/*
 * Copyright 2004-2012 the original author or authors.
 * 
 * Licensed 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.springframework.webflow.context.servlet;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.springframework.webflow.core.collection.AttributeMap;

/**
 * Flow URL handler that implements the default Web Flow 1.x URL format. Here for backwards compatibility.
 * 
 * @author Keith Donald
 */
public class WebFlow1FlowUrlHandler implements FlowUrlHandler {

	private static final String DEFAULT_URL_ENCODING_SCHEME = "UTF-8";

	private String urlEncodingScheme = DEFAULT_URL_ENCODING_SCHEME;

	public String getFlowExecutionKey(HttpServletRequest request) {
		return request.getParameter("_flowExecutionKey");
	}

	public String getFlowId(HttpServletRequest request) {
		return request.getParameter("_flowId");
	}

	public String createFlowExecutionUrl(String flowId, String flowExecutionKey, HttpServletRequest request) {
		StringBuilder url = new StringBuilder();
		url.append(request.getRequestURI());
		url.append('?');
		appendQueryParameter(url, "_flowId", flowId);
		url.append('&');
		appendQueryParameter(url, "_flowExecutionKey", flowExecutionKey);
		return url.toString();
	}

	public String createFlowDefinitionUrl(String flowId, AttributeMap<?> input, HttpServletRequest request) {
		StringBuilder url = new StringBuilder();
		url.append(request.getRequestURI());
		url.append('?');
		appendQueryParameter(url, "_flowId", flowId);
		if (input != null && !input.isEmpty()) {
			url.append('&');
			appendQueryParameters(url, input.asMap());
		}
		return url.toString();
	}

	private <T> void appendQueryParameters(StringBuilder url, Map<String, T> parameters) {
		Iterator<Map.Entry<String, T>> entries = parameters.entrySet().iterator();
		while (entries.hasNext()) {
			Map.Entry<String, T> entry = entries.next();
			appendQueryParameter(url, entry.getKey(), entry.getValue());
			if (entries.hasNext()) {
				url.append('&');
			}
		}
	}

	private void appendQueryParameter(StringBuilder url, Object key, Object value) {
		String encodedKey = encode(key);
		String encodedValue = encode(value);
		url.append(encodedKey).append('=').append(encodedValue);
	}

	private String encode(Object value) {
		return value != null ? urlEncode(String.valueOf(value)) : "";
	}

	private String urlEncode(String value) {
		try {
			return URLEncoder.encode(String.valueOf(value), urlEncodingScheme);
		} catch (UnsupportedEncodingException e) {
			throw new IllegalArgumentException("Cannot url encode " + value);
		}
	}

}