Merge pull request #2 from dwelch2344/10bc4e980bf96ce2cdc7c59aa557ae62790061e1

Implemented HostEditor

Author: danlangford

src/com/danlangford/selectoserve/HostEditor.java

@@ -0,0 +1,80 @@
+package com.danlangford.selectoserve;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.Scanner;
+
+
+public class HostEditor {
+
+	private static final String NL = System.getProperty("line.separator");
+	
+	public void update(String hostPath, String user, String address) {
+		if( nullOrEmpty(hostPath, user, address) ) throw new RuntimeException("All parameters are required"); 
+		
+		File host = new File(hostPath);
+		if( !host.exists() ) throw new RuntimeException("Host File Doesn't exist: " + hostPath);
+		if( !host.canRead() || !host.canWrite() ) throw new RuntimeException("Host file must allow read/write");
+		
+		try {
+			File newHost = File.createTempFile("tmd", "hostfile");
+			BufferedWriter out = new BufferedWriter(new FileWriter(newHost));
+			
+			boolean found = false;
+			
+			Scanner scanner = new Scanner(host);
+			while(scanner.hasNext()) {
+				found |= onReadLine(scanner.nextLine(), out, user, address);
+			}
+			
+			if(!found) {
+				out.write(address + "\t" + user + "\t#" + user + NL);
+			}
+			
+			out.flush();
+			out.close();
+			
+			scanner.close();
+			newHost.renameTo(host);
+		} catch (IOException e) {
+			throw new RuntimeException("I/O error", e);
+		}
+	}
+	
+	private boolean onReadLine(String line, BufferedWriter out, String user, String address) throws IOException {
+		String[] inputs = line.split("\\s+");
+		
+		// handle a line with no words
+		boolean skipLine = inputs.length < 3;
+		// handle comment lines
+		skipLine = skipLine || inputs[0].trim().isEmpty() || inputs[0].trim().charAt(0) == '#';		
+		
+		// at this point, 0 = ip, 1 = name, 2 = username comment
+		// if it's not our user, don't touch it
+		skipLine = skipLine || !("#" + user).equalsIgnoreCase(inputs[2]);
+		
+		if(skipLine) {
+			out.write(line + NL);
+			return false;
+		}
+		
+		out.write(address + "\t" + user + "\t#" + user + NL);
+		return true;
+	}
+	
+	private boolean nullOrEmpty(String... values) {
+		for(String value : values) {
+			if( value == null || value.trim().isEmpty() ) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	public static void main(String[] args) throws Exception{
+		HostEditor editor = new HostEditor();
+		editor.update("/etc/hosts", "andre", "192.168.1.100");
+	}
+}