helper: move mimewrap() to the only place where it is called

1 files changed, 112 insertions, 1 deletions

diff --git a/alot/db/envelope.py b/alot/db/envelope.py
index d5b84b3e..8340ba4e 100644
--- a/alot/db/envelope.py
+++ b/alot/db/envelope.py
@@ -8,6 +8,9 @@ import re
 import email
 import email.policy
 from email.encoders import encode_7or8bit
+from email.mime.audio import MIMEAudio
+from email.mime.base import MIMEBase
+from email.mime.image import MIMEImage
 from email.mime.text import MIMEText
 from email.mime.multipart import MIMEMultipart
 from email.mime.application import MIMEApplication
@@ -15,6 +18,7 @@ import email.charset as charset
 from urllib.parse import unquote
 
 import gpg
+import magic
 
 from .attachment import Attachment
 from .. import __version__
@@ -25,6 +29,113 @@ from ..errors import GPGProblem, GPGCode
 
 charset.add_charset('utf-8', charset.QP, charset.QP, 'utf-8')
 
+def _libmagic_version_at_least(version):
+    """
+    checks if the libmagic library installed is more recent than a given
+    version.
+
+    :param version: minimum version expected in the form XYY (i.e. 5.14 -> 514)
+                    with XYY >= 513
+    """
+    if hasattr(magic, 'open'):
+        magic_wrapper = magic._libraries['magic']
+    elif hasattr(magic, 'from_buffer'):
+        magic_wrapper = magic.libmagic
+    else:
+        raise Exception('Unknown magic API')
+
+    if not hasattr(magic_wrapper, 'magic_version'):
+        # The magic_version function has been introduced in libmagic 5.13,
+        # if it's not present, we can't guess right, so let's assume False
+        return False
+
+    # Depending on the libmagic/ctypes version, magic_version is a function or
+    # a callable:
+    if callable(magic_wrapper.magic_version):
+        return magic_wrapper.magic_version() >= version
+
+    return magic_wrapper.magic_version >= version
+
+def _guess_encoding(blob):
+    """
+    uses file magic to determine the encoding of the given data blob.
+
+    :param blob: file content as read by file.read()
+    :type blob: data
+    :returns: encoding
+    :rtype: str
+    """
+    # this is a bit of a hack to support different versions of python magic.
+    # Hopefully at some point this will no longer be necessary
+    #
+    # the version with open() is the bindings shipped with the file source from
+    # http://darwinsys.com/file/ - this is what is used by the python-magic
+    # package on Debian/Ubuntu.  However it is not available on pypi/via pip.
+    #
+    # the version with from_buffer() is available at
+    # https://github.com/ahupp/python-magic and directly installable via pip.
+    #
+    # for more detail see https://github.com/pazz/alot/pull/588
+    if hasattr(magic, 'open'):
+        m = magic.open(magic.MAGIC_MIME_ENCODING)
+        m.load()
+        return m.buffer(blob)
+    elif hasattr(magic, 'from_buffer'):
+        m = magic.Magic(mime_encoding=True)
+        return m.from_buffer(blob)
+    else:
+        raise Exception('Unknown magic API')
+
+# TODO: make this work on blobs, not paths
+def _mimewrap(path, filename, ctype):
+    """Take the contents of the given path and wrap them into an email MIME
+    part according to the content type.  The content type is auto detected from
+    the actual file contents and the file name if it is not given.
+
+    :param path: the path to the file contents
+    :type path: str
+    :param filename: the file name to use in the generated MIME part
+    :type filename: str or None
+    :param ctype: the content type of the file contents in path
+    :type ctype: str or None
+    :returns: the message MIME part storing the data from path
+    :rtype: subclasses of email.mime.base.MIMEBase
+    """
+
+    with open(path, 'rb') as f:
+        content = f.read()
+    if not ctype:
+        ctype = helper.guess_mimetype(content)
+        # libmagic < 5.12 incorrectly detects excel/powerpoint files as
+        # 'application/msword' (see #179 and #186 in libmagic bugtracker)
+        # This is a workaround, based on file extension, useful as long
+        # as distributions still ship libmagic 5.11.
+        if (ctype == 'application/msword' and
+            not _libmagic_version_at_least(513)):
+            mimetype, _ = mimetypes.guess_type(path)
+            if mimetype:
+                ctype = mimetype
+
+    maintype, subtype = ctype.split('/', 1)
+    if maintype == 'text':
+        part = MIMEText(content.decode(_guess_encoding(content), 'replace'),
+                        _subtype=subtype,
+                        _charset='utf-8')
+    elif maintype == 'image':
+        part = MIMEImage(content, _subtype=subtype)
+    elif maintype == 'audio':
+        part = MIMEAudio(content, _subtype=subtype)
+    else:
+        part = MIMEBase(maintype, subtype)
+        part.set_payload(content)
+        # Encode the payload using Base64
+        email.encoders.encode_base64(part)
+    # Set the filename parameter
+    if not filename:
+        filename = os.path.basename(path)
+    part.add_header('Content-Disposition', 'attachment',
+                    filename=filename)
+    return part
 
 class Envelope:
     """
@@ -170,7 +281,7 @@ class Envelope:
             self.attachments.append(attachment)
         elif isinstance(attachment, str):
             path = os.path.expanduser(attachment)
-            part = helper.mimewrap(path, filename, ctype)
+            part = _mimewrap(path, filename, ctype)
             self.attachments.append(Attachment(part))
         else:
             raise TypeError('attach accepts an Attachment or str')