package geniusweb.javavenv;

import java.io.IOException;
import java.io.InputStream;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;

/**
 * A straight python call. Handles all the connection stuff: connecting to the
 * input and output streams so that we can try to follow what python is doing.
 * NOTE generally this is for internal use, instead use {@link PythonVenv}
 */
public class Call {
	private final List<String> allargs = new LinkedList<>();
	// size 2, we expect both stdin and stderr to always post something here.
	private final BlockingQueue<Object> result = new ArrayBlockingQueue<Object>(
			2);
	private final int deadlinems;

	/**
	 * Call python with given arguments. call {@link #run()} to run. We
	 * recommend thatn you use {@link PythonVenv} to run commands instead of
	 * this direct call.
	 * 
	 * @param pythonexe  a working python3 exe, typically
	 *                   "/usr/local/bin/python3" or something in a venv on temp
	 *                   disk.
	 * @param args       the other args for the call
	 * @param deadlinems the deadline (ms) after which the call should be
	 *                   cancelled.
	 */

	public Call(String pythonexe, List<String> args, int deadlinems) {
		if (pythonexe == null || args == null)
			throw new IllegalArgumentException("args must be not null");
		allargs.add(pythonexe);
		allargs.addAll(args);
		this.deadlinems = deadlinems;
	}

	/**
	 * 
	 * @return the result of the python call (that is, what the program printed
	 *         out)
	 * @throws InterruptedException if the call does not terminate in time.
	 * @throws IOException          if we can not connect properly to the python
	 *                              process
	 * @throws PythonError          if the python program printed to stderr, eg
	 *                              when an error occured. We try to capture all
	 *                              the error lines as text in the pythonerror
	 *                              object.
	 */
	public String run() throws InterruptedException, IOException, PythonError {
		ProcessBuilder processBuilder = new ProcessBuilder(allargs);
		// System.out.println("all args " + allargs);
		Process p;
		p = processBuilder.start();

		Runnable stdinreader = new Runnable() {
			@Override
			public void run() {
				String totalreply = "";
				byte[] cbuf = new byte[500];
				InputStream is = p.getInputStream();
				try {
					while (true) {
						int n = is.read(cbuf);
						if (n == -1)
							break;
						totalreply += new String(cbuf, 0, n, "UTF8");
					}
					result.add(totalreply);
				} catch (IOException e) {
					result.add(e);
				}
			}
		};

		Runnable errorlogger = new Runnable() {
			@Override
			public void run() {
				byte[] cbuf = new byte[500];
				InputStream is = p.getErrorStream();
				String totalerror = "";
				try {
					while (true) {
						int n = is.read(cbuf);
						if (n == -1)
							break;
						totalerror += new String(cbuf, 0, n, "UTF8");
					}
					if (!totalerror.isEmpty())
						result.add(new PythonError(totalerror));
					else
						result.add("");
				} catch (IOException e) {
					result.add(e);
				}
			}

		};
		new Thread(stdinreader).start();
		new Thread(errorlogger).start();

		// now we wait till both are finished.
		// wait till both are finished. Order is irrelevant.
		Object res1 = result.poll(deadlinems, TimeUnit.MILLISECONDS);
		if (res1 == null)
			throw new InterruptedException("Python code failed to return");
		Object res2 = result.poll(100, TimeUnit.MILLISECONDS);
		if (res2 == null)
			throw new InterruptedException(
					"Second python channel failed to close");
		// If there is a non-empty error, return it, otherwise return res
		rethrowIfException(res1);
		rethrowIfException(res2);
		if (!((String) res1).isEmpty())
			return (String) res1;
		return (String) res2;

	}

	@Override
	public String toString() {
		return "python " + allargs;
	}

	private void rethrowIfException(Object obj)
			throws IOException, PythonError {
		if (obj instanceof Exception) {
			throw new PythonError("Failed to execute " + this, (Exception) obj);
		}
	}

}