//----------------------------------------------------------------------------
//  Copyright (C) 2013  The IPython Development Team
//
//  Distributed under the terms of the BSD License.  The full license is in
//  the file COPYING, distributed as part of this software.
//----------------------------------------------------------------------------

//============================================================================
// WidgetModel, WidgetView, and WidgetManager
//============================================================================
/**
 * Base Widget classes
 * @module IPython
 * @namespace IPython
 * @submodule widget
 */

"use strict";

// Use require.js 'define' method so that require.js is intelligent enough to
// syncronously load everything within this file when it is being 'required' 
// elsewhere.
define(["components/underscore/underscore-min",
         "components/backbone/backbone-min",
        ], function(underscore, backbone){


    //--------------------------------------------------------------------
    // WidgetModel class
    //--------------------------------------------------------------------
    var WidgetModel = Backbone.Model.extend({
        constructor: function(comm_manager, comm, widget_manager) {
            this.comm_manager = comm_manager;
            this.widget_manager = widget_manager;
            this.pending_msgs = 0;
            this.msg_throttle = 3;
            this.msg_buffer = null;
            this.views = {};
            this._custom_msg_callbacks = [];

            // Remember comm associated with the model.
            this.comm = comm;
            comm.model = this;

            // Hook comm messages up to model.
            comm.on_close($.proxy(this._handle_comm_closed, this));
            comm.on_msg($.proxy(this._handle_comm_msg, this));

            return Backbone.Model.apply(this);
        },


        update_other_views: function(caller) {
            this.last_modified_view = caller;
            this.save(this.changedAttributes(), {patch: true});

            for (var cell in this.views) {
                var views = this.views[cell];
                for (var view_index in views) {
                    var view = views[view_index];
                    if (view !== caller) {
                        view.update();    
                    }
                }
            }
        },
    

        send: function(content, cell) {

            // Used the last modified view as the sender of the message.  This
            // will insure that any python code triggered by the sent message
            // can create and display widgets and output.
            if (cell === undefined) {
                if (this.last_modified_view != undefined && 
                    this.last_modified_view.cell != undefined) {
                    cell = this.last_modified_view.cell;
                }
            }
            var callbacks = this._make_callbacks(cell);
            var data = {'custom_content': content};
            this.comm.send(data, callbacks);   
        },


        on_view_displayed: function (callback) {
            this._view_displayed_callback = callback;
        },


        on_close: function (callback) {
            this._close_callback = callback;
        },


        on_msg: function (callback, remove) {
            if (remove) {
                var found_index = -1;
                for (var index in this._custom_msg_callbacks) {
                    if (callback === this._custom_msg_callbacks[index]) {
                        found_index = index;
                        break;
                    }
                }

                if (found_index >= 0) {
                    this._custom_msg_callbacks.splice(found_index, 1);
                }
            } else {
                this._custom_msg_callbacks.push(callback)    
            }
        },


        _handle_custom_msg: function (content) {
            for (var index in this._custom_msg_callbacks) {
                try {
                    this._custom_msg_callbacks[index](content);
                } catch (e) {
                    console.log("Exception in widget model msg callback", e, content);
                }
            }
        },


        // Handle when a widget is closed.
        _handle_comm_closed: function (msg) {
            this._execute_views_method('remove');
            delete this.comm.model; // Delete ref so GC will collect widget model.
        },


        // Handle incomming comm msg.
        _handle_comm_msg: function (msg) {
            var method = msg.content.data.method;
            switch (method){
                case 'display':

                    // Try to get the cell.
                    var cell = this._get_msg_cell(msg.parent_header.msg_id);
                    if (cell == null) {
                        console.log("Could not determine where the display" + 
                            " message was from.  Widget will not be displayed")
                    } else {
                        this._display_view(msg.content.data.view_name, 
                        msg.content.data.parent,
                        cell);
                    }
                    break;
                case 'update':
                    this._handle_update(msg.content.data.state);
                    break;
                case 'add_class':
                case 'remove_class':
                    var selector = msg.content.data.selector;
                    var class_list = msg.content.data.class_list;
                    this._execute_views_method(method, selector, class_list);
                    break;
                case 'custom':
                    this._handle_custom_msg(msg.content.data.custom_content);
                    break;
            }
        },


