# -*- coding: utf-8 -*-

'''

Parser for multipart/form-data

==============================

This module provides a parser for the multipart/form-data format. It can read

from a file, a socket or a WSGI environment. The parser can be used to replace

cgi.FieldStorage (without the bugs) and works with Python 2.5+ and 3.x (2to3).

Licence (MIT)

-------------

    Copyright (c) 2010, Marcel Hellkamp.

    Inspired by the Werkzeug library: http://werkzeug.pocoo.org/

    Permission is hereby granted, free of charge, to any person obtaining a copy

    of this software and associated documentation files (the "Software"), to deal

    in the Software without restriction, including without limitation the rights

    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

    copies of the Software, and to permit persons to whom the Software is

    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in

    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

    THE SOFTWARE.

'''

__author__ = 'Marcel Hellkamp'

__version__ = '0.1'

__license__ = 'MIT'

from tempfile import TemporaryFile

from wsgiref.headers import Headers

import re, sys

try:

    from io import BytesIO

except ImportError: # pragma: no cover (fallback for Python 2.5)

    from StringIO import StringIO as BytesIO

##############################################################################

################################ Helper & Misc ################################

##############################################################################

# Some of these were copied from bottle: http://bottle.paws.de/

try:

    from collections import MutableMapping as DictMixin

except ImportError: # pragma: no cover (fallback for Python 2.5)

    from UserDict import DictMixin

class MultiDict(DictMixin):

    """ A dict that remembers old values for each key """

    def __init__(self, *a, **k):

        self.dict = dict()

        for k, v in dict(*a, **k).iteritems():

            self[k] = v

    def __len__(self): return len(self.dict)

    def __iter__(self): return iter(self.dict)

    def __contains__(self, key): return key in self.dict

    def __delitem__(self, key): del self.dict[key]

    def keys(self): return self.dict.keys()

    def __getitem__(self, key): return self.get(key, KeyError, -1)

    def __setitem__(self, key, value): self.append(key, value)

    def append(self, key, value): self.dict.setdefault(key, []).append(value)

    def replace(self, key, value): self.dict[key] = [value]

    def getall(self, key): return self.dict.get(key) or []

    def get(self, key, default=None, index=-1):

        if key not in self.dict and default != KeyError:

            return [default][index]

        return self.dict[key][index]

    def iterallitems(self):

        for key, values in self.dict.iteritems():

            for value in values:

                yield key, value

def tob(data, enc='utf8'): # Convert strings to bytes (py2 and py3)

    return data.encode(enc) if isinstance(data, unicode) else data

def copy_file(stream, target, maxread=-1, buffer_size=2*16):

    ''' Read from :stream and write to :target until :maxread or EOF. '''

    size, read = 0, stream.read

    while 1:

        to_read = buffer_size if maxread < 0 else min(buffer_size, maxread-size)

        part = read(to_read)

        if not part: return size

        target.write(part)

        size += len(part)

##############################################################################

################################ Header Parser ################################

##############################################################################

_special = re.escape('()<>@,;:\\"/[]?={} \t')

_re_special = re.compile('[%s]' % _special)

_qstr = '"(?:\\\\.|[^"])*"' # Quoted string

_value = '(?:[^%s]+|%s)' % (_special, _qstr) # Save or quoted string

_option = '(?:;|^)\s*([^%s]+)\s*=\s*(%s)' % (_special, _value)

_re_option = re.compile(_option) # key=value part of an Content-Type like header

def header_quote(val):

    if not _re_special.search(val):

        return val

    return '"' + val.replace('\\','\\\\').replace('"','\\"') + '"'

def header_unquote(val, filename=False):

    if val[0] == val[-1] == '"':

        val = val[1:-1]

        if val[1:3] == ':\\' or val[:2] == '\\\\': 

            val = val.split('\\')[-1] # fix ie6 bug: full path --> filename

        return val.replace('\\\\','\\').replace('\\"','"')

    return val

def parse_options_header(header, options=None):

    if ';' not in header:

        return header.lower().strip(), {}

    ctype, tail = header.split(';', 1)

    options = options or {}

    for match in _re_option.finditer(tail):

        key = match.group(1).lower()

        value = header_unquote(match.group(2), key=='filename')

        options[key] = value

    return ctype, options

##############################################################################

################################## Multipart ##################################

##############################################################################

class MultipartError(ValueError): pass

class MultipartParser(object):

    def __init__(self, stream, boundary, content_length=-1,

                 disk_limit=2**30, mem_limit=2**20, memfile_limit=2**18,

                 buffer_size=2**16, charset='latin1'):

        ''' Parse a multipart/form-data byte stream. This object is an iterator

            over the parts of the message.

