package jmri.jmrix.openlcb;

import org.mockito.ArgumentMatcher;
import org.mockito.verification.VerificationMode;
import org.openlcb.AbstractConnection;
import org.openlcb.Connection;
import org.openlcb.InitializationCompleteMessage;
import org.openlcb.Message;
import org.openlcb.NodeID;
import org.openlcb.OlcbInterface;
import org.openlcb.can.AliasMap;
import org.openlcb.can.CanFrame;
import org.openlcb.can.GridConnect;
import org.openlcb.can.MessageBuilder;
import org.openlcb.can.OpenLcbCanFrame;

import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.Semaphore;

import static org.mockito.Mockito.*;

/**
 * Test helper class that instantiates an OlcbInterface and allows making expectations on what is sent to the bus, as
 * well as allows injecting response messages from the bus.
 * <p>
 * Created by bracz on 1/9/16.
 */
public class OlcbTestHelper {
    // This mock object is handed over to the interface to have all messages sent to it. Expectations on sent messages
    // are on this object.
    protected Connection outputConnectionMock = mock(AbstractConnection.class);
    // Interface object that collects all critical OpenLCB components.
    protected OlcbInterface iface = null;
    protected AliasMap aliasMap = new AliasMap();
    // If true, messages injected by the test script using sendMessage will be turned into CAN frames first, and
    // then the respective frames will be sent to the OpenLCB stack. Note that these are the *incoming* messages
    // from the bus.
    protected boolean testWithCanFrameRendering = false;
    // Prints injected frames from sendMessage.
    private boolean debugFrames = false;
    // Connection wrapper that allows capturing and printing the *outgoing* messages that are generated by us and sent
    // to the bus.
    private FakeConnection fakeConnection;
    // Helper object for single-threaded operation.
    FakeExecutionThread thread;

    /* A Connection class that forwards all messages to a
     * mock connection passed in at construction time.
     * Supports printing the messages for debugging.
     */
    public static class FakeConnection extends AbstractConnection {
        private final Connection mock;
        public boolean debugMessages = false;

        public FakeConnection(Connection mock) {
            this.mock = mock;
        }

        @Override
        public synchronized void put(Message msg, Connection sender) {
            if (debugMessages) {
                System.err.println("Mock send: " + msg.toString());
            }
            mock.put(msg, sender);
        }

    }

    public OlcbTestHelper() {
        expectInit();
    }

    public void dispose() {
        if (thread != null) {
            thread.waitForEmpty();
        }
        expectNoMessages();
        iface.dispose();
        iface = null;
    }

    /**
     * Initializes the interface objects, and clears the startup messages in the mock.
     */
    private void expectInit() {
        NodeID id = new NodeID(new byte[]{1, 2, 0, 0, 1, 1});
        aliasMap.insert(0x333, id);
        fakeConnection = new FakeConnection(outputConnectionMock);
        iface = new OlcbInterface(id, fakeConnection);
        expectMessage(new InitializationCompleteMessage(iface.getNodeId()));
    }

    /**
     * If a test calls this function, all outgoing messages will be routed through a single send thread.
     */
    public void enableSingleThreaded() {
        thread = new FakeExecutionThread();
        iface.setLoopbackThread(thread);
        iface.runOnThreadPool(thread);
    }

    /**
     * Helper class for the single-threaded operation. This class gets plugged into the OlcbInterface as the callback
     * for executing outgoing message send operations.
     */
    static class FakeExecutionThread implements OlcbInterface.SyncExecutor, Runnable {
        private final BlockingQueue<QEntry> outputQueue = new LinkedBlockingQueue<>();

        /**
         * Blocks until the send thread has no more runnables.
         */
        public void waitForEmpty() {
            while (!outputQueue.isEmpty()) {
                try {
                    Thread.sleep(20);
                } catch (InterruptedException e) {
                    return;
                }
            }
        }

        @Override
        public void schedule(Runnable r) throws InterruptedException {
            QEntry q = new QEntry(r);
            outputQueue.add(q);
            q.sem.acquire();
        }

        @Override
        public void run() {
            while (!Thread.currentThread().isInterrupted()) {
                QEntry m;
                try {
                    m = outputQueue.take();
                    m.callback.run();
                    m.sem.release();
                } catch (InterruptedException e) {
                    return;
                }
            }
        }

        private static class QEntry {
            QEntry(Runnable r) {
                callback = r;
            }

            Runnable callback;
            Semaphore sem = new Semaphore(0);
        }

    }

    /**
     * Defines an alias for a remote node. This is equivalent to sending an AMD frame for the given alias and node ID
     * via sendFrame. It essentially simulates a remote node showing up on the bus.
     *
     * @param alias node alias
     * @param nid   node ID
     */
    public void setRemoteAlias(int alias, NodeID nid) {
        aliasMap.insert(alias, nid);
    }

    /** Prints all outgoing messages that get sent to the mock. For debugging purposes. */
    public void printAllSentMessages() {
        fakeConnection.debugMessages = true;
    }

