import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

public class ChainReaction implements ChainReactionInterface {
    private final Map<Integer, Node> nodes = new HashMap<>();
    private volatile int workingThreads = 0;
    private volatile boolean simulationStarted = false;
    private volatile boolean initializationInProgress = false;
    private DamagePropagationInterface damagePropagationInterface;

    @Override
    public synchronized void addObject(int id) {
        nodes.put(id, new Node(id));
    }

    @Override
    public synchronized void neighbour(int idA, int idB) {
        if (idA != idB) {
            Node nodeA = nodes.get(idA);
            Node nodeB = nodes.get(idB);

            nodeA.addNeighbor(nodeB);
            nodeB.addNeighbor(nodeA);
        }
    }

    @Override
    public boolean resultReady() {
        return simulationStarted && !initializationInProgress && workingThreads == 0;
    }

    @Override
    public boolean isDestroyed(int id) {
        return nodes.get(id).isDestroyed();
    }

    @Override
    public synchronized void setDamagePropagator(DamagePropagationInterface dpi) {
        this.damagePropagationInterface = dpi;
    }

    @Override
    public void destroyed(int id) {
        initializationInProgress = true;
        simulationStarted = true;

        Node node = nodes.get(id);
        boolean destroyed = false;
        if (node.isLive()) {
            synchronized (node) {
                if (node.isLive()) {
                    node.destroy();
                    destroyed = true;
                }
            }
        }

        if (destroyed) {
            findNeighboursToDestroy(node).stream()
                    .map(DestroyingRunnable::new)
                    .forEach(this::startTrackedThread);
        }

        initializationInProgress = false;
    }

    private List<Node> findNeighboursToDestroy(Node node) {
        List<Node> neighboursToDestroy = new LinkedList<>();
        for (Node neighbour : node.getNeighbours()) {
            if (neighbour.isLive()) {
                synchronized (neighbour) {
                    if (neighbour.isLive() && damagePropagationInterface.destroyedBy(node.id, neighbour.id)) {
                        neighbour.markToDestroy();
                        neighboursToDestroy.add(neighbour);
                    }
                }
            }
        }
        return neighboursToDestroy;
    }

    private void startTrackedThread(DestroyingRunnable runnable) {
        new Thread(new TrackingRunnable(runnable)).start();
    }

    private class DestroyingRunnable implements Runnable {
        private final Node node;

        private DestroyingRunnable(Node node) {
            this.node = node;
        }

        @Override
        public void run() {
            node.destroy();

            List<Node> neighboursToProcess = findNeighboursToDestroy(node);
            if (!neighboursToProcess.isEmpty()) {
                neighboursToProcess.subList(1, neighboursToProcess.size()).stream()
                        .map(DestroyingRunnable::new)
                        .forEach(ChainReaction.this::startTrackedThread);

                new DestroyingRunnable(neighboursToProcess.get(0)).run();
            }
        }
    }

    private class TrackingRunnable implements Runnable {
        private final Runnable runnable;

        private TrackingRunnable(Runnable runnable) {
            this.runnable = runnable;
        }

        @Override
        public void run() {
            try {
                synchronized (ChainReaction.this) {
                    workingThreads++;
                }
                runnable.run();
            } finally {
                synchronized (ChainReaction.this) {
                    workingThreads--;
                }
            }
        }
    }

    private static class Node {
        private final int id;
        private final List<Node> neighbours = new LinkedList<>();
        private volatile NodeState state = NodeState.LIVE;

        private Node(int id) {
            this.id = id;
        }

        private List<Node> getNeighbours() {
            return neighbours;
        }

        private void addNeighbor(Node neighbor) {
            neighbours.add(neighbor);
        }

        private boolean isLive() {
            return state == NodeState.LIVE;
        }

        private boolean isDestroyed() {
            return state == NodeState.DESTROYED;
        }

        private void markToDestroy() {
            state = NodeState.MARKED_TO_DESTROY;
        }

        private void destroy() {
            System.out.println("DESTROYED " + id);
            state = NodeState.DESTROYED;
        }

        private enum NodeState {
            LIVE, MARKED_TO_DESTROY, DESTROYED
        }
    }
}