import re
from urllib.request import urlopen, Request
import os
import mimetypes
import mimetools

def get_content_type(filepath):
    return mimetypes.guess_type(filepath)[0] or 'application/octet-stream'

def encode_multipart_formdata(fields, files=[]):
    """
    fields is a sequence of (name, value) elements for regular form fields.
    files is a sequence of (name, filepath) elements for data to be uploaded as files
    Return (content_type, body) ready for httplib.HTTP instance
    """
    BOUNDARY = mimetools.choose_boundary()
    CRLF = 'rn'
    L = []
    for (key, value) in fields:
        L.append('--' + BOUNDARY)
        L.append('Content-Disposition: form-data; name="%s"' % key)
        L.append('')
        L.append(value)
    for (key, filepath) in files:
        L.append('--' + BOUNDARY)
        L.append('Content-Disposition: form-data; name="%s"; filename="%s"' % (key, os.path.basename(filepath)))
        L.append('Content-Type: %s' % get_content_type(filepath))
        L.append('')
        L.append(open(filepath, 'rb').read())
    L.append('--' + BOUNDARY + '--')
    L.append('')
    body = CRLF.join(L)
    content_type = 'multipart/form-data; boundary=%s' % BOUNDARY
    return content_type, body