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package com.tinkerpop.gremlin.server.op.session;

import com.codahale.metrics.Timer;
import com.tinkerpop.gremlin.driver.Tokens;
import com.tinkerpop.gremlin.driver.message.RequestMessage;
import com.tinkerpop.gremlin.driver.message.ResponseMessage;
import com.tinkerpop.gremlin.driver.message.ResponseStatusCode;
import com.tinkerpop.gremlin.server.Context;
import com.tinkerpop.gremlin.server.GremlinServer;
import com.tinkerpop.gremlin.server.handler.StateKey;
import com.tinkerpop.gremlin.server.op.OpProcessorException;
import com.tinkerpop.gremlin.server.util.MetricManager;
import com.tinkerpop.gremlin.util.function.TriConsumer;
import com.tinkerpop.gremlin.util.iterator.IteratorUtils;
import io.netty.channel.ChannelHandlerContext;
import org.javatuples.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.script.Bindings;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;

import static com.codahale.metrics.MetricRegistry.name;

/**
 * Operations to be used by the {@link SessionOpProcessor}.
 *
 * @author Stephen Mallette (http://stephen.genoprime.com)
 */
public final class SessionOps {
    private static final Logger logger = LoggerFactory.getLogger(SessionOps.class);

    /**
     * Script engines are evaluated in a per session context where imports/scripts are isolated per session.
     */
    private static ConcurrentHashMap sessions = new ConcurrentHashMap<>();

    private static final Timer evalOpTimer = MetricManager.INSTANCE.getTimer(name(GremlinServer.class, "op", "eval"));

    static {
        MetricManager.INSTANCE.getGuage(sessions::size, name(GremlinServer.class, "sessions"));
    }

    public static void evalOp(final Context context) throws OpProcessorException {
        evalOp(context, (Context ctx, RequestMessage msg, Object o) -> {
            ctx.getChannelHandlerContext().write(Pair.with(msg, IteratorUtils.convertToIterator(o)));
        });
    }

    public static void evalOp(final Context context, TriConsumer handler) {
        final Timer.Context timerContext = evalOpTimer.time();
        final ChannelHandlerContext ctx = context.getChannelHandlerContext();
        final RequestMessage msg = context.getRequestMessage();

        final Session session = getSession(context, msg);

        // place the session on the channel context so that it can be used during serialization.  in this way
        // the serialization can occur on the same thread used to execute the gremlin within the session.  this
        // is important given the threadlocal nature of Graph implementation transactions.
        context.getChannelHandlerContext().channel().attr(StateKey.SESSION).set(session);

        final String script = (String) msg.getArgs().get(Tokens.ARGS_GREMLIN);
        final Optional language = Optional.ofNullable((String) msg.getArgs().get(Tokens.ARGS_LANGUAGE));
        final Bindings bindings = session.getBindings();
        final Map requestBindings = Optional.ofNullable((Map) msg.getArgs().get(Tokens.ARGS_BINDINGS)).orElse(new HashMap<>());

        // parameter bindings override session bindings
        bindings.putAll(requestBindings);

        final CompletableFuture