function openerp_pos_models(instance, module){ //module is instance.point_of_sale
    var QWeb = instance.web.qweb;
	var _t = instance.web._t;

    var round_di = instance.web.round_decimals;
    var round_pr = instance.web.round_precision
    
    // The PosModel contains the Point Of Sale's representation of the backend.
    // Since the PoS must work in standalone ( Without connection to the server ) 
    // it must contains a representation of the server's PoS backend. 
    // (taxes, product list, configuration options, etc.)  this representation
    // is fetched and stored by the PosModel at the initialisation. 
    // this is done asynchronously, a ready deferred alows the GUI to wait interactively 
    // for the loading to be completed 
    // There is a single instance of the PosModel for each Front-End instance, it is usually called
    // 'pos' and is available to all widgets extending PosWidget.

    module.PosModel = Backbone.Model.extend({
        initialize: function(session, attributes) {
            Backbone.Model.prototype.initialize.call(this, attributes);
            var  self = this;
            this.session = session;                 
            this.flush_mutex = new $.Mutex();                   // used to make sure the orders are sent to the server once at time
            this.pos_widget = attributes.pos_widget;

            this.proxy = new module.ProxyDevice(this);              // used to communicate to the hardware devices via a local proxy
            this.barcode_reader = new module.BarcodeReader({'pos': this, proxy:this.proxy});  // used to read barcodes
            this.proxy_queue = new module.JobQueue();           // used to prevent parallels communications to the proxy
            this.db = new module.PosDB();                       // a local database used to search trough products and categories & store pending orders
            this.debug = jQuery.deparam(jQuery.param.querystring()).debug !== undefined;    //debug mode 
            
            // Business data; loaded from the server at launch
            this.accounting_precision = 2; //TODO
            this.company_logo = null;
            this.company_logo_base64 = '';
            this.currency = null;
            this.company = null;
            this.user = null;
            this.users = [];
            this.partners = [];
            this.cashier = null;
            this.cashregisters = [];
            this.bankstatements = [];
            this.taxes = [];
            this.pos_session = null;
            this.config = null;
            this.units = [];
            this.units_by_id = {};
            this.pricelist = null;
            window.posmodel = this;

            // these dynamic attributes can be watched for change by other models or widgets
            this.set({
                'synch':            { state:'connected', pending:0 }, 
                'orders':           new module.OrderCollection(),
                'selectedOrder':    null,
            });

            this.bind('change:synch',function(pos,synch){
                clearTimeout(self.synch_timeout);
                self.synch_timeout = setTimeout(function(){
                    if(synch.state !== 'disconnected' && synch.pending > 0){
                        self.set('synch',{state:'disconnected', pending:synch.pending});
                    }
                },3000);
            });

            this.get('orders').bind('remove', function(order,_unused_,options){ 
                self.on_removed_order(order,options.index,options.reason); 
            });
            
            // We fetch the backend data on the server asynchronously. this is done only when the pos user interface is launched,
            // Any change on this data made on the server is thus not reflected on the point of sale until it is relaunched. 
            // when all the data has loaded, we compute some stuff, and declare the Pos ready to be used. 
            this.ready = this.load_server_data()
                .then(function(){
                    if(self.config.use_proxy){
                        return self.connect_to_proxy();
                    }
                });
            
        },

        // releases ressources holds by the model at the end of life of the posmodel
        destroy: function(){
            // FIXME, should wait for flushing, return a deferred to indicate successfull destruction
            // this.flush();
            this.proxy.close();
            this.barcode_reader.disconnect();
            this.barcode_reader.disconnect_from_proxy();
        },
        connect_to_proxy: function(){
            var self = this;
            var  done = new $.Deferred();
            this.barcode_reader.disconnect_from_proxy();
            this.pos_widget.loading_message(_t('Connecting to the PosBox'),0);
            this.pos_widget.loading_skip(function(){
                    self.proxy.stop_searching();
                });
            this.proxy.autoconnect({
                    force_ip: self.config.proxy_ip || undefined,
                    progress: function(prog){ 
                        self.pos_widget.loading_progress(prog);
                    },
                }).then(function(){
                    if(self.config.iface_scan_via_proxy){
                        self.barcode_reader.connect_to_proxy();
                    }
                }).always(function(){
                    done.resolve();
                });
            return done;
        },

