package it.cavallium.strangedb.java.database;

import it.cavallium.strangedb.database.DatabaseCore;
import it.cavallium.strangedb.database.references.ReferenceInfo;
import it.cavallium.strangedb.java.objects.EnhancedObject;
import it.cavallium.strangedb.functionalinterfaces.FunctionWithIO;
import it.cavallium.strangedb.java.objects.EnhancedObjectIndices;
import it.unimi.dsi.fastutil.longs.LongArrayList;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;

import static it.cavallium.strangedb.database.references.DatabaseReferencesMetadata.*;
import static it.cavallium.strangedb.java.database.DatabaseObjectsIO.ENHANCED_OBJECT_METADATA_CLEANER;
import static it.cavallium.strangedb.java.database.DatabaseObjectsIO.REFERENCES_LIST_CLEANER;

public class DatabaseJava extends DatabaseCore implements IDatabaseTools {
	private final IDatabaseTools databaseTools;
	private final DatabaseObjectsIO objectsIO;
	private EnhancedObject loadedRootObject;
	private boolean hasLoadedRootObject;

	public DatabaseJava(Path dataFile, Path blocksMetaFile, Path referencesMetaFile) throws IOException {
		super(dataFile, blocksMetaFile, referencesMetaFile);
		this.databaseTools = this;
		this.objectsIO = new DatabaseObjectsIO(databaseTools, referencesIO);
		this.hasLoadedRootObject = false;
	}

	@Override
	public synchronized void close() throws IOException {
		if (this.closed) {
			throw new IOException("The database has been already closed!");
		}
		if (hasLoadedRootObject) {
			this.objectsIO.setEnhancedObject(0, loadedRootObject);
		}
		super.close();
	}

	public <T extends EnhancedObject> T loadRoot(FunctionWithIO<IDatabaseTools, T> ifAbsent) throws IOException {
		if (hasLoadedRootObject) {
			throw new RuntimeException("Root already set!");
		}
		T root;
		if (referencesMetadata.getFirstFreeReference() > 0) {
			root = objectsIO.loadEnhancedObject(0);
		} else {
			if (objectsIO.newNullObject() != 0) {
				throw new IOException("Can't allocate root!");
			} else {
				root = ifAbsent.apply(DatabaseJava.this);
				objectsIO.setEnhancedObject(0, root);
			}
		}
		loadedRootObject = root;
		hasLoadedRootObject = true;
		return root;
	}

	public <T extends EnhancedObject> T loadRoot(FunctionWithIO<IDatabaseTools, T> ifAbsent, Class<?> forcedClassType) throws IOException {
		if (hasLoadedRootObject) {
			throw new RuntimeException("Root already set!");
		}
		T root;
		if (referencesMetadata.getFirstFreeReference() > 0) {
			root = objectsIO.loadEnhancedObject(0, forcedClassType);
		} else {
			if (objectsIO.newNullObject() != 0) {
				throw new IOException("Can't allocate root!");
			} else {
				root = ifAbsent.apply(DatabaseJava.this);
				objectsIO.setEnhancedObject(0, root);
			}
		}
		loadedRootObject = root;
		hasLoadedRootObject = true;
		return root;
	}

	@Override
	public void closeAndClean() throws IOException {
		if (!this.closed) {
			this.close();
		}
		Path newDataFile = dataFile.resolveSibling("compressed-data-file.tmp");
		Path newBlocksFile = blocksMetaFile.resolveSibling("compressed-blocks-file.tmp");
		Path newReferencesFile = referencesMetaFile.resolveSibling("compressed-references-file.tmp");
		Path backupDataFile = dataFile.resolveSibling("backup-data.db.bak");
		Path backupBlocksFile = blocksMetaFile.resolveSibling("backup-blocks.dat.bak");
		Path backupReferencesFile = referencesMetaFile.resolveSibling("backup-references.dat.bak");
		Files.copy(dataFile, backupDataFile, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES);
		Files.copy(blocksMetaFile, backupBlocksFile, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES);
		Files.copy(referencesMetaFile, backupReferencesFile, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES);
		Files.move(dataFile, newDataFile, StandardCopyOption.REPLACE_EXISTING);
		Files.move(blocksMetaFile, newBlocksFile, StandardCopyOption.REPLACE_EXISTING);
		Files.move(referencesMetaFile, newReferencesFile, StandardCopyOption.REPLACE_EXISTING);
		DatabaseJava databaseToClean = instantiateNewDatabase(newDataFile, newBlocksFile, newReferencesFile);
		DatabaseJava newDatabase = instantiateNewDatabase(dataFile, blocksMetaFile, referencesMetaFile);

