package it.cavallium.dbengine.database.disk;

import static it.cavallium.dbengine.database.LLUtils.MARKER_ROCKSDB;

import io.micrometer.core.instrument.MeterRegistry;
import io.net5.buffer.api.Buffer;
import io.net5.buffer.api.BufferAllocator;
import io.net5.buffer.api.MemoryManager;
import io.net5.buffer.api.Send;
import it.cavallium.dbengine.database.LLDelta;
import it.cavallium.dbengine.database.LLUtils;
import it.cavallium.dbengine.database.serialization.SerializationFunction;
import it.cavallium.dbengine.rpc.current.data.DatabaseOptions;
import java.io.IOException;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.rocksdb.ColumnFamilyHandle;
import org.rocksdb.ReadOptions;
import org.rocksdb.RocksDBException;
import org.rocksdb.Transaction;
import org.rocksdb.TransactionDB;
import org.rocksdb.TransactionOptions;
import org.rocksdb.WriteOptions;
import reactor.core.scheduler.Schedulers;

public final class PessimisticRocksDBColumn extends AbstractRocksDBColumn<TransactionDB> {

	private static final TransactionOptions DEFAULT_TX_OPTIONS = new TransactionOptions();

	public PessimisticRocksDBColumn(TransactionDB db,
			DatabaseOptions databaseOptions,
			BufferAllocator alloc,
			ColumnFamilyHandle cfh, MeterRegistry meterRegistry) {
		super(db, databaseOptions, alloc, cfh, meterRegistry);
	}

	@Override
	protected boolean commitOptimistically(Transaction tx) throws RocksDBException {
		tx.commit();
		return true;
	}

	@Override
	protected Transaction beginTransaction(@NotNull WriteOptions writeOptions) {
		return getDb().beginTransaction(writeOptions, DEFAULT_TX_OPTIONS);
	}

	@Override
	public @NotNull UpdateAtomicResult updateAtomic(@NotNull ReadOptions readOptions,
			@NotNull WriteOptions writeOptions,
			Send<Buffer> keySend,
			SerializationFunction<@Nullable Send<Buffer>, @Nullable Buffer> updater,
			UpdateAtomicResultMode returnMode) throws IOException, RocksDBException {
		try (Buffer key = keySend.receive()) {
			try {
				var cfh = getCfh();
				var keyArray = LLUtils.toArray(key);
				if (Schedulers.isInNonBlockingThread()) {
					throw new UnsupportedOperationException("Called update in a nonblocking thread");
				}
				try (var tx = beginTransaction(writeOptions)) {
					Send<Buffer> sentPrevData;
					Send<Buffer> sentCurData;
					boolean changed;
					var prevDataArray = tx.getForUpdate(readOptions, cfh, keyArray, true);
					if (logger.isTraceEnabled()) {
						logger.trace(MARKER_ROCKSDB,
								"Reading {}: {} (before update)",
								LLUtils.toStringSafe(key),
								LLUtils.toStringSafe(prevDataArray)
						);
					}
					Buffer prevData;
					if (prevDataArray != null) {
						prevData = MemoryManager.unsafeWrap(prevDataArray);
					} else {
						prevData = null;
					}
					try (prevData) {
						Buffer prevDataToSendToUpdater;
						if (prevData != null) {
							prevDataToSendToUpdater = prevData.copy();
						} else {
							prevDataToSendToUpdater = null;
						}

						@Nullable Buffer newData;
						try (var sentData = prevDataToSendToUpdater == null ? null : prevDataToSendToUpdater.send()) {
							newData = updater.apply(sentData);
						}
						try (newData) {
							var newDataArray = newData == null ? null : LLUtils.toArray(newData);
							if (logger.isTraceEnabled()) {
								logger.trace(MARKER_ROCKSDB,
										"Updating {}. previous data: {}, updated data: {}",
										LLUtils.toStringSafe(key),
										LLUtils.toStringSafe(prevDataArray),
										LLUtils.toStringSafe(newDataArray)
								);
							}
							if (prevData != null && newData == null) {
								if (logger.isTraceEnabled()) {
									logger.trace(MARKER_ROCKSDB, "Deleting {} (after update)", LLUtils.toStringSafe(key));
								}
								tx.delete(cfh, keyArray, true);
								changed = true;
								tx.commit();
							} else if (newData != null && (prevData == null || !LLUtils.equals(prevData, newData))) {
								if (logger.isTraceEnabled()) {
									logger.trace(MARKER_ROCKSDB,
											"Writing {}: {} (after update)",
											LLUtils.toStringSafe(key),
											LLUtils.toStringSafe(newData)
									);
								}
								tx.put(cfh, keyArray, newDataArray);
								changed = true;
								tx.commit();
							} else {
								changed = false;
								tx.rollback();
							}
							sentPrevData = prevData == null ? null : prevData.send();
							sentCurData = newData == null ? null : newData.send();
						}
					}
					return switch (returnMode) {
						case NOTHING -> {
							if (sentPrevData != null) {
								sentPrevData.close();
							}
							if (sentCurData != null) {
								sentCurData.close();
							}
							yield RESULT_NOTHING;
						}
						case CURRENT -> {
							if (sentPrevData != null) {
								sentPrevData.close();
							}
							yield new UpdateAtomicResultCurrent(sentCurData);
						}
						case PREVIOUS -> {
							if (sentCurData != null) {
								sentCurData.close();
							}
							yield new UpdateAtomicResultPrevious(sentPrevData);
						}
						case BINARY_CHANGED -> new UpdateAtomicResultBinaryChanged(changed);
						case DELTA -> new UpdateAtomicResultDelta(LLDelta.of(sentPrevData, sentCurData).send());
					};
				}
			} catch (Throwable ex) {
				throw new IOException("Failed to update key " + LLUtils.toStringSafe(key), ex);
			}
		}
	}

	@Override
	public boolean supportsTransactions() {
		return true;
	}
}