Shared (inherited) clean_FOO methods for common message fields

[hugorodgerbrown]

Each backend service has a unique implementation that extracts the relevant data as part of their implementation of the parse method. In reality, although each backend is unique, they are all extracting strings from an HTTP request object, and there are some shared rules around how to treat this data - e.g. the various email RFCs.

Proposed solution is to have a set of clean_FOO methods in the base RequestParser class that the the implementation can call that implement these basic rules.

e.g.

import email

class RequestParser()
    def clean_to(self, value):
        """Parse string and return list of (name, <address>) tuples."""
        return email.utils.getaddresses(value)

    def parse(self, request):
        raise NotImplementedError(u"Must be implemented by inheriting class.")

# and in the implementation
class MyRequestParser(RequestParser):
    def parse(self, request):
        to = self.clean_to(request.POST.get('recipient')
        [...]

Suggested methods:

• clean_sender - parse email address
• clean_recipients - parse email addresses
• clean_html_message - parse HTML, mark safe,
• clean_txt_message - parse text, convert to UTF-8 encoded unicode
• clean_subject - parse subject, convert to UTF-8 encoded unicode
• clean_cc_recipients - parse email addresses
• clean_bcc_recipients - parse email addresses
• clean_attachments - handle file type restrictions, max/min sizes etc.