/*
 * Copyright (c) 2018 - 2023, Entgra (Pvt) Ltd. (http://www.entgra.io) All Rights Reserved.
 *
 * Entgra (Pvt) Ltd. 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 io.entgra.device.mgt.core.ui.request.interceptor;

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import io.entgra.device.mgt.core.device.mgt.core.config.DeviceConfigurationManager;
import io.entgra.device.mgt.core.device.mgt.core.config.DeviceManagementConfig;
import io.entgra.device.mgt.core.ui.request.interceptor.beans.AuthData;
import io.entgra.device.mgt.core.ui.request.interceptor.util.HandlerConstants;
import io.entgra.device.mgt.core.ui.request.interceptor.util.HandlerUtil;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.HttpHeaders;
import org.apache.http.HttpStatus;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.ContentType;
import io.entgra.device.mgt.core.ui.request.interceptor.beans.ProxyResponse;
import org.apache.http.entity.StringEntity;

import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.Base64;

@MultipartConfig
@WebServlet("/default-oauth2-credentials")
public class DefaultOauth2TokenHandler extends HttpServlet {
    private static final Log log = LogFactory.getLog(DefaultTokenHandler.class);

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
        try {
            HttpSession httpSession = req.getSession(false);
            if (httpSession != null) {
                AuthData authData = (AuthData) httpSession.getAttribute(HandlerConstants.SESSION_AUTH_DATA_KEY);
                if (authData == null) {
                    HandlerUtil.sendUnAuthorizeResponse(resp);
                    return;
                }
                AuthData defaultAuthData = (AuthData) httpSession
                        .getAttribute(HandlerConstants.SESSION_DEFAULT_AUTH_DATA_KEY);
                if (defaultAuthData != null) {
                    String accessToken = defaultAuthData.getAccessToken();
                    String accessTokenWithoutPrefix = accessToken.substring(accessToken.indexOf("_") + 1);

                    HttpPost tokenEndpoint = new HttpPost(HandlerUtil.getKeyManagerUrl(req.getScheme()) + HandlerConstants.INTROSPECT_ENDPOINT);
                    tokenEndpoint.setHeader(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_FORM_URLENCODED.toString());
                    DeviceManagementConfig dmc = DeviceConfigurationManager.getInstance().getDeviceManagementConfig();
                    String adminUsername = dmc.getKeyManagerConfigurations().getAdminUsername();
                    String adminPassword = dmc.getKeyManagerConfigurations().getAdminPassword();
                    tokenEndpoint.setHeader(HttpHeaders.AUTHORIZATION, HandlerConstants.BASIC + Base64.getEncoder()
                            .encodeToString((adminUsername + HandlerConstants.COLON + adminPassword).getBytes()));
                    StringEntity tokenEPPayload = new StringEntity("token=" + accessTokenWithoutPrefix,
                            ContentType.APPLICATION_FORM_URLENCODED);
                    tokenEndpoint.setEntity(tokenEPPayload);
                    ProxyResponse tokenStatus = HandlerUtil.execute(tokenEndpoint);

                    if (HandlerConstants.DEFAULT_TOKEN_IS_EXPIRED.equals(tokenStatus.getData())) {
                        tokenStatus = HandlerUtil.retryRequestWithRefreshedToken(req, tokenEndpoint, HandlerUtil.getKeyManagerUrl(req.getScheme()), true);
                        if (!HandlerUtil.isResponseSuccessful(tokenStatus)) {
                            HandlerUtil.handleError(resp, tokenStatus);
                            return;
                        }
                    } else {
                        HandlerUtil.handleSuccess(resp, constructSuccessProxyResponse(defaultAuthData.getAccessToken()));
                        return;
                    }
                }
                processDefaultTokenRequest(httpSession, authData, req, resp);
            } else {
                HandlerUtil.sendUnAuthorizeResponse(resp);
            }
        } catch (IOException e) {
            log.error("Error occurred when processing GET request to get default token.", e);
        }
    }

    private void processDefaultTokenRequest(HttpSession httpSession, AuthData authData, HttpServletRequest req, HttpServletResponse resp) throws IOException {
        String clientId = authData.getClientId();
        String clientSecret = authData.getClientSecret();

        String queryString = req.getQueryString();
        String scopeString = "";
        if (StringUtils.isNotEmpty(queryString)) {
            scopeString = req.getParameter("scopes");
            if (scopeString != null) {
                scopeString = "?scopes=" + scopeString;
            }
        }