            :param stream: A file-like stream. Must implement ``.read(size)``.

            :param boundary: The multipart boundary as a byte string.

            :param content_length: The maximum number of bytes to read.

        '''

        self.stream, self.boundary = stream, boundary

        self.content_length = content_length

        self.disk_limit = disk_limit

        self.memfile_limit = memfile_limit

        self.mem_limit = min(mem_limit, self.disk_limit)

        self.buffer_size = min(buffer_size, self.mem_limit)

        self.charset = charset

        if self.buffer_size - 6 < len(boundary): # "--boundary--\r\n"

            raise MultipartError('Boundary does not fit into buffer_size.')

        self._done = []

        self._part_iter = None

    def __iter__(self):

        ''' Iterate over the parts of the multipart message. '''

        if not self._part_iter:

            self._part_iter = self._iterparse()

        for part in self._done:

            yield part

        for part in self._part_iter:

            self._done.append(part)

            yield part

    def parts(self):

        ''' Returns a list with all parts of the multipart message. '''

        return list(iter(self))

    def get(self, name, default=None):

        ''' Return the first part with that name or a default value (None). '''

        for part in self:

            if name == part.name:

                return part

        return default

    def get_all(self, name):

        ''' Return a list of parts with that name. '''

        return [p for p in self if p.name == name]

    def _lineiter(self):

        ''' Iterate over a binary file-like object line by line. Each line is

            returned as a (line, line_ending) tuple. If the line does not fit

            into self.buffer_size, line_ending is empty and the rest of the line

            is returned with the next iteration.

        '''

        read = self.stream.read

        maxread, maxbuf = self.content_length, self.buffer_size

        _bcrnl = tob('\r\n')

        _bcr = _bcrnl[:1]

        _bnl = _bcrnl[1:]

        _bempty = _bcrnl[:0] # b'rn'[:0] -> b''

        buffer = _bempty # buffer for the last (partial) line

        while 1:

            data = read(maxbuf if maxread < 0 else min(maxbuf, maxread))

            maxread -= len(data)

            lines = (buffer+data).splitlines(True)

            len_first_line = len(lines[0])

            # be sure that the first line does not become too big

            if len_first_line > self.buffer_size:

                # at the same time don't split a '\r\n' accidentally

                if (len_first_line == self.buffer_size+1 and

                    lines[0].endswith(_bcrnl)):

                    splitpos = self.buffer_size - 1

                else:

                    splitpos = self.buffer_size

                lines[:1] = [lines[0][:splitpos],

                             lines[0][splitpos:]]

            if data:

                buffer = lines[-1]

                lines = lines[:-1]

            for line in lines:

                if line.endswith(_bcrnl): yield line[:-2], _bcrnl

                elif line.endswith(_bnl): yield line[:-1], _bnl

                elif line.endswith(_bcr): yield line[:-1], _bcr

                else:                     yield line, _bempty

            if not data:

                break

    def _iterparse(self):

        lines, line = self._lineiter(), ''

        separator = tob('--') + tob(self.boundary)

        terminator = tob('--') + tob(self.boundary) + tob('--')

        # Consume first boundary. Ignore leading blank lines

        for line, nl in lines:

            if line: break

        if line != separator:

            raise MultipartError("Stream does not start with boundary")

        # For each part in stream...

        mem_used, disk_used = 0, 0 # Track used resources to prevent DoS

        is_tail = False # True if the last line was incomplete (cutted)

        opts = {'buffer_size': self.buffer_size,

                'memfile_limit': self.memfile_limit,

                'charset': self.charset}

        part = MultipartPart(**opts)

        for line, nl in lines:

            if line == terminator and not is_tail:

                part.file.seek(0)

                yield part

                break

            elif line == separator and not is_tail:

                if part.is_buffered(): mem_used  += part.size

                else:                  disk_used += part.size

                part.file.seek(0)

                yield part

                part = MultipartPart(**opts)

            else:

                is_tail = not nl # The next line continues this one

                part.feed(line, nl)

                if part.is_buffered():

                    if part.size + mem_used > self.mem_limit:

