# Copyright (C) 2001-2006 Python Software Foundation
# Author: Barry Warsaw
# Contact: [email protected]

"""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)