// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package io.v.android.impl.google.rpc.protocols.bt;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.util.Log;

import com.google.common.base.Splitter;
import com.google.common.collect.ImmutableList;

import org.joda.time.Duration;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.Executor;

import io.v.impl.google.rt.VRuntimeImpl;
import io.v.android.v23.V;
import io.v.v23.context.VContext;
import io.v.v23.rpc.Callback;
import io.v.v23.verror.VException;

/**
 * Handles bluetooth connection establishment on Android.
 * <p>
 * Used as a helper class for native code which sets up and registers the bluetooth protocol with
 * the vanadium RPC service.
 */
class Bluetooth {
    private static final String TAG = "Bluetooth";
    private static final List<Integer> BLUETOOTH_PORTS = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9,
            10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31);

    static Listener listen(VContext ctx, String btAddr) throws VException {
        String macAddr = getMACAddress(ctx, btAddr);
        int port = getPortNumber(btAddr);
        BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
        List<Integer> ports = null;
        if (port == 0) {  // listen on the first available port.
            ports = new ArrayList(BLUETOOTH_PORTS);
            Collections.shuffle(ports);
        } else {  // listen on a specific port only
            ports = ImmutableList.of(port);
        }
        Executor executor = VRuntimeImpl.getRuntimeExecutor(ctx);
        if (executor == null) {
            throw new VException("NULL executor in context: did you derive this context from " +
                    "the context returned by V.init()?");
        }
        VException lastError = null;
        for (int portNum : ports) {
            try {
                BluetoothServerSocket socket = listenOnPort(portNum);
                Log.d(TAG, String.format("listening on port %d", portNum));
                return new Listener(executor, socket, String.format("%s/%d", macAddr, portNum));
            } catch (VException e) {
                // OK, try the next one
                lastError = e;
            }
        }
        throw lastError;
    }

    static void dial(VContext ctx, String btAddr, final Duration timeout,
                     final Callback<Stream> callback) throws VException {
        final String macAddr = getMACAddress(ctx, btAddr);
        final int port = getPortNumber(btAddr);
        final Executor executor = VRuntimeImpl.getRuntimeExecutor(ctx);
        if (executor == null) {
            throw new VException("NULL executor in context: did you derive this context from " +
                    "the context returned by V.init()?");
        }
        executor.execute(new Runnable() {
            @Override
            public void run() {
                final BluetoothDevice device =
                        BluetoothAdapter.getDefaultAdapter().getRemoteDevice(macAddr);
                try {
                    // Create a socket to the remote device.
                    // NOTE(spetrovic): Android's public methods currently only allow connection to
                    // a UUID, which goes through SDP.  Since we already have a remote port number,
                    // we connect to it directly, invoking a hidden method using reflection.
                    Method m = device.getClass().getMethod("createInsecureRfcommSocket",
                            new Class[]{int.class});
                    final BluetoothSocket socket = (BluetoothSocket) m.invoke(device, port);
                    // Connect.
                    Timer timer = null;
                    if (timeout.getMillis() != 0) {
                        timer = new Timer();
                        timer.schedule(new TimerTask() {
                            @Override
                            public void run() {
                                try {
                                    socket.close();
                                } catch (IOException e) {
                                    System.err.println("Couldn't close BluetoothSocket.");
                                }
                            }
                        }, timeout.getMillis());
                    }
                    try {
                        socket.connect();
                    } catch (IOException e) {
                        callback.onFailure(new VException("Couldn't connect: " + e.getMessage()));
                    } finally {
                        if (timer != null) {
                            timer.cancel();
                        }
                    }
                    // There is no way currently to retrieve the local port number for the
                    // connection, but that's probably OK.
                    String localAddr = String.format("%s/%d", localMACAddress(ctx), 0);
                    String remoteAddr = String.format("%s/%d", macAddr, port);
                    callback.onSuccess(new Stream(executor, socket, localAddr, remoteAddr));
                } catch (Exception e) {
                    callback.onFailure(new VException("Couldn't invoke createInsecureRfcommSocket: "
                            + e.getMessage()));
                }

