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//
//  ========================================================================
//  Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package com.signalfx.shaded.jetty.client;

import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedDeque;

import com.signalfx.shaded.jetty.client.api.Request;
import com.signalfx.shaded.jetty.client.api.Response;
import com.signalfx.shaded.jetty.util.AttributesMap;
import com.signalfx.shaded.jetty.util.log.Log;
import com.signalfx.shaded.jetty.util.log.Logger;

public class HttpConversation extends AttributesMap
{
    private static final Logger LOG = Log.getLogger(HttpConversation.class);

    private final Deque exchanges = new ConcurrentLinkedDeque<>();
    private volatile List listeners;

    public Deque getExchanges()
    {
        return exchanges;
    }

    /**
     * Returns the list of response listeners that needs to be notified of response events.
     * This list changes as the conversation proceeds, as follows:
     * 
     * 
     * request R1 send => conversation.updateResponseListeners(null)
     * 
     * exchanges in conversation: E1
     * listeners to be notified: E1.listeners
     * 
     * 
     * 
     * response R1 arrived, 401 => conversation.updateResponseListeners(AuthenticationProtocolHandler.listener)
     * 
     * exchanges in conversation: E1
     * listeners to be notified: AuthenticationProtocolHandler.listener
     * 
     * 
     * 
     * request R2 send => conversation.updateResponseListeners(null)
     * 
     * exchanges in conversation: E1 + E2
     * listeners to be notified: E2.listeners + E1.listeners
     * 
     * 
     * 
     * response R2 arrived, 302 => conversation.updateResponseListeners(RedirectProtocolHandler.listener)
     * 
     * exchanges in conversation: E1 + E2
     * listeners to be notified: E2.listeners + RedirectProtocolHandler.listener
     * 
     * 
     * 
     * request R3 send => conversation.updateResponseListeners(null)
     * 
     * exchanges in conversation: E1 + E2 + E3
     * listeners to be notified: E3.listeners + E1.listeners
     * 
     * 
     * 
     * response R3 arrived, 200 => conversation.updateResponseListeners(null)
     * 
     * exchanges in conversation: E1 + E2 + E3
     * listeners to be notified: E3.listeners + E1.listeners
     * 
     * 
     * 
     * Basically the override conversation listener replaces the first exchange response listener,
     * and we also notify the last exchange response listeners (if it's not also the first).
     *
     * This scheme allows for protocol handlers to not worry about other protocol handlers, or to worry
     * too much about notifying the first exchange response listeners, but still allowing a protocol
     * handler to perform completion activities while another protocol handler performs new ones (as an
     * example, the {@link AuthenticationProtocolHandler} stores the successful authentication credentials
     * while the {@link RedirectProtocolHandler} performs a redirect).
     *
     * @return the list of response listeners that needs to be notified of response events
     */
    public List getResponseListeners()
    {
        return listeners;
    }

    /**
     * Requests to update the response listener, eventually using the given override response listener,
     * that must be notified instead of the first exchange response listeners.
     * This works in conjunction with {@link #getResponseListeners()}, returning the appropriate response
     * listeners that needs to be notified of response events.
     *
     * @param overrideListener the override response listener
     */
    public void updateResponseListeners(Response.ResponseListener overrideListener)
    {
        // Create a new instance to avoid that iterating over the listeners
        // will notify a listener that may send a new request and trigger
        // another call to this method which will build different listeners
        // which may be iterated over when the iteration continues.
        HttpExchange firstExchange = exchanges.peekFirst();
        HttpExchange lastExchange = exchanges.peekLast();
        List listeners = new ArrayList<>(firstExchange.getResponseListeners().size() + lastExchange.getResponseListeners().size());
        if (firstExchange == lastExchange)
        {
            // We don't have a conversation, just a single request.
            if (overrideListener != null)
                listeners.add(overrideListener);
            else
                listeners.addAll(firstExchange.getResponseListeners());
        }
        else
        {
            // We have a conversation (e.g. redirect, authentication).
            // Order is important, we want to notify the last exchange first.
            listeners.addAll(lastExchange.getResponseListeners());
            if (overrideListener != null)
                listeners.add(overrideListener);
            else
                listeners.addAll(firstExchange.getResponseListeners());
        }
        if (LOG.isDebugEnabled())
            LOG.debug("Exchanges in conversation {}, override={}, listeners={}", exchanges.size(), overrideListener, listeners);
        this.listeners = listeners;
    }

    /**
     * Returns the total timeout for the conversation.
     * The conversation total timeout is the total timeout
     * of the first request in the conversation.
     *
     * @return the total timeout of the conversation
     * @see Request#getTimeout()
     */
    public long getTimeout()
    {
        HttpExchange firstExchange = exchanges.peekFirst();
        return firstExchange == null ? 0 : firstExchange.getRequest().getTimeout();
    }

    public boolean abort(Throwable cause)
    {
        HttpExchange exchange = exchanges.peekLast();
        return exchange != null && exchange.abort(cause);
    }

    @Override
    public String toString()
    {
        return String.format("%s[%x]", HttpConversation.class.getSimpleName(), hashCode());
    }
}