    /**
     * Sends one or more OpenLCB message, as represented by the given CAN frames, to the interface's inbound port. This
     * represents traffic that a far away node is sending. The frame should be specified in the GridConnect protocol.
     *
     * @param frames is one or more CAN frames in the GridConnect protocol format.
     */
    protected void sendFrame(String frames) {
        List<CanFrame> parsedFrames = GridConnect.parse(frames);
        MessageBuilder d = new MessageBuilder(aliasMap);
        for (CanFrame f : parsedFrames) {
            aliasMap.processFrame(new OpenLcbCanFrame(f));
            List<Message> l = d.processFrame(f);
            if (l != null) {
                for (Message m : l) {
                    iface.getInputConnection().put(m, null);
                }
            }
        }
    }

    /**
     * Sends an OpenLCB message to the interface's inbound port. This represents traffic that a far away node is
     * sending.
     *
     * @param msg inbound message from a far node
     */
    protected void sendMessage(Message msg) {
        if (testWithCanFrameRendering) {
            MessageBuilder d = new MessageBuilder(aliasMap);
            List<? extends CanFrame> actualFrames = d.processMessage(msg);
            StringBuilder b = new StringBuilder();
            for (CanFrame f : actualFrames) {
                b.append(GridConnect.format(f));
            }
            if (debugFrames)
                System.err.println("Input frames: " + b);
            sendFrame(b.toString());
        } else {
            iface.getInputConnection().put(msg, null);
        }
    }

    /**
     * Moves all outgoing messages to the pending messages queue.
     */
    protected void consumeMessages() {
        iface.flushSendQueue();
    }

    /**
     * Expects that the next outgoing message (not yet matched with an expectation) is the given CAN frame.
     *
     * @param expectedFrame GridConnect-formatted CAN frame.
     * @param cardinality   how many times to expect this frame, e.g. 'times(2)' or omit for once.
     */
    protected void expectFrame(String expectedFrame, VerificationMode cardinality) {
        class MessageMatchesFrame implements ArgumentMatcher<Message> {
            private final String frame;
            private String actual = "";

            public MessageMatchesFrame(String frame) {
                this.frame = frame;
            }

            @Override
            public boolean matches(Message message) {
                MessageBuilder d = new MessageBuilder(aliasMap);
                List<? extends CanFrame> actualFrames = d.processMessage(message);
                StringBuilder b = new StringBuilder();
                for (CanFrame f : actualFrames) {
                    b.append(GridConnect.format(f));
                }
                String r = b.toString();
                if (!frame.equals(r)) {
                    actual = actual + r;
                }
                return frame.equals(r);
            }

            @Override
            public String toString() {
                //printed in verification errors
                return "[OpenLCB message with CAN rendering of " + frame + "][actual " + actual + "]";
            }

        }

        consumeMessages();
        verify(outputConnectionMock, cardinality).put(argThat(new MessageMatchesFrame(expectedFrame)), any());
    }

    /**
     * Expects that the next outgoing message (not yet matched with an expectation) is the given CAN frame.
     *
     * @param expectedFrame GridConnect-formatted CAN frame.
     */
    protected void expectFrame(String expectedFrame) {
        expectFrame(expectedFrame, times(1));
    }


    /**
     * Expects that the next outgoing message (not yet matched with an expectation) is the given message.
     *
     * @param expectedMessage message that should have been sent to the bus from the local stack.
     */
    protected void expectMessage(Message expectedMessage) {
        consumeMessages();
        verify(outputConnectionMock).put(eq(expectedMessage), any());
    }

    /**
     * Expects a single outgoing message and that no other outgoing messages are unmatched by expectations.
     *
     * @param expectedMessage message that should have been sent to the bus from the local stack.
     */
    protected void expectMessageAndNoMore(Message expectedMessage) {
        expectMessage(expectedMessage);
        expectNoMessages();
    }

    /**
     * Expects that there are no unconsumed outgoing messages.
     */
    protected void expectNoFrames() {
        consumeMessages();
        verifyNoMoreInteractions(outputConnectionMock);
        clearInvocations(outputConnectionMock);
    }

    /**
     * Expects that there are no unconsumed outgoing messages.
     */
    protected void expectNoMessages() {
        expectNoFrames();
    }

    /**
     * Simulates an interaction initiated by a remote node on the OpenLCB bus.
     * @param send The remote node sends this frame to the bus (i.e., this frame will be injected as an inbound frame).
     * @param expect The local stack is expected to react with this frame. (i.e., this frame will be consumed from the
     *              outbound frames generated by the local stack).
     */
    protected void sendFrameAndExpectResult(String send, String expect) {
        sendFrame(send);
        expectFrame(expect);
        expectNoFrames();
    }

    /**
     * Simulates an interaction initiated by a remote node on the OpenLCB bus.
     * @param send The remote node sends this frmessage to the bus (i.e., this message will be injected inbound).
     * @param expect The local stack is expected to react with this message. (i.e., this message will be consumed from the
     *              outbound messages generated by the local stack).
     */
    protected void sendMessageAndExpectResult(Message send, Message expect) {
        sendMessage(send);
        expectMessage(expect);
    }
}