/*
 * Copyright 2005 Joe Walker
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Declare a constructor function to which we can add real functions.
 * @constructor
 */
function DWREngine() { }

/**
 * Set an alternative error handler from the default alert box.
 * @see http://getahead.ltd.uk/dwr/browser/engine/errors
 */
DWREngine.setErrorHandler = function(handler) {
  DWREngine._errorHandler = handler;
};

/**
 * Set an alternative warning handler from the default alert box.
 * @see http://getahead.ltd.uk/dwr/browser/engine/errors
 */
DWREngine.setWarningHandler = function(handler) {
  DWREngine._warningHandler = handler;
};

/**
 * Set a default timeout value for all calls. 0 (the default) turns timeouts off.
 * @see http://getahead.ltd.uk/dwr/browser/engine/errors
 */
DWREngine.setTimeout = function(timeout) {
  DWREngine._timeout = timeout;
};

/**
 * The Pre-Hook is called before any DWR remoting is done.
 * @see http://getahead.ltd.uk/dwr/browser/engine/hooks
 */
DWREngine.setPreHook = function(handler) {
  DWREngine._preHook = handler;
};

/**
 * The Post-Hook is called after any DWR remoting is done.
 * @see http://getahead.ltd.uk/dwr/browser/engine/hooks
 */
DWREngine.setPostHook = function(handler) {
  DWREngine._postHook = handler;
};

/** XHR remoting method constant. See DWREngine.setMethod() */
DWREngine.XMLHttpRequest = 1;

/** XHR remoting method constant. See DWREngine.setMethod() */
DWREngine.IFrame = 2;

/**
 * Set the preferred remoting method.
 * @param newmethod One of DWREngine.XMLHttpRequest or DWREngine.IFrame
 * @see http://getahead.ltd.uk/dwr/browser/engine/options
 */
DWREngine.setMethod = function(newmethod) {
  if (newmethod != DWREngine.XMLHttpRequest && newmethod != DWREngine.IFrame) {
    DWREngine._handleError("Remoting method must be one of DWREngine.XMLHttpRequest or DWREngine.IFrame");
    return;
  }
  DWREngine._method = newmethod;
};

/**
 * Which HTTP verb do we use to send results? Must be one of "GET" or "POST".
 * @see http://getahead.ltd.uk/dwr/browser/engine/options
 */
DWREngine.setVerb = function(verb) {
  if (verb != "GET" && verb != "POST") {
    DWREngine._handleError("Remoting verb must be one of GET or POST");
    return;
  }
  DWREngine._verb = verb;
};

/**
 * Ensure that remote calls happen in the order in which they were sent? (Default: false)
 * @see http://getahead.ltd.uk/dwr/browser/engine/ordering
 */
DWREngine.setOrdered = function(ordered) {
  DWREngine._ordered = ordered;
};

/**
 * Do we ask the XHR object to be asynchronous? (Default: true)
 * @see http://getahead.ltd.uk/dwr/browser/engine/options
 */
DWREngine.setAsync = function(async) {
  DWREngine._async = async;
};

/**
 * The default message handler.
 * @see http://getahead.ltd.uk/dwr/browser/engine/errors
 */
DWREngine.defaultMessageHandler = function(message) {
  if (typeof message == "object" && message.name == "Error" && message.description) {
    alert("Error: " + message.description);
  }
  else {
    alert(message);
  }
};

/**
 * For reduced latency you can group several remote calls together using a batch.
 * @see http://getahead.ltd.uk/dwr/browser/engine/batch
 */
DWREngine.beginBatch = function() {
  if (DWREngine._batch) {
    DWREngine._handleError("Batch already started.");
    return;
  }
  // Setup a batch
  DWREngine._batch = {};
  DWREngine._batch.map = {};
  DWREngine._batch.paramCount = 0;
  DWREngine._batch.map.callCount = 0;
  DWREngine._batch.metadata = {};
  DWREngine._batch.preHooks = [];
  DWREngine._batch.postHooks = [];
};

/**
 * Finished grouping a set of remote calls together. Go and execute them all.
 * @see http://getahead.ltd.uk/dwr/browser/engine/batch
 */
DWREngine.endBatch = function(options) {
  var batch = DWREngine._batch;
  if (batch == null) {
    DWREngine._handleError("No batch in progress.");
    return;
  }
  // Merge the global batch level properties into the batch meta data
  if (options && options.preHook) batch.preHooks.unshift(options.preHook);
  if (options && options.postHook) batch.postHooks.push(options.postHook);
  if (DWREngine._preHook) batch.preHooks.unshift(DWREngine._preHook);
  if (DWREngine._postHook) batch.postHooks.push(DWREngine._postHook);

  if (!batch.method) batch.method = DWREngine._method;
  if (!batch.verb) batch.verb = DWREngine._verb;
  if (!batch.async) batch.async = DWREngine._async;

  batch.completed = false;

  // If we are in ordered mode, then we don't send unless the list of sent
  // items is empty
  if (!DWREngine._ordered) {
    DWREngine._sendData(batch);
    DWREngine._batches[DWREngine._batches.length] = batch;
  }
  else {
    if (DWREngine._batches.length == 0) {
      // We aren't waiting for anything, go now.
      DWREngine._sendData(batch);
      DWREngine._batches[DWREngine._batches.length] = batch;
    }
    else {
      // Push the batch onto the waiting queue
      DWREngine._batchQueue[DWREngine._batchQueue.length] = batch;
    }
  }

  DWREngine._batch = null;
};

//==============================================================================
// Only private stuff below here
//==============================================================================

/** A function to call if something fails. */
DWREngine._errorHandler = DWREngine.defaultMessageHandler;

