/**
 *  Copyright (C) 2010 Cloud.com, Inc.  All rights reserved.
 * 
 * This software is licensed under the GNU General Public License v3 or later.
 * 
 * It is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

package com.cloud.cluster;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.net.URLDecoder;

import org.apache.commons.httpclient.HttpStatus;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpException;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.entity.BasicHttpEntity;
import org.apache.http.protocol.HttpContext;
import org.apache.http.protocol.HttpRequestHandler;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;

import com.cloud.agent.Listener;
import com.cloud.agent.api.Answer;
import com.cloud.agent.api.ChangeAgentAnswer;
import com.cloud.agent.api.ChangeAgentCommand;
import com.cloud.agent.api.Command;
import com.cloud.agent.api.TransferAgentCommand;
import com.cloud.exception.AgentUnavailableException;
import com.cloud.exception.OperationTimedoutException;
import com.cloud.serializer.GsonHelper;
import com.google.gson.Gson;

public class ClusterServiceServletHttpHandler implements HttpRequestHandler {
    private static final Logger s_logger = Logger.getLogger(ClusterServiceServletHttpHandler.class);

    private final Gson gson;
    private final ClusterManager manager;

    public ClusterServiceServletHttpHandler(ClusterManager manager) {
        this.manager = manager;

        gson = GsonHelper.getGson();
    }

    @Override
    public void handle(HttpRequest request, HttpResponse response, HttpContext context)
    throws HttpException, IOException {

        try {
            if(s_logger.isTraceEnabled()) {
                s_logger.trace("Start Handling cluster HTTP request");
            }

            parseRequest(request);
            handleRequest(request, response);

            if(s_logger.isTraceEnabled()) {
                s_logger.trace("Handle cluster HTTP request done");
            }

        } catch(Throwable e) {
            if(s_logger.isTraceEnabled()) {
                s_logger.trace("Unexpected exception " + e.toString());
            }

            writeResponse(response, HttpStatus.SC_INTERNAL_SERVER_ERROR, null);
        }
    }

    @SuppressWarnings("deprecation")
    private void parseRequest(HttpRequest request) throws IOException {
        if(request instanceof HttpEntityEnclosingRequest) {
            HttpEntityEnclosingRequest entityRequest = (HttpEntityEnclosingRequest)request;

            String body = EntityUtils.toString(entityRequest.getEntity());
            if(body != null) {
                String[] paramArray = body.split("&");
                if(paramArray != null) {
                    for (String paramEntry : paramArray) {
                        String[] paramValue = paramEntry.split("=");
                        if (paramValue.length != 2) {
                            continue;
                        }

                        String name = URLDecoder.decode(paramValue[0]);
                        String value = URLDecoder.decode(paramValue[1]);

                        if(s_logger.isTraceEnabled()) {
                            s_logger.trace("Parsed request parameter " + name + "=" + value);
                        }
                        request.getParams().setParameter(name, value);
                    }
                }
            }
        }
    }

    private void writeResponse(HttpResponse response, int statusCode, String content) {
        if(content == null) {
            content = "";
        }
        response.setStatusCode(statusCode);
        BasicHttpEntity body = new BasicHttpEntity();
        body.setContentType("text/html; charset=UTF-8");

        byte[] bodyData = content.getBytes();
        body.setContent(new ByteArrayInputStream(bodyData));
        body.setContentLength(bodyData.length);
        response.setEntity(body);
    }

    protected void handleRequest(HttpRequest req, HttpResponse response) {
        String method = (String)req.getParams().getParameter("method");

        int nMethod = RemoteMethodConstants.METHOD_UNKNOWN;
        String responseContent = null;
        try {
            if(method != null) {
                nMethod = Integer.parseInt(method);
            }

            switch(nMethod) {
            case RemoteMethodConstants.METHOD_EXECUTE :
                responseContent = handleExecuteMethodCall(req);
                break;

            case RemoteMethodConstants.METHOD_EXECUTE_ASYNC :
                responseContent = handleExecuteAsyncMethodCall(req);
                break;

            case RemoteMethodConstants.METHOD_ASYNC_RESULT :
                responseContent = handleAsyncResultMethodCall(req);
                break;

            case RemoteMethodConstants.METHOD_PING :
                responseContent = handlePingMethodCall(req);
                break;

            case RemoteMethodConstants.METHOD_UNKNOWN :
            default :
                assert(false);
                s_logger.error("unrecognized method " + nMethod);
                break;
            }
        } catch(Throwable e) {
            s_logger.error("Unexpected exception when processing cluster service request : ", e);
        }

        if(responseContent != null) {
            writeResponse(response, HttpStatus.SC_OK, responseContent);
        } else {
            writeResponse(response, HttpStatus.SC_BAD_REQUEST, null);
        }
    }

    private String handleExecuteMethodCall(HttpRequest req) {
        String agentId = (String)req.getParams().getParameter("agentId");
        String gsonPackage = (String)req.getParams().getParameter("gsonPackage");
        String stopOnError = (String)req.getParams().getParameter("stopOnError");

        if(s_logger.isDebugEnabled()) {
            s_logger.debug("|->" + agentId + " " + gsonPackage);
        }

        Command [] cmds = null;
        try {
            cmds = gson.fromJson(gsonPackage, Command[].class);
        } catch(Throwable e) {
            assert(false);
            s_logger.error("Excection in gson decoding : ", e);
        }

        if (cmds.length == 1 && cmds[0] instanceof ChangeAgentCommand) {  //intercepted
            ChangeAgentCommand cmd = (ChangeAgentCommand)cmds[0];

            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Intercepting command for agent change: agent " + cmd.getAgentId() + " event: " + cmd.getEvent());
            }
            boolean result = false;
            try {
                result = manager.executeAgentUserRequest(cmd.getAgentId(), cmd.getEvent());
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("Result is " + result);
                }

