/*******************************************************************************
 * Copyright (C) 2021 the Eclipse BaSyx Authors
 * 
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 * 
 * SPDX-License-Identifier: EPL-2.0
 ******************************************************************************/
package org.eclipse.basyx.vab.modelprovider.filesystem.filesystem;

import java.io.FileWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * Implements a generic file system
 * 
 * @author schnicke
 *
 */
public class GenericFileSystem implements FileSystem {

	@Override
	public String readFile(String path) throws IOException {
		path = toLowerCase(path);
		return new String(Files.readAllBytes(getPath(path)), StandardCharsets.UTF_8);
	}

	@Override
	public void writeFile(String path, String content) throws IOException {
		path = toLowerCase(path);
		FileWriter f = new FileWriter(path, false);
		f.write(content);
		f.close();
	}

	@Override
	public void deleteFile(String path) throws IOException {
		path = toLowerCase(path);
		Files.deleteIfExists(getPath(path));
	}

	@Override
	public void createDirectory(String path) throws IOException {
		path = toLowerCase(path);
		Files.createDirectories(getPath(path));
	}

	@Override
	public List<File> readDirectory(String path) throws IOException {
		path = toLowerCase(path);
		List<File> files = new ArrayList<>();

		// Use try to ensure that close is called
		try (Stream<Path> directory = Files.list(getPath(path))) {
			files.addAll(directory.filter(Files::isRegularFile)
					.map(p -> new File(restoreCase(p.toString().replace("\\", "/")), FileType.DATA)).collect(Collectors.toList()));
		}

		// Use try to ensure that close is called
		try (Stream<Path> directory = Files.list(getPath(path))) {
			files.addAll(directory.filter(Files::isDirectory)
					.map(p -> new File(restoreCase(p.toString().replace("\\", "/")), FileType.DIRECTORY))
					.collect(Collectors.toList()));
		}

		return files;
	}

	@Override
	public void deleteDirectory(String path) throws IOException {
		path = toLowerCase(path);
		try {
			Files.walk(getPath(path)).sorted(Comparator.reverseOrder()).map(p -> p.toFile()).forEach(f -> f.delete());
		} catch (NoSuchFileException e) {
			//Do nothing if the File to delete doesn't exist
		}
	}
	
	@Override
	public FileType getType(String path) {
		path = toLowerCase(path);
		
		if(!Files.exists(getPath(path)))
			return null;
		
		if(Files.isDirectory(getPath(path)))
			return FileType.DIRECTORY;
		
		return FileType.DATA;
	}

	private Path getPath(String path) {
		return FileSystems.getDefault().getPath(path);
	}
	
	/**
	 * Replaces each capital character by (_small character) ([A-Z] by _[a-z]) and
	 * each _ by __
	 */
	private String toLowerCase(String path) {
		return path.replaceAll("([A-Z_])", "_$1").toLowerCase();
	}

	/**
	 * Replaces each (_small character) by a capital character (_[a-z] by [A-Z]) and
	 * each __ by _
	 */
	private String restoreCase(String path) {
		StringBuffer result = new StringBuffer();
		Matcher m = Pattern.compile("_([_a-z])").matcher(path);

		while (m.find())
			m.appendReplacement(result, m.group(1).toUpperCase());
		
		m.appendTail(result);

		return result.toString();
	}

}