/*
 * Copyright 2009-2012 Roland Huss
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 j * 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.
 */

/* =================================
 * Jolokia Javascript Client Library
 * =================================
 *
 * Requires jquery.js and json2.js
 * (if no native JSON.stringify() support is available)
 */

(function() {

    var _jolokiaConstructorFunc = function ($) {

        // Default paramerters for GET and POST requests
        var DEFAULT_CLIENT_PARAMS = {
            type:"POST",
            jsonp:false
        };

        var GET_AJAX_PARAMS = {
            type:"GET"
        };

        var POST_AJAX_PARAMS = {
            type:"POST",
            processData:false,
            dataType:"json",
            contentType:"text/json"
        };

        // Processing parameters which are added to the
        // URL as query parameters if given as options
        var PROCESSING_PARAMS = ["maxDepth", "maxCollectionSize", "maxObjects", "ignoreErrors", "canonicalNaming",
                                 "serializeException", "includeStackTrace", "ifModifiedSince"];

        /**
         * Constructor for creating a client to the Jolokia agent.
         *
         * An object containing the default parameters can be provided as argument. For the possible parameters
         * see {@link #request()}.
         *
         * @param param either a string in which case it is used as the URL to the agent or
         *              an object with the default parameters as key-value pairs
         */
        function Jolokia(param) {
            // If called without 'new', we are constructing an object
            // nevertheless
            if (!(this instanceof arguments.callee)) {
                return new Jolokia(param);
            }

            // Jolokia Javascript Client version
            this.CLIENT_VERSION = "1.2.2";

            // Registered requests for fetching periodically
            var jobs = [];

            // Options used for every request
            var agentOptions = {};

            // State of the scheduler
            var pollerIsRunning = false;

            // Allow a single URL parameter as well
            if (typeof param === "string") {
                param = {url:param};
            }
            $.extend(agentOptions, DEFAULT_CLIENT_PARAMS, param);

            // ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
            // Public methods

            /**
             * The request method using one or more JSON requests and sending it to the agent. Beside the
             * request a bunch of options can be given, which are merged with the options provided
             * at the constructor (where the options given here take precedence).
             *
             * Known options are:
             *
             * <dl>
             *   <dt>url</dt>
             *   <dd>Agent URL, which is mandatory</dd>
             *   <dt>method</dt>
             *   <dd>
             *     Either "post" or "get" depending on the desired HTTP method (case does not matter).
             *     Please note, that bulk requests are not possible with "get". On the other
             *     hand, JSONP requests are not possible with "post" (which obviously implies
             *     that bulk request cannot be used with JSONP requests). Also, when using a
             *     <code>read</code> type request for multiple attributes, this also can
             *     only be sent as "post" requests. If not given, a HTTP method is determined
             *     dyamically. If a method is selected which doesn't fit to the request, an error
             *     is raised.
             *   </dd>
             *   <dt>jsonp</dt>
             *   <dd>
             *     Whether the request should be sent via JSONP (a technique for allowing cross
             *     domain request circumventing the infamous "same-origin-policy"). This can be
             *     used only with HTTP "get" requests.
             *    </dd>
             *   <dt>success</dt>
             *   <dd>
             *     Callback function which is called for a successful request. The callback receives
             *     the response as single argument. If no <code>success</code> callback is given, then
             *     the request is performed synchronously and gives back the response as return
             *     value.
             *   </dd>
             *   <dt>error</dt>
             *   <dd>
             *     Callback in case a Jolokia error occurs. A Jolokia error is one, in which the HTTP request
             *     suceeded with a status code of 200, but the response object contains a status other
             *     than OK (200) which happens if the request JMX operation fails. This callback receives
             *     the full Jolokia response object (with a key <code>error</code> set). If no error callback
             *     is given, but an asynchronous operation is performed, the error response is printed
             *     to the Javascript console by default.
             *   </dd>
             *   <dt>ajaxError</dt>
             *   <dd>
             *     Global error callback called when the Ajax request itself failed. It obtains the same arguments
             *     as the error callback given for <code>jQuery.ajax()</code>, i.e. the <code>XmlHttpResonse</code>,
             *     a text status and an error thrown. Refer to the jQuery documentation for more information about
             *     this error handler.
             *   </dd>
             *   <dt>username</dt>
             *   <dd>A username used for HTTP authentication</dd>
             *   <dt>password</dt>
             *   <dd>A password used for HTTP authentication</dd>
             *   <dt>timeout</dt>
             *   <dd>Timeout for the HTTP request</dd>
             *   <dt>maxDepth</dt>
             *   <dd>Maximum traversal depth for serialization of complex return values</dd>
             *   <dt>maxCollectionSize</dt>
             *   <dd>
             *      Maximum size of collections returned during serialization.
             *      If larger, the collection is returned truncated.
             *   </dd>
             *   <dt>maxObjects</dt>
             *   <dd>
             *      Maximum number of objects contained in the response.
             *   </dd>
             *   <dt>ignoreErrors</dt>
             *   <dd>
             *     If set to true, errors during JMX operations and JSON serialization
             *     are ignored. Otherwise if a single deserialization fails, the whole request
             *     returns with an error. This works only for certain operations like pattern reads..
             *   </dd>
             * </dl>
             *
             * @param request the request to send
             * @param params parameters used for sending the request
             * @return the response object if called synchronously or nothing if called for asynchronous operation.
             */
            this.request = function (request, params) {
                var opts = $.extend({}, agentOptions, params);
                assertNotNull(opts.url, "No URL given");

