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.client.DatabaseOptions;
import it.cavallium.dbengine.database.LLDelta;
import it.cavallium.dbengine.database.LLUtils;
import it.cavallium.dbengine.database.serialization.SerializationFunction;
import it.cavallium.dbengine.lucene.ExponentialPageLimits;
import java.io.IOException;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.locks.LockSupport;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.rocksdb.ColumnFamilyHandle;
import org.rocksdb.OptimisticTransactionDB;
import org.rocksdb.ReadOptions;
import org.rocksdb.RocksDBException;
import org.rocksdb.Status.Code;
import org.rocksdb.Transaction;
import org.rocksdb.WriteBatch;
import org.rocksdb.WriteOptions;
import reactor.core.scheduler.Schedulers;

public final class OptimisticRocksDBColumn extends AbstractRocksDBColumn<OptimisticTransactionDB> {

	private static final boolean ALWAYS_PRINT_OPTIMISTIC_RETRIES = false;

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

	@Override
	protected boolean commitOptimistically(Transaction tx) throws RocksDBException {
		try {
			tx.commit();
			return true;
		} catch (RocksDBException ex) {
			var status = ex.getStatus() != null ? ex.getStatus().getCode() : Code.Ok;
			if (status == Code.Busy || status == Code.TryAgain) {
				return false;
			}
			throw ex;
		}
	}

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

	@Override
	public void write(WriteOptions writeOptions, WriteBatch writeBatch) throws RocksDBException {
		getDb().write(writeOptions, writeBatch);
	}

	@Override
	public @NotNull UpdateAtomicResult updateAtomic(@NotNull ReadOptions readOptions,
			@NotNull WriteOptions writeOptions,
			Send<Buffer> keySend,
			SerializationFunction<@Nullable Send<Buffer>, @Nullable Buffer> updater,
			boolean existsAlmostCertainly,
			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)) {
					boolean committedSuccessfully;
					int retries = 0;
					ExponentialPageLimits retryTime = null;
					Send<Buffer> sentPrevData;
					Send<Buffer> sentCurData;
					boolean changed;
					do {
						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);
							prevDataArray = null;
						} 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;
									committedSuccessfully = commitOptimistically(tx);
								} 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;
									committedSuccessfully = commitOptimistically(tx);
								} else {
									changed = false;
									committedSuccessfully = true;
									tx.rollback();
								}
								sentPrevData = prevData == null ? null : prevData.send();
								sentCurData = newData == null ? null : newData.send();
								if (!committedSuccessfully) {
									tx.undoGetForUpdate(cfh, keyArray);
									tx.rollback();
									if (sentPrevData != null) {
										sentPrevData.close();
									}
									if (sentCurData != null) {
										sentCurData.close();
									}
									retries++;

									if (retries == 1) {
										retryTime = new ExponentialPageLimits(0, 2, 2000);
									}
									long retryNs = 1000000L * retryTime.getPageLimit(retries);

									// +- 30%
									retryNs = retryNs + ThreadLocalRandom.current().nextLong(-retryNs * 30L / 100L, retryNs * 30L / 100L);

									if (retries >= 5 && retries % 5 == 0 || ALWAYS_PRINT_OPTIMISTIC_RETRIES) {
										logger.warn(MARKER_ROCKSDB, "Failed optimistic transaction {} (update):"
												+ " waiting {} ms before retrying for the {} time", LLUtils.toStringSafe(key), retryNs / 1000000d, retries);
									} else if (logger.isDebugEnabled(MARKER_ROCKSDB)) {
										logger.debug(MARKER_ROCKSDB, "Failed optimistic transaction {} (update):"
												+ " waiting {} ms before retrying for the {} time", LLUtils.toStringSafe(key), retryNs / 1000000d, retries);
									}
									// Wait for n milliseconds
									if (retryNs > 0) {
										LockSupport.parkNanos(retryNs);
									}
								}
							}
						}
					} while (!committedSuccessfully);
					if (retries > 5) {
						logger.warn(MARKER_ROCKSDB, "Took {} retries to update key {}", retries, LLUtils.toStringSafe(key));
					}
					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;
	}
}