package eu.openaire.urls_controller.controllers;

import eu.openaire.urls_controller.models.UrlReport;
import eu.openaire.urls_controller.models.WorkerInfo;
import eu.openaire.urls_controller.payloads.requests.WorkerReport;
import eu.openaire.urls_controller.services.UrlsService;
import eu.openaire.urls_controller.util.FileUtils;
import eu.openaire.urls_controller.util.GenericUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import javax.servlet.http.HttpServletRequest;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.regex.Pattern;


@RestController
@RequestMapping("/urls")
public class UrlsController {

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

    @Autowired
    private UrlsService urlsService;

    @Autowired
    private FileUtils fileUtils;

    private static final Pattern MALICIOUS_INPUT_STRING = Pattern.compile(".*[';`\"]+.*");

    @Value("${services.pdfaggregation.controller.assignmentLimit}")
    private int assignmentLimit;

    public static final ConcurrentHashMap<String, WorkerInfo> workersInfoMap = new ConcurrentHashMap<>(6);

    public static final AtomicInteger numOfWorkers = new AtomicInteger(0);


    public static ExecutorService backgroundExecutor;

    public static final List<Future<Boolean>> futuresOfBackgroundTasks = Collections.synchronizedList(new ArrayList<>());

    private final String workerReportsDirPath;


    public UrlsController(@Value("${services.pdfaggregation.controller.workerReportsDirPath}") String workerReportsDirPath,
                          @Value("${services.pdfaggregation.controller.numOfBackgroundThreads}") int numOfBackgroundThreads)
    {
        if ( !workerReportsDirPath.endsWith("/") )
            workerReportsDirPath += "/";

        this.workerReportsDirPath = workerReportsDirPath;   // This dir will be created later.

        if ( numOfBackgroundThreads <= 0 )
            throw new RuntimeException("The given \"numOfBackgroundThreads\" is not a positive number: " + numOfBackgroundThreads);

        logger.info("Will use " + numOfBackgroundThreads + " threads for background tasks, such as processing worker-reports or bulk-import procedures.");
        backgroundExecutor = Executors.newFixedThreadPool(numOfBackgroundThreads);   // At most < numOfBackgroundThreads > tasks will be running in parallel.
    }


    @GetMapping("")
    public ResponseEntity<?> getAssignments(@RequestParam String workerId, @RequestParam int workerAssignmentsLimit, HttpServletRequest request) {

        // As the Impala-driver is buggy and struggles to support parameterized queries in some types of prepared-statements, we have to sanitize the "workerId" ourselves.
        if ( MALICIOUS_INPUT_STRING.matcher(workerId).matches() ) {
            String errorMsg = "Possibly malicious \"workerId\" received: " + workerId;
            logger.error(errorMsg);
            return ResponseEntity.status(HttpStatus.FORBIDDEN).body(errorMsg);
        }

        logger.info("Worker with id: \"" + workerId + "\", requested up to " + workerAssignmentsLimit + " assignments. The assignments-limit of the controller is: " + assignmentLimit);

        // Sanitize the "assignmentsLimit". Do not let an overload happen in the Controller's or the Impala's server.
        int assignmentsLimit = workerAssignmentsLimit;
        if ( assignmentsLimit == 0 ) {
            String errorMsg = "The given \"workerAssignmentsLimit\" was ZERO!";
            logger.error(errorMsg);
            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorMsg);
        } else if ( assignmentsLimit > assignmentLimit ) {
            logger.warn("The given \"workerAssignmentsLimit\" (" + workerAssignmentsLimit + ") was larger than the Controller's limit (" + assignmentLimit + "). Will use the Controller's limit.");
            assignmentsLimit = assignmentLimit;
        }

        if ( ShutdownController.shouldShutdownService ) {
            // There might be the case that the Controller has not sent shutDown requests to the Workers yet, or it has, BUT:
            // 1) A worker requests for new assignments before the shutDown request in handled by its side.
            // 2) A new Worker joins the Service (unexpected, but anyway).
            String warnMsg = "The Service is about to shutdown, after all under-processing assignments and/or bulkImport requests are handled. No new requests are accepted!";
            logger.warn(warnMsg);  // It's likely not an actual error, but still it's not accepted.
            return ResponseEntity.status(HttpStatus.CONFLICT).body(warnMsg);    // The worker will wait 15 mins and upon going to retry it will notice that it should not do a new request then or it may have already shutdown in the meantime.
        }

        if ( request == null ) {
            logger.error("The \"HttpServletRequest\" is null!");
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
        }
        String remoteAddr = GenericUtils.getRequestorAddress(request);