                var ajaxParams = {};

                // Copy over direct params for the jQuery ajax call
                $.each(["username", "password", "timeout"], function (i, key) {
                    if (opts[key]) {
                        ajaxParams[key] = opts[key];
                    }
                });

                if (extractMethod(request, opts) === "post") {
                    $.extend(ajaxParams, POST_AJAX_PARAMS);
                    ajaxParams.data = JSON.stringify(request);
                    ajaxParams.url = ensureTrailingSlash(opts.url);
                } else {
                    $.extend(ajaxParams, GET_AJAX_PARAMS);
                    ajaxParams.dataType = opts.jsonp ? "jsonp" : "json";
                    ajaxParams.url = opts.url + "/" + constructGetUrlPath(request);
                }

                // Add processing parameters as query parameters
                ajaxParams.url = addProcessingParameters(ajaxParams.url, opts);

                // Global error handler
                if (opts.ajaxError) {
                    ajaxParams.error = opts.ajaxError;
                }

                // Dispatch Callbacks to error and success handlers
                if (opts.success) {
                    var success_callback = constructCallbackDispatcher(opts.success);
                    var error_callback = constructCallbackDispatcher(opts.error);
                    ajaxParams.success = function (data) {
                        var responses = $.isArray(data) ? data : [ data ];
                        for (var idx = 0; idx < responses.length; idx++) {
                            var resp = responses[idx];
                            if (Jolokia.isError(resp)) {
                                error_callback(resp, idx);
                            } else {
                                success_callback(resp, idx);
                            }
                        }
                    };

                    // Perform the request
                    $.ajax(ajaxParams);
                    return null;
                } else {
                    // Synchronous operation requested (i.e. no callbacks provided)
                    if (opts.jsonp) {
                        throw Error("JSONP is not supported for synchronous requests");
                    }
                    ajaxParams.async = false;
                    var xhr = $.ajax(ajaxParams);
                    if (httpSuccess(xhr)) {
                        return $.parseJSON(xhr.responseText);
                    } else {
                        return null;
                    }
                }
            };

            // ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
            // Scheduler related methods

            /**
             * Register one or more requests for periodically polling the agent along with a callback to call on receipt
             * of the response.
             *
             * The first argument can be either an object or a function. The remaining arguments are interpreted
             * as Jolokia request objects
             *
             * If a function is given or an object with an attribute <code>callback</code> holding a function, then
             * this function is called with all responses received as argument, regardless whether the individual response
             * indicates a success or error state.
             *
             * If the first argument is an object with two callback attributes <code>success</code> and <code>error</code>,
             * these functions are called for <em>each</em> response separately, depending whether the response
             * indicates success or an error state. If multiple requests have been registered along with this callback object,
             * the callback is called multiple times, one for each request in the same order as the request are given.
             * As second argument, the handle which is returned by this method is given and as third argument the index
             * within the list of requests.
             *
             * If the first argument is an object, an additional 'config' attribute with processing parameters can
             * be given which is used as default for the registered requests.
             * Request with a 'config' section take precedence.
             *
             * @param callback and options specification.
             * @param request, request, .... One or more requests to be registered for this single callback
             * @return handle which can be used for unregistering the request again or for correlation purposes in the callbacks
             */
            this.register = function() {
                if (arguments.length < 2) {
                    throw "At a least one request must be provided";
                }
                var callback = arguments[0],
                    requests = Array.prototype.slice.call(arguments,1),
                    job;
                if (typeof callback === 'object') {
                    if (callback.success && callback.error) {
                        job = {
                            success: callback.success,
                            error: callback.error
                        };
                    } else if (callback.callback) {
                        job = {
                            callback: callback.callback
                        };
                    } else {
                        throw "Either 'callback' or ('success' and 'error') callback must be provided " +
                              "when registering a Jolokia job";
                    }
                    job = $.extend(job,{
                        config: callback.config,
                        onlyIfModified: callback.onlyIfModified
                    });
                } else if (typeof callback === 'function') {
                    // Simplest version without config possibility
                    job = {
                        success: null,
                        error: null,
                        callback: callback
                    };
                } else {
                    throw "First argument must be either a callback func " +
                          "or an object with 'success' and 'error' attributes";
                }
                if (!requests) {
                    throw "No requests given";
                }
                job.requests = requests;
                var idx = jobs.length;
                jobs[idx] = job;
                return idx;
            };