        // helper function to load data from the server
        fetch: function(model, fields, domain, ctx){
            this._load_progress = (this._load_progress || 0) + 0.05; 
            this.pos_widget.loading_message(_t('Loading')+' '+model,this._load_progress);
            return new instance.web.Model(model).query(fields).filter(domain).context(ctx).all()
        },
        // loads all the needed data on the sever. returns a deferred indicating when all the data has loaded. 
        load_server_data: function(){
            var self = this;

            var loaded = self.fetch('res.users',['name','company_id'],[['id','=',this.session.uid]]) 
                .then(function(users){
                    self.user = users[0];

                    return self.fetch('res.company',
                    [
                        'currency_id',
                        'email',
                        'website',
                        'company_registry',
                        'vat',
                        'name',
                        'phone',
                        'partner_id',
                    ],
                    [['id','=',users[0].company_id[0]]],
                    {show_address_only: true});
                }).then(function(companies){
                    self.company = companies[0];

                    return self.fetch('product.uom', null, null);
                }).then(function(units){
                    self.units = units;
                    var units_by_id = {};
                    for(var i = 0, len = units.length; i < len; i++){
                        units_by_id[units[i].id] = units[i];
                    }
                    self.units_by_id = units_by_id;
                    
                    return self.fetch('res.users', ['name','ean13'], [['ean13', '!=', false]]);
                }).then(function(users){
                    self.users = users;

                    return self.fetch('res.partner', ['name','ean13'], [['ean13', '!=', false]]);
                }).then(function(partners){
                    self.partners = partners;

                    return self.fetch('account.tax', ['name','amount', 'price_include', 'type']);
                }).then(function(taxes){
                    self.taxes = taxes;

                    return self.fetch(
                        'pos.session', 
                        ['id', 'journal_ids','name','user_id','config_id','start_at','stop_at'],
                        [['state', '=', 'opened'], ['user_id', '=', self.session.uid]]
                    );
                }).then(function(pos_sessions){
                    self.pos_session = pos_sessions[0];

                    return self.fetch(
                        'pos.config',
                        ['name','journal_ids','journal_id','pricelist_id',
                         'iface_self_checkout', 'iface_led', 'iface_cashdrawer',
                         'iface_payment_terminal', 'iface_electronic_scale', 'iface_barscan', 
                         'iface_vkeyboard','iface_print_via_proxy','iface_scan_via_proxy',
                         'iface_cashdrawer','iface_invoicing','iface_big_scrollbars',
                         'receipt_header','receipt_footer','proxy_ip',
                         'state','sequence_id','session_ids'],
                        [['id','=', self.pos_session.config_id[0]]]
                    );
                }).then(function(configs){
                    self.config = configs[0];
                    self.config.use_proxy = self.config.iface_payment_terminal || 
                                            self.config.iface_electronic_scale ||
                                            self.config.iface_print_via_proxy  ||
                                            self.config.iface_scan_via_proxy   ||
                                            self.config.iface_cashdrawer;

                    return self.fetch('product.pricelist',['currency_id'],[['id','=',self.config.pricelist_id[0]]]);
                }).then(function(pricelists){
                    self.pricelist = pricelists[0];

                    return self.fetch('res.currency',['symbol','position','rounding','accuracy'],[['id','=',self.pricelist.currency_id[0]]]);
                }).then(function(currencies){
                    self.currency = currencies[0];

                    /*
                    return (new instance.web.Model('decimal.precision')).call('get_precision',[['Account']]);
                }).then(function(precision){
                    self.accounting_precision = precision;
                    console.log("PRECISION",precision);
*/
                    return self.fetch('product.packaging',['ean','product_tmpl_id']);
                }).then(function(packagings){
                    self.db.add_packagings(packagings);

                    return self.fetch('pos.category', ['id','name','parent_id','child_id','image']);
                }).then(function(categories){
                    self.db.add_categories(categories);

                    return self.fetch(
                        'product.product',
                        ['name', 'list_price','price','pos_categ_id', 'taxes_id', 'ean13', 'default_code', 'variants',
                         'to_weight', 'uom_id', 'uos_id', 'uos_coeff', 'mes_type', 'description_sale', 'description',
                         'product_tmpl_id'],
                        [['sale_ok','=',true],['available_in_pos','=',true]],
                        {pricelist: self.pricelist.id} // context for price
                    );
                }).then(function(products){
                    self.db.add_products(products);

                    return self.fetch(
                        'account.bank.statement',
                        ['account_id','currency','journal_id','state','name','user_id','pos_session_id'],
                        [['state','=','open'],['pos_session_id', '=', self.pos_session.id]]
                    );
                }).then(function(bankstatements){
                    var journals = [];
                    _.each(bankstatements,function(statement) {
                        journals.push(statement.journal_id[0]);
                    });
                    self.bankstatements = bankstatements;
                    return self.fetch('account.journal', undefined, [['id','in', journals]]);
                }).then(function(journals){
                    self.journals = journals; 

