package org.warp.jcwdb;

import it.unimi.dsi.fastutil.longs.Long2LongLinkedOpenHashMap;
import it.unimi.dsi.fastutil.longs.Long2LongMap;

import java.io.IOException;
import java.nio.file.Path;
import java.util.function.Consumer;

public class MixedIndexDatabase implements IndexManager {
	private final Long2LongMap mostAccessedIndices;
	private final FileIndexManager fileIndices;
	private final CacheIndexManager cacheIndices;

	public MixedIndexDatabase(TypesManager typesManager, Path dataFile, Path metadataFile) throws IOException {
		this.mostAccessedIndices = new Long2LongLinkedOpenHashMap();
		this.fileIndices = new FileIndexManager(dataFile, metadataFile);
		this.cacheIndices = new CacheIndexManager();
	}

	@Override
	public <T> T get(long index, DBReader<T> reader) throws IOException {
		incrementUsage(index);
		if (cacheIndices.has(index)) {
			return cacheIndices.get(index, reader);
		} else {
			return fileIndices.get(index, reader);
		}
	}

	@Override
	public int getType(long index) throws IOException {
		if (cacheIndices.has(index)) {
			return cacheIndices.getType(index);
		} else {
			return fileIndices.getType(index);
		}
	}

	@Override
	public long getHash(long index) throws IOException {
		if (cacheIndices.has(index)) {
			return cacheIndices.getHash(index);
		} else {
			return fileIndices.getHash(index);
		}
	}

	@Override
	public <T> long add(DBDataOutput<T> writer) throws IOException {
		return fileIndices.add(writer);
	}

	@Override
	public <T> IndexDetails set(long index, DBDataOutput<T> writer) throws IOException {
		if (cacheIndices.has(index)) {
			return cacheIndices.set(index, writer);
		} else {
			return fileIndices.set(index, writer);
		}
	}

	@Override
	public void delete(long index) throws IOException {
		cacheIndices.delete(index);
		fileIndices.delete(index);
	}

	@Override
	public boolean has(long index) {
		return cacheIndices.has(index) || fileIndices.has(index);
	}

	private void incrementUsage(long index) {
		mostAccessedIndices.put(index, mostAccessedIndices.getOrDefault(index, 0) + 1);
	}

	@Override
	public void close() throws IOException {
		// TODO: move all cached indices to filesIndices before closing.
		this.cacheIndices.close();
		this.fileIndices.close();
	}

	@Override
	public long clean() {
		return fileIndices.clean()
				+ cacheIndices.clean();
	}
}