Server.java

package Proxy;

import java.net.*;
import java.io.*;
import java.util.ArrayList;

/**
 *Class that manages the petitions to the proxy and creates a process to handle each petition
 * 
 */
public class Server implements Runnable{
    private Socket server;
    
    
    public Server(Socket socket) throws IOException{
        this.server = socket;
    }
    
    public OutputStream getOutputStream() throws IOException{
        return this.server.getOutputStream();
    }
    
    public InputStream getInputStream() throws IOException{
        return this.server.getInputStream();
    }
    
    //Here are the modifications of the content returned to the client
    private BufferedWriter modify(BufferedReader input)throws IOException{
        int trueSize = 0;
        BufferedWriter output = new BufferedWriter
                (new OutputStreamWriter(this.server.getOutputStream()));
        boolean onText = false;
        //responseLines contains 1 line of the response in each element of the array
        ArrayList<String> responseLines = new ArrayList<>();
        
        //initializing responseLines        
        do{
            responseLines.add(input.readLine());
        }while(responseLines.get(responseLines.size() - 1) != null);
        responseLines.remove(responseLines.size()-1);
                
        //Checks for possible modifications in each line of the content
        //unless it is still reading the http header info
        for(int i = 0; i < responseLines.size(); i++){
            if(onText){
                responseLines.set(i, responseLines.get(i).replaceAll("(?i)\\.\\/.*stockholm.*\\.(jpg|jpeg|png|gif)",
                        "https://c8.alamy.com/comp/FYC0H3/spring-in-the-iconic-park-tradgardsforeningen-in-linkoping-sweden-FYC0H3.jpg"));
                responseLines.set(i, responseLines.get(i).replace("./smiley.jpg",
                        "https://statuecollectibles.cz/images_upd/products/7/paj3z7hnrlty.jpg"));   
                responseLines.set(i, responseLines.get(i).replace("Smiley", "Trolly"));
                responseLines.set(i, responseLines.get(i).replace("Stockholm", "Linköping"));
                        
                byte[] bytes = (responseLines.get(i) + "\r\n").getBytes("UTF-8");
                trueSize += bytes.length;
            }
            if(responseLines.get(i).matches("")){
                onText = true;
            }
        }
        
        //Corrects the content length after the modifications are done and writes the message to output
        for(int i = 0; i < responseLines.size(); i++){
            if(responseLines.get(i).contains("Content-Length:"))
                responseLines.set(i, responseLines.get(i).replace(responseLines.get(i), "Content-Length: " + trueSize));
                    
            System.out.println("RESPONSELINE: " + responseLines.get(i));
            output.write(responseLines.get(i));
            output.newLine();
        }
                
        return output;
    }    
    
    @Override
    public void run(){
        try {
            
            System.out.println("Thread created for a new connection.");
            
            //Buffers to read the HTTP request from the browser
            BufferedReader inFromBrowser = new BufferedReader
                (new InputStreamReader(this.server.getInputStream()));
            BufferedWriter outToBrowser;
            
            String header = inFromBrowser.readLine();
            
            System.out.println("Browsers request: " + header);
            
            if(header == null || header.isEmpty()){
                this.server.close();
                return;
            }
            
            String[] headerList = header.split(" ");
            if(headerList.length < 2){
                this.server.close();
            }
            
            URI url = new URI(headerList[1]);
            URL target = url.toURL();
            String host = target.getHost();
            int port;
            if(target.getPort() == -1){
                port = 80;
            } else {
                port = target.getPort();
            }
            
            System.out.println("Connecting to: " + host + ":" + port);
            
            
            
            try{
                Client client = new Client(host, port);
                //Buffers manage the connection to the server
                BufferedWriter outToWeb;
                BufferedReader inFromWeb = new BufferedReader
                    (new InputStreamReader(client.getInputStream()));
                
                outToWeb = client.write(inFromBrowser, header);
                
                outToWeb.flush();
                
                outToBrowser = modify(inFromWeb);
                
                outToBrowser.flush();
                
                System.out.println("Response sent.");
            } catch (IOException ex){
                System.err.println("Web Connection error: " + ex.getMessage());
            }
            this.server.close();
        } catch (IOException | URISyntaxException ex) {
            System.err.println("Browser Connection error: " + ex.getMessage());
        } 
    }
}