                    // associate the bank statements with their journals. 
                    var bankstatements = self.bankstatements;
                    for(var i = 0, ilen = bankstatements.length; i < ilen; i++){
                        for(var j = 0, jlen = journals.length; j < jlen; j++){
                            if(bankstatements[i].journal_id[0] === journals[j].id){
                                bankstatements[i].journal = journals[j];
                                bankstatements[i].self_checkout_payment_method = journals[j].self_checkout_payment_method;
                            }
                        }
                    }
                    self.cashregisters = bankstatements;

                    // Load the company Logo

                    self.company_logo = new Image();
                    self.company_logo.crossOrigin = 'anonymous';
                    var  logo_loaded = new $.Deferred();
                    self.company_logo.onload = function(){
                        var img = self.company_logo;
                        var ratio = 1;
                        var targetwidth = 300;
                        var maxheight = 150;
                        if( img.width !== targetwidth ){
                            ratio = targetwidth / img.width;
                        }
                        if( img.height * ratio > maxheight ){
                            ratio = maxheight / img.height;
                        }
                        var width  = Math.floor(img.width * ratio);
                        var height = Math.floor(img.height * ratio);
                        var c = document.createElement('canvas');
                            c.width  = width;
                            c.height = height
                        var ctx = c.getContext('2d');
                            ctx.drawImage(self.company_logo,0,0, width, height);
                        
                        self.company_logo_base64 = c.toDataURL();
                        window.logo64 = self.company_logo_base64;
                        logo_loaded.resolve();
                    };
                    self.company_logo.onerror = function(){
                        logo_loaded.reject();
                    };
                    self.company_logo.src = window.location.origin + '/web/binary/company_logo';

                    return logo_loaded;
                });
        
            return loaded;
        },

        // this is called when an order is removed from the order collection. It ensures that there is always an existing
        // order and a valid selected order
        on_removed_order: function(removed_order,index,reason){
            if(reason === 'abandon' && this.get('orders').size() > 0){
                // when we intentionally remove an unfinished order, and there is another existing one
                this.set({'selectedOrder' : this.get('orders').at(index) || this.get('orders').last()});
            }else{
                // when the order was automatically removed after completion, 
                // or when we intentionally delete the only concurrent order
                this.add_new_order();
            }
        },

        //creates a new empty order and sets it as the current order
        add_new_order: function(){
            var order = new module.Order({pos:this});
            this.get('orders').add(order);
            this.set('selectedOrder', order);
        },

        //removes the current order
        delete_current_order: function(){
            this.get('selectedOrder').destroy({'reason':'abandon'});
        },

        // saves the order locally and try to send it to the backend. 
        // it returns a deferred that succeeds after having tried to send the order and all the other pending orders.
        push_order: function(order) {
            var self = this;
            this.proxy.log('push_order',order.export_as_JSON());
            var order_id = this.db.add_order(order.export_as_JSON());
            var pushed = new $.Deferred();

            this.set('synch',{state:'connecting', pending:self.db.get_orders().length});

            this.flush_mutex.exec(function(){
                var flushed = self._flush_all_orders();

                flushed.always(function(){
                    pushed.resolve();
                });

                return flushed;
            });
            return pushed;
        },

        // saves the order locally and try to send it to the backend and make an invoice
        // returns a deferred that succeeds when the order has been posted and successfully generated
        // an invoice. This method can fail in various ways:
        // error-no-client: the order must have an associated partner_id. You can retry to make an invoice once
        //     this error is solved
        // error-transfer: there was a connection error during the transfer. You can retry to make the invoice once
        //     the network connection is up 

        push_and_invoice_order: function(order){
            var self = this;
            var invoiced = new $.Deferred(); 

            if(!order.get_client()){
                invoiced.reject('error-no-client');
                return invoiced;
            }

            var order_id = this.db.add_order(order.export_as_JSON());

            this.set('synch',{state:'connecting', pending:self.db.get_orders().length});

            this.flush_mutex.exec(function(){
                var done = new $.Deferred(); // holds the mutex

                // send the order to the server
                // we have a 30 seconds timeout on this push.
                // FIXME: if the server takes more than 30 seconds to accept the order,
                // the client will believe it wasn't successfully sent, and very bad
                // things will happen as a duplicate will be sent next time
                // so we must make sure the server detects and ignores duplicated orders

                var transfer = self._flush_order(order_id, {timeout:30000, to_invoice:true});
                
                transfer.fail(function(){
                    invoiced.reject('error-transfer');
                    done.reject();
                });

