prolog-point-of-sale/views/products.pl

:- http_handler(root(.), products_view(Method), [method(Method), methods([get, post])]).
:- http_handler(root('style.css'), http_reply_file('style.css', []), []).

price_str(Price, PriceStr) :-
    Euro is Price / 100,
    format(atom(PriceStr), '€ ~2f', Euro).

products_add -->
    {http_session_data(user(_))}, !,  % Check if we're logged in
    html(
        div([
            h2('Add product'),
            form([method=post], [
                div([
                    label(for=name, 'Name'),
                    input([
                        type=text,
                        placeholder='Name',
                        name=name,
                        id=name,
                        required
                    ])
                ]),

                div([
                    label(for=price, 'Price'),
                    input([
                        type=text,
                        placeholder='Price',
                        name=price,
                        id=price,
                        required
                    ])
                ]),

                div(input(type=submit))
            ])
        ])
    ).
products_add --> [].  % If not, do not show

products_list([]) --> [].
products_list([product(Name, Price)|Products]) -->
    {price_str(Price, PriceStr)},
    html([
        a([
            class(product),
            'data-name'(Name),
            href('/cart/add/'+Name)
        ], [
            div(class(product__name), [Name]),
            div(class(product__price), [PriceStr])
        ])
    ]),
    products_list(Products).

cart([]) --> [].
cart([Name|Items]) -->
    {
        product(Name, Cents),
        price_str(Cents, Price)
    },
    html([
        div(class(cart__entry), [
            div(class(cart__name), Name),
            div(class(cart__price), Price)
        ])
    ]),
    cart(Items).

account -->
    {http_session_data(user(Username))}, !,
    html([
        div(['Hello ', Username, '!']),
        a(href('/logout'), 'Log out')
    ]).
account -->
    html(a(href('/login'), 'Log in')).

products_view(get, _Request) :-
    http_session_id(SessionId),
    (bagof(product(X, Y), product(X, Y), Products); Products = []),
    (bagof(Name, cart_entry(SessionId, Name), CartEntries); CartEntries = []),
    reply_html_page(
        [
            title('point of shit'),
            link([
                type('text/css'),
                rel('stylesheet'),
                href('style.css')
            ])
        ],
        [
            h1('Products'),
            main([
                div(class(products), \products_list(Products)),
                div(class(cart), \cart(CartEntries))
            ]),
            \products_add,
            h2('Account'),
            \account
        ]
    ).

products_view(post, Request) :-
    % Check if we're logged in
    \+ http_session_data(user(_)), !,
    http_session_assert(reason('You need to be logged in to do this.')),
    http_redirect(see_other, root(login), Request).

products_view(post, Request) :-
    http_read_data(Request, [name=Name, price=Price], []),
    atom_number(Price, PriceNumber),
    Cents is round(PriceNumber * 100),
    retractall_product(Name, _),
    assert_product(Name, Cents),
    http_redirect(see_other, root(.), Request).