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							//Oppgavetekst: Lag en webserver med foelgende funksjoner:
// * Server filer
// * List opp mapper og filer i en mappe - saakalt directory index
// * Sender en 404-side naar noen spoer om en fil som ikke finnes
// * Kjoer Python-scripts, filer som ender i .py, og send resultatet til nettlesere

import java.util.Scanner;
import java.util.HashMap;
import java.io.*;
import java.nio.file.Paths;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpServer;
import com.sun.net.httpserver.HttpHandler;
import java.net.InetSocketAddress;
import java.net.URLDecoder;

class Templates {
	public static String sysInfo =
		"<hr>"+
		"<p>"+
			"Web Server running on "+
			System.getProperty("os.name")+" "+
			System.getProperty("os.version")+" "+
			System.getProperty("os.arch")+
		"</p>";

	public static String err404 =
		"<!DOCTYPE html>"+
		"<html>"+
			"<head>"+
				"<title>Error 404</title>"+
			"</head>"+
			"<body>"+
				"<h1>404 Not Found</h1>"+
				"<p>The file {{$1}} was not found.</p>"+
			sysInfo+
			"</body>"+
		"</html>";

	public static String index =
		"<!DOCTYPE html>"+
		"<html>"+
			"<head>"+
				"<title>Index</title>"+
			"</head>"+
			"<body>"+
				"<ul>"+
					"<li><a href='..'>..</a></li>"+
					"{{$1}}"+
				"</ul>"+
			sysInfo+
			"</body>"+
		"</html>";

	public static String indexEntry =
		"<li>"+
			"<a href='{{$1}}'>{{$1}}</a>"+
		"</li>";

	//Convenience function; many templates have only one argument,
	//pointless to have to build up a String[] just for that
	public static String templatify(String str, String arg) {
		String[] args = {arg};
		return templatify(str, args);
	}

	//Build a template, replacing things within {{ and }} with
	//the arguments provided
	public static String templatify(String str, String[] args) {
		for (int i = 0; i < args.length; ++i) {
			str = str.replace("{{$"+(i+1)+"}}", args[i]);
		}

		return str;
	}
}

class RequestHandler implements HttpHandler {
	private File root;

	@Override public void handle(HttpExchange t) throws IOException {
		OutputStream out = t.getResponseBody();
		String url = t.getRequestURI().toString().split("\\?")[0];
		int lmul = 1;

		//HEAD requests want to only receive headers, but that's
		//somewhat hard to implement with this structure.
		//We'll just kill the connection if that happens.
		if (t.getRequestMethod().equalsIgnoreCase("HEAD")) {
			out.close();
			return;
		}

		File f = new File(root, url);

		if (!f.exists()) {
			send404(f, url, out, t);
		} else if (f.isDirectory())
			sendIndex(f, url, out, t);
		else {
			if (url.endsWith(".py"))
				sendPython(f, url, out, t);
			else
				sendFile(f, url, out, t);
		}

		out.close();
	}

	RequestHandler(File r) {
		root = r;
	}

	//404 when a file which doesn't exist is requested
	private static void send404(File f, String url, OutputStream out, HttpExchange t) throws IOException {
		byte[] res = Templates.templatify(Templates.err404, url).getBytes();
		t.sendResponseHeaders(404, res.length);
		out.write(res);
	}

	//Directory index when a directory is requested
	private static void sendIndex(File dir, String url, OutputStream out, HttpExchange t) throws IOException {
		File[] files = dir.listFiles();
		String entries = "";

		//Loop through files in the requested directory,
		//building up the list of entries
		for (int i = 0; i < files.length; ++i) {
			File f = files[i];
			String name = f.toPath().getFileName().toString();
			if (f.isDirectory())
				name += "/";
	
			entries += Templates.templatify(Templates.indexEntry, name);
		}

		//Combine the entries with the rest of the index' HTML,
		//and send to the client
		byte[] res = Templates.templatify(Templates.index, entries).getBytes();
		t.sendResponseHeaders(200, res.length);
		out.write(res);
	}

	//Send file when a file is requested
	private static void sendFile(File f, String url, OutputStream out, HttpExchange t) throws IOException {
		Scanner s = new Scanner(f);
		t.sendResponseHeaders(200, f.length());

		while (s.hasNextLine()) {
			out.write((s.nextLine()+"\n").getBytes());
		}
	}

	//Execute python script and send the output to the browser
	private static void sendPython(File f, String url, OutputStream out, HttpExchange t) throws IOException {
		String[] command = {"python", f.toPath().toString()};
		Process proc = Runtime.getRuntime().exec(command);

		BufferedReader stdin = new BufferedReader(new InputStreamReader(proc.getInputStream()));
		BufferedReader stderr = new BufferedReader(new InputStreamReader(proc.getErrorStream()));

		String res = "";
		String s = null;

		//Print the output from the python script
		while ((s = stdin.readLine()) != null) {
			res += s+"\n";
		}

		//Print the errors from the python script
		while ((s = stderr.readLine()) != null) {
			res += s+"\n";
		}

		t.getResponseHeaders().add("Content-Type", "text/plain");
		t.sendResponseHeaders(200, res.length());
		out.write(res.getBytes());
	}
}

class MinOppgave4 {
	private static HttpServer server;
	private static File root = new File("www");
	private static int port = 8000;

	//Simple command line interface
	public static String onCommand(String str) {
		String[] tokens = str.split("\\s+");

		switch (tokens[0]) {
		case "help":
			return
				"help: Display this help text\n"+
				"stop: Stop the web server";

		case "stop":
			System.exit(0);
			return "";

		default:
			return
				"Unknown command: "+tokens[0]+"\n"+
				"Type 'help' for help.";
		}
	}

	public static void main(String[] args) throws IOException {
		Scanner s = new Scanner(System.in);

		//Create an HTTP server
		server = HttpServer.create(new InetSocketAddress(port), 0);

		//Add request handler
		server.createContext("/", new RequestHandler(root));

		//Start the server
		server.start();
		System.out.println("Server started. Visit http://localhost:"+port+" in a web browser.");
		System.out.println("Try modifying the contents of the directory "+root.toPath().getFileName()+".");

		//Simple command line interface
		System.out.print("> ");
		while (s.hasNextLine()) {
			System.out.println(onCommand(s.nextLine()));
			System.out.print("> ");
		}
	}
}