Add a plugin API for ticket outputs

src/pretix/base/ticketoutput.py

@@ -0,0 +1,116 @@
+from collections import OrderedDict
+from django import forms
+
+from django.http import HttpRequest, HttpResponse
+from django.utils.translation import ugettext_lazy as _
+from pretix.base.forms import SettingsForm
+from pretix.base.models import Order
+
+from pretix.base.settings import SettingsSandbox
+
+
+class BaseTicketOutput:
+    """
+    This is the base class for all ticket outputs.
+    """
+
+    def __init__(self, event):
+        self.event = event
+        self.settings = SettingsSandbox('ticketoutput', self.identifier, event)
+
+    def __str__(self):
+        return self.identifier
+
+    @property
+    def is_enabled(self) -> bool:
+        """
+        Returns, whether or whether not this output is enabled.
+        By default, this is determined by the value of the ``_enabled`` setting.
+        """
+        return self.settings.get('_enabled', as_type=bool)
+
+    def generate(self, request: HttpRequest, order: Order) -> HttpResponse:
+        """
+        This method should generate the download file and return it to the user.
+        """
+        raise NotImplementedError()
+
+    @property
+    def verbose_name(self) -> str:
+        """
+        A human-readable name for this ticket output. This should
+        be short but self-explaining. Good examples include 'PDF tickets'
+        and 'Passbook'.
+        """
+        raise NotImplementedError()  # NOQA
+
+    @property
+    def identifier(self) -> str:
+        """
+        A short and unique identifier for this ticket output.
+        This should only contain lowercase letters and in most
+        cases will be the same as your packagename.
+        """
+        raise NotImplementedError()  # NOQA
+
+    @property
+    def settings_form_fields(self) -> dict:
+        """
+        When the event's administrator administrator visits the event configuration
+        page, this method is called to return the configuration fields available.
+
+        It should therefore return a dictionary where the keys should be (unprefixed)
+        settings keys and the values should be corresponding Django form fields.
+
+        The default implementation returns the appropriate fields for the ``_enabled``
+        setting mentioned above.
+
+        We suggest that you return an ``OrderedDict`` object instead of a dictionary
+        and make use of the default implementation. Your implementation could look
+        like this::
+
+            @property
+            def settings_form_fields(self):
+                return OrderedDict(
+                    list(super().settings_form_fields.items()) + [
+                        ('paper_size',
+                         forms.CharField(
+                             label=_('Paper size'),
+                             required=False
+                         ))
+                    ]
+                )
+
+        .. WARNING:: It is highly discouraged to alter the ``_enabled`` field of the default
+                     implementation.
+        """
+        return OrderedDict([
+            ('_enabled',
+             forms.ChoiceField(
+                 label=_('Enable output'),
+                 required=False,
+                 choices=SettingsForm.BOOL_CHOICES,
+             )),
+        ])
+
+    def settings_content_render(self, request: HttpRequest) -> str:
+        """
+        When the event's administrator administrator visits the event configuration
+        page, this method is called. It may return HTML containing additional information
+        that is displayed below the form fields configured in ``settings_form_fields``.
+        """
+        pass
+
+    @property
+    def download_button_text(self) -> str:
+        """
+        The text on the download button in the frontend.
+        """
+        return _('Download ticket')
+
+    @property
+    def download_button_icon(self) -> str:
+        """
+        The name of the icon on the download button in the frontend
+        """
+        return None