        WorkerInfo workerInfo = workersInfoMap.get(workerId);
        if ( workerInfo != null ) { // This worker has already been identified.
            String savedWorkerIp = workerInfo.getWorkerIP();
            if ( !savedWorkerIp.equals(remoteAddr) ) {
                logger.warn("The worker with id \"" + workerId + "\" has changed IP from \"" + savedWorkerIp + "\" to \"" + remoteAddr + "\".");
                workerInfo.setWorkerIP(remoteAddr); // Set the new IP. The update will be reflected in the map.
            }   // In this case, the worker may have previously informed the Controller it has shutdown or it may have crashed.

            if ( workerInfo.getHasShutdown() ) {
                logger.info("The worker with id \"" + workerId + "\" was restarted.");
                workerInfo.setHasShutdown(false);
                numOfWorkers.decrementAndGet();
            }
        } else {
            logger.info("The worker \"" + workerId + "\" is requesting assignments for the first time. Going to store its IP [" + remoteAddr + "] in memory.");
            workersInfoMap.put(workerId, new WorkerInfo(remoteAddr, false));
            numOfWorkers.incrementAndGet();
        }

        return urlsService.getAssignments(workerId, assignmentsLimit);
    }


    @PostMapping("addWorkerReport")
    public ResponseEntity<?> addWorkerReport(@RequestBody WorkerReport workerReport)
    {
        if ( workerReport == null ) {
            String errorMsg = "No \"WorkerReport\" was given!";
            logger.error(errorMsg);
            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorMsg);
        }

        String curWorkerId = workerReport.getWorkerId();
        if ( curWorkerId == null ) {
            String errorMsg = "No \"workerId\" was included inside the \"WorkerReport\"!";
            logger.error(errorMsg);
            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorMsg);
        }

        // As the Impala-driver is buggy and struggles to support parameterized queries in some types of prepared-statements, we have to sanitize the "workerId" ourselves.
        if ( MALICIOUS_INPUT_STRING.matcher(curWorkerId).matches() ) {
            String errorMsg = "Possibly malicious \"workerId\" received: " + curWorkerId;
            logger.error(errorMsg);
            return ResponseEntity.status(HttpStatus.FORBIDDEN).body(errorMsg);
        }

        int sizeOfUrlReports = 0;
        List<UrlReport> urlReports = workerReport.getUrlReports();
        if ( (urlReports == null) || ((sizeOfUrlReports = urlReports.size()) == 0) ) {
            String errorMsg = "The given \"WorkerReport\" from worker with ID \"" + curWorkerId + "\" was empty (without any UrlReports)!";
            logger.error(errorMsg);
            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorMsg);
        }

        long curReportAssignmentsCounter = workerReport.getAssignmentRequestCounter();
        logger.info("Received the WorkerReport for batch-assignments_" + curReportAssignmentsCounter + ", from the worker with id: " + curWorkerId + ". It contains " + sizeOfUrlReports + " urlReports. Going to request the fullTexts from the Worker and insert the UrlReports into the database.");

        // Make sure this worker's report directory is created.
        Path currentWorkerReportLocationDir = Paths.get(this.workerReportsDirPath, curWorkerId);
        try {
            Files.createDirectories(currentWorkerReportLocationDir);    // No-op if dir exists. It does not throw a "alreadyExistsException"
        } catch (Exception e) {
            String errorMsg = "Could not create the \"currentWorkerReportLocationDir\" for worker \"" + curWorkerId + "\" : " + currentWorkerReportLocationDir;
            logger.error(errorMsg, e);
            return ResponseEntity.internalServerError().body(errorMsg);
        }

        // Create the report file and write the worker-report to it.
        String workerReportFile = currentWorkerReportLocationDir + "/" + curWorkerId + "_assignments_" + curReportAssignmentsCounter + "_report.json";
        // In case a file with the same name already exists (e.g. from a previous run of the Service), then it will be overwritten.
        logger.debug("Going to write the worker report to json-file: \"" + workerReportFile + "\".");
        fileUtils.writeToFile(workerReportFile, workerReport.getJsonReport(), false);  // Only one thread is writing to this specific file.
        // The above method will overwrite a possibly existing file. So in case of a crash, it's better to back up the reports before starting the Controller again (as the assignments-counter will start over, from 0).

        int finalSizeOUrlReports = sizeOfUrlReports;
        try {
            UrlsController.futuresOfBackgroundTasks.add(
                    backgroundExecutor.submit(
                            () -> urlsService.addWorkerReport(curWorkerId, curReportAssignmentsCounter, urlReports, finalSizeOUrlReports)
                    )
            );
        } catch (RejectedExecutionException ree) {
            String errorMsg = "The WorkerReport from worker \"" + curWorkerId + "\" and assignments_" + curReportAssignmentsCounter + " have failed to be executed!";
            logger.error(errorMsg, ree);
            return ResponseEntity.internalServerError().body(errorMsg);
        }

        String msg = "The 'addWorkerReport' request for worker with id: '" + curWorkerId + "' and assignments_" + curReportAssignmentsCounter + " , was accepted and will be scheduled for execution.";
        logger.info(msg);
        return ResponseEntity.ok().body(msg);
    }

}