xml to sax to tree in kotlin

x.kt

package x

import java.util.Stack
import java.io.File
import javax.xml.parsers.*
import org.xml.sax.*
import org.xml.sax.helpers.*

class Node(val l:String, val q:String, val u:String, val a:Map<String,String>) {
    val children:MutableList<Node> = mutableListOf<Node>()
    constructor(q:String):this("<localName>",q,"<uri>",mapOf<String,String>())
    override fun toString():String { return "<$u::$q:$l $a, ${children.size}>" }
    fun addChild(n:Node) { children.add(n) }
}

fun Node.linearize():List<Node> {
    return listOf(this) + this.children.map(Node::linearize).flatten()
}

fun Attributes.mapped():Map<String,String> {
    return (0..this.getLength()-1)
	    .map({ i -> this.getLocalName(i) to this.getValue(i) })
	    .toMap()
}

class Xml(val pred:(String)->Boolean):DefaultHandler() {

    val matches:MutableList<Pair<String,Map<String,String>>> = mutableListOf()
    val stack:Stack<Node> = Stack<Node>().apply { push(Node("root")) }

    override fun startElement(u:String, l:String, q:String, a:Attributes) {
	val m = a.mapped()
	if (this.pred(q)) { matches.add(q to m) }
	stack.push(Node(l, q, u, m)) // shift?
    }

    override fun endElement(uri:String, localName:String, qName:String) {
	val n = stack.pop()
	stack.peek().addChild(n) // reduce
    }

    override fun toString():String {
	return "<Xml(${matches.size}) $matches>"
    }

}

fun xml(source:String="gest.xml", tag:String="a"):Xml {
    val handler = Xml({ s -> s == tag})
    val parser = SAXParserFactory.newInstance().newSAXParser()
    val file = File(source)
    parser.parse(file, handler)
    return handler
}

fun main(args: Array<String>) {
    args.forEach { a ->
	println()
	println(a)
	println("----")
	xml(a).let { h -> h.stack.peek().linearize().forEach(::println) }
    }
}