package eu.dnetlib.data.mdstore;

import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

import javax.transaction.Transactional;

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.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;

import eu.dnetlib.data.mdstore.repository.MDStoreCurrentVersionRepository;
import eu.dnetlib.data.mdstore.repository.MDStoreRepository;
import eu.dnetlib.data.mdstore.repository.MDStoreVersionRepository;
import eu.dnetlib.data.mdstore.repository.MDStoreWithInfoRepository;
import eu.dnetlib.dhp.schema.mdstore.MDStore;
import eu.dnetlib.dhp.schema.mdstore.MDStoreCurrentVersion;
import eu.dnetlib.dhp.schema.mdstore.MDStoreVersion;
import eu.dnetlib.dhp.schema.mdstore.MDStoreWithInfo;
import eu.dnetlib.errors.MDStoreManagerException;

@Service
public class MDStoreService {

	@Autowired
	private MDStoreRepository mdstoreRepository;
	@Autowired
	private MDStoreVersionRepository mdstoreVersionRepository;
	@Autowired
	private MDStoreCurrentVersionRepository mdstoreCurrentVersionRepository;
	@Autowired
	private MDStoreWithInfoRepository mdstoreWithInfoRepository;
	@Autowired
	private JdbcTemplate jdbcTemplate;

	@Value("${dhp.mdstore-manager.hdfs.base-path}")
	private String hdfsBasePath;

	private static final Logger log = LoggerFactory.getLogger(MDStoreService.class);

	public Iterable<MDStoreWithInfo> listMdStores() {
		return mdstoreWithInfoRepository.findAll();
	}

	public List<String> listMdStoreIDs() {
		return mdstoreRepository.findAll().stream().map(MDStore::getId).collect(Collectors.toList());
	}

	public long countMdStores() {
		return mdstoreRepository.count();
	}

	public Iterable<MDStoreVersion> listVersions(final String mdId) {
		return mdstoreVersionRepository.findByMdstore(mdId);
	}

	public List<String> listExpiredVersions() {
		return jdbcTemplate
			.queryForList("select v.id from mdstore_versions v left outer join mdstore_current_versions cv on (v.id = cv.current_version) where v.writing = false and v.readcount = 0 and cv.mdstore is null;", String.class);
	}

	public MDStoreWithInfo findMdStore(final String mdId) throws MDStoreManagerException {
		return mdstoreWithInfoRepository.findById(mdId).orElseThrow(() -> new MDStoreManagerException("Missing mdstore: " + mdId));
	}

	public MDStoreVersion findVersion(final String versionId) throws MDStoreManagerException {
		return mdstoreVersionRepository.findById(versionId).orElseThrow(() -> new MDStoreManagerException("Missing mdstore version: " + versionId));
	}

	@Transactional
	public String createMDStore(final String format,
		final String layout,
		final String interpretation,
		final String dsName,
		final String dsId,
		final String apiId) {

		final MDStore md = MDStore.newInstance(format, layout, interpretation, dsName, dsId, apiId, hdfsBasePath);
		mdstoreRepository.save(md);

		final MDStoreVersion v = MDStoreVersion.newInstance(md.getId(), false, hdfsBasePath);
		v.setLastUpdate(new Date());
		mdstoreVersionRepository.save(v);
		mdstoreCurrentVersionRepository.save(MDStoreCurrentVersion.newInstance(v));

		return md.getId();
	}

	@Transactional
	public String deleteMdStore(final String mdId) throws MDStoreManagerException {

		final Optional<MDStore> md = mdstoreRepository.findById(mdId);

		if (!md.isPresent()) {
			log.error("MDStore not found: " + mdId);
			throw new MDStoreManagerException("MDStore not found: " + mdId);
		}

		if (mdstoreVersionRepository.countByMdstoreAndReadCountGreaterThan(mdId, 0) > 0) {
			log.error("Read transactions found on mdstore: " + mdId);
			throw new MDStoreManagerException("Read transactions found on mdstore: " + mdId);
		}