            /**
             * Unregister a one or more request which has been registered with {@link #registerRequest}. As parameter
             * the handle returned during the registration process must be given
             * @param handle
             */
            this.unregister = function(handle) {
                if (handle < jobs.length) {
                    jobs[handle] = undefined;
                }
            };

            /**
             * Return an array of handles for currently registered jobs.
             * @return Array of job handles or an empty array
             */
            this.jobs = function() {
                var ret = [],
                    len = jobs.length;
                for (var i = 0; i < len; i++) {
                    if (jobs[i]) {
                        ret.push(i);
                    }
                }
                return ret;
            };

            /**
             * Start the poller. The interval between two polling attempts can be optionally given or are taken from
             * the parameter <code>fetchInterval</code> given at construction time. If no interval is given at all,
             * 30 seconds is the default.
             *
             * If the poller is already running (i.e. {@link #isRunning()} is <code>true</code> then the scheduler
             * is restarted, but only if the new interval differs from the currently active one.
             *
             * @param interval interval in milliseconds between two polling attempts
             */
            this.start = function(interval) {
                interval = interval || agentOptions.fetchInterval || 30000;
                if (pollerIsRunning) {
                    if (interval === agentOptions.fetchInterval) {
                        // Nothing to do
                        return;
                    }
                    // Re-start with new interval
                    this.stop();
                }
                agentOptions.fetchInterval = interval;
                this.timerId = setInterval(callJolokia(this,jobs), interval);

                pollerIsRunning = true;
            };

            /**
             * Stop the poller. If the poller is not running, no operation is performed.
             */
            this.stop = function() {
                if (!pollerIsRunning && this.timerId != undefined) {
                    return;
                }
                clearInterval(this.timerId);
                this.timerId = null;

                pollerIsRunning = false;
            };

            /**
             * Check whether the poller is running.
             * @return true if the poller is running, false otherwise.
             */
            this.isRunning = function() {
                return pollerIsRunning;
            };

            // ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
        }


        // ========================================================================
        // Private Methods:

        // Create a function called by a timer, which requests the registered requests
        // calling the stored callback on receipt. jolokia and jobs are put into the closure
        function callJolokia(jolokia,jobs) {
            return function() {
                var errorCbs = [],
                    successCbs = [],
                    i, j,
                    len = jobs.length;
                var requests = [];
                for (i = 0; i < len; i++) {
                    var job = jobs[i];
                    // Can happen when job has been deleted
                    // TODO: Can be probably optimized so that only the existing keys of jobs can be visited
                    if (!job) { continue;  }
                    var reqsLen = job.requests.length;
                    if (job.success) {
                        // Success/error pair of callbacks. For multiple request,
                        // these callback will be called multiple times
                        var successCb = cbSuccessClosure(job,i);
                        var errorCb = cbErrorClosure(job,i);
                        for (j = 0; j < reqsLen; j++) {
                            requests.push(prepareRequest(job,j));
                            successCbs.push(successCb);
                            errorCbs.push(errorCb);
                        }
                    } else {
                        // Job should have a single callback (job.callback) which will be
                        // called once with all responses at once as an array
                        var callback = cbCallbackClosure(job,jolokia);
                        // Add callbacks which collect the responses
                        for (j = 0; j < reqsLen - 1; j++) {
                            requests.push(prepareRequest(job,j));
                            successCbs.push(callback.cb);
                            errorCbs.push(callback.cb);
                        }
                        // Add final callback which finally will call the job.callback with all
                        // collected responses.
                        requests.push(prepareRequest(job,reqsLen-1));
                        successCbs.push(callback.lcb);
                        errorCbs.push(callback.lcb);
                    }
                }
                var opts = {
                    // Dispatch to the build up callbacks, request by request
                    success: function(resp, j) {
                        return successCbs[j].apply(jolokia, [resp, j]);
                    },
                    error: function(resp, j) {
                        return errorCbs[j].apply(jolokia, [resp, j]);
                    }
                };
                return jolokia.request(requests, opts);
            };
        }

