/*

 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.oracle.jmx.remote.rest.http;

import com.oracle.jmx.remote.rest.json.JSONObject;

import com.sun.net.httpserver.Headers;

import com.sun.net.httpserver.HttpExchange;

import javax.management.remote.rest.PlatformRestAdapter;

import java.io.*;

import java.net.URI;

import java.net.URL;

import java.net.URLDecoder;

import java.net.URLEncoder;

import java.nio.charset.StandardCharsets;

import java.util.Base64;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

import java.util.stream.Collectors;

public class HttpUtil {

    public static String getRequestCharset(HttpExchange ex) {

        String charset = null;

        List<String> contentType = ex.getRequestHeaders().get("Content-type");

        if (contentType != null) {

            for (String kv : contentType) {

                for (String value : kv.split(";")) {

                    value = value.trim();

                    if (value.toLowerCase().startsWith("charset=")) {

                        charset = value.substring("charset=".length());

                    }

                }

            }

        }

        return charset;

    }

    public static String getAcceptCharset(HttpExchange ex) {

        List<String> acceptCharset = ex.getRequestHeaders().get("Accept-Charset");

        if (acceptCharset != null && acceptCharset.size() > 0) {

            return acceptCharset.get(0);

        }

        return null;

    }

    public static String getGetRequestResource(HttpExchange ex) throws UnsupportedEncodingException {

        String charset = getRequestCharset(ex);

        String httpHandlerPath = ex.getHttpContext().getPath();

        String requestURIpath = ex.getRequestURI().getPath();

        String getRequestPath = requestURIpath.substring(httpHandlerPath.length());

        if (charset != null) {

            return URLDecoder.decode(getRequestPath, charset);

        } else {

            return getRequestPath;

        }

    }

    public static String getGetRequestQuery(HttpExchange ex) throws UnsupportedEncodingException {

        String charset = getRequestCharset(ex);

        String query = ex.getRequestURI().getQuery();

        if (charset != null && query != null) {

            return URLDecoder.decode(query, charset);

        } else {

            return query;

        }

    }

    public static Map<String, String> getGetRequestQueryMap(HttpExchange ex)

            throws UnsupportedEncodingException {

        String query = ex.getRequestURI().getQuery();

        Map<String, String> queryParams = new LinkedHashMap<>();

        if (query == null || query.isEmpty()) {

            return queryParams;

        }

        query = URLDecoder.decode(query, StandardCharsets.UTF_8.displayName());

        String[] params = query.trim().split("&");

        for (String param : params) {

            int idx = param.indexOf('=');

                queryParams.put(param.substring(0, idx), param.substring(idx + 1));

            }

        }

        return queryParams;

    }

    public static String getCredentials(HttpExchange exchange) {

        Headers rmap = exchange.getRequestHeaders();

        String auth = rmap.getFirst("Authorization");

        if (auth != null && !auth.isEmpty()) {

            int sp = auth.indexOf(' ');

            byte[] b = Base64.getDecoder().decode(auth.substring(sp + 1));

            String authCredentials = new String(b);

        }

        return "";

    }

    public static String readRequestBody(HttpExchange he) throws IOException {

        String charset = getRequestCharset(he);

        StringBuilder stringBuilder = new StringBuilder();

        InputStreamReader in = charset != null ? new InputStreamReader(he.getRequestBody(), charset) : new InputStreamReader(he.getRequestBody());

        BufferedReader br = new BufferedReader(in);

        String line;

        while ((line = br.readLine()) != null) {

            String decode = charset != null ? URLDecoder.decode(line, charset) : line;

            stringBuilder.append(decode);

        }

        return stringBuilder.toString();

    }

    public static void sendResponse(HttpExchange exchange, HttpResponse response) throws IOException {

        String charset = getRequestCharset(exchange);

        String acceptCharset = HttpUtil.getAcceptCharset(exchange);

        if (acceptCharset != null) {

            charset = acceptCharset;

        }

        // Set response headers explicitly

        String msg = charset == null ? response.getBody() : URLEncoder.encode(response.getBody(), charset);

        byte[] bytes = msg.getBytes();

        Headers resHeaders = exchange.getResponseHeaders();

            resHeaders.add("Content-Type", "application/json; charset=" + charset);

        } else {

            resHeaders.add("Content-Type", "application/json;");

        }

        exchange.sendResponseHeaders(response.getCode(), bytes.length);

        try (OutputStream os = exchange.getResponseBody()) {

            os.write(bytes);

        }

    }

    public static <T> List<T> filterByPage(HttpExchange exchange, List<T> input, int pageSize) throws UnsupportedEncodingException {

        Map<String, String> queryParams = HttpUtil.getGetRequestQueryMap(exchange);

        int currPage = 1;

        if (queryParams != null && !queryParams.isEmpty()) {

            String pageStr = queryParams.get("page");

            if (pageStr != null && !pageStr.isEmpty()) {

                currPage = Integer.parseInt(pageStr);

                currPage = currPage > 1 ? currPage : 1;

            }

        }

        int start = (currPage - 1) * pageSize;

        int end = Math.min(input.size(), start + pageSize);

        if (start < end) {

            return input.subList(start, end);

        } else {

            return null;

        }

    }

    public static <T> JSONObject getPaginationLinks(HttpExchange exchange, List<T> input, int pageSize) throws UnsupportedEncodingException {

        if (pageSize >= input.size()) {

            return null;

        }

        Map<String, String> queryParams = HttpUtil.getGetRequestQueryMap(exchange);

        int currPage = 1;

        if (queryParams != null && !queryParams.isEmpty()) {

            String pageStr = queryParams.get("page");

            if (pageStr != null && !pageStr.isEmpty()) {

                currPage = Integer.parseInt(pageStr);

            }

        }

        String path = PlatformRestAdapter.getDomain() + exchange.getRequestURI().getPath() + "?";

        Map<String, String> queryMap = getGetRequestQueryMap(exchange);

        if (queryMap != null) {

            queryMap.remove("page");

            if (!queryMap.isEmpty()) {

                String query = queryMap.keySet().stream()

                        .map(k -> k + "=" + queryMap.get(k))

                        .collect(Collectors.joining("&"));

                path = path + query + "&";

            }

        }

        int totalPages = (input.size() % pageSize == 0) ? input.size() / pageSize : input.size() / pageSize + 1;

        JSONObject jobj = new JSONObject();

        jobj.put("first", path.replaceAll(".$", ""));

        if (currPage == 2) {

            jobj.put("prev", path.replaceAll(".$", ""));

        } else if (currPage > 2) {

            jobj.put("prev", path + "page=" + (currPage - 1));

        }

        if (currPage < totalPages) {

            jobj.put("next", path + "page=" + (currPage + 1));

        }

        jobj.put("last", path + "page=" + totalPages);

        return jobj;

    }

    public static String escapeUrl(String input) {

        try {

            URL url = new URL(input);

            URI uri = new URI(url.getProtocol(), url.getUserInfo(), url.getHost(), url.getPort(), url.getPath(), url.getQuery(), url.getRef());

            return uri.toURL().toString();

        } catch (Exception ex) {

            return null;

        }

    }

}