            } catch (AgentUnavailableException e) {
                s_logger.warn("Agent is unavailable", e);
                return null;
            }

            Answer[] answers = new Answer[1];
            answers[0] = new ChangeAgentAnswer(cmd, result);
            return gson.toJson(answers);
        } else if (cmds.length == 1 && cmds[0] instanceof TransferAgentCommand) {
            TransferAgentCommand cmd = (TransferAgentCommand) cmds[0];

            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Intercepting command for agent rebalancing: agent " + cmd.getAgentId() + " event: " + cmd.getEvent());
            }
            boolean result = false;
            try {
                result = manager.rebalanceAgent(cmd.getAgentId(), cmd.getEvent(), cmd.getCurrentOwner(), cmd.getFutureOwner());
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("Result is " + result);
                }

            } catch (AgentUnavailableException e) {
                s_logger.warn("Agent is unavailable", e);
                return null;
            } catch (OperationTimedoutException e) {
                s_logger.warn("Operation timed out", e);
                return null;
            }
            Answer[] answers = new Answer[1];
            answers[0] = new Answer(cmd, result, null);
            return gson.toJson(answers);
        }

        try {
            long startTick = System.currentTimeMillis();
            if(s_logger.isDebugEnabled()) {
                s_logger.debug("Send |-> " + agentId + " " + gsonPackage + " to agent manager");
            }

            Answer[] answers = manager.sendToAgent(Long.parseLong(agentId), cmds,
                    Integer.parseInt(stopOnError) != 0 ? true : false);

            if(answers != null) {
                String jsonReturn =  gson.toJson(answers);

                if(s_logger.isDebugEnabled()) {
                    s_logger.debug("Completed |-> " + agentId + " " + gsonPackage +
                            " in " + (System.currentTimeMillis() - startTick) + " ms, return result: " + jsonReturn);
                }

                return jsonReturn;
            } else {
                if(s_logger.isDebugEnabled()) {
                    s_logger.debug("Completed |-> " + agentId + " " + gsonPackage +
                            " in " + (System.currentTimeMillis() - startTick) + " ms, return null result");
                }
            }
        } catch(AgentUnavailableException e) {
            s_logger.warn("Agent is unavailable", e);
        } catch (OperationTimedoutException e) {
            s_logger.warn("Timed Out", e);
        }

        return null;
    }

    private String handleExecuteAsyncMethodCall(HttpRequest  req) {
        String agentId = (String)req.getParams().getParameter("agentId");
        String gsonPackage = (String)req.getParams().getParameter("gsonPackage");
        String stopOnError = (String)req.getParams().getParameter("stopOnError");
        String callingPeer = (String)req.getParams().getParameter("caller");

        if(s_logger.isDebugEnabled()) {
            s_logger.debug("Async " + callingPeer + " |-> " + agentId + " " + gsonPackage);
        }

        Command [] cmds = null;
        try {
            cmds = gson.fromJson(gsonPackage, Command[].class);
        } catch(Throwable e) {
            assert(false);
            s_logger.error("Excection in gson decoding : ", e);
        }

        Listener listener = new ClusterAsyncExectuionListener(manager, callingPeer);
        long seq = -1;
        try {
            long startTick = System.currentTimeMillis();
            if(s_logger.isDebugEnabled()) {
                s_logger.debug("Send Async " + callingPeer + " |-> " + agentId + " " + gsonPackage + " to agent manager");
            }

            seq = manager.sendToAgent(Long.parseLong(agentId), cmds,
                    Integer.parseInt(stopOnError) != 0 ? true : false, listener);

            if(s_logger.isDebugEnabled()) {
                s_logger.debug("Complated Async " + callingPeer + " |-> " + agentId + " " + gsonPackage + " in " +
                        + (System.currentTimeMillis() - startTick) + " ms, returned seq: " + seq);
            }
        } catch (AgentUnavailableException e) {
            s_logger.warn("Agent is unavailable", e);
            seq = -1;
        }

        return gson.toJson(seq);
    }

    private String handleAsyncResultMethodCall(HttpRequest  req) {
        String agentId = (String)req.getParams().getParameter("agentId");
        String gsonPackage = (String)req.getParams().getParameter("gsonPackage");
        String seq = (String)req.getParams().getParameter("seq");
        String executingPeer = (String)req.getParams().getParameter("executingPeer");

        if(s_logger.isDebugEnabled()) {
            s_logger.debug("Async callback " + executingPeer + "." + agentId + " |-> " + gsonPackage);
        }

        Answer[] answers = null;
        try {
            answers = gson.fromJson(gsonPackage, Answer[].class);
        } catch(Throwable e) {
            assert(false);
            s_logger.error("Excection in gson decoding : ", e);
        }

        long startTick = System.currentTimeMillis();
        if(manager.onAsyncResult(executingPeer, Long.parseLong(agentId), Long.parseLong(seq), answers)) {
            if(s_logger.isDebugEnabled()) {
                s_logger.debug("Completed local callback in " + (System.currentTimeMillis() - startTick) +
                " ms, return recurring=true, let async listener contine on");
            }

            return "recurring=true";
        }

        if(s_logger.isDebugEnabled()) {
            s_logger.debug("Completed local callback in " + (System.currentTimeMillis() - startTick) +
            " ms, return recurring=false, indicate to tear down async listener");
        }

        return "recurring=false";
    }

    private String handlePingMethodCall(HttpRequest req) {
        String callingPeer = (String)req.getParams().getParameter("callingPeer");

        if(s_logger.isDebugEnabled()) {
            s_logger.debug("Handle ping request from " + callingPeer);
        }

        return "true";
    }
}