Dual/src/com/luca0n/dual/common/Dual.java

/*
Dual: a simple manager for custom hostnames

Copyright (C) 2021 luca0N!

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, either version 3 of the License, or (at your option) any later
version.

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, see <https://www.gnu.org/licenses/>.

Contact me by e-mail via <luca0n [at] luca0n [dot] com>.
*/

package com.luca0n.dual.common;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.FileSystems;
import java.nio.file.Path;

import com.luca0n.dual.common.ConfigSyntaxException;
import com.luca0n.dual.common.NoSuchNamespaceException;
import com.luca0n.dual.common.NoSuchKeyException;
import com.luca0n.dual.common.UnsupportedOperatingSystemException;
import com.luca0n.dual.config.Config;
import com.luca0n.dual.config.ConfigUtil;

/**
 * @version 1.0
 * @since 2021-03-21
 */
public class Dual {
	public static final String NAME = "Dual";
	public static final String VERSION = "1.0";
	private static final String AUTO_GEN_COMMENT = "This entry was auto-generated by " + NAME + ".";
	public static final int VERSION_CODE = 1;

	private static final String[] SUPPORTED_OPERATING_SYSTEMS = {
		"Linux",
		"Windows"
	};

	public static void main(String[] args){
		try {
			run();
		} catch (Exception e){
			e.printStackTrace();
			System.exit(1);
		}
	}
	public static void run() throws ConfigSyntaxException,
		NoSuchNamespaceException, NoSuchKeyException, IOException,
		UnsupportedOperatingSystemException {
		// Read configuration file
		Config c = ConfigUtil.fromFile(ConfigUtil.DEFAULT_CONFIG);

		Config.Namespace n = c.getNamespace("Dual");

		if (n == null)
			throw new NoSuchNamespaceException("Could not find required namespace Dual in the default configuration file.");

		String type = n.getValue("FetchType"),
			source = n.getValue("Source"),
			target = n.getValue("Target"),
			hostsPath = n.getValue("hostsPath");

		// Check for null values.
		if (source == null)
			throw new NoSuchKeyException("Could not find required key Dual.Source in the default configuration file.");
		else if (target == null)
			throw new NoSuchKeyException("Could not find required key Dual.Target in the default configuration file.");

		System.out.printf("%s: All tests passed.\n", NAME);

		if (type == null){
			type = "Resolve";
			System.out.printf("%s: WARNING: no FetchType specified. Assuming Resolve FetchType...\n", NAME);
		}

		System.out.printf("%s: Using %s FetchType and %s Source.\n", NAME, type, source);
		System.out.printf("%s: Using %s hostname.\n", NAME, target);

		// Check OS.
		String os = System.getProperty("os.name");
		boolean supportedOs = false;
		for (String sos : SUPPORTED_OPERATING_SYSTEMS)
			if (os.contains(sos)){
				supportedOs = true;
				break;
			}

		if (!supportedOs && hostsPath == null){
			StringBuilder msg = new StringBuilder();
			msg.append("Unsupported operating system: ")
				.append(os)
				.append(". ")
				.append("This program must be run under ");

			for (int x = 0; x < SUPPORTED_OPERATING_SYSTEMS.length; x++){
				if (x == SUPPORTED_OPERATING_SYSTEMS.length - 1)
					msg.append(" or ")
						.append(SUPPORTED_OPERATING_SYSTEMS[x])
						.append(". ");
				else if (x == 0)
					msg.append(SUPPORTED_OPERATING_SYSTEMS[x]);
				else
					msg.append(", ")
						.append(SUPPORTED_OPERATING_SYSTEMS[x]);
			}

			msg.append("If you want to override this system requirement, please provide a path to the hosts file on your operating system.");

			throw new UnsupportedOperatingSystemException(msg.toString());
		}

		System.out.printf(hostsPath == null ? "%s: using %s settings.\n" : "%s: using custom settings for %s.\n", NAME, os);

		// Open hosts file.
		
		if (hostsPath == null){
			boolean isWindows = os.contains(SUPPORTED_OPERATING_SYSTEMS[1]);
			hostsPath = isWindows ? "C:\\WINDOWS\\System32\\drivers\\etc\\hosts" : "/etc/hosts";
		}

		System.out.printf("%s: opening %s...\n", NAME, hostsPath);

		Path path = FileSystems.getDefault().getPath(hostsPath);
		byte[] fileBytes = Files.readAllBytes(path);

		String[] lines = new String(fileBytes).split(System.lineSeparator());

		for (String line : lines){
			// Check if this line is a comment.
			if (line.startsWith("#"))
				// Ignore this line.
				continue;
			
			String[] contents = line.split("#")[0];
			// Check if this line was auto-generated by this program.
			if (contents.length == 2){
				// Check line comment.
				if (contents[1].equals(AUTO_GEN_COMMENT)){
					// Remove this entry if we're going to replace it.
					
				}
			}


		}

	}
}