/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
 */

package org.apache.vysper.xml.fragment;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Stack;
import java.util.Map.Entry;


/**
 * Naive implementation, will be replaced in later stages of this change
 */
public class StackNamespaceResolver implements NamespaceResolver {
	
	private Stack<XMLElement> elements = new Stack<XMLElement>();
	
	public StackNamespaceResolver() {
	}

	public void push(XMLElement elm) {
		elements.push(elm);
	}

	public void pop() {
		elements.pop();
	}

	public Map<String, String> getNamespaceDeclarations() {
		Map<String, String> ns = new LinkedHashMap<String, String>();
		if(!elements.isEmpty()) {
			XMLElement topElm = elements.peek();
			for(Entry<String, String> entry : topElm.getDeclaredNamespaces().entrySet()) {
				ns.put(entry.getKey(), entry.getValue());
			}
			
			// look for any generated prefixes for attributes
			for(Attribute attribute : topElm.getAttributes()) {
				String attrNs = attribute.getNamespaceUri();
				if(attrNs.length() > 0 && resolvePrefix(attrNs, false) == null) {
					// attribute is in a namespace, and that namespace is not declared
					ns.put(resolvePrefix(attrNs), attrNs);						
				}
			}
			
			
			// add the element declaration as well, if not already defined
			if(topElm.getNamespaceURI().length() > 0) {
				// declared in a namespace
				if(!ns.containsValue(topElm.getNamespaceURI())) {
					// the namespace is not declared as an attribute on topElm
					// is it declared on a parent?
					// pop the element to test for declaration on the parent
					pop();
					if(resolvePrefix(topElm.getNamespaceURI(), false) == null) {
						ns.put(topElm.getNamespacePrefix(), topElm.getNamespaceURI());
					}
					// restore stack
					push(topElm);
				}
			} else {
				// is there a parent in a namespace? if so, we need to reset the default namespace
				if(elements.size() > 1 
						&& elements.get(elements.size() - 2).getNamespaceURI().length() > 0
						&& !ns.containsKey("")) {
					ns.put("", "");
				}
			}
		}		
		
		return ns;
	}
	
	public String resolveUri(String prefix) {
		// check for the reserved xml namespace
		if(prefix.equals("xml")) {
			return Namespaces.XML;
		} else {
			for(int i = elements.size() - 1; i>=0; i--) {
				String uri = resolveUri(elements.get(i), prefix);
				if(uri != null) {
					return uri;
				}
			}
		}
		
		// is the current element declared with this prefix, 
		// if so, return the declared namespace
		if(!elements.isEmpty() && prefix.equals(elements.peek().getNamespacePrefix())) {
			// the namespace URI must not be defined for another prefix
			String uri = elements.peek().getNamespaceURI();
			String resolvedPrefix = resolvePrefix(uri, false); 
			if(resolvedPrefix == null || resolvedPrefix.equals(prefix)) {
				return uri;
			}
		}
		
		// could not resolve URI
		return null;
	}
	
	private String resolveUri(XMLElement elm, String prefix) {
		return elm.getDeclaredNamespaces().get(prefix);
	}
	
	public String resolvePrefix(String uri) {
		return resolvePrefix(uri, true);
	}
	
	private String resolvePrefix(String uri, boolean generatePrefix) {
		// check for the reserved xml namespace
		if(uri.equals(Namespaces.XML)) {
			return "xml";
		} else {
			for(int i = elements.size() - 1; i>=0; i--) {
				String prefix = resolvePrefix(elements.get(i), uri);
				if(prefix != null) {
					return prefix;
				}
			}
		}
		
		// is the current element in this namespace, if so, return the default prefix
		if(!elements.isEmpty() && uri.equals(elements.peek().getNamespaceURI())) {
			return elements.peek().getNamespacePrefix();
		}

		if(generatePrefix) {
			// TODO replace with prefix generation
			return "ns1";
		} else {
			return null;
		}
		
	}
	
	private String resolvePrefix(XMLElement elm, String uri) {
		for(Entry<String, String> entry : elm.getDeclaredNamespaces().entrySet()) {
			if(entry.getValue().equals(uri)) {
				return entry.getKey();
			}
		}
		
		return null;
	}
}