                // on success, get the order id generated by the server
                transfer.pipe(function(order_server_id){    
                    // generate the pdf and download it
                    self.pos_widget.do_action('point_of_sale.pos_invoice_report',{additional_context:{ 
                        active_ids:order_server_id,
                    }});
                    invoiced.resolve();
                    done.resolve();
                });

                return done;

            });

            return invoiced;
        },

        // attemps to send all pending orders ( stored in the pos_db ) to the server,
        // and remove the successfully sent ones from the db once
        // it has been confirmed that they have been sent correctly.
        flush: function() {
            var self = this;
            var flushed = new $.Deferred();

            this.flush_mutex.exec(function(){
                var done = new $.Deferred();

                self._flush_all_orders()
                    .done(  function(){ flushed.resolve();})
                    .fail(  function(){ flushed.reject(); })
                    .always(function(){ done.resolve();   });

                return done;
            });

            return flushed;
        },

        // attempts to send the locally stored order of id 'order_id'
        // the sending is asynchronous and can take some time to decide if it is successful or not
        // it is therefore important to only call this method from inside a mutex
        // this method returns a deferred indicating wether the sending was successful or not
        // there is a timeout parameter which is set to 2 seconds by default. 
        _flush_order: function( order_id, options) {
            return this._flush_all_orders([this.db.get_order(order_id)], options);
        },
        
        // attempts to send all the locally stored orders. As with _flush_order, it should only be
        // called from within a mutex. 
        // this method returns a deferred that always succeeds when all orders have been tried to be sent,
        // even if none of them could actually be sent. 
        _flush_all_orders: function () {
            var self = this;
            self.set('synch', {
                state: 'connecting',
                pending: self.get('synch').pending
            });
            return self._save_to_server(self.db.get_orders()).done(function () {
                var pending = self.db.get_orders().length;
                self.set('synch', {
                    state: pending ? 'connecting' : 'connected',
                    pending: pending
                });
            });
        },

        // send an array of orders to the server
        // available options:
        // - timeout: timeout for the rpc call in ms
        _save_to_server: function (orders, options) {
            if (!orders || !orders.length) {
                var result = $.Deferred();
                result.resolve();
                return result;
            }
                
            options = options || {};

            var self = this;
            var timeout = typeof options.timeout === 'number' ? options.timeout : 7500 * orders.length;

            // we try to send the order. shadow prevents a spinner if it takes too long. (unless we are sending an invoice,
            // then we want to notify the user that we are waiting on something )
            var posOrderModel = new instance.web.Model('pos.order');
            return posOrderModel.call('create_from_ui',
                [_.map(orders, function (order) {
                    order.to_invoice = options.to_invoice || false;
                    return order;
                })],
                undefined,
                {
                    shadow: !options.to_invoice,
                    timeout: timeout
                }
            ).then(function () {
                _.each(orders, function (order) {
                    self.db.remove_order(order.id);
                });
            }).fail(function (unused, event){
                // prevent an error popup creation by the rpc failure
                // we want the failure to be silent as we send the orders in the background
                event.preventDefault();
                console.error('Failed to send orders:', orders);
            });
        },

        scan_product: function(parsed_code){
            var self = this;
            var selectedOrder = this.get('selectedOrder');
            if(parsed_code.encoding === 'ean13'){
                var product = this.db.get_product_by_ean13(parsed_code.base_code);
            }else if(parsed_code.encoding === 'reference'){
                var product = this.db.get_product_by_reference(parsed_code.code);
            }

            if(!product){
                return false;
            }

            if(parsed_code.type === 'price'){
                selectedOrder.addProduct(product, {price:parsed_code.value});
            }else if(parsed_code.type === 'weight'){
                selectedOrder.addProduct(product, {quantity:parsed_code.value, merge:false});
            }else{
                selectedOrder.addProduct(product);
            }
            return true;
        },
    });