        // Handle when a widget is updated via the python side.
        _handle_update: function (state) {
            this.updating = true;
            try {
                for (var key in state) {
                    if (state.hasOwnProperty(key)) {
                        if (key == "_css"){

                            // Set the css value of the model as an attribute
                            // instead of a backbone trait because we are only 
                            // interested in backend css -> frontend css.  In
                            // other words, if the css dict changes in the
                            // frontend, we don't need to push the changes to
                            // the backend.
                            this.css = state[key];
                        } else {
                            this.set(key, state[key]); 
                        }
                    }
                }
                this.id = this.comm.comm_id;
                this.save();
            } finally {
                this.updating = false;
            }
        },


        _handle_status: function (cell, msg) {
            //execution_state : ('busy', 'idle', 'starting')
            if (msg.content.execution_state=='idle') {
                
                // Send buffer if this message caused another message to be
                // throttled.
                if (this.msg_buffer != null &&
                    this.msg_throttle == this.pending_msgs) {

                    var cell = this._get_msg_cell(msg.parent_header.msg_id);
                    var callbacks = this._make_callbacks(cell);
                    var data = {sync_method: 'update', sync_data: this.msg_buffer};
                    this.comm.send(data, callbacks);   
                    this.msg_buffer = null;
                } else {

                    // Only decrease the pending message count if the buffer
                    // doesn't get flushed (sent).
                    --this.pending_msgs;
                }
            }
        },


        // Custom syncronization logic.
        _handle_sync: function (method, options) {
            var model_json = this.toJSON();

            // Only send updated state if the state hasn't been changed 
            // during an update.
            if (!this.updating) {
                if (this.pending_msgs >= this.msg_throttle) {
                    // The throttle has been exceeded, buffer the current msg so
                    // it can be sent once the kernel has finished processing 
                    // some of the existing messages.
                    if (method=='patch') {
                        if (this.msg_buffer == null) {
                            this.msg_buffer = $.extend({}, model_json); // Copy
                        }
                        for (var attr in options.attrs) {
                            this.msg_buffer[attr] = options.attrs[attr];
                        }
                    } else {
                        this.msg_buffer = $.extend({}, model_json); // Copy
                    }

                } else {
                    // We haven't exceeded the throttle, send the message like 
                    // normal.  If this is a patch operation, just send the 
                    // changes.
                    var send_json = model_json;
                    if (method=='patch') {
                        send_json = {};
                        for (var attr in options.attrs) {
                            send_json[attr] = options.attrs[attr];
                        }
                    }

                    var data = {sync_method: method, sync_data: send_json};

                    var cell = null;
                    if (this.last_modified_view != undefined && this.last_modified_view != null) {
                        cell = this.last_modified_view.cell;    
                    }
                    
                    var callbacks = this._make_callbacks(cell);
                    this.comm.send(data, callbacks);    
                    this.pending_msgs++;
                }
            }
            
            // Since the comm is a one-way communication, assume the message 
            // arrived.
            return model_json;
        },


        _handle_view_displayed: function(view) {
            if (this._view_displayed_callback) {
                try {
                    this._view_displayed_callback(view)
                } catch (e) {
                    console.log("Exception in widget model view displayed callback", e, view, this);
                }
            }
        },


        _execute_views_method: function (/* method_name, [argument0], [argument1], [...] */) {
            var method_name = arguments[0];
            var args = null;
            if (arguments.length > 1) {
                args = [].splice.call(arguments,1);
            }

            for (var cell in this.views) {
                var views = this.views[cell];
                for (var view_index in views) {
                    var view = views[view_index];
                    var method = view[method_name];
                    if (args === null) {
                        method.apply(view);
                    } else {
                        method.apply(view, args);
                    }
                }
            }
        },


        // Create view that represents the model.
        _display_view: function (view_name, parent_comm_id, cell) {
            var new_views = [];

            // Try creating and adding the view to it's parent.
            var displayed = false;
            if (parent_comm_id != undefined) {
                var parent_comm = this.comm_manager.comms[parent_comm_id];
                var parent_model = parent_comm.model;
                var parent_views = parent_model.views[cell];
                for (var parent_view_index in parent_views) {
                    var parent_view = parent_views[parent_view_index];
                    if (parent_view.display_child != undefined) {
                        var view = this._create_view(view_name, cell);
                        if (view != null) {
                            new_views.push(view);
                            parent_view.display_child(view);
                            displayed = true;
                            this._handle_view_displayed(view);
                        }
                    }
                }
            }