        // Prepare a request with the proper configuration
        function prepareRequest(job,idx) {
            var request = job.requests[idx],
                config = job.config || {},
                // Add the proper ifModifiedSince parameter if already called at least once
                extra = job.onlyIfModified && job.lastModified ? { ifModifiedSince: job.lastModified } : {};

            request.config = $.extend({}, config, request.config, extra);
            return request;
        }

        // Closure for a full callback which stores the responses in an (closed) array
        // which the finally is feed in to the callback as array
        function cbCallbackClosure(job,jolokia) {
            var responses = [],
                callback = job.callback,
                lastModified = 0;

            return {
                cb : addResponse,
                lcb : function(resp,j) {
                    addResponse(resp);
                    // Callback is called only if at least one non-cached response
                    // is obtained. Update job's timestamp internally
                    if (responses.length > 0) {
                        job.lastModified = lastModified;
                        callback.apply(jolokia,responses);
                    }
                }
            };

            function addResponse(resp,j) {
                // Only remember responses with values and remember lowest timetamp, too.
                if (resp.status != 304) {
                    if (lastModified == 0 || resp.timestamp < lastModified ) {
                        lastModified = resp.timestamp;
                    }
                    responses.push(resp);
                }
            }
        }

        // Own function for creating a closure to avoid reference to mutable state in the loop
        function cbErrorClosure(job, i) {
            var callback = job.error;
            return function(resp,j) {
                // If we get a "304 - Not Modified" 'error', we do nothing
                if (resp.status == 304) {
                    return;
                }
                if (callback) {
                    callback(resp,i,j)
                }
            }
        }

        function cbSuccessClosure(job, i) {
            var callback = job.success;
            return function(resp,j) {
                if (callback) {
                    // Remember last success callback
                    if (job.onlyIfModified) {
                        job.lastModified = resp.timestamp;
                    }
                    callback(resp,i,j)
                }
            }
        }

        // Construct a callback dispatcher for appropriately dispatching
        // to a single callback or within an array of callbacks
        function constructCallbackDispatcher(callback) {
            if (callback == null) {
                return function (response) {
                    console.warn("Ignoring response " + JSON.stringify(response));
                };
            } else if (callback === "ignore") {
                // Ignore the return value
                return function () {
                };
            }
            var callbackArray = $.isArray(callback) ? callback : [ callback ];
            return function (response, idx) {
                callbackArray[idx % callbackArray.length](response, idx);
            }
        }

        // Extract the HTTP-Method to use and make some sanity checks if
        // the method was provided as part of the options, but dont fit
        // to the request given
        function extractMethod(request, opts) {
            var methodGiven = opts && opts.method ? opts.method.toLowerCase() : null,
                    method;
            if (methodGiven) {
                if (methodGiven === "get") {
                    if ($.isArray(request)) {
                        throw new Error("Cannot use GET with bulk requests");
                    }
                    if (request.type.toLowerCase() === "read" && $.isArray(request.attribute)) {
                        throw new Error("Cannot use GET for read with multiple attributes");
                    }
                    if (request.target) {
                        throw new Error("Cannot use GET request with proxy mode");
                    }
                    if (request.config) {
                        throw new Error("Cannot use GET with request specific config");
                    }
                }
                method = methodGiven;
            } else {
                // Determine method dynamically
                method = $.isArray(request) ||
                         request.config ||
                         (request.type.toLowerCase() === "read" && $.isArray(request.attribute)) ||
                         request.target ?
                        "post" : "get";
            }
            if (opts.jsonp && method === "post") {
                throw new Error("Can not use JSONP with POST requests");
            }
            return method;
        }

        // Add processing parameters given as request options
        // to an URL as GET query parameters
        function addProcessingParameters(url, opts) {
            var sep = url.indexOf("?") > 0 ? "&" : "?";
            $.each(PROCESSING_PARAMS, function (i, key) {
                if (opts[key] != null) {
                    url += sep + key + "=" + opts[key];
                    sep = "&";
                }
            });
            return url;
        }

