package eu.openaire.urls_worker.controllers;

import eu.openaire.urls_worker.components.plugins.PublicationsRetrieverPlugin;
import eu.openaire.urls_worker.services.FileStorageService;
import eu.openaire.urls_worker.util.FilesCompressor;
import org.apache.commons.io.FileDeleteStrategy;
import org.apache.commons.io.FileUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.InputStreamResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

@RestController
@RequestMapping("full-texts/")
public class FullTextsController {

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

    @Autowired
    private FileStorageService fileStorageService;


    @GetMapping("getFullTexts/{assignmentsCounter:[\\d]+}/{totalBatches:[\\d]+}/{batchCounter:[\\d]+}/{fileNamesWithExtensions}")
    public Object getFullTexts(@PathVariable long assignmentsCounter, @PathVariable int totalBatches, @PathVariable int batchCounter, @PathVariable List<String> fileNamesWithExtensions)
    {
        int fileNamesListNum = fileNamesWithExtensions.size();
        if ( (fileNamesListNum == 1) && (fileNamesWithExtensions.get(0).length() == 0) ) {  // In case the last "/" in the url was given (without any files following), then this list will not be empty, but have one empty item instead.
            // In case the url does not end in "/", then Spring will automatically return an "HTTP-BadRequest".
            String errorMsg = "An empty \"fileNamesWithExtensions\" list was given from assignments_" + assignmentsCounter + ", for batch_" + batchCounter;
            logger.error(errorMsg);
            return ResponseEntity.badRequest().body(errorMsg);
        }

        if ( totalBatches == 0 ) {
            String errorMsg = "The given \"totalBatches\" (" + totalBatches + ") was < 0 >!";
            logger.error(errorMsg);
            return ResponseEntity.badRequest().body(errorMsg);
        }
        else if ( batchCounter > totalBatches ) {
            String errorMsg = "The given \"batchCounter\" (" + batchCounter + ") is greater than the \"totalBatches\" (" + totalBatches + ")!";
            logger.error(errorMsg);
            return ResponseEntity.badRequest().body(errorMsg);
        }

        logger.info("Received a \"getFullTexts\" request for returning a tar-file containing " + fileNamesListNum + " full-texts, from assignments_" + assignmentsCounter + ", for batch_" + batchCounter + " (out of " + totalBatches + ").");

        String currentAssignmentsBaseFullTextsPath = fileStorageService.assignmentsBaseLocation + "assignments_" + assignmentsCounter + "_fullTexts" + File.separator;

        if ( ! (new File(currentAssignmentsBaseFullTextsPath).isDirectory()) ) {
            String errorMsg = "The base directory for assignments_" + assignmentsCounter + " was not found: " + currentAssignmentsBaseFullTextsPath;
            logger.error(errorMsg);
            return ResponseEntity.badRequest().body(errorMsg);
        }

        File zstdFile = FilesCompressor.compressMultipleFilesIntoOne(assignmentsCounter, batchCounter, fileNamesWithExtensions, currentAssignmentsBaseFullTextsPath);
        if ( zstdFile == null ) {
            String errorMsg = "Failed to create the zstd file for \"batchCounter\"-" + batchCounter;
            logger.error(errorMsg);
            return ResponseEntity.internalServerError().body(errorMsg);
            // The related files will be deleted later, upon completing the Worker-report process, in "AssignmentsHandler.postWorkerReport()".
        }

        if ( batchCounter == totalBatches )
            logger.debug("Will return the " + ((totalBatches > 1) ? "last" : "only one") + " batch (" + batchCounter + ") of assignments_" + assignmentsCounter + " to the Controller.");

        String zstdName = zstdFile.getName();
        String zstdTarFileFullPath = currentAssignmentsBaseFullTextsPath + zstdName;
        try {
            return ResponseEntity.ok()
                    .contentType(MediaType.APPLICATION_OCTET_STREAM)
                    .header(HttpHeaders.CONTENT_DISPOSITION, "inline; filename=\"" + zstdName + "\"")
                    .body(new InputStreamResource(new BufferedInputStream(Files.newInputStream(Paths.get(zstdTarFileFullPath)), FilesCompressor.bufferSize)));
        } catch (Exception e) {
            String errorMsg = "Could not load the FileInputStream of the zstd-tar-file \"" + zstdTarFileFullPath + "\"!";
            logger.error(errorMsg, e);
            return ResponseEntity.internalServerError().body(errorMsg);
        } finally {
            // In some cases, the full-texts might be too large and their total number too,
            // so if we leave them be, and wait for all batches to finish, we may get a "java.io.IOException: No space left on device" error.
            deleteFulltextBatchFiles(currentAssignmentsBaseFullTextsPath, assignmentsCounter, batchCounter, fileNamesWithExtensions);
            // The ".tar.zstd" file of this batch, for which we pass a steam to the Controller, will be deleted after the next batch, or after all batches are transferred and handles by the Controller.
        }

