/*
 * 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.kylin.rest.controller;

import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import javax.servlet.http.HttpServletResponse;

import net.sf.ehcache.Cache;
import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Element;

import org.apache.commons.io.IOUtils;
import org.apache.kylin.rest.exception.ForbiddenException;
import org.apache.kylin.rest.exception.InternalErrorException;
import org.apache.kylin.rest.request.MetaRequest;
import org.apache.kylin.rest.response.SQLResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.supercsv.io.CsvListWriter;
import org.supercsv.io.ICsvListWriter;
import org.supercsv.prefs.CsvPreference;

import com.codahale.metrics.annotation.Timed;
import org.apache.kylin.common.KylinConfig;
import org.apache.kylin.cube.CubeInstance;
import org.apache.kylin.rest.constant.Constant;
import org.apache.kylin.rest.model.Query;
import org.apache.kylin.rest.model.SelectedColumnMeta;
import org.apache.kylin.rest.model.TableMeta;
import org.apache.kylin.rest.request.PrepareSqlRequest;
import org.apache.kylin.rest.request.SQLRequest;
import org.apache.kylin.rest.request.SaveSqlRequest;
import org.apache.kylin.rest.service.QueryService;
import org.apache.kylin.rest.util.QueryUtil;

/**
 * Handle query requests.
 * 
 * @author xduo
 */
@Controller
public class QueryController extends BasicController {

    private static final Logger logger = LoggerFactory.getLogger(QueryController.class);

    public static final String SUCCESS_QUERY_CACHE = "SuccessQueryCache";
    public static final String EXCEPTION_QUERY_CACHE = "ExceptionQueryCache";

    @Autowired
    private QueryService queryService;

    @Autowired
    private CacheManager cacheManager;

    @RequestMapping(value = "/query", method = RequestMethod.POST)
    @ResponseBody
    @Timed(name = "query")
    public SQLResponse query(@RequestBody SQLRequest sqlRequest) {
        long startTimestamp = System.currentTimeMillis();

        SQLResponse response = doQuery(sqlRequest);
        response.setDuration(System.currentTimeMillis() - startTimestamp);

        queryService.logQuery(sqlRequest, response, new Date(startTimestamp), new Date(System.currentTimeMillis()));

        return response;
    }

    @RequestMapping(value = "/query/prestate", method = RequestMethod.POST, produces = "application/json")
    @ResponseBody
    @Timed(name = "query")
    public SQLResponse prepareQuery(@RequestBody PrepareSqlRequest sqlRequest) {
        long startTimestamp = System.currentTimeMillis();

        SQLResponse response = doQuery(sqlRequest);
        response.setDuration(System.currentTimeMillis() - startTimestamp);

        queryService.logQuery(sqlRequest, response, new Date(startTimestamp), new Date(System.currentTimeMillis()));

        if (response.getIsException()) {
            String errorMsg = response.getExceptionMessage();
            throw new InternalErrorException(QueryUtil.makeErrorMsgUserFriendly(errorMsg));
        }

        return response;
    }

    @RequestMapping(value = "/saved_queries", method = RequestMethod.POST)
    @ResponseBody
    @Timed(name = "saveQuery")
    public void saveQuery(@RequestBody SaveSqlRequest sqlRequest) throws IOException {
        String creator = SecurityContextHolder.getContext().getAuthentication().getName();
        Query newQuery = new Query(sqlRequest.getName(), sqlRequest.getProject(), sqlRequest.getSql(), sqlRequest.getDescription());

        queryService.saveQuery(creator, newQuery);
    }

    @RequestMapping(value = "/saved_queries/{id}", method = RequestMethod.DELETE)
    @ResponseBody
    @Timed(name = "removeQuery")
    public void removeQuery(@PathVariable String id) throws IOException {
        String creator = SecurityContextHolder.getContext().getAuthentication().getName();
        queryService.removeQuery(creator, id);
    }

    @RequestMapping(value = "/saved_queries", method = RequestMethod.GET)
    @ResponseBody
    @Timed(name = "getQueries")
    public List<Query> getQueries() throws IOException {
        String creator = SecurityContextHolder.getContext().getAuthentication().getName();
        return queryService.getQueries(creator);
    }

    @RequestMapping(value = "/query/format/{format}", method = RequestMethod.GET)
    @ResponseBody
    @Timed(name = "downloadResult")
    public void downloadQueryResult(@PathVariable String format, SQLRequest sqlRequest, HttpServletResponse response) {
        SQLResponse result = doQuery(sqlRequest);
        response.setContentType("text/" + format + ";charset=utf-8");
        response.setHeader("Content-Disposition", "attachment; filename=\"result." + format + "\"");
        ICsvListWriter csvWriter = null;

        try {
            csvWriter = new CsvListWriter(response.getWriter(), CsvPreference.STANDARD_PREFERENCE);