		if (mdstoreVersionRepository.countByMdstoreAndWriting(mdId, true) > 0) {
			log.error("Write transactions found on mdstore: " + mdId);
			throw new MDStoreManagerException("Write transactions found on mdstore: " + mdId);
		}

		mdstoreCurrentVersionRepository.deleteById(mdId);
		mdstoreVersionRepository.deleteByMdstore(mdId);
		mdstoreRepository.deleteById(mdId);

		return md.get().getHdfsPath();
	}

	@Transactional
	public MDStoreVersion startReading(final String mdId) throws MDStoreManagerException {
		final MDStoreCurrentVersion cv =
			mdstoreCurrentVersionRepository.findById(mdId).orElseThrow(() -> new MDStoreManagerException("Missing mdstore: " + mdId));
		final MDStoreVersion v = mdstoreVersionRepository.findById(cv.getCurrentVersion())
			.orElseThrow(() -> new MDStoreManagerException("Missing version: " + cv.getCurrentVersion()));
		v.setReadCount(v.getReadCount() + 1);
		mdstoreVersionRepository.save(v);
		return v;
	}

	@Transactional
	public MDStoreVersion endReading(final String versionId) throws MDStoreManagerException {
		final MDStoreVersion v = mdstoreVersionRepository.findById(versionId).orElseThrow(() -> new MDStoreManagerException("Version not found"));
		v.setReadCount(Math.max(0, v.getReadCount() - 1));
		return v;
	}

	@Transactional
	public MDStoreVersion resetReading(final String versionId) throws MDStoreManagerException {
		final MDStoreVersion v = mdstoreVersionRepository.findById(versionId).orElseThrow(() -> new MDStoreManagerException("Version not found"));
		v.setReadCount(0);
		return v;
	}

	@Transactional
	public MDStoreVersion prepareMdStoreVersion(final String mdId) {
		final MDStoreVersion v = MDStoreVersion.newInstance(mdId, true, hdfsBasePath);
		mdstoreVersionRepository.save(v);
		return v;
	}

	@Transactional
	public MDStoreVersion commitMdStoreVersion(final String versionId, final long size) throws MDStoreManagerException {
		final MDStoreVersion v = mdstoreVersionRepository.findById(versionId).orElseThrow(() -> new MDStoreManagerException("Invalid version: " + versionId));
		mdstoreCurrentVersionRepository.save(MDStoreCurrentVersion.newInstance(v));
		v.setWriting(false);
		v.setSize(size);
		v.setLastUpdate(new Date());
		mdstoreVersionRepository.save(v);

		return v;
	}

	@Transactional
	public String deleteMdStoreVersion(final String versionId, final boolean force) throws MDStoreManagerException {

		final MDStoreVersion v = mdstoreVersionRepository.findById(versionId).orElseThrow(() -> new MDStoreManagerException("Version not found"));

		if (mdstoreCurrentVersionRepository
			.countByCurrentVersion(versionId) > 0) {
			throw new MDStoreManagerException("I cannot delete this version because it is the current version");
		}

		if (!force) {
			if (v.isWriting()) { throw new MDStoreManagerException("I cannot delete this version because it is in write mode"); }
			if (v.getReadCount() > 0) { throw new MDStoreManagerException("I cannot delete this version because it is in read mode"); }
		}

		mdstoreVersionRepository.delete(v);

		return v.getHdfsPath();
	}

	public Set<String> listValidHdfsPaths() {
		return new HashSet<>(jdbcTemplate
			.queryForList(" select hdfs_path from mdstores union all select hdfs_path from mdstore_versions", String.class));
	}

	public String getHdfsBasePath() {
		return hdfsBasePath;
	}

	public void setHdfsBasePath(final String hdfsBasePath) {
		this.hdfsBasePath = hdfsBasePath;
	}

}