        // The related fulltext and (zstd-)tar files will be deleted in "AssignmentsHandler.postWorkerReport()", after the Controller has finished transferring them. They will be deleted even in case of a Controller-error.
        // In case of an error and file-deletion, the related id-url records will just be re-processed in the future by some (maybe different) Worker.
    }


    @GetMapping("getFullText/{assignmentsCounter:[\\d]+}/{fileNameWithExtension:[\\w_:]+.[\\w]{2,10}}")
    public ResponseEntity<?> getFullText(@PathVariable long assignmentsCounter, @PathVariable String fileNameWithExtension) {

        logger.info("Received a \"getFullText\" request.");
        String fullTextFileFullPath = fileStorageService.assignmentsBaseLocation + "assignments_" + assignmentsCounter + "_fullTexts" + File.separator + fileNameWithExtension;
        File file = new File(fullTextFileFullPath);
        if ( !file.isFile() ) {
            logger.error("The file \"" + fullTextFileFullPath + "\" does not exist!");
            return ResponseEntity.notFound().build();
        }

        try {
            return ResponseEntity.ok()
                    .contentType(MediaType.APPLICATION_OCTET_STREAM)
                    .header(HttpHeaders.CONTENT_DISPOSITION, "inline; filename=\"" + file.getName() + "\"")
                    .body(new InputStreamResource(new BufferedInputStream(Files.newInputStream(Paths.get(fullTextFileFullPath)), FilesCompressor.bufferSize)));
        } catch (Exception e) {
            String errorMsg = "Could not load the FileInputStream of the full-text-file \"" + fullTextFileFullPath + "\"!";
            logger.error(errorMsg, e);
            return ResponseEntity.internalServerError().body(errorMsg);
        }
    }


    public static boolean deleteDirectory(long curAssignments)
    {
        String directoryPath = PublicationsRetrieverPlugin.assignmentsBasePath;

        if ( curAssignments != -1 ) {
            directoryPath += "assignments_" + curAssignments + "_fullTexts" + File.separator;
            logger.debug("Going to delete the files inside the directory of assignments_" + curAssignments);
        } else
            logger.debug("Going to delete the parent directory: " + directoryPath);

        try {
            FileUtils.deleteDirectory(new File(directoryPath));
            return true;
        } catch (IOException e) {
            logger.error("The following directory could not be deleted: " + directoryPath, e);
            return false;
        } catch (IllegalArgumentException iae) {
            logger.error("This assignments-dir does not exist: " + directoryPath);
            return false;
        }
    }


    public static void deleteFulltextBatchFiles(String assignmentsBatchDir, long assignmentsCounter, long fulltextsBatch, List<String> filenames)
    {
        // We will delete all the files related to the given fulltexts-batch, along with the created tar and zstd files.

        for ( String fileName : filenames )
            deleteFile(assignmentsBatchDir + fileName);

        // Now let's delete the ".tar" and ".tar.zstd" files as well.
        String partialNonBatchFileName = assignmentsBatchDir + "assignments_" + assignmentsCounter + "_full-texts_";
        deleteFile(partialNonBatchFileName + fulltextsBatch + ".tar");

        // The ".tar.zstd" file of this batch will be deleted by the next batch or in the end of these assignments.
        // Now we will delete the zstd file of the previous assignments.
        if ( fulltextsBatch >= 2 )
            deleteFile(partialNonBatchFileName + (fulltextsBatch -1) + ".tar.zstd");

        // We do not use a fulltexts-batch directory, since even if it makes the deletion faster, it will make the full-texts delivery to the controller slower,
        // since we will need to move the requested full-texts to that directory before continuing with tarring and compressing the files and sending them over to the Controller.
        // Also, we cannot pre-create such directories, since it will add complexity in the download process and also some of the full-texts may not be requested by the Controller (because of duplicates).
    }


    public static boolean deleteFile(String fileFullPathString)
    {
        try {
            FileDeleteStrategy.FORCE.delete(new File(fileFullPathString));
        } catch (IOException e) {
            logger.error("Error when deleting the file: " + fileFullPathString);
            return false;
        }
        return true;
    }

}