    // An orderline represent one element of the content of a client's shopping cart.
    // An orderline contains a product, its quantity, its price, discount. etc. 
    // An Order contains zero or more Orderlines.
    module.Orderline = Backbone.Model.extend({
        initialize: function(attr,options){
            this.pos = options.pos;
            this.order = options.order;
            this.product = options.product;
            this.price   = options.product.price;
            this.quantity = 1;
            this.quantityStr = '1';
            this.discount = 0;
            this.discountStr = '0';
            this.type = 'unit';
            this.selected = false;
        },
        // sets a discount [0,100]%
        set_discount: function(discount){
            var disc = Math.min(Math.max(parseFloat(discount) || 0, 0),100);
            this.discount = disc;
            this.discountStr = '' + disc;
            this.trigger('change',this);
        },
        // returns the discount [0,100]%
        get_discount: function(){
            return this.discount;
        },
        get_discount_str: function(){
            return this.discountStr;
        },
        get_product_type: function(){
            return this.type;
        },
        // sets the quantity of the product. The quantity will be rounded according to the 
        // product's unity of measure properties. Quantities greater than zero will not get 
        // rounded to zero
        set_quantity: function(quantity){
            if(quantity === 'remove'){
                this.order.removeOrderline(this);
                return;
            }else{
                var quant = parseFloat(quantity) || 0;
                var unit = this.get_unit();
                if(unit){
                    this.quantity    = round_pr(quant, unit.rounding);
                    this.quantityStr = this.quantity.toFixed(Math.ceil(Math.log(1.0 / unit.rounding) / Math.log(10)));
                }else{
                    this.quantity    = quant;
                    this.quantityStr = '' + this.quantity;
                }
            }
            this.trigger('change',this);
        },
        // return the quantity of product
        get_quantity: function(){
            return this.quantity;
        },
        get_quantity_str: function(){
            return this.quantityStr;
        },
        get_quantity_str_with_unit: function(){
            var unit = this.get_unit();
            if(unit && unit.name !== 'Unit(s)'){
                return this.quantityStr + ' ' + unit.name;
            }else{
                return this.quantityStr;
            }
        },
        // return the unit of measure of the product
        get_unit: function(){
            var unit_id = (this.product.uos_id || this.product.uom_id);
            if(!unit_id){
                return undefined;
            }
            unit_id = unit_id[0];
            if(!this.pos){
                return undefined;
            }
            return this.pos.units_by_id[unit_id];
        },
        // return the product of this orderline
        get_product: function(){
            return this.product;
        },
        // selects or deselects this orderline
        set_selected: function(selected){
            this.selected = selected;
            this.trigger('change',this);
        },
        // returns true if this orderline is selected
        is_selected: function(){
            return this.selected;
        },
        // when we add an new orderline we want to merge it with the last line to see reduce the number of items
        // in the orderline. This returns true if it makes sense to merge the two
        can_be_merged_with: function(orderline){
            if( this.get_product().id !== orderline.get_product().id){    //only orderline of the same product can be merged
                return false;
            }else if(this.get_product_type() !== orderline.get_product_type()){
                return false;
            }else if(this.get_discount() > 0){             // we don't merge discounted orderlines
                return false;
            }else if(this.price !== orderline.price){
                return false;
            }else{ 
                return true;
            }
        },
        merge: function(orderline){
            this.set_quantity(this.get_quantity() + orderline.get_quantity());
        },
        export_as_JSON: function() {
            return {
                qty: this.get_quantity(),
                price_unit: this.get_unit_price(),
                discount: this.get_discount(),
                product_id: this.get_product().id,
            };
        },
        //used to create a json of the ticket, to be sent to the printer
        export_for_printing: function(){
            return {
                quantity:           this.get_quantity(),
                unit_name:          this.get_unit().name,
                price:              this.get_unit_price(),
                discount:           this.get_discount(),
                product_name:       this.get_product().name,
                price_display :     this.get_display_price(),
                price_with_tax :    this.get_price_with_tax(),
                price_without_tax:  this.get_price_without_tax(),
                tax:                this.get_tax(),
                product_description:      this.get_product().description,
                product_description_sale: this.get_product().description_sale,
            };
        },
        // changes the base price of the product for this orderline
        set_unit_price: function(price){
            this.price = round_di(parseFloat(price) || 0, 2);
            this.trigger('change',this);
        },
        get_unit_price: function(){
            var rounding = this.pos.currency.rounding;
            return round_pr(this.price,rounding);
        },
        get_display_price: function(){
            var rounding = this.pos.currency.rounding;
            return  round_pr(round_pr(this.get_unit_price() * this.get_quantity(),rounding) * (1- this.get_discount()/100.0),rounding);
        },
        get_price_without_tax: function(){
            return this.get_all_prices().priceWithoutTax;
        },
        get_price_with_tax: function(){
            return this.get_all_prices().priceWithTax;
        },
        get_tax: function(){
            return this.get_all_prices().tax;
        },
        get_tax_details: function(){
            return this.get_all_prices().taxDetails;
        },
        get_all_prices: function(){
            var self = this;
            var currency_rounding = this.pos.currency.rounding;
            var base = round_pr(this.get_quantity() * this.get_unit_price() * (1.0 - (this.get_discount() / 100.0)), currency_rounding);
            var totalTax = base;
            var totalNoTax = base;
            
