/*
 * Copyright (C) 2023 Laurent CLOUET
 * Author Laurent CLOUET <laurent.clouet@nopnop.net>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package com.sheepit.client.config;

import com.sheepit.client.logger.Log;
import com.sheepit.client.datamodel.server.Chunk;
import com.sheepit.client.utils.Utils;
import lombok.AllArgsConstructor;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileSystemException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;

@AllArgsConstructor
public class DirectoryManager {
	private Configuration configuration;
	
	public String getActualStoragePathFor(Chunk chunk) {
		return isSharedEnabled() ? getSharedPathFor(chunk) : getCachePathFor(chunk);
	}
	
	public String getCachePathFor(Chunk chunk) {
		return configuration.getWoolCacheDirectory().getAbsolutePath() + File.separator + chunk.getId() + ".wool";
	}
	
	public String getSharedPathFor(Chunk chunk) {
		return configuration.getSharedDownloadsDirectory().getAbsolutePath() + File.separator + chunk.getId() + ".wool";
	}
	
	public boolean isSharedEnabled() {
		return configuration.getSharedDownloadsDirectory() != null && configuration.getSharedDownloadsDirectory().exists();
	}
	
	public boolean copyChunkFromSharedToCache(Chunk chunk) {
		return copyFileFromSharedToCache(getSharedPathFor(chunk), getCachePathFor(chunk));
	}
	
	private boolean copyFileFromSharedToCache(String source, String target) {
		Path existingArchivePath = Paths.get(source);
		Path targetArchivePath = Paths.get(target);
		
		if (existingArchivePath.equals(targetArchivePath)) {
			// target are the same, do nothing
			return true;
		}
		
		try {
			Files.deleteIfExists(targetArchivePath);  // createLink only works if the target does not exist
			try {
				Files.createLink(targetArchivePath, existingArchivePath);
				Log.getInstance().debug("Created hardlink from " + targetArchivePath + " to " + existingArchivePath);
			}
			catch (UnsupportedOperationException // underlying file system does not support hard-linking
				   | FileSystemException       // cache-dir and shared-zip are on separate file systems, even though hard-linking is supported
				   | SecurityException         // user is not allowed to create hard-links
				ignore) {
				// Creating hardlinks might not be supported on some filesystems
				Log.getInstance().debug("Failed to create hardlink, falling back to copying file to " + targetArchivePath);
				Files.copy(existingArchivePath, targetArchivePath, StandardCopyOption.REPLACE_EXISTING);
			}
		}
		catch (IOException e) {
			Log.getInstance().error("Error while copying " + source + " from shared downloads directory to working dir");
			return false;
		}
		
		return true;
	}
	
	/**
	 * Creates cache directory
	 */
	public void createCacheDir() {
		this.removeWorkingDirectory();
		
		this.configuration.getWorkingDirectory().mkdirs();
		this.configuration.getWoolCacheDirectory().mkdirs();
		
		if (this.configuration.getSharedDownloadsDirectory() != null) {
			this.configuration.getSharedDownloadsDirectory().mkdirs();

			if (this.configuration.getSharedDownloadsDirectory().exists() == false) {
				System.err.println("DirectoryManager::createCacheDir Unable to create common directory " + this.configuration.getSharedDownloadsDirectory().getAbsolutePath());
			}
		}
	}
	
	/**
	 * Cleans working directory and also deletes it if the user hasn't specified a cache directory
	 */
	public void removeWorkingDirectory() {
		if (this.configuration.isUserHasSpecifiedACacheDir()) {
			this.cleanWorkingDirectory();
		}
		else {
			Utils.delete(this.configuration.getWorkingDirectory());
		}
	}
	
	/**
	 * Deletes the working and storage directories
	 */
	public void cleanWorkingDirectory() {
		this.cleanDirectory(this.configuration.getWorkingDirectory());
		this.cleanDirectory(this.configuration.getWoolCacheDirectory());
	}
	
	/**
	 * Cleans a directory and removes files in it from the md5 cache
	 * @param dir representing the directory to be cleaned
	 * @return false if the dir null, true otherwise
	 */
	private boolean cleanDirectory(File dir) {
		if (dir == null) {
			return false;
		}
		
