parsers.py

"""
Parsers are used to parse the content of incoming HTTP requests.

They give us a generic way of being able to handle various media types
on the request, such as form content or json encoded data.
"""
from __future__ import unicode_literals
from django.conf import settings
from django.core.files.uploadhandler import StopFutureHandlers
from django.http import QueryDict
from django.http.multipartparser import MultiPartParser as DjangoMultiPartParser
from django.http.multipartparser import MultiPartParserError, parse_header, ChunkIter
from rest_framework.compat import etree, six, yaml
from rest_framework.exceptions import ParseError
from rest_framework import renderers
import json
import datetime
import decimal


class DataAndFiles(object):
    def __init__(self, data, files):
        self.data = data
        self.files = files


class BaseParser(object):
    """
    All parsers should extend `BaseParser`, specifying a `media_type`
    attribute, and overriding the `.parse()` method.
    """

    media_type = None

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Given a stream to read from, return the parsed representation.
        Should return parsed data, or a `DataAndFiles` object consisting of the
        parsed data and files.
        """
        raise NotImplementedError(".parse() must be overridden.")


class JSONParser(BaseParser):
    """
    Parses JSON-serialized data.
    """

    media_type = 'application/json'
    renderer_class = renderers.UnicodeJSONRenderer

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Parses the incoming bytestream as JSON and returns the resulting data.
        """
        parser_context = parser_context or {}
        encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)

        try:
            data = stream.read().decode(encoding)
            return json.loads(data)
        except ValueError as exc:
            raise ParseError('JSON parse error - %s' % six.text_type(exc))


class YAMLParser(BaseParser):
    """
    Parses YAML-serialized data.
    """

    media_type = 'application/yaml'

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Parses the incoming bytestream as YAML and returns the resulting data.
        """
        assert yaml, 'YAMLParser requires pyyaml to be installed'

        parser_context = parser_context or {}
        encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)

        try:
            data = stream.read().decode(encoding)
            return yaml.safe_load(data)
        except (ValueError, yaml.parser.ParserError) as exc:
            raise ParseError('YAML parse error - %s' % six.text_type(exc))


class FormParser(BaseParser):
    """
    Parser for form data.
    """

    media_type = 'application/x-www-form-urlencoded'

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Parses the incoming bytestream as a URL encoded form,
        and returns the resulting QueryDict.
        """
        parser_context = parser_context or {}
        encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
        data = QueryDict(stream.read(), encoding=encoding)
        return data


class MultiPartParser(BaseParser):
    """
    Parser for multipart form data, which may include file data.
    """

    media_type = 'multipart/form-data'

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Parses the incoming bytestream as a multipart encoded form,
        and returns a DataAndFiles object.

        `.data` will be a `QueryDict` containing all the form parameters.
        `.files` will be a `QueryDict` containing all the form files.
        """
        parser_context = parser_context or {}
        request = parser_context['request']
        encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
        meta = request.META.copy()
        meta['CONTENT_TYPE'] = media_type
        upload_handlers = request.upload_handlers

        try:
            parser = DjangoMultiPartParser(meta, stream, upload_handlers, encoding)
            data, files = parser.parse()
            return DataAndFiles(data, files)
        except MultiPartParserError as exc:
            raise ParseError('Multipart form parse error - %s' % str(exc))


class XMLParser(BaseParser):
    """
    XML parser.
    """

    media_type = 'application/xml'

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Parses the incoming bytestream as XML and returns the resulting data.
        """
        assert etree, 'XMLParser requires defusedxml to be installed'

        parser_context = parser_context or {}
        encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
        parser = etree.DefusedXMLParser(encoding=encoding)
        try:
            tree = etree.parse(stream, parser=parser, forbid_dtd=True)
        except (etree.ParseError, ValueError) as exc:
            raise ParseError('XML parse error - %s' % six.text_type