            var product =  this.get_product(); 
            var taxes_ids = product.taxes_id;
            var taxes =  self.pos.taxes;
            var taxtotal = 0;
            var taxdetail = {};
            _.each(taxes_ids, function(el) {
                var tax = _.detect(taxes, function(t) {return t.id === el;});
                if (tax.price_include) {
                    var tmp;
                    if (tax.type === "percent") {
                        tmp =  base - round_pr(base / (1 + tax.amount),currency_rounding); 
                    } else if (tax.type === "fixed") {
                        tmp = round_pr(tax.amount * self.get_quantity(),currency_rounding);
                    } else {
                        throw "This type of tax is not supported by the point of sale: " + tax.type;
                    }
                    tmp = round_pr(tmp,currency_rounding);
                    taxtotal += tmp;
                    totalNoTax -= tmp;
                    taxdetail[tax.id] = tmp;
                } else {
                    var tmp;
                    if (tax.type === "percent") {
                        tmp = tax.amount * base;
                    } else if (tax.type === "fixed") {
                        tmp = tax.amount * self.get_quantity();
                    } else {
                        throw "This type of tax is not supported by the point of sale: " + tax.type;
                    }
                    tmp = round_pr(tmp,currency_rounding);
                    taxtotal += tmp;
                    totalTax += tmp;
                    taxdetail[tax.id] = tmp;
                }
            });
            return {
                "priceWithTax": totalTax,
                "priceWithoutTax": totalNoTax,
                "tax": taxtotal,
                "taxDetails": taxdetail,
            };
        },
    });

    module.OrderlineCollection = Backbone.Collection.extend({
        model: module.Orderline,
    });

    // Every Paymentline contains a cashregister and an amount of money.
    module.Paymentline = Backbone.Model.extend({
        initialize: function(attributes, options) {
            this.amount = 0;
            this.cashregister = options.cashregister;
            this.name = this.cashregister.journal_id[1];
            this.selected = false;
        },
        //sets the amount of money on this payment line
        set_amount: function(value){
            this.amount = round_di(parseFloat(value) || 0, 2);
            this.trigger('change:amount',this);
        },
        // returns the amount of money on this paymentline
        get_amount: function(){
            return this.amount;
        },
        set_selected: function(selected){
            if(this.selected !== selected){
                this.selected = selected;
                this.trigger('change:selected',this);
            }
        },
        // returns the associated cashregister
        //exports as JSON for server communication
        export_as_JSON: function(){
            return {
                name: instance.web.datetime_to_str(new Date()),
                statement_id: this.cashregister.id,
                account_id: this.cashregister.account_id[0],
                journal_id: this.cashregister.journal_id[0],
                amount: this.get_amount()
            };
        },
        //exports as JSON for receipt printing
        export_for_printing: function(){
            return {
                amount: this.get_amount(),
                journal: this.cashregister.journal_id[1],
            };
        },
    });

    module.PaymentlineCollection = Backbone.Collection.extend({
        model: module.Paymentline,
    });
    

    // An order more or less represents the content of a client's shopping cart (the OrderLines) 
    // plus the associated payment information (the Paymentlines) 
    // there is always an active ('selected') order in the Pos, a new one is created
    // automaticaly once an order is completed and sent to the server.
    module.Order = Backbone.Model.extend({
        initialize: function(attributes){
            Backbone.Model.prototype.initialize.apply(this, arguments);
            this.uid =     this.generateUniqueId();
            this.set({
                creationDate:   new Date(),
                orderLines:     new module.OrderlineCollection(),
                paymentLines:   new module.PaymentlineCollection(),
                name:           "Order " + this.uid,
                client:         null,
            });
            this.pos = attributes.pos; 
            this.selected_orderline   = undefined;
            this.selected_paymentline = undefined;
            this.screen_data = {};  // see ScreenSelector
            this.receipt_type = 'receipt';  // 'receipt' || 'invoice'
            return this;
        },
        generateUniqueId: function() {
            return new Date().getTime();
        },
        addProduct: function(product, options){
            options = options || {};
            var attr = JSON.parse(JSON.stringify(product));
            attr.pos = this.pos;
            attr.order = this;
            var line = new module.Orderline({}, {pos: this.pos, order: this, product: product});

            if(options.quantity !== undefined){
                line.set_quantity(options.quantity);
            }
            if(options.price !== undefined){
                line.set_unit_price(options.price);
            }

            var last_orderline = this.getLastOrderline();
            if( last_orderline && last_orderline.can_be_merged_with(line) && options.merge !== false){
                last_orderline.merge(line);
            }else{
                this.get('orderLines').add(line);
            }
            this.selectLine(this.getLastOrderline());
        },
        removeOrderline: function( line ){
            this.get('orderLines').remove(line);
            this.selectLine(this.getLastOrderline());
        },
        getLastOrderline: function(){
            return this.get('orderLines').at(this.get('orderLines').length -1);
        },
        addPaymentline: function(cashregister) {
            var paymentLines = this.get('paymentLines');
            var newPaymentline = new module.Paymentline({},{cashregister:cashregister});
            if(cashregister.journal.type !== 'cash'){
                newPaymentline.set_amount( Math.max(this.getDueLeft(),0) );
            }
            paymentLines.add(newPaymentline);
            this.selectPaymentline(newPaymentline);