                        raise MultipartError("Memory limit reached.")

                elif part.size + disk_used > self.disk_limit:

                    raise MultipartError("Disk limit reached.")

        if line != terminator:

            raise MultipartError("Unexpected end of multipart stream.")

class MultipartPart(object):

    def __init__(self, buffer_size=2**16, memfile_limit=2**18, charset='latin1'):

        self.headerlist = []

        self.headers = None

        self.file = False

        self.size = 0

        self._buf = tob('')

        self.disposition, self.name, self.filename = None, None, None

        self.content_type, self.charset = None, charset

        self.memfile_limit = memfile_limit

        self.buffer_size = buffer_size

    def feed(self, line, nl=''):

        if self.file:

            return self.write_body(line, nl)

        return self.write_header(line, nl)

    def write_header(self, line, nl):

        line = line.decode(self.charset or 'latin1')

        if not nl: raise MultipartError('Unexpected end of line in header.')

        if not line.strip(): # blank line -> end of header segment

            self.finish_header()

        elif line[0] in ' \t' and self.headerlist:

            name, value = self.headerlist.pop()

            self.headerlist.append((name, value+line.strip()))

        else:

            if ':' not in line:

                raise MultipartError("Syntax error in header: No colon.")

            name, value = line.split(':', 1)

            self.headerlist.append((name.strip(), value.strip()))

    def write_body(self, line, nl):

        if not line and not nl: return # This does not even flush the buffer

        self.size += len(line) + len(self._buf)

        self.file.write(self._buf + line)

        self._buf = nl

        if self.content_length > 0 and self.size > self.content_length:

            raise MultipartError('Size of body exceeds Content-Length header.')

        if self.size > self.memfile_limit and isinstance(self.file, BytesIO):

            # TODO: What about non-file uploads that exceed the memfile_limit?

            self.file, old = TemporaryFile(mode='w+b'), self.file

            old.seek(0)

            copy_file(old, self.file, self.size, self.buffer_size)

    def finish_header(self):

        self.file = BytesIO()

        self.headers = Headers(self.headerlist)

        cdis = self.headers.get('Content-Disposition','')

        ctype = self.headers.get('Content-Type','')

        clen = self.headers.get('Content-Length','-1')

        if not cdis:

            raise MultipartError('Content-Disposition header is missing.')

        self.disposition, self.options = parse_options_header(cdis)

        self.name = self.options.get('name')

        self.filename = self.options.get('filename')

        self.content_type, options = parse_options_header(ctype)

        self.charset = options.get('charset') or self.charset

        self.content_length = int(self.headers.get('Content-Length','-1'))

    def is_buffered(self):

        ''' Return true if the data is fully buffered in memory.'''

        return isinstance(self.file, BytesIO)

    @property

    def value(self):

        ''' Data decoded with the specified charset '''

        pos = self.file.tell()

        self.file.seek(0)

        val = self.file.read()

        self.file.seek(pos)

        return val.decode(self.charset)

    def save_as(self, path):

        fp = open(path, 'wb')

        pos = self.file.tell()

        try:

            self.file.seek(0)

            size = copy_file(self.file, fp)

        finally:

            self.file.seek(pos)

        return size

##############################################################################

#################################### WSGI ####################################

##############################################################################

def parse_form_data(environ, charset='utf8', strict=False, **kw):

    ''' Parse form data from an environ dict and return a (forms, files) tuple.

        Both tuple values are dictionaries with the form-field name as a key

        (unicode) and lists as values (multiple values per key are possible).

        The forms-dictionary contains form-field values as unicode strings.

        The files-dictionary contains :class:`MultipartPart` instances, either

        because the form-field was a file-upload or the value is to big to fit

        into memory limits.

        :param environ: An WSGI environment dict.

        :param charset: The charset to use if unsure. (default: utf8)

        :param strict: If True, raise :exc:`MultipartError` on any parsing

                       errors. These are silently ignored by default.

    '''

    forms, files = MultiDict(), MultiDict()

    try:

        if environ.get('REQUEST_METHOD','GET').upper() not in ('POST', 'PUT'):

            raise MultipartError("Request method other than POST or PUT.")

        content_length = int(environ.get('CONTENT_LENGTH', '-1'))

        content_type = environ.get('CONTENT_TYPE', '')

        if not content_type:

            raise MultipartError("Missing Content-Type header.")