE = entryToUpdate match
+              case (ScalarNode(keyName, _), valueNode) =>
+                val updatedNode = NodeVisitor(valueNode, rest).setValue(value)
+                updatedNode
+              case _ => Left(TraverseError(s"Not found $field in mapping"))
+
+            updatedValueE.map { updatedValue =>
+              mapping.copy(
+                mappings.updated(entryToUpdate._1, updatedValue)
+              )
+            }
+          case None => Left(TraverseError(s"Not found $field in mapping"))
+      case IntSelector(index) :: rest =>
+        Left(
+          TraverseError(
+            s"Expeceted plain test, insted found index: $index"
+          )
+        )
+      case _ => Left(TraverseError(s"Expeceted plain text, insted found end of path"))
+
+  def setValue(value: String): Either[TraverseError, Node] = node match
+    case scalar: ScalarNode     => updateScalarNode(value, scalar)
+    case sequence: SequenceNode => updateSequenceNode(value, sequence)
+    case mapping: MappingNode   => updateMappingNode(value, mapping)
+
+object NodeVisitor:
+
+  def apply(node: Node, selectors: List[NodeSelector]): NodeVisitor =
+    new NodeVisitor(node, selectors)
+
+  extension (either: Either[TraverseError, NodeVisitor])
+    def apply(field: String): Either[TraverseError, NodeVisitor] = either.map(_.apply(field))
+
+  extension (either: Either[TraverseError, NodeVisitor])
+    def apply(index: Int): Either[TraverseError, NodeVisitor] = either.map(_.apply(index))
+
+  extension (either: Either[TraverseError, NodeVisitor])
+    def setValue(value: String): Either[TraverseError, Node] = either.flatMap(_.setValue(value))

yaml/shared/src/main/scala/org/virtuslab/yaml/Yaml.scala

@@ -35,6 +35,15 @@ extension (str: String)
       t    <- node.as[T]
     yield t
 
+  def asNode: Either[YamlError, Node] =
+    for
+      events <- {
+        val parser = ParserImpl(Scanner(str))
+        parser.getEvents()
+      }
+      node <- ComposerImpl.fromEvents(events)
+    yield node
+
 extension [T](t: T)
   /**
    * Serialize a [[T]] into a YAML string.

yaml/shared/src/main/scala/org/virtuslab/yaml/YamlError.scala

@@ -23,6 +23,8 @@ object ParseError:
 
 final case class ComposerError(msg: String) extends YamlError
 
+final case class TraverseError(msg: String) extends YamlError
+
 final case class ConstructError(msg: String) extends YamlError
 object ConstructError:
   private def from(errorMsg: String, node: Option[Node], expected: Option[String]): ConstructError =

yaml/shared/src/main/scala/org/virtuslab/yaml/syntax/NodeSelector.scala

@@ -0,0 +1,13 @@
+package org.virtuslab.yaml.syntax
+
+import org.virtuslab.yaml.Node
+
+sealed trait NodeSelector:
+  def show: String
+
+object NodeSelector:
+
+  case class IntSelector(index: Int) extends NodeSelector:
+    override def show: String = index.toString
+  case class StringSelector(field: String) extends NodeSelector:
+    override def show: String = field

yaml/shared/src/test/scala/org/virtuslab/yaml/TestOps.scala

@@ -0,0 +1,11 @@
+package org.virtuslab.yaml
+
+object TestOps {
+
+  extension [E <: YamlError, T](either: Either[E, T])
+    def orThrow: T =
+      either match
+        case Left(e)  => throw new RuntimeException(e.msg)
+        case Right(t) => t
+
+}

yaml/shared/src/test/scala/org/virtuslab/yaml/travers/NodeVisitorSuite.scala

@@ -0,0 +1,53 @@
+package org.virtuslab.yaml.travers
+
+import org.virtuslab.yaml.*
+import org.virtuslab.yaml.TestOps.*
+import org.virtuslab.yaml.Node
+import org.virtuslab.yaml.NodeVisitor._
+
+class NodeVisitorSuite extends munit.FunSuite {
+
+  test("should update ports for web") {
+
+    val yaml =
+      s"""version: "3.9"
+         |services:
+         |  web:
+         |    build: .
+         |    volumes:
+         |      - .:/code
+         |      - logvolume01:/var/log
+         |    ports:
+         |      - "5000:5000"
+         |  redis:
+         |    image: "redis:alpine"
+         |""".stripMargin
+
+    val node: Node = yaml.asNode.orThrow
+    val modifiedNode: Node =
+      node
+        .modify("services")("web")("ports")(0)
+        .setValue("6000:6000")
+        .modify("services")("redis")("image")
+        .setValue("openjdk:11")
+        .orThrow
+
+    val modifiedYaml = modifiedNode.asYaml
+
+    val exptectedYaml =
+      s"""version: 3.9
+         |services: 
+         |  web: 
+         |    build: .
+         |    volumes: 
+         |      - .:/code
+         |      - logvolume01:/var/log
+         |    ports: 
+         |      - 6000:6000
+         |  redis: 
+         |    image: openjdk:11
+         |""".stripMargin
+
+    assertEquals(modifiedYaml, exptectedYaml)
+  }
+}