        },
        removePaymentline: function(line){
            if(this.selected_paymentline === line){
                this.selectPaymentline(undefined);
            }
            this.get('paymentLines').remove(line);
        },
        getName: function() {
            return this.get('name');
        },
        getSubtotal : function(){
            return (this.get('orderLines')).reduce((function(sum, orderLine){
                return sum + orderLine.get_display_price();
            }), 0);
        },
        getTotalTaxIncluded: function() {
            return (this.get('orderLines')).reduce((function(sum, orderLine) {
                return sum + orderLine.get_price_with_tax();
            }), 0);
        },
        getDiscountTotal: function() {
            return (this.get('orderLines')).reduce((function(sum, orderLine) {
                return sum + (orderLine.get_unit_price() * (orderLine.get_discount()/100) * orderLine.get_quantity());
            }), 0);
        },
        getTotalTaxExcluded: function() {
            return (this.get('orderLines')).reduce((function(sum, orderLine) {
                return sum + orderLine.get_price_without_tax();
            }), 0);
        },
        getTax: function() {
            return (this.get('orderLines')).reduce((function(sum, orderLine) {
                return sum + orderLine.get_tax();
            }), 0);
        },
        getTaxDetails: function(){
            var details = {};
            var fulldetails = [];
            var taxes_by_id = {};
            
            for(var i = 0; i < this.pos.taxes.length; i++){
                taxes_by_id[this.pos.taxes[i].id] = this.pos.taxes[i];
            }

            this.get('orderLines').each(function(line){
                var ldetails = line.get_tax_details();
                for(var id in ldetails){
                    if(ldetails.hasOwnProperty(id)){
                        details[id] = (details[id] || 0) + ldetails[id];
                    }
                }
            });
            
            for(var id in details){
                if(details.hasOwnProperty(id)){
                    fulldetails.push({amount: details[id], tax: taxes_by_id[id]});
                }
            }

            return fulldetails;
        },
        getPaidTotal: function() {
            return (this.get('paymentLines')).reduce((function(sum, paymentLine) {
                return sum + paymentLine.get_amount();
            }), 0);
        },
        getChange: function() {
            return this.getPaidTotal() - this.getTotalTaxIncluded();
        },
        getDueLeft: function() {
            return this.getTotalTaxIncluded() - this.getPaidTotal();
        },
        // sets the type of receipt 'receipt'(default) or 'invoice'
        set_receipt_type: function(type){
            this.receipt_type = type;
        },
        get_receipt_type: function(){
            return this.receipt_type;
        },
        // the client related to the current order.
        set_client: function(client){
            this.set('client',client);
        },
        get_client: function(){
            return this.get('client');
        },
        get_client_name: function(){
            var client = this.get('client');
            return client ? client.name : "";
        },
        // the order also stores the screen status, as the PoS supports
        // different active screens per order. This method is used to
        // store the screen status.
        set_screen_data: function(key,value){
            if(arguments.length === 2){
                this.screen_data[key] = value;
            }else if(arguments.length === 1){
                for(key in arguments[0]){
                    this.screen_data[key] = arguments[0][key];
                }
            }
        },
        //see set_screen_data
        get_screen_data: function(key){
            return this.screen_data[key];
        },
        // exports a JSON for receipt printing
        export_for_printing: function(){
            var orderlines = [];
            this.get('orderLines').each(function(orderline){
                orderlines.push(orderline.export_for_printing());
            });

            var paymentlines = [];
            this.get('paymentLines').each(function(paymentline){
                paymentlines.push(paymentline.export_for_printing());
            });
            var client  = this.get('client');
            var cashier = this.pos.cashier || this.pos.user;
            var company = this.pos.company;
            var date = new Date();

