/**
 * @file HttpUtil.java
 * 
 * @brief 
 * HttpUtil is a single class containing methods to conveniently perform HTTP 
 * requests. HttpUtil only uses regular java io and net functionality and does 
 * not depend on external libraries. 
 * The class contains methods to perform a get, post, put, and delete request,
 * and supports posting forms. Optionally, one can provide headers.
 *
 * Example usage:
 * 
 *     // get
 *     String res = HttpUtil.get("http://www.google.com");
 * 
 *     // post
 *     String res = HttpUtil.post("http://sendmedata.com", "This is the data");
 *
 *     // post form
 *     Map<String, String> params = new HashMap<String, String>();
 *     params.put("firstname", "Joe");
 *     params.put("lastname", "Smith");
 *     params.put("age", "28");
 *     String res = HttpUtil.postForm("http://site.com/newuser", params);
 *
 *     // append query parameters to url
 *     String url = "http://mydatabase.com/users";
 *     Map<String, String> params = new HashMap<String, String>();
 *     params.put("orderby", "name");
 *     params.put("limit", "10");
 *     String fullUrl = HttpUtil.appendQueryParams(url, params);
 *     // fullUrl = "http://mydatabase.com/user?orderby=name&limit=10"
 *
 * @license
 * 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.
 *
 * Copyright (c) 2012 Almende B.V.
 *
 * @author 	Jos de Jong, <jos@almende.org>
 * @date	  2012-05-14
 */

package com.almende.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

public class HttpUtil {
	/**
	 * Send a get request
	 * @param url
	 * @return response
	 * @throws IOException 
	 */
	static public String get(String url) throws IOException {
		return get(url, null);
	}

	/**
	 * Send a get request
	 * @param url         Url as string
	 * @param headers     Optional map with headers
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String get(String url,
			Map<String, String> headers) throws IOException {
		return fetch("GET", url, null, headers);
	}

	/**
	 * Send a post request
	 * @param url         Url as string
	 * @param body        Request body as string
	 * @param headers     Optional map with headers
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String post(String url, String body,
			Map<String, String> headers) throws IOException {
		return fetch("POST", url, body, headers);
	}

	/**
	 * Send a post request
	 * @param url         Url as string
	 * @param body        Request body as string
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String post(String url, String body) throws IOException {
		return post(url, body, null);
	}

    /**
     * Post a json string
     * @param url         Url as string
     * @param jsonStr     a json string
     * @return response   Response as string
     * @throws IOException
     */
    static public String postJson(String url, String jsonStr) throws IOException {
        Map<String, String> headers = new HashMap<>();
        headers.put("Content-Type", "application/json;charset=UTF-8");
        return post(url, jsonStr, headers);
    }

	/**
	 * Post a form with parameters
	 * @param url         Url as string
	 * @param params      map with parameters/values
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String postForm(String url, Map<String, String> params) 
			throws IOException {
		return postForm(url, params, null);
	}

	/**
	 * Post a form with parameters
	 * @param url         Url as string
	 * @param params      Map with parameters/values
	 * @param headers     Optional map with headers
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String postForm(String url, Map<String, String> params,
			Map<String, String> headers) throws IOException {
		// set content type
		if (headers == null) {
			headers = new HashMap<String, String>();
		}
		headers.put("Content-Type", "application/x-www-form-urlencoded");

		// parse parameters
		String body = "";
		if (params != null) {
			boolean first = true;
			for (String param : params.keySet()) {
				if (first) {
					first = false;
				}
				else {
					body += "&";
				}
				String value = params.get(param);
				body += URLEncoder.encode(param, "UTF-8") + "=";
				body += URLEncoder.encode(value, "UTF-8");
			}
		}

		return post(url, body, headers);
	}

	/**
	 * Send a put request
	 * @param url         Url as string
	 * @param body        Request body as string
	 * @param headers     Optional map with headers
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String put(String url, String body,
			Map<String, String> headers) throws IOException {
		return fetch("PUT", url, body, headers);
	}

	/**
	 * Send a put request
	 * @param url         Url as string
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String put(String url, String body) throws IOException {
		return put(url, body, null);
	}
	