        // ========================================================================
        // GET-Request handling

        // Create the URL used for a GET request
        function constructGetUrlPath(request) {
            var type = request.type;
            assertNotNull(type, "No request type given for building a GET request");
            type = type.toLowerCase();
            var extractor = GET_URL_EXTRACTORS[type];
            assertNotNull(extractor, "Unknown request type " + type);
            var result = extractor(request);
            var parts = result.parts || {};
            var url = type;
            $.each(parts, function (i, v) {
                url += "/" + Jolokia.escape(v)
            });
            if (result.path) {
                url += (result.path[0] == '/' ? "" : "/") + result.path;
            }
            return url;
        }

        // For POST requests it is recommended to have a trailing slash at the URL
        // in order to avoid a redirect which then results in a GET request.
        // See also https://bugs.eclipse.org/bugs/show_bug.cgi?id=331194#c1
        // for an explanation
        function ensureTrailingSlash(url) {
            // Squeeze any URL to a single one, optionally adding one
            return url.replace(/\/*$/, "/");
        }

        // Extractors used for preparing a GET request, i.e. for creating a stack
        // of arguments which gets appended to create the proper access URL
        // key: lowercase request type.
        // The return value is an object with two properties: The 'parts' to glue together, where
        // each part gets escaped and a 'path' which is appended literally
        var GET_URL_EXTRACTORS = {
            "read":function (request) {
                return { parts:[ request.mbean, request.attribute ], path:request.path };
            },
            "write":function (request) {
                return { parts:[request.mbean, request.attribute, valueToString(request.value)], path:request.path};
            },
            "exec":function (request) {
                var ret = [ request.mbean, request.operation ];
                if (request.arguments && request.arguments.length > 0) {
                    $.each(request.arguments, function (index, value) {
                        ret.push(valueToString(value));
                    });
                }
                return {parts:ret};
            },
            "version":function () {
                return {};
            },
            "search":function (request) {
                return { parts:[request.mbean]};
            },
            "list":function (request) {
                return { path:request.path};
            }
        };

        // Convert a value to a string for passing it to the Jolokia agent via
        // a get request (write, exec). Value can be either a single object or an array
        function valueToString(value) {
            if (value == null) {
                return "[null]";
            }
            if ($.isArray(value)) {
                var ret = "";
                for (var i = 0; i < value.length; i++) {
                    ret += value == null ? "[null]" : singleValueToString(value[i]);
                    if (i < value.length - 1) {
                        ret += ",";
                    }
                }
                return ret;
            } else {
                return singleValueToString(value);
            }
        }

        // Single value conversion for write/exec GET requests
        function singleValueToString(value) {
            if (typeof value === "string" && value.length == 0) {
                return "\"\"";
            } else {
                return value.toString();
            }
        }

        // Check whether a synchronous request was a success or not
        // Taken from jQuery 1.4
        function httpSuccess(xhr) {
            try {
                return !xhr.status && location.protocol === "file:" ||
                       xhr.status >= 200 && xhr.status < 300 ||
                       xhr.status === 304 || xhr.status === 1223;
            } catch (e) {
            }
            return false;
        }

        // ===============================================================================================
        // Utility methods:

        function assertNotNull(object, message) {
            if (object == null) {
                throw new Error(message);
            }
        }

        // ================================================================================================

        // Escape a path part, can be used as a static method outside this function too
        Jolokia.prototype.escape = Jolokia.escape = function (part) {
            return encodeURIComponent(part.replace(/!/g, "!!").replace(/\//g, "!/"));
        };

        /**
         * Utility method which checks whether a response is an error or a success
         * @param resp response to check
         * @return true if response is an error, false otherwise
         */
        Jolokia.prototype.isError = Jolokia.isError = function(resp) {
            return resp.status == null || resp.status != 200;
        };

        // Return back exported function/constructor
        return Jolokia;
    };

    // =====================================================================================================
    // Register either as global or as AMD module

    (function (root, factory) {
        if (typeof define === 'function' && define.amd) {
            // AMD. Register as a named module
            define(["jquery"], factory);
        } else {
            // Browser globals
            root.Jolokia = factory(root.jQuery);
        }
    }(this, function (jQuery) {
        return _jolokiaConstructorFunc(jQuery);
    }));
}());

