DocSearchServer.java

import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.InetAddress;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Collections;

class FileHelpers {
    static List<File> getFiles(Path start) throws IOException {
        File f = start.toFile();
        List<File> result = new ArrayList<>();
        if(f.isDirectory()) {
            File[] paths = f.listFiles();
            for(File subFile: paths) {
                result.addAll(getFiles(subFile.toPath()));
            }
        }
        else {
            result.add(start.toFile());
        }
        return result;
    }
    static String readFile(File f) throws IOException {
        return new String(Files.readAllBytes(f.toPath()));
    }
}

class Handler implements URLHandler {
    Path base;
    Handler(String directory) throws IOException {
      this.base = Paths.get(directory);
    }
    public String handleRequest(URI url) throws IOException {
       List<File> paths = FileHelpers.getFiles(this.base);
       if (url.getPath().equals("/")) {
           return String.format("There are %d total files to search.", paths.size());
       } else if (url.getPath().equals("/search")) {
           String[] parameters = url.getQuery().split("=");
           if (parameters[0].equals("q")) {
               String result = "";
               List<String> foundPaths = new ArrayList<>();
               for(File f: paths) {
                   if(FileHelpers.readFile(f).contains(parameters[1])) {
                       foundPaths.add(f.toString());
                   }
               }
               Collections.sort(foundPaths);
               result = String.join("\n", foundPaths);
               return String.format("Found %d paths:\n%s", foundPaths.size(), result);
           }
           else {
               return "Couldn't find query parameter q";
           }
       }
       else {
           return "Don't know how to handle that path!";
       }
    }
}

public class DocSearchServer {
    public static void main(String[] args) throws IOException {
        if(args.length == 0){
            System.out.println("Missing port number! Try any number between 1024 to 49151");
            return;
        }

        int port = Integer.parseInt(args[0]);

        Server.start(port, new Handler(args[1]));
    }
}