/** A function to call to alert the user to some breakage. */
DWREngine._warningHandler = DWREngine.defaultMessageHandler;

/** A function to be called before requests are marshalled. Can be null. */
DWREngine._preHook = null;

/** A function to be called after replies are received. Can be null. */
DWREngine._postHook = null;

/** An array of the batches that we have sent and are awaiting a reply on. */
DWREngine._batches = [];

/** In ordered mode, the array of batches waiting to be sent */
DWREngine._batchQueue = [];

/** A map of all the known current call metadata objects */
DWREngine._callData = {};

/** What is the default remoting method */
DWREngine._method = DWREngine.XMLHttpRequest;

/** What is the default remoting verb (ie GET or POST) */
DWREngine._verb = "POST";

/** Do we attempt to ensure that calls happen in the order in which they were sent? */
DWREngine._ordered = false;

/** Do we make the calls async? */
DWREngine._async = true;

/** The current batch (if we are in batch mode) */
DWREngine._batch = null;

/** The global timeout */
DWREngine._timeout = 0;

/** ActiveX objects to use when we want to convert an xml string into a DOM object. */
DWREngine._DOMDocument = ["Msxml2.DOMDocument.5.0", "Msxml2.DOMDocument.4.0", "Msxml2.DOMDocument.3.0", "MSXML2.DOMDocument", "MSXML.DOMDocument", "Microsoft.XMLDOM"];

/** The ActiveX objects to use when we want to do an XMLHttpRequest call. */
DWREngine._XMLHTTP = ["Msxml2.XMLHTTP.5.0", "Msxml2.XMLHTTP.4.0", "MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP", "Microsoft.XMLHTTP"];

/**
 * @private Send a request. Called by the Javascript interface stub
 * @param path part of URL after the host and before the exec bit without leading or trailing /s
 * @param scriptName The class to execute
 * @param methodName The method on said class to execute
 * @param func The callback function to which any returned data should be passed
 *       if this is null, any returned data will be ignored
 * @param vararg_params The parameters to pass to the above class
 */
DWREngine._execute = function(path, scriptName, methodName, vararg_params) {
  var singleShot = false;
  if (DWREngine._batch == null) {
    DWREngine.beginBatch();
    singleShot = true;
  }
  // To make them easy to manipulate we copy the arguments into an args array
  var args = [];
  for (var i = 0; i < arguments.length - 3; i++) {
    args[i] = arguments[i + 3];
  }
  // All the paths MUST be to the same servlet
  if (DWREngine._batch.path == null) {
    DWREngine._batch.path = path;
  }
  else {
    if (DWREngine._batch.path != path) {
      DWREngine._handleError("Can't batch requests to multiple DWR Servlets.");
      return;
    }
  }
  // From the other params, work out which is the function (or object with
  // call meta-data) and which is the call parameters
  var params;
  var callData;
  var firstArg = args[0];
  var lastArg = args[args.length - 1];

  if (typeof firstArg == "function") {
    callData = { callback:args.shift() };
    params = args;
  }
  else if (typeof lastArg == "function") {
    callData = { callback:args.pop() };
    params = args;
  }
  else if (typeof lastArg == "object" && lastArg.callback != null && typeof lastArg.callback == "function") {
    callData = args.pop();
    params = args;
  }
  else if (firstArg == null) {
    // This could be a null callback function, but if the last arg is also
    // null then we can't tell which is the function unless there are only
    // 2 args, in which case we don't care!
    if (lastArg == null && args.length > 2) {
      if (DWREngine._warningHandler) {
        DWREngine._warningHandler("Ambiguous nulls at start and end of parameter list. Which is the callback function?");
      }
    }
    callData = { callback:args.shift() };
    params = args;
  }
  else if (lastArg == null) {
    callData = { callback:args.pop() };
    params = args;
  }
  else {
    if (DWREngine._warningHandler) {
      DWREngine._warningHandler("Missing callback function or metadata object.");
    }
    return;
  }

  // Get a unique ID for this call
  var random = Math.floor(Math.random() * 10001);
  var id = (random + "_" + new Date().getTime()).toString();
  DWREngine._callData[id] = callData;
  var prefix = "c" + DWREngine._batch.map.callCount + "-";

  if (callData.preHook) DWREngine._batch.preHooks.unshift(callData.preHook);
  if (callData.postHook) DWREngine._batch.postHooks.push(callData.postHook);
  if (!callData.errorHandler) callData.errorHandler = DWREngine._errorHandler;
  if (!callData.warningHandler) callData.warningHandler = DWREngine._warningHandler;
  if (!callData.timeout) callData.timeout = DWREngine._timeout;

  // merge the metadata from this call into the batch
  if (callData != null)  {
    for (var prop in callData) {
      DWREngine._batch.metadata[prop] = callData[prop];
    }
  }
  DWREngine._batch.map[prefix + "scriptName"] = scriptName;
  DWREngine._batch.map[prefix + "methodName"] = methodName;
  DWREngine._batch.map[prefix + "id"] = id;

  // Serialize the parameters into batch.map
  DWREngine._addSerializeFunctions();
  for (i = 0; i < params.length; i++) {
    DWREngine._serializeAll(DWREngine._batch, [], params[i], prefix + "param" + i);
  }
  DWREngine._removeSerializeFunctions();

  // Now we have finished remembering the call, we incr the call count
  DWREngine._batch.map.callCount++;
  if (singleShot) {
    DWREngine.endBatch();
  }
};

/**
 * @private Actually send the block of data in the batch object.
 */
DWREngine._sendData = function(batch) {
  // If the batch is empty, don't send anything