import java.net.*;
import java.nio.charset.Charset;
import java.io.*;
import java.util.HashMap;
import java.util.Date;
import java.awt.Desktop;
import java.net.URI;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Main implements Runnable {

    BufferedReader req;
    OutputStream res;
    String path = null;
    HashMap<String,String> headers = new HashMap<String,String>();
    HashMap<String,String> parms = new HashMap<String,String>();
    Socket sock;
    boolean override_status = false;
    String mime = "text/html";
    Charset charset = Charset.defaultCharset();

    public static void main(String[] args) throws Exception {

        // Listen for a connection from a client
        ServerSocket serverSocket = new ServerSocket(1234);
        if(Desktop.isDesktopSupported())
            Desktop.getDesktop().browse(new URI("http://localhost:1234"));
        else
            System.out.println("Please direct your browser to http://localhost:1234.");
        ExecutorService executor = Executors.newFixedThreadPool(5);
        while(true) {
            Main client = new Main();
            client.sock = serverSocket.accept();
            client.req = new BufferedReader(new InputStreamReader(client.sock.getInputStream()));
            client.res = client.sock.getOutputStream();
            executor.execute(client);
        }
    }

    @Override
    public void run() {

        String dateString = (new Date()).toGMTString();
        String inputLine;
        try {
            while ((inputLine = req.readLine()) != null) {
            //System.out.println("The client said: " + inputLine);
            if(path==null) {
                int a = inputLine.indexOf(" ")+1;
                path = inputLine.substring(a,inputLine.indexOf(" ",a));
            }
            if(inputLine.length() <= 2)
                break;
            }
        } catch(Exception ex) {
            ex.printStackTrace();
        }

        try {
            byte[] payload = process();

            if(!override_status)
                res.write("HTTP/1.1 200 OK\r\n".getBytes(charset));
            res.write(("Content-Length: " + Integer.toString(payload.length) + "\r\n").getBytes(charset));
            if(mime!=null) {
                res.write(("Content-Type: " + mime + "\r\n").getBytes(charset));
            } else {
                // initiate file download.
                res.write(("Content-Type: application/octet-stream\r\nContent-Disposition: attachment; filename=" + path.substring(path.indexOf("/")+1).replace("/","_")+"\r\n").getBytes(charset));
            }
            res.write(("Date: "  + dateString + "\r\n").getBytes(charset));
            res.write(("Last-Modified: " + dateString + "\r\n").getBytes(charset));
            res.write("Connection: close\r\n".getBytes(charset));
            res.write("\r\n".getBytes(charset));

            // Send the payload
            res.write(payload);

            res.close();
        } catch(Exception ex) {
            try {
                ex.printStackTrace();
                res.write("HTTP/1.1 500 Internal Server Error\r\n".getBytes(charset));
                res.write(("Date: " + dateString + "\r\n").getBytes(charset));
                res.write("Connection: close\r\n".getBytes(charset));
                res.write("\r\n".getBytes(charset));

                res.close();
            } catch(Exception ex_) {
                ex_.printStackTrace();
            }
        }
    }

    public static String get_mime(String extension) {
        switch(extension) {
            case ".ico":
                return "image/x-icon";
            case ".png":
                return "image/png";
            case ".jpg":
            case ".jpeg":
                return "image/jpeg";
            case ".gif":
                return "image/gif";
            case ".js":
                return "text/javascript";
            case ".css":
                return "text/css";
            case ".html":
                return "text/html";
            default: return null;
        }
    }

    private byte[] read_file(String fn) throws FileNotFoundException, IOException {
        System.out.println("Reading file " + fn);
        File file = new File(fn);
        FileInputStream fis = new FileInputStream(file);
        byte[] data = new byte[(int) file.length()];
        fis.read(data);
        fis.close();
        return data;
    }

    protected byte[] process() throws IOException{
        try {
            switch(path) {
                case "/":
                    // index.html
                    return read_file("index.html");
                case "/dir_list":
                    // return list of files.
                    // directories will end with a trailing "/" character.
                    return read_file("dir_list.txt");
                default:
                    // this must be a filename.
                    // return that or a 404.
                    String extension = path.substring(path.lastIndexOf("."));
                    mime = get_mime(extension);
                    return read_file(path.substring(path.indexOf("/")+1));
            }
        } catch(FileNotFoundException e) {
            e.printStackTrace();
            override_status = true;
            res.write("HTTP/1.1 404 NOT FOUND\r\n".getBytes(charset));
            return new byte[]{};
        }
    }
}