            // If no parent view is defined or exists.  Add the view's 
            // element to cell's widget div.
            if (!displayed) {
                var view = this._create_view(view_name, cell);
                if (view != null) {
                    new_views.push(view);

                    if (cell.widget_subarea != undefined && cell.widget_subarea != null) {
                        cell.widget_area.show();
                        cell.widget_subarea.append(view.$el);
                        this._handle_view_displayed(view);
                    }
                }
            }

            // Force the new view(s) to update their selves
            for (var view_index in new_views) {
                var view = new_views[view_index];
                view.update();
            }
        },


        // Create a view
        _create_view: function (view_name, cell) {
            var view_type = this.widget_manager.widget_view_types[view_name]; 
            if (view_type != undefined && view_type != null) {
                var view = new view_type({model: this});
                view.render();
                if (this.views[cell]==undefined) {
                    this.views[cell] = []
                }
                this.views[cell].push(view);
                view.cell = cell;

                // Handle when the view element is remove from the page.
                var that = this;
                view.$el.on("remove", function(){ 
                    var index = that.views[cell].indexOf(view);
                    if (index > -1) {
                        that.views[cell].splice(index, 1);
                    }
                    view.remove(); // Clean-up view 
                    if (that.views[cell].length()==0) {
                        delete that.views[cell];
                    }

                    // Close the comm if there are no views left.
                    if (that.views.length()==0) {
                        if (that._close_callback) {
                            try {
                                that._close_callback(that)
                            } catch (e) {
                                console.log("Exception in widget model close callback", e, that);
                            }
                        }
                        that.comm.close();     
                        delete that.comm.model; // Delete ref so GC will collect widget model.
                    }
                });
                return view;    
            }
            return null;
        },


        // Build a callback dict.
        _make_callbacks: function (cell) {
            var callbacks = {};
            if (cell != null) {
                
                // Try to get output handlers
                var handle_output = null;
                var handle_clear_output = null;
                if (cell.output_area != undefined && cell.output_area != null) {
                    handle_output = $.proxy(cell.output_area.handle_output, cell.output_area);
                    handle_clear_output = $.proxy(cell.output_area.handle_clear_output, cell.output_area);
                }

                // Create callback dict usign what is known
                var that = this;
                callbacks = {
                    iopub : {
                        output : handle_output,
                        clear_output : handle_clear_output,

                        status : function(msg){
                            that._handle_status(cell, msg);
                        },

                        // Special function only registered by widget messages.
                        // Allows us to get the cell for a message so we know
                        // where to add widgets if the code requires it.
                        get_cell : function() {
                            return cell;
                        },
                    },
                };
            }
            return callbacks;
        },


        // Get the output area corresponding to the msg_id.
        // cell is an instance of IPython.Cell
        _get_msg_cell: function (msg_id) {

            // First, check to see if the msg was triggered by cell execution.
            var cell = this.widget_manager.get_msg_cell(msg_id);
            if (cell != null) {
                return cell;
            }

            // Second, check to see if a get_cell callback was defined
            // for the message.  get_cell callbacks are registered for
            // widget messages, so this block is actually checking to see if the
            // message was triggered by a widget.
            var kernel = this.comm_manager.kernel;
            var callbacks = kernel.get_callbacks_for_msg(msg_id);
            if (callbacks != undefined && 
                callbacks.iopub != undefined && 
                callbacks.iopub.get_cell != undefined) {

                return callbacks.iopub.get_cell();
            }
            
            // Not triggered by a cell or widget (no get_cell callback 
            // exists).
            return null;
        },

    });