		long firstFreeReference = databaseToClean.referencesMetadata.getFirstFreeReference();
		long referencesCount = 0;
		long blocksCount = databaseToClean.blocksMetadata.getTotalBlocksCount();
		long writtenReferences = 0;
		long writtenBlocks = 0;

		LongArrayList idsToKeep = new LongArrayList();
		cleanRef(databaseToClean, idsToKeep, 0);

		for (int referenceID = 0; referenceID < firstFreeReference; referenceID++) {
			try {
				ReferenceInfo ref = databaseToClean.referencesMetadata.getCleanReference(referenceID);
				if (!NONEXISTENT_REFERENCE_INFO.equals(ref)) {
					referencesCount++;
					if (idsToKeep.contains(referenceID)) {
						ByteBuffer buffer = databaseToClean.referencesIO.readFromReference(referenceID);
						newDatabase.referencesIO.writeToReference(referenceID, ref.getCleanerId(), buffer.limit(), buffer);
						writtenReferences++;
						if (buffer.limit() > 0) {
							writtenBlocks++;
						}
					}
				}
			} catch (IOException ex) {
				System.out.println("Error while reading reference " + referenceID + ". References written: " + writtenReferences);
			}
		}
		System.out.println("[Java Cleaner] References written: " + writtenReferences + ". Removed " + (blocksCount - writtenBlocks) + " blocks. Removed " + (referencesCount - writtenReferences) + " references.");
		databaseToClean.close();
		newDatabase.close();
		Files.deleteIfExists(newDataFile);
		Files.deleteIfExists(newBlocksFile);
		Files.deleteIfExists(newReferencesFile);
	}

	private void cleanRef(DatabaseJava db, LongArrayList idsToKeep, long ref) throws IOException {
		idsToKeep.add(ref);
		ReferenceInfo refInfo = db.referencesMetadata.getCleanReference(ref);
		if (!NONEXISTENT_REFERENCE_INFO.equals(refInfo)) {
			switch (refInfo.getCleanerId()) {
				case ENHANCED_OBJECT_METADATA_CLEANER: {
					EnhancedObjectIndices enhancedObjectUids = db.objectsIO.loadEnhancedObjectUids(ref);
					for (long fieldUid : enhancedObjectUids.fieldUids) {
						cleanRef(db, idsToKeep, fieldUid);
					}
					for (long propUid : enhancedObjectUids.propertyUids) {
						cleanRef(db, idsToKeep, propUid);
					}
					cleanRef(db, idsToKeep, enhancedObjectUids.nativeDataUid);
					break;
				}
				case ERRORED_CLEANER: {
					System.err.println("Errored cleaner found! Skipping...");
					break;
				}
				case REFERENCES_LIST_CLEANER: {
					LongArrayList refList = db.objectsIO.loadReferencesList(ref);
					for (long elemRef : refList) {
						cleanRef(db, idsToKeep, elemRef);
					}
					break;
				}
				case BLANK_DATA_CLEANER: {
					break;
				}
				default: {
					System.err.println("Unrecognized cleaner found! Skipping...");
				}
			}
		}
	}

	public void registerClass(Class<?> type, int id) {
		this.objectsIO.registerClass(type, id);
	}

	protected DatabaseJava instantiateNewDatabase(Path dataFile, Path blocksMetaFile, Path referencesMetaFile) throws IOException {
		DatabaseJava newDatabaseJava = new DatabaseJava(dataFile, blocksMetaFile, referencesMetaFile);
		this.getObjectsIO().getRegisteredClasses().forEach(newDatabaseJava::registerClass);
		return newDatabaseJava;
	}

	@Override
	public void initializeEnhancedObject(EnhancedObject enhancedObject) throws IOException {
		this.objectsIO.getDataInitializer().initializeDbObject(enhancedObject);
	}

	@Override
	public DatabaseObjectsIO getObjectsIO() {
		return objectsIO;
	}

}