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package ch.inftec.ju.util.xml;

import java.util.HashMap;
import java.util.Map;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Text;

import ch.inftec.ju.util.JuRuntimeException;

/**
 * Helper class to build XMLs based on DOM (Document Object Model).
 * 
 * By default, the generated Document will be set as standalone=yes.
 * @author tgdmemae
 *
 */
public class XmlBuilder {
	private final XmlBuilder parentBuilder;
	private final Document document;
	private final Element element;
	
	private final Map namespaces = new HashMap<>();
	
	static XmlBuilder createRootBuilder(String rootElementName, String namespacePrefix, String namespaceUri) {
		try {
			DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
			DocumentBuilder docBuilder = factory.newDocumentBuilder();
			Document document = docBuilder.newDocument();
			document.setXmlStandalone(true);
			
			Element rootElement = null;
			if (namespacePrefix != null) {
				rootElement = document.createElementNS(namespaceUri, rootElementName);
				rootElement.setPrefix(namespacePrefix);
			} else {
				rootElement = document.createElement(rootElementName);	
			}
			
			document.appendChild(rootElement);
			
			XmlBuilder xb = new XmlBuilder(null, document, rootElement);
			if (namespacePrefix != null) {
				xb.addNamespace(namespacePrefix, namespaceUri);
			}
			return xb;
		} catch (Exception ex) {
			throw new JuRuntimeException("Couldn't initialize XML Document");
		}
	}
	
	private XmlBuilder(XmlBuilder parentBuilder, Document document, Element element) throws JuRuntimeException {
		this.parentBuilder = parentBuilder;
		this.document = document;
		this.element = element;
	}
	
	/**
	 * Adds a new Namespace to this builder.
	 * @param prefix Namespace prefix, e.g. ns
	 * @param uri Namespace URI, e.g http://inftec.ch/ns
	 * @return
	 */
	public XmlBuilder addNamespace(String prefix, String uri) {
		if (this.namespaces.containsKey(prefix)) {
			throw new IllegalArgumentException(String.format("Namespace with prefix %s has already been added"));
		}
		this.namespaces.put(prefix, uri);
		return this;
	}
	
	/**
	 * Sets an attribute for the current element.
	 * @param name Attribute name
	 * @param value Attribute value
	 * @return This builder to allow for chaining
	 */
	public XmlBuilder setAttribute(String name, String value) {
		this.element.setAttribute(name,  value);
		return this;
	}
	
	/**
	 * Adds text to the current element.
	 * @param text Text to be added
	 * @return This builder to allow for chaining
	 */
	public XmlBuilder addText(String text) {
		Text textNode = this.document.createTextNode(text);
		this.element.appendChild(textNode);
		return this;
	}
	
	/**
	 * Adds a child element to the current element using the default namespace.
	 * 

	 * Call endChild as soon as the child node has been configured
	 * @param elementName Name of the child element
	 * @return XmlBuilder to modify the child element
	 */
	public XmlBuilder addChild(String elementName) {
		Element child = this.document.createElement(elementName);
		this.element.appendChild(child);
		return new XmlBuilder(this, this.document, child);
	}
	
	/**
	 * Adds a child element with the specified namespace prefix.
	 * 

	 * The namespace must have been added to a root element before.
	 * 

	 * Call endChild as soon as the child node has been configured
	 * @param elementName Element name
	 * @param namespacePrefix Namespace prefix of a registered namespace
	 * @return XmlBuilder to modify the child element
	 */
	public XmlBuilder addChild(String elementName, String namespacePrefix) {
		Element child = this.document.createElementNS(this.getNamespaceUri(namespacePrefix), elementName);
		child.setPrefix(namespacePrefix);
		this.element.appendChild(child);
		return new XmlBuilder(this, this.document, child);
	}
	
	private String getNamespaceUri(String prefix) {
		if (this.namespaces.containsKey(prefix)) {
			return this.namespaces.get(prefix);
		} else if (this.parentBuilder != null) {
			return this.parentBuilder.getNamespaceUri(prefix);
		} else {
			throw new IllegalArgumentException("Unknown namespace: " + prefix);
		}
	}
	
	/**
	 * Ends the adding of a child and returns the parent builder
	 * to continue constructing the XML.
	 * @return Parent XmlBuilder
	 */
	public XmlBuilder endChild() {
		if (this.parentBuilder == null) {
			throw new IllegalStateException("Cannot call endChild on root builder");
		}
		
		return this.parentBuilder;
	}

	/**
	 * Gets the document generated by this builder. Usually, you will want to call
	 * this method on the root builder, even though all builders return the same
	 * document.
	 * 
	 * This method always returns the same instance of document.
	 * @return Document instance created by this builder
	 */
	public Document getDocument() {
		return this.document;
	}
}