    //--------------------------------------------------------------------
    // WidgetView class
    //--------------------------------------------------------------------
    var WidgetView = Backbone.View.extend({
        
        initialize: function() {
            this.visible = true;
            this.model.on('change',this.update,this);
        },
        
        add_class: function(selector, class_list){
            var elements = this._get_selector_element(selector);
            if (elements.length > 0) {
                elements.addClass(class_list);
            }
        },
        
        remove_class: function(selector, class_list){
            var elements = this._get_selector_element(selector);
            if (elements.length > 0) {
                elements.removeClass(class_list);
            }
        },
    
    
        send: function(content) {
            this.model.send(content, this.cell);
        },

        update: function() {
            if (this.model.get('visible') != undefined) {
                if (this.visible != this.model.get('visible')) {
                    this.visible = this.model.get('visible');
                    if (this.visible) {
                        this.$el.show();
                    } else {
                        this.$el.hide();
                    }
                }
            }

            if (this.model.css != undefined) {
                for (var selector in this.model.css) {
                    if (this.model.css.hasOwnProperty(selector)) {

                        // Apply the css traits to all elements that match the selector.
                        var elements = this._get_selector_element(selector);
                        if (elements.length > 0) {
                            var css_traits = this.model.css[selector];    
                            for (var css_key in css_traits) {
                                if (css_traits.hasOwnProperty(css_key)) {
                                    elements.css(css_key, css_traits[css_key]);
                                }
                            }
                        }
                    }
                }
            }
        },

        _get_selector_element: function(selector) {
            // Get the elements via the css selector.  If the selector is
            // blank, apply the style to the $el_to_style element.  If
            // the $el_to_style element is not defined, use apply the 
            // style to the view's element.
            var elements = this.$el.find(selector);
            if (selector===undefined || selector===null || selector=='') {
                if (this.$el_to_style == undefined) {
                    elements = this.$el;
                } else {
                    elements = this.$el_to_style;
                }
            }
            return elements;
        },
    });


    //--------------------------------------------------------------------
    // WidgetManager class
    //--------------------------------------------------------------------
    var WidgetManager = function(){
        this.comm_manager = null;
        this.widget_model_types = {};
        this.widget_view_types = {};
        
        var that = this;
        Backbone.sync = function(method, model, options, error) {
            var result = model._handle_sync(method, options);
            if (options.success) {
              options.success(result);
            }
        }; 
    }


    WidgetManager.prototype.attach_comm_manager = function (comm_manager) {
        this.comm_manager = comm_manager;

        // Register already register widget model types with the comm manager.
        for (var widget_model_name in this.widget_model_types) {
            this.comm_manager.register_target(widget_model_name, $.proxy(this._handle_com_open, this));
        }
    }


    WidgetManager.prototype.register_widget_model = function (widget_model_name, widget_model_type) {
        // Register the widget with the comm manager.  Make sure to pass this object's context
        // in so `this` works in the call back.
        if (this.comm_manager!=null) {
            this.comm_manager.register_target(widget_model_name, $.proxy(this._handle_com_open, this));
        }
        this.widget_model_types[widget_model_name] = widget_model_type;
    }


    WidgetManager.prototype.register_widget_view = function (widget_view_name, widget_view_type) {
        this.widget_view_types[widget_view_name] = widget_view_type;
    }


    WidgetManager.prototype.get_msg_cell = function (msg_id) {
        if (IPython.notebook != undefined && IPython.notebook != null) {
            return IPython.notebook.get_msg_cell(msg_id);
        }
    }
    
    
    WidgetManager.prototype.on_create_widget = function (callback) {
        this._create_widget_callback = callback;
    }


    WidgetManager.prototype._handle_create_widget = function (widget_model) {
        if (this._create_widget_callback) {
            try {
                this._create_widget_callback(widget_model);
            } catch (e) {
                console.log("Exception in WidgetManager callback", e, widget_model);
            }
        }
    }


    WidgetManager.prototype._handle_com_open = function (comm, msg) {
        var widget_type_name = msg.content.target_name;
        var widget_model = new this.widget_model_types[widget_type_name](this.comm_manager, comm, this);
        this._handle_create_widget(widget_model);
    }
    

    //--------------------------------------------------------------------
    // Init code
    //--------------------------------------------------------------------
    IPython.WidgetManager = WidgetManager;
    IPython.WidgetModel = WidgetModel;
    IPython.WidgetView = WidgetView;

    if (IPython.widget_manager==undefined || IPython.widget_manager==null) {
        IPython.widget_manager = new WidgetManager();    
    }

    return IPython.widget_manager;
});