            return {
                orderlines: orderlines,
                paymentlines: paymentlines,
                subtotal: this.getSubtotal(),
                total_with_tax: this.getTotalTaxIncluded(),
                total_without_tax: this.getTotalTaxExcluded(),
                total_tax: this.getTax(),
                total_paid: this.getPaidTotal(),
                total_discount: this.getDiscountTotal(),
                tax_details: this.getTaxDetails(),
                change: this.getChange(),
                name : this.getName(),
                client: client ? client.name : null ,
                invoice_id: null,   //TODO
                cashier: cashier ? cashier.name : null,
                header: this.pos.config.receipt_header || '',
                footer: this.pos.config.receipt_footer || '',
                precision: {
                    price: 2,
                    money: 2,
                    quantity: 3,
                },
                date: { 
                    year: date.getFullYear(), 
                    month: date.getMonth(), 
                    date: date.getDate(),       // day of the month 
                    day: date.getDay(),         // day of the week 
                    hour: date.getHours(), 
                    minute: date.getMinutes() ,
                    isostring: date.toISOString(),
                    localestring: date.toLocaleString(),
                }, 
                company:{
                    email: company.email,
                    website: company.website,
                    company_registry: company.company_registry,
                    contact_address: company.partner_id[1], 
                    vat: company.vat,
                    name: company.name,
                    phone: company.phone,
                    logo:  this.pos.company_logo_base64,
                },
                currency: this.pos.currency,
            };
        },
        export_as_JSON: function() {
            var orderLines, paymentLines;
            orderLines = [];
            (this.get('orderLines')).each(_.bind( function(item) {
                return orderLines.push([0, 0, item.export_as_JSON()]);
            }, this));
            paymentLines = [];
            (this.get('paymentLines')).each(_.bind( function(item) {
                return paymentLines.push([0, 0, item.export_as_JSON()]);
            }, this));
            return {
                name: this.getName(),
                amount_paid: this.getPaidTotal(),
                amount_total: this.getTotalTaxIncluded(),
                amount_tax: this.getTax(),
                amount_return: this.getChange(),
                lines: orderLines,
                statement_ids: paymentLines,
                pos_session_id: this.pos.pos_session.id,
                partner_id: this.get_client() ? this.get_client().id : false,
                user_id: this.pos.cashier ? this.pos.cashier.id : this.pos.user.id,
                uid: this.uid,
            };
        },
        getSelectedLine: function(){
            return this.selected_orderline;
        },
        selectLine: function(line){
            if(line){
                if(line !== this.selected_orderline){
                    if(this.selected_orderline){
                        this.selected_orderline.set_selected(false);
                    }
                    this.selected_orderline = line;
                    this.selected_orderline.set_selected(true);
                }
            }else{
                this.selected_orderline = undefined;
            }
        },
        deselectLine: function(){
            if(this.selected_orderline){
                this.selected_orderline.set_selected(false);
                this.selected_orderline = undefined;
            }
        },
        selectPaymentline: function(line){
            if(line !== this.selected_paymentline){
                if(this.selected_paymentline){
                    this.selected_paymentline.set_selected(false);
                }
                this.selected_paymentline = line;
                if(this.selected_paymentline){
                    this.selected_paymentline.set_selected(true);
                }
                this.trigger('change:selected_paymentline',this.selected_paymentline);
            }
        },
    });

    module.OrderCollection = Backbone.Collection.extend({
        model: module.Order,
    });

    /*
     The numpad handles both the choice of the property currently being modified
     (quantity, price or discount) and the edition of the corresponding numeric value.
     */
    module.NumpadState = Backbone.Model.extend({
        defaults: {
            buffer: "0",
            mode: "quantity"
        },
        appendNewChar: function(newChar) {
            var oldBuffer;
            oldBuffer = this.get('buffer');
            if (oldBuffer === '0') {
                this.set({
                    buffer: newChar
                });
            } else if (oldBuffer === '-0') {
                this.set({
                    buffer: "-" + newChar
                });
            } else {
                this.set({
                    buffer: (this.get('buffer')) + newChar
                });
            }
            this.trigger('set_value',this.get('buffer'));
        },
        deleteLastChar: function() {
            if(this.get('buffer') === ""){
                if(this.get('mode') === 'quantity'){
                    this.trigger('set_value','remove');
                }else{
                    this.trigger('set_value',this.get('buffer'));
                }
            }else{
                var newBuffer = this.get('buffer').slice(0,-1) || "";
                this.set({ buffer: newBuffer });
                this.trigger('set_value',this.get('buffer'));
            }
        },
        switchSign: function() {
            console.log('switchsing');
            var oldBuffer;
            oldBuffer = this.get('buffer');
            this.set({
                buffer: oldBuffer[0] === '-' ? oldBuffer.substr(1) : "-" + oldBuffer 
            });
            this.trigger('set_value',this.get('buffer'));
        },
        changeMode: function(newMode) {
            this.set({
                buffer: "0",
                mode: newMode
            });
        },
        reset: function() {
            this.set({
                buffer: "0",
                mode: "quantity"
            });
        },
        resetValue: function(){
            this.set({buffer:'0'});
        },
    });
}