package starter

import org.w3c.dom.Document
import org.w3c.dom.NodeList
import org.xml.sax.InputSource
import java.io.ByteArrayInputStream
import java.io.StringWriter
import javax.xml.parsers.DocumentBuilderFactory
import javax.xml.transform.OutputKeys
import javax.xml.transform.TransformerFactory
import javax.xml.transform.dom.DOMSource
import javax.xml.transform.stream.StreamResult
import javax.xml.xpath.XPathConstants
import javax.xml.xpath.XPathFactory


/*
    @see https://stackoverflow.com/a/33541820
 */
fun prettyPrintXml(xml: String, indent: Int = 4): String {
    // Turn xml string into a document
    val document: Document = DocumentBuilderFactory.newInstance()
            .newDocumentBuilder()
            .parse(InputSource(ByteArrayInputStream(xml.encodeToByteArray())))

    // Remove whitespaces outside tags
    document.normalize()
    val xPath = XPathFactory.newInstance().newXPath()
    val nodeList = xPath.evaluate("//text()[normalize-space()='']",
            document,
            XPathConstants.NODESET) as NodeList
    for (i in 0 until nodeList.length) {
        val node = nodeList.item(i)
        node.parentNode.removeChild(node)
    }

    // Setup pretty print options
    val transformerFactory = TransformerFactory.newInstance()
    transformerFactory.setAttribute("indent-number", indent)
    val transformer = transformerFactory.newTransformer()
    transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8")
    transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes")
    transformer.setOutputProperty(OutputKeys.INDENT, "yes")

    // Return pretty print xml string
    val stringWriter = StringWriter()
    transformer.transform(DOMSource(document), StreamResult(stringWriter))
    return stringWriter.toString()
}