(url, link_text)

        '''

        self._title = title

        self._links = links

    def title(self):

        return self._title

    def headings(self):

        return []

    def rows(self, content_type):

        print self._links

        for url, link_text in self._links:

            yield [

                self._linked_text(content_type, url, link_text)

            ]

def report_view(title, form_type=None):

    ''' Decorator that converts a report view function into something that

    displays a Report.

    Arguments:

        title (str):

            The title of the report.

        form_type (Optional[forms.Form]):

            A form class that can make this report display things. If not

            supplied, no form will be displayed.

    '''

    # Create & return view

    def _report(view):

        report_view = ReportView(view, title, form_type)

        report_view = user_passes_test(views._staff_only)(report_view)

        report_view = wraps(view)(report_view)

        # Add this report to the list of reports.

        _all_report_views.append(report_view)

        return report_view

    return _report

class ReportView(object):

    def __init__(self, inner_view, title, form_type):

        # Consolidate form_type so it has content type and section

        self.inner_view = inner_view

        self.title = title

        self.form_type = form_type

    def __call__(self, request, *a, **k):

        data = ReportViewRequestData(self, request, *a, **k)

        return self.render(data)

    def get_form(self, request):

        # Create a form instance

        if self.form_type is not None:

            form = self.form_type(request.GET)

            # Pre-validate it

            form.is_valid()

        else:

            form = None

        return form

    @classmethod

    def wrap_reports(cls, reports, content_type):

        reports = [

            _ReportTemplateWrapper(content_type, report)

            for report in reports

        ]

        return reports

    def render(self, data):

        renderers = {

            "text/csv": self._render_as_csv,

            "text/html": self._render_as_html,

            None: self._render_as_html,

        }

        render = renderers[data.content_type]

        return render(data)

    def _render_as_html(self, data):

        ctx = {

            "title": self.title,

            "form": data.form,

            "reports": data.reports,

        }

        return render(data.request, "registrasion/report.html", ctx)

    def _render_as_csv(self, data):

        report = data.reports[data.section]

        # Create the HttpResponse object with the appropriate CSV header.

        response = HttpResponse(content_type='text/csv')

        writer = csv.writer(response)

        encode = lambda i: i.encode("utf8") if isinstance(i, unicode) else i

        writer.writerow(list(encode(i) for i in report.headings()))

        for row in report.rows():

            writer.writerow(list(encode(i) for i in row))

        return response

class ReportViewRequestData(object):

    def __init__(self, report_view, request, *a, **k):

        self.report_view = report_view

        self.request = request

        # Calculate other data

        self.form = report_view.get_form(request)

        # Content type and section come from request.GET

        self.content_type = request.GET.get("content_type")

        self.section = request.GET.get("section")

        self.section = int(self.section) if self.section else None

        # Reports come from calling the inner view

        reports = report_view.inner_view(request, self.form, *a, **k)

        # Normalise to a list

        if isinstance(reports, Report):

            reports = [reports]

        # Wrap them in appropriate format

        reports = ReportView.wrap_reports(reports, self.content_type)

        self.reports = reports

def get_all_reports():

    ''' Returns all the views that have been registered with @report '''

    return list(_all_report_views)

def discount_status(request, form):

    ''' Summarises the usage of a given discount. '''

    discounts = form.cleaned_data["discount"]

    items = commerce.DiscountItem.objects.filter(

        Q(discount__in=discounts),

    ).select_related("cart", "product", "product__category")

    items = group_by_cart_status(

        items,

        ["discount",],

        ["discount", "discount__description",],

    )

    headings = [

        "Discount", "Paid", "Reserved", "Unreserved", "Refunded",

    ]

    data = []

    for item in items:

        data.append([

            item["discount__description"],

            item["total_paid"],

            item["total_reserved"],

            item["total_unreserved"],

            item["total_refunded"],

        ])

    return ListReport("Usage by item", headings, data)

@report_view("Paid invoices by date", form_type=forms.ProductAndCategoryForm)

def paid_invoices_by_date(request, form):

    ''' Shows the number of paid invoices containing given products or

    categories per day. '''

    products = form.cleaned_data["product"]

    categories = form.cleaned_data["category"]

    invoices = commerce.Invoice.objects.filter(

        (

            Q(lineitem__product__in=products) |

            Q(lineitem__product__category__in=categories)

        ),

        status=commerce.Invoice.STATUS_PAID,

    )

    # Invoices with payments will be paid at the time of their latest payment

    payments = commerce.PaymentBase.objects.all()

    payments = payments.filter(

        invoice__in=invoices,

    )

    payments = payments.order_by("invoice")

    invoice_max_time = payments.values("invoice").annotate(

        max_time=Max("time")

    )

    # Zero-value invoices will have no payments, so they're paid at issue time

    zero_value_invoices = invoices.filter(value=0)

    times = itertools.chain(

        (line["max_time"] for line in invoice_max_time),

        (invoice.issue_time for invoice in zero_value_invoices),

    )

    by_date = collections.defaultdict(int)

    for time in times:

        date = datetime.datetime(

            year=time.year, month=time.month, day=time.day

        )

        by_date[date] += 1

    data = [(date, count) for date, count in sorted(by_date.items())]

    data = [(date.strftime("%Y-%m-%d"), count) for date, count in data]

    return ListReport(

        "Paid Invoices By Date",

        ["date", "count"],

        data,

    )

