Sketch of Borrow Library Items use case in trygve

borrow_library_items.k

context BorrowLibraryItems
{
    //Using init() method for initialization rather than constructor.
    //See https://github.com/jcoplien/trygve/issues/69
    //
    public BorrowLibraryItems init(User borrower, ItemRecordRepository itemRecordRepository) {    
        Catalog = itemRecordRepository;
        ItemsToBorrow = new List<ItemRecord>();
        Librarian = this;
        Borrower = borrower;
        
        BorrowLibraryItemsController ctrl = new BorrowLibraryItemsController();
        ctrl.init();
        Controller = ctrl;
    }
    
    //start the use case
    public void start() {
        Controller.renderInitialScreen();
        Librarian.askToBeginScanning();
    }
    
    role Librarian {
        public void askToBeginScanning() {
            Controller.setInstructions("Please begin scanning the items you would like to check out.");
        }
        
        public void askForNextItem() {
            Controller.setInstructions("If you have more item(s) to check out, scan the next item now. " 
                + "If you are done, press the Continue button.");
        }
        
        public void askToConfirmScannedItems() {
            ItemsToBorrow.display();
            Controller.setInstructions("Please verify that these are the items you intend to check out.");
        }
        
        //TODO
        //public void provideReceipt()
    }
    
    stageprop Borrower {
        public void borrowItems() {
            for (int i = 0; i < ItemsToBorrow.size(); i++) {
                new BorrowItem().init(ItemsToBorrow.get(i)).borrow();
            }
            Librarian.provideReceipt();
        }
    }
    requires {
        int id();
    }
    
    stageprop Controller {
        public void renderInitialScreen() const {
            //These are the two views that appear on the first screen
            renderInstructionsView();
            renderItemsToBorrowView(); //note: this list is empty at this point
        }
    
        //Called when the borrower scans an item with the barcode scanner
        public void scanItem(int itemId) const {
            ItemRecord item = Catalog.getItemRecordById(itemId);
            ItemsToBorrow.add(item);
            Librarian.askForNextItem();
        }
        
        //TODO
        //public void removeItem(ItemRecord item)
        
        public void proceedToConfirmation() const {
            Librarian.askToConfirmScannedItems();
        }
        
        //Called after the borrower reviews his/her selections and confirms them
        public void confirmItemsToBorrow() const {
            Borrower.borrowItems();
        }
        
        //TODO
        //public void printReceipt()
        
        public void renderInstructionsView() const {
            instructionsView().render();
        }
        
        public void renderItemsToBorrowView() const {
            itemsToBorrowView().render(ItemsToBorrow);
        }
        
        public void setInstructions(String instructions) const {
            instructionsView().setInstructions(instructions);
            instructionsView().refresh();
        }
        
        public void refreshItemsToBorrowView() const {
            itemsToBorrowView().refresh();
        }
    }
    requires {
        public InstructionsView instructionsView() const;
        public ItemsToBorrowView itemsToBorrowView() const;
        //...
    }
    
    role ItemsToBorrow {
        public void display() {
            Controller.refreshItemsToBorrowView();
        }
    }
    requires {
        int size();
        void add(ItemRecord item);
        void remove(ItemRecord item);
    }
    
    stageprop Catalog {
    	public ItemRecord getItemRecordById(int id) {
    		return getById(id);
    	}
    }
    requires {
        ItemRecord getById(int id) const;
    }
    
    
    ///////////////////
    context BorrowItem {
        public BorrowItem init(ItemRecord item) {
            Item = item;
        }
        
        stageprop Item {} requires {
            int id();
            //Question: should the ItemRecord include a property for the allowed loan duration,
            //or should that be stored somewhere else?
        }
        
        public void borrow() {        
            Loan loan = new Loan(Borrower, Item);
            //TODO validate and save to DB
        }
    }
}

class BorrowLibraryItemsController
{
    private InstructionsView instructionsView_;
    private ItemsToBorrowView itemsToBorrowView_;
    //...

    public void init() {
        instructionsView_ = new InstructionsView(this);
        itemsToBorrowView_ = new ItemsToBorrowView(this);
        //...
    }
    
    public InstructionsView instructionsView() const {return instructionsView_;}
    public ItemsToBorrowView itemsToBorrowView() const {return itemsToBorrowView_;}
    //...
}

class ItemRecordRepository {
    public ItemRecord getById(int id) const {
        //get the library item record from the database and return it
    }
}

class MainController {
    private User currentUser_;

    /*
    public void init() {
        ...
    }

    public boolean authenticate() {
        ...
    }
    */

    public void borrowLibraryItems() {
        new BorrowLibraryItems()
            .init(currentUser_, new ItemRecordRepository())
            .start();
    }
}

{
    MainController controller = new MainController();
    controller.init();
    controller.borrowLibraryItems();
}