            List<String> headerList = new ArrayList<String>();

            for (SelectedColumnMeta column : result.getColumnMetas()) {
                headerList.add(column.getName());
            }

            String[] headers = new String[headerList.size()];
            csvWriter.writeHeader(headerList.toArray(headers));

            for (List<String> row : result.getResults()) {
                csvWriter.write(row);
            }
        } catch (IOException e) {
            logger.error("", e);
        } finally {
            IOUtils.closeQuietly(csvWriter);
        }
    }

    @RequestMapping(value = "/tables_and_columns", method = RequestMethod.GET)
    @ResponseBody
    public List<TableMeta> getMetadata(MetaRequest metaRequest) {
        try {
            return queryService.getMetadata(metaRequest.getProject());
        } catch (SQLException e) {
            logger.error(e.getLocalizedMessage(), e);
            throw new InternalErrorException(e.getLocalizedMessage(), e);
        }
    }

    private SQLResponse doQuery(SQLRequest sqlRequest) {
        String sql = sqlRequest.getSql();
        String project = sqlRequest.getProject();
        logger.info("Using project: " + project);
        logger.info("The original query:  " + sql);

        String serverMode = KylinConfig.getInstanceFromEnv().getServerMode();
        if (!(Constant.SERVER_MODE_QUERY.equals(serverMode.toLowerCase()) || Constant.SERVER_MODE_ALL.equals(serverMode.toLowerCase()))) {
            throw new InternalErrorException("Query is not allowed in " + serverMode + " mode.");
        }

        if (sql.toLowerCase().contains("select") == false) {
            logger.debug("Directly return expection as not supported");
            throw new InternalErrorException(QueryUtil.makeErrorMsgUserFriendly("Not Supported SQL."));
        }

        SQLResponse sqlResponse = searchQueryInCache(sqlRequest);
        try {
            if (null == sqlResponse) {
                sqlResponse = queryService.query(sqlRequest);

                long durationThreshold = KylinConfig.getInstanceFromEnv().getQueryDurationCacheThreshold();
                long scancountThreshold = KylinConfig.getInstanceFromEnv().getQueryScanCountCacheThreshold();
                if (!sqlResponse.getIsException() && (sqlResponse.getDuration() > durationThreshold || sqlResponse.getTotalScanCount() > scancountThreshold)) {
                    cacheManager.getCache(SUCCESS_QUERY_CACHE).put(new Element(sqlRequest, sqlResponse));
                }
            }

            checkQueryAuth(sqlResponse);

            return sqlResponse;
        } catch (AccessDeniedException ade) {
            // Access exception is bind with each user, it will not be cached
            logger.error("Exception when execute sql", ade);
            throw new ForbiddenException(ade.getLocalizedMessage());
        } catch (Throwable e) { // calcite may throw AssertError
            SQLResponse exceptionRes = new SQLResponse(null, null, 0, true, e.getMessage());
            Cache exceptionCache = cacheManager.getCache(EXCEPTION_QUERY_CACHE);
            exceptionCache.put(new Element(sqlRequest, exceptionRes));

            logger.error("Exception when execute sql", e);
            throw new InternalErrorException(QueryUtil.makeErrorMsgUserFriendly(e.getLocalizedMessage()));
        }
    }

    private SQLResponse searchQueryInCache(SQLRequest sqlRequest) {
        SQLResponse response = null;
        Cache exceptionCache = cacheManager.getCache(EXCEPTION_QUERY_CACHE);
        Cache queryCache = cacheManager.getCache(SUCCESS_QUERY_CACHE);

        if (KylinConfig.getInstanceFromEnv().isQueryCacheEnabled() && null != exceptionCache.get(sqlRequest)) {
            Element element = exceptionCache.get(sqlRequest);
            response = (SQLResponse) element.getObjectValue();
            response.setHitCache(true);
        } else if (KylinConfig.getInstanceFromEnv().isQueryCacheEnabled() && null != queryCache.get(sqlRequest)) {
            Element element = queryCache.get(sqlRequest);
            response = (SQLResponse) element.getObjectValue();
            response.setHitCache(true);
        }

        return response;
    }

    private void checkQueryAuth(SQLResponse sqlResponse) throws AccessDeniedException {
        if (!sqlResponse.getIsException() && KylinConfig.getInstanceFromEnv().isQuerySecureEnabled()) {
            CubeInstance cubeInstance = this.queryService.getCubeManager().getCube(sqlResponse.getCube());
            queryService.checkAuthorization(cubeInstance);
        }
    }

    public void setQueryService(QueryService queryService) {
        this.queryService = queryService;
    }

    public void setCacheManager(CacheManager cacheManager) {
        this.cacheManager = cacheManager;
    }

}