	/**
	 * Send a delete request
	 * @param url         Url as string
	 * @param headers     Optional map with headers
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String delete(String url,
			Map<String, String> headers) throws IOException {
		return fetch("DELETE", url, null, headers);
	}
	
	/**
	 * Send a delete request
	 * @param url         Url as string
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String delete(String url) throws IOException {
		return delete(url, null);
	}
	
	/**
	 * Append query parameters to given url
	 * @param url         Url as string
	 * @param params      Map with query parameters
	 * @return url        Url with query parameters appended
	 * @throws IOException 
	 */
	static public String appendQueryParams(String url, 
			Map<String, String> params) throws IOException {
		String fullUrl = url;
		if (params != null) {
			boolean first = (fullUrl.indexOf('?') == -1);
			for (String param : params.keySet()) {
				if (first) {
					fullUrl += '?';
					first = false;
				}
				else {
					fullUrl += '&';
				}
				String value = params.get(param);
				fullUrl += URLEncoder.encode(param, "UTF-8") + '=';
				fullUrl += URLEncoder.encode(value, "UTF-8");
			}
		}
		
		return fullUrl;
	}
	
	/**
	 * Retrieve the query parameters from given url
	 * @param url         Url containing query parameters
	 * @return params     Map with query parameters
	 * @throws IOException 
	 */
	static public Map<String, String> getQueryParams(String url) 
			throws IOException {
		Map<String, String> params = new HashMap<String, String>();
	
		int start = url.indexOf('?');
		while (start != -1) {
			// read parameter name
			int equals = url.indexOf('=', start);
			String param = "";
			if (equals != -1) {
				param = url.substring(start + 1, equals);
			}
			else {
				param = url.substring(start + 1);
			}
			
			// read parameter value
			String value = "";
			if (equals != -1) {
				start = url.indexOf('&', equals);
				if (start != -1) {
					value = url.substring(equals + 1, start);
				}
				else {
					value = url.substring(equals + 1);
				}
			}
			
			params.put(URLDecoder.decode(param, "UTF-8"), 
				URLDecoder.decode(value, "UTF-8"));
		}
		
		return params;
	}

	/**
	 * Returns the url without query parameters
	 * @param url         Url containing query parameters
	 * @return url        Url without query parameters
	 * @throws IOException 
	 */
	static public String removeQueryParams(String url) 
			throws IOException {
		int q = url.indexOf('?');
		if (q != -1) {
			return url.substring(0, q);
		}
		else {
			return url;
		}
	}
	
	/**
	 * Send a request
	 * @param method      HTTP method, for example "GET" or "POST"
	 * @param url         Url as string
	 * @param body        Request body as string
	 * @param headers     Optional map with headers
	 * @return response   Response as string
	 * @throws IOException 
	 */
	static public String fetch(String method, String url, String body,
			Map<String, String> headers) throws IOException {
		// connection
		URL u = new URL(url);
		HttpURLConnection conn = (HttpURLConnection)u.openConnection();
		conn.setConnectTimeout(120000);
		conn.setReadTimeout(120000);

		// method
		if (method != null) {
			conn.setRequestMethod(method);
		}

		// headers
		if (headers != null) {
			for(String key : headers.keySet()) {
				conn.addRequestProperty(key, headers.get(key));
			}
		}

		// body
		if (body != null) {
			conn.setDoOutput(true);
			OutputStream os = conn.getOutputStream();
			os.write(body.getBytes());
			os.flush();
			os.close();
		}
		
		// response
		InputStream is = conn.getInputStream();
		String response = streamToString(is);
		
		// handle redirects
		if (conn.getResponseCode() == 301) {
			String location = conn.getHeaderField("Location");
			return fetch(method, location, body, headers);
		}
		
		return response;
	}

	/**
	 * Read an input stream from conn into a string
	 * @param in
	 * @return
	 * @throws IOException
	 */
	static public String streamToString(InputStream in) throws IOException {
		InputStreamReader isr = new InputStreamReader(in, "UTF-8");
		BufferedReader br = new BufferedReader(isr);

		String data;
		StringBuilder out = new StringBuilder();
		while ((data = br.readLine()) != null) {
			out.append(data);
		}
		br.close();
		return out.toString();
	}
}