        String iotsCoreUrl = req.getScheme() + HandlerConstants.SCHEME_SEPARATOR
                + System.getProperty(HandlerConstants.IOT_GW_HOST_ENV_VAR)
                + HandlerConstants.COLON + HandlerUtil.getGatewayPort(req.getScheme());
        String tokenUrl = iotsCoreUrl + "/api/device-mgt/v1.0/devices/" + clientId
                + "/" + clientSecret + "/default-token" + scopeString;

        HttpGet defaultTokenRequest = new HttpGet(tokenUrl);
        defaultTokenRequest
                .setHeader(HttpHeaders.AUTHORIZATION, HandlerConstants.BEARER + authData.getAccessToken());
        defaultTokenRequest
                .setHeader(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_FORM_URLENCODED.toString());
        ProxyResponse tokenResultResponse = HandlerUtil.execute(defaultTokenRequest);

        if (tokenResultResponse.getExecutorResponse().contains(HandlerConstants.EXECUTOR_EXCEPTION_PREFIX)) {
            log.error("Error occurred while invoking the API to get default token data.");
            HandlerUtil.handleError(resp, tokenResultResponse);
            return;
        }
        String tokenResult = tokenResultResponse.getData();
        if (tokenResult == null) {
            log.error("Invalid default token response is received.");
            HandlerUtil.handleError(resp, tokenResultResponse);
            return;
        }

        JsonParser jsonParser = new JsonParser();
        JsonElement jTokenResult = jsonParser.parse(tokenResult);
        if (jTokenResult.isJsonObject()) {
            JsonObject jTokenResultAsJsonObject = jTokenResult.getAsJsonObject();
            AuthData newDefaultAuthData = new AuthData();
            newDefaultAuthData.setClientId(clientId);
            newDefaultAuthData.setClientSecret(clientSecret);

            String defaultToken = jTokenResultAsJsonObject.get("accessToken").getAsString();
            newDefaultAuthData.setAccessToken(defaultToken);
            newDefaultAuthData.setRefreshToken(jTokenResultAsJsonObject.get("refreshToken").getAsString());
            newDefaultAuthData.setScope(jTokenResultAsJsonObject.get("scopes").getAsString());
            httpSession.setAttribute(HandlerConstants.SESSION_DEFAULT_AUTH_DATA_KEY, newDefaultAuthData);

            HandlerUtil.handleSuccess(resp, constructSuccessProxyResponse(defaultToken));
        }
    }

    /**
     * Get Success Proxy Response
     * @param defaultAccessToken Access token which has default scope
     * @return {@link ProxyResponse}
     */
    private ProxyResponse constructSuccessProxyResponse (String defaultAccessToken) {

        URIBuilder ub = new URIBuilder();
        ub.setScheme(HandlerConstants.WSS_PROTOCOL);
        ub.setHost(System.getProperty(HandlerConstants.IOT_REMOTE_SESSION_HOST_ENV_VAR));
        ub.setPort(Integer.parseInt(System.getProperty(HandlerConstants.IOT_REMOTE_SESSION_HTTPS_PORT_ENV_VAR)));
        ub.setPath(HandlerConstants.REMOTE_SESSION_CONTEXT);

        URIBuilder ub2 = new URIBuilder();
        ub2.setScheme(HandlerConstants.WSS_PROTOCOL);
        ub2.setHost(System.getProperty(HandlerConstants.IOT_GW_HOST_ENV_VAR));
        ub2.setPort(Integer.parseInt(System.getProperty(HandlerConstants.IOT_GATEWAY_WEBSOCKET_WSS_PORT_ENV_VAR)));

        URIBuilder ub3 = new URIBuilder();
        ub3.setScheme(HandlerConstants.WS_PROTOCOL);
        ub3.setHost(System.getProperty(HandlerConstants.IOT_GW_HOST_ENV_VAR));
        ub3.setPort(Integer.parseInt(System.getProperty(HandlerConstants.IOT_GATEWAY_WEBSOCKET_WS_PORT_ENV_VAR)));

        JsonObject responseJsonObj = new JsonObject();
        responseJsonObj.addProperty("default-access-token", defaultAccessToken);
        responseJsonObj.addProperty("remote-session-base-url", ub.toString());
        responseJsonObj.addProperty("secured-websocket-gateway-url", ub2.toString());
        responseJsonObj.addProperty("unsecured-websocket-gateway-url", ub3.toString());

        Gson gson = new Gson();
        String payload = gson.toJson(responseJsonObj);

        ProxyResponse proxyResponse = new ProxyResponse();
        proxyResponse.setCode(HttpStatus.SC_OK);
        proxyResponse.setStatus(ProxyResponse.Status.SUCCESS);
        proxyResponse.setData(payload);
        return proxyResponse;
    }
}
