# Copyright (C) 2001-2006 Python Software Foundation
# Author: Barry Warsaw
# Contact: email-sig@python.org

"""Various types of useful iterators and generators."""

__all__ = [
 'body_line_iterator',
 'typed_subpart_iterator',
 'walk',
 # Do not include _structure() since it's part of the debugging API.
 ]

import sys
from io import StringIO



# This function will become a method of the Message class
def walk(self):
 """Walk over the message tree, yielding each subpart.

 The walk is performed in depth-first order. This method is a
 generator.
 """
 yield self
 if self.is_multipart():
 for subpart in self.get_payload():
 yield from subpart.walk()



# These two functions are imported into the Iterators.py interface module.
def body_line_iterator(msg, decode=False):
 """Iterate over the parts, returning string payloads line-by-line.

 Optional decode (default False) is passed through to .get_payload().
 """
 for subpart in msg.walk():
 payload = subpart.get_payload(decode=decode)
 if isinstance(payload, str):
 yield from StringIO(payload)


def typed_subpart_iterator(msg, maintype='text', subtype=None):
 """Iterate over the subparts with a given MIME type.

 Use `maintype' as the main MIME type to match against; this defaults to
 "text". Optional `subtype' is the MIME subtype to match against; if
 omitted, only the main type is matched.
 """
 for subpart in msg.walk():
 if subpart.get_content_maintype() == maintype:
 if subtype is None or subpart.get_content_subtype() == subtype:
 yield subpart



def _structure(msg, fp=None, level=0, include_default=False):
 """A handy debugging aid"""
 if fp is None:
 fp = sys.stdout
 tab = ' ' * (level * 4)
 print(tab + msg.get_content_type(), end='', file=fp)
 if include_default:
 print(' [%s]' % msg.get_default_type(), file=fp)
 else:
 print(file=fp)
 if msg.is_multipart():
 for subpart in msg.get_payload():
 _structure(subpart, fp, level+1, include_default)