package eu.openaire.urls_controller.util;

import io.minio.*;
import io.minio.messages.Bucket;
import io.minio.messages.Item;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

@Component
public class S3ObjectStore {

    private static final Logger logger = LoggerFactory.getLogger(S3ObjectStore.class);

    private final String s3Protocol = "s3://";
    @Value("${services.pdfaggregation.controller.s3.endpoint}")
    private String endpoint = null;   // This is useful to be "public", to test file-locations.
    @Value("${services.pdfaggregation.controller.s3.accessKey}")
    private String accessKey = null;
    @Value("${services.pdfaggregation.controller.s3.secretKey}")
    private String secretKey = null;
    @Value("${services.pdfaggregation.controller.s3.region}")
    private String region = null;
    @Value("${services.pdfaggregation.controller.s3.bucketName}")
    private String bucketName = null;

    @Value("${services.pdfaggregation.controller.s3.shouldEmptyBucket}")
    private boolean shouldEmptyBucket = false;  // Set true only for testing!
    @Value("${services.pdfaggregation.controller.s3.shouldShowAllS3Buckets}")
    private boolean shouldShowAllS3Buckets = false;

    @Value("${services.pdfaggregation.controller.isTestEnvironment}")
    private boolean isTestEnvironment = false;

    private MinioClient minioClient;


    @PostConstruct
    public void init() throws Exception {
        this.minioClient = MinioClient.builder().endpoint(endpoint).credentials(accessKey, secretKey).region(region).build();

        boolean bucketExists = minioClient.bucketExists(BucketExistsArgs.builder().bucket(bucketName).build());

        // Keep this commented-out to avoid objects-deletion by accident. The code is open-sourced, so it's easy to enable this ability if we really want it (e.g. for testing).
        /*if ( shouldEmptyBucket && isTestEnvironment && bucketExists )
            emptyBucket(bucketName, false);*/

        // Make the bucket, if not exist.
        if ( !bucketExists ) {
            logger.info("Bucket \"" + bucketName + "\" does not exist! Going to create it..");
            minioClient.makeBucket(MakeBucketArgs.builder().bucket(bucketName).build());
        } else
            logger.debug("Bucket \"" + bucketName + "\" already exists.");

        if ( shouldShowAllS3Buckets ) {
            List<Bucket> buckets = null;
            try {
                buckets = minioClient.listBuckets();
                logger.debug("The buckets in the S3 ObjectStore are:");
                for ( Bucket bucket : buckets ) {
                    logger.debug(bucket.name());
                }
            } catch (Exception e) {
                logger.warn("Could not listBuckets: " + e.getMessage());
            }
        }
    }


    private static final Pattern EXTENSION_PATTERN = Pattern.compile("(\\.[^.]+)$");

    /**
     * @param fileObjKeyName = "**File object key name**";
     * @param fileFullPath = "**Path of the file to upload**";
     * @return the url of the uploaded file
     */
    public String uploadToS3(String fileObjKeyName, String fileFullPath) throws Exception {
        String contentType = null;

        // Take the Matcher to retrieve the extension.
        Matcher extensionMatcher = EXTENSION_PATTERN.matcher(fileFullPath);
        if ( extensionMatcher.find() ) {
            String extension = null;
            if ( (extension = extensionMatcher.group(0)) == null )
                contentType = "application/pdf";
            else {
                if ( extension.equals("pdf") )
                    contentType = "application/pdf";
                /*else if ( *//* TODO - other-extension-match *//* )
                    contentType = "application/EXTENSION"; */
                else
                    contentType = "application/pdf";    // Default.
            }
        } else {
            logger.warn("The file with key \"" + fileObjKeyName + "\" does not have a file-extension! Setting the \"pdf\"-mimeType.");
            contentType = "application/pdf";
        }

        minioClient.uploadObject(UploadObjectArgs.builder()
                .bucket(bucketName)
                .object(fileObjKeyName).filename(fileFullPath)
                .contentType(contentType).build());

        // What if the fileObjKeyName already exists? (Default action from S3-Object-Store --> overwrite)
        // Each Worker handles some of these cases, but in case of id-urls splitting between different workers or re-attempting some temporarily faulty urls later, duplicate fileNames may appear.
        // However, the Controller uses the file-hash (instead of the duplicate -number), so it is 99.99% guaranteed that no overwrites will ever occur.

        String s3Url = s3Protocol + bucketName + "/" + fileObjKeyName;  // Be aware: This url works only if the access to the bucket is public.
        //logger.debug("Uploaded file \"" + fileObjKeyName + "\". The s3Url is: " + s3Url);
        return s3Url;
    }


    public void emptyBucket(String bucketName, boolean shouldDeleteBucket)
    {
        logger.warn("Going to " + (shouldDeleteBucket ? "delete" : "empty") + " bucket \"" + bucketName + "\"!");

        // First list the objects of the bucket.
        Iterable<Result<Item>> results;
        try {
            results = minioClient.listObjects(ListObjectsArgs.builder().bucket(bucketName).build());
        } catch (Exception e) {
            logger.error("Could not retrieve the list of objects of bucket \"" + bucketName + "\"!");
            return;
        }

        int countDeletedFiles = 0;
        int countFilesNotDeleted = 0;
        long totalSize = 0;
        Item item;

        // Then, delete the objects.
        for ( Result<Item> resultItem : results ) {
            try {
                item = resultItem.get();
            } catch (Exception e) {
                logger.error("Could not get the item-object of one of the S3-Objects returned from the bucket!", e);
                countFilesNotDeleted ++;
                continue;
            }
            totalSize += item.size();

            if ( !deleteFile(item.objectName(), bucketName) ) { // The reason and for what object, is already logged.
                logger.error("Cannot proceed with bucket deletion, since only an empty bucket can be removed!");
                countFilesNotDeleted ++;
            } else
                countDeletedFiles ++;
        }

        if ( shouldDeleteBucket ) {
            if ( countFilesNotDeleted == 0 ) {
                // Lastly, delete the empty bucket. We need to do this last, as in case it's not empty, we get an error!
                try {
                    minioClient.removeBucket(RemoveBucketArgs.builder().bucket(bucketName).build());
                    logger.info("Bucket \"" + bucketName + "\" was deleted!");
                } catch (Exception e) {
                    logger.error("Bucket \"" + bucketName + "\" could not be deleted!", e);
                }
            } else
                logger.error("Cannot execute the \"removeBucket\" command for bucket \"" + bucketName + "\", as " + countFilesNotDeleted + " files failed to be deleted!");
        } else
            logger.info("Bucket \"" + bucketName + "\" was emptied!");

        logger.info(countDeletedFiles + " files were deleted, amounting to " + ((totalSize/1024)/1024) + " MB.");
    }


    public boolean isLocationInStore(String location) {
        return location.startsWith(s3Protocol);
    }


    public boolean deleteFile(String fileObjKeyName, String bucketName)
    {
        try {
            minioClient.removeObject(RemoveObjectArgs.builder().bucket(bucketName).object(fileObjKeyName).build());
        } catch (Exception e) {
            logger.error("Could not delete the file \"" + fileObjKeyName + "\" from the S3 ObjectStore, exception: " + e.getMessage(), e);
            return false;
        }
        return true;
    }

}