		File[] files = dir.listFiles();
		if (files != null) {
			for (File file : files) {
				if (file.isDirectory()) {
					Utils.delete(file);
				}
				else {
					try {
						String extension = file.getName().substring(file.getName().lastIndexOf('.')).toLowerCase();
						String name = file.getName().substring(0, file.getName().length() - 1 * extension.length());
						if (".wool".equals(extension)) {
							// check if the md5 of the file is ok
							String md5_local = Utils.md5(file.getAbsolutePath());
							
							if (md5_local.equals(name) == false) {
								file.delete();
							}
							
							// TODO: remove old one
						}
						else {
							file.delete();
						}
					}
					catch (StringIndexOutOfBoundsException e) { // because the file does not have an . in his path
						file.delete();
					}
				}
			}
		}
		return true;
	}
	
	/**
	 * @return a list of archives (files with extensions .zip or .wool) in the
	 * working, storage, and shared downloads directories as long as they are not null
	 */
	public List<File> getLocalCacheFiles() {
		List<File> files_local = new LinkedList<File>();
		List<File> files = new LinkedList<File>();
		if (this.configuration.getWorkingDirectory() != null) {
			File[] filesInDirectory = this.configuration.getWorkingDirectory().listFiles();
			if (filesInDirectory != null) {
				files.addAll(Arrays.asList(filesInDirectory));
			}
		}
		if (this.configuration.getWoolCacheDirectory() != null) {
			File[] filesInDirectory = this.configuration.getWoolCacheDirectory().listFiles();
			if (filesInDirectory != null) {
				files.addAll(Arrays.asList(filesInDirectory));
			}
		}
		if (this.configuration.getSharedDownloadsDirectory() != null) {
			File[] filesInDirectory = this.configuration.getSharedDownloadsDirectory().listFiles();
			if (filesInDirectory != null) {
				files.addAll(Arrays.asList(filesInDirectory));
			}
		}
		
		for (File file : files) {
			if (file.isFile()) {
				try {
					String extension = file.getName().substring(file.getName().lastIndexOf('.')).toLowerCase();
					String name = file.getName().substring(0, file.getName().length() - 1 * extension.length());
					if (".wool".equals(extension)) {
						// check if the md5 of the file is ok
						String md5_local = Utils.md5(file.getAbsolutePath());
						
						if (md5_local.equals(name)) {
							files_local.add(file);
						}
					}
				}
				catch (StringIndexOutOfBoundsException e) { // because the file does not have an . his path
				}
			}
		}
		return files_local;
	}
	
	/**
	 * Runs through all SheepIt related directories and checks if files and folders are all readable, writeable
	 * and in case of directories, checks if the contents can be listed and if usable space is enough.
	 * Only logs instances where something was detected, otherwise is it will only print "FilesystemHealthCheck started"
	 * @return an ArrayList of Strings containing all logs of the FSHealth check
	 */
	public List<String> filesystemHealthCheck() {
		List<String> logs = new ArrayList<>();
		String f = "FSHealth: ";
		logs.add(f + "FilesystemHealthCheck started");
		List<File> dirsToCheck = new ArrayList<>();
		List<File> dirsChecked = new ArrayList<>();
		dirsToCheck.add(configuration.getWorkingDirectory().getAbsoluteFile());
		if (configuration.getSharedDownloadsDirectory() != null && dirsToCheck.contains(configuration.getSharedDownloadsDirectory().getAbsoluteFile()) == false) {
			dirsToCheck.add(configuration.getSharedDownloadsDirectory().getAbsoluteFile());
		}
		if (configuration.getWoolCacheDirectory() != null && dirsToCheck.contains(configuration.getWoolCacheDirectory().getAbsoluteFile()) == false) {
			dirsToCheck.add(configuration.getWoolCacheDirectory().getAbsoluteFile());
		}
		ListIterator<File> dirs = dirsToCheck.listIterator();
		while (dirs.hasNext()) {
			File dir = dirs.next();
			dirs.remove();
			dirsChecked.add(dir);
			File[] fileList = dir.listFiles();
			if (fileList == null) {
				logs.add(f + "File list of " + dir + " is null");
			}
			else {
				for (File file : fileList) {
					file = file.getAbsoluteFile();
					//logs.add(f + file);
					boolean canRead = file.canRead();
					boolean canWrite = file.canWrite();
					boolean isDir = file.isDirectory();
					if (canRead == false) {
						logs.add(f + "Can't read from " + file);
					}
					if (canWrite == false) {
						logs.add(f + "Can't write to " + file);
					}
					if (canRead && canWrite && isDir) {
						if (dirsChecked.contains(file)) {
							logs.add(f + "Dir " + file + " already checked. Loop detected");
						}
						else {
							dirs.add(file);
						}
						long usableSpace = file.getUsableSpace();
						if (usableSpace < 512 * 1024) {
							logs.add(f + "Usable space is " + usableSpace + " for " + file);
						}
					}
				}
			}
		}
		return logs;
	}
}