            }
        });
    }

    private static BluetoothServerSocket listenOnPort(int port) throws VException {
        // Use reflection to reach the hidden "listenUsingInsecureRfcommOn(port)" method.
        BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
        try {
            Method m = adapter.getClass().
                    getMethod("listenUsingInsecureRfcommOn", new Class[]{int.class});
            return (BluetoothServerSocket) m.invoke(adapter, port);
        } catch (Exception e) {
            throw new VException("Error invoking listenUsingInsecureRfcommOn: "
                    + e.getMessage());
        }
    }

    private static String localMACAddress(VContext ctx) {
        // TODO(suharshs): Android has disallowed getting the local address.
        // This is a remaining working hack that gets the local bluetooth address,
        // just to get things working.
        return android.provider.Settings.Secure.getString(
            V.getAndroidContext(ctx).getContentResolver(), "bluetooth_address");
    }

    private static String getMACAddress(VContext ctx, String btAddr) throws VException {
        List<String> parts = Splitter.on("/").omitEmptyStrings().splitToList(btAddr);
        switch (parts.size()) {
            case 0:
                throw new VException(String.format(
                        "Couldn't split bluetooth address \"%s\" using \"/\" separator: " +
                                "got zero parts!", btAddr));
            case 1:
                return localMACAddress(ctx);
            case 2:
                String address = parts.get(0).toUpperCase();
                if (!BluetoothAdapter.checkBluetoothAddress(address)) {
                    throw new VException("Invalid bluetooth address: " + btAddr);
                }
                return address;
            default:
                throw new VException(String.format(
                        "Couldn't parse bluetooth address \"%s\": too many \"/\".", btAddr));
        }
    }

    private static int getPortNumber(String btAddr) throws VException {
        List<String> parts = Splitter.on("/").splitToList(btAddr);
        switch (parts.size()) {
            case 0:
                throw new VException(String.format(
                        "Couldn't split bluetooth address \"%s\" using \"/\" separator: " +
                                "got zero parts!", btAddr));
            case 1:
            case 2:
                try {
                    int port = Integer.parseInt((parts.get(parts.size() - 1)));
                    if (port < 0 || port > 32) {
                        throw new VException(String.format("Illegal port number %q in bluetooth " +
                                "address \"%s\".", port, btAddr));
                    }
                    return port;
                } catch (NumberFormatException e) {
                    throw new VException(String.format(
                            "Couldn't parse port number in bluetooth address \"%s\": %s",
                            btAddr, e.getMessage()));
                }
            default:
                throw new VException(String.format(
                        "Couldn't parse bluetooth address \"%s\": too many \"/\".", btAddr));
        }
    }

    static class Listener {
        private final Executor executor;
        private final BluetoothServerSocket serverSocket;
        private final String localAddress;

        Listener(Executor executor, BluetoothServerSocket serverSocket, String address) {
            this.executor = executor;
            this.serverSocket = serverSocket;
            this.localAddress = address;
        }

        void accept(final Callback<Stream> callback) {
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        BluetoothSocket socket = serverSocket.accept();
                        // There is no way currently to retrieve the remote end's channel number,
                        // but that's probably OK.
                        String remoteAddress =
                                String.format("%s/%d", socket.getRemoteDevice().getAddress(), 0);
                        callback.onSuccess(new Stream(
                                executor, socket, localAddress, remoteAddress));
                    } catch (IOException e) {
                        callback.onFailure(new VException(e.getMessage()));
                    }
                }
            });
        }

        void close() throws IOException {
            serverSocket.close();
        }

        String address() {
            return localAddress;
        }
    }

    static class Stream {
        private final Executor executor;
        private final BluetoothSocket socket;
        private final String localAddress;
        private final String remoteAddress;

        Stream(Executor executor, BluetoothSocket socket, String localAddress,
               String remoteAddress) {
            this.executor = executor;
            this.socket = socket;
            this.localAddress = localAddress;
            this.remoteAddress = remoteAddress;
        }

        void read(final int n, final Callback<byte[]> callback) {
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        byte[] buf = new byte[n];
                        int num = socket.getInputStream().read(buf);
                        callback.onSuccess(num == buf.length ? buf : Arrays.copyOf(buf, num));
                    } catch (IOException e) {
                        callback.onFailure(new VException(e.getMessage()));
                    }
                }
            });
        }

        void write(final byte[] data, final Callback<Void> callback) {
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        socket.getOutputStream().write(data);
                        callback.onSuccess(null);
                    } catch (IOException e) {
                        callback.onFailure(new VException(e.getMessage()));
                    }
                }
            });
        }

        void close() throws IOException {
            socket.close();
        }

        String localAddress() {
            return this.localAddress;
        }

        String remoteAddress() {
            return this.remoteAddress;
        }
    }

    private Bluetooth() {}
}