@report_view("Credit notes")

def credit_notes(request, form):

    ''' Shows all of the credit notes in the system. '''

    notes = commerce.CreditNote.objects.all().select_related(

        "creditnoterefund",

        "creditnoteapplication",

        "invoice",

        "invoice__user__attendee__attendeeprofilebase",

    )

    return QuerysetReport(

        "Credit Notes",

        ["id", "invoice__user__attendee__attendeeprofilebase__invoice_recipient", "status", "value"],  # NOQA

        notes,

        headings=["id", "Owner", "Status", "Value"],

        link_view=views.credit_note,

    )

@report_view("Invoices")

def invoices(request,form):

    ''' Shows all of the invoices in the system. '''

    invoices = commerce.Invoice.objects.all().order_by("status")

    return QuerysetReport(

        "Invoices",

        ["id", "recipient", "value", "get_status_display"],

        invoices,

        headings=["id", "Recipient", "Value", "Status"],

        link_view=views.invoice,

    )

class AttendeeListReport(ListReport):

    def get_link(self, argument):

        return reverse(self._link_view) + "?user=%d" % int(argument)

@report_view("Attendee", form_type=forms.UserIdForm)

def attendee(request, form, user_id=None):

    ''' Returns a list of all manifested attendees if no attendee is specified,

    else displays the attendee manifest. '''

    if user_id is None:

        return attendee_list(request)

    attendee = people.Attendee.objects.get(user__id=user_id)

    name = attendee.attendeeprofilebase.attendee_name()

    reports = []

    profile_data = []

    try:

        profile = people.AttendeeProfileBase.objects.get_subclass(

            attendee=attendee

        )

        fields = profile._meta.get_fields()

    except people.AttendeeProfileBase.DoesNotExist:

        fields = []

    exclude = set(["attendeeprofilebase_ptr", "id"])

    for field in fields:

        if field.name in exclude:

            # Not actually important

            continue

        if not hasattr(field, "verbose_name"):

            continue  # Not a publicly visible field

        value = getattr(profile, field.name)

        if isinstance(field, models.ManyToManyField):

            value = ", ".join(str(i) for i in value.all())

        profile_data.append((field.verbose_name, value))

    cart = CartController.for_user(attendee.user)

    reservation = cart.cart.reservation_duration + cart.cart.time_last_updated

    profile_data.append(("Current cart reserved until", reservation))

    reports.append(ListReport("Profile", ["", ""], profile_data))

    links = []

    links.append((

        reverse(views.amend_registration, args=[user_id]),

        "Amend current cart",

    ))

    links.append((

        reverse(views.extend_reservation, args=[user_id]),

        "Extend reservation",

    ))

    reports.append(Links("Actions for " + name, links))

    # Paid and pending  products

    ic = ItemController(attendee.user)

    reports.append(ListReport(

        "Paid Products",

        ["Product", "Quantity"],

        [(pq.product, pq.quantity) for pq in ic.items_purchased()],

    ))

    reports.append(ListReport(

        "Unpaid Products",

        ["Product", "Quantity"],

        [(pq.product, pq.quantity) for pq in ic.items_pending()],

    ))

    # Invoices

    invoices = commerce.Invoice.objects.filter(

        user=attendee.user,

    )

    reports.append(QuerysetReport(

        "Invoices",

        ["id", "get_status_display", "value"],

        invoices,

        headings=["Invoice ID", "Status", "Value"],

        link_view=views.invoice,

    ))

    # Credit Notes

    credit_notes = commerce.CreditNote.objects.filter(

        invoice__user=attendee.user,

    ).select_related("invoice", "creditnoteapplication", "creditnoterefund")

    reports.append(QuerysetReport(

        "Credit Notes",

        ["id", "status", "value"],

        credit_notes,

        link_view=views.credit_note,

    ))

    # All payments

    payments = commerce.PaymentBase.objects.filter(

        invoice__user=attendee.user,

    ).select_related("invoice")

    reports.append(QuerysetReport(

        "Payments",

        ["invoice__id", "id", "reference", "amount"],

        payments,

        link_view=views.invoice,

    ))

    return reports

def attendee_list(request):

    ''' Returns a list of all attendees. '''

    attendees = people.Attendee.objects.select_related(

        "attendeeprofilebase",

        "user",

    )

    profiles = AttendeeProfile.objects.filter(

        attendee__in=attendees

    ).select_related(

        "attendee", "attendee__user",

    )

    profiles_by_attendee = dict((i.attendee, i) for i in profiles)

    attendees = attendees.annotate(

        has_registered=Count(

            Q(user__invoice__status=commerce.Invoice.STATUS_PAID)

        ),

    )

    headings = [

        "User ID", "Name", "Email", "Has registered",

    ]

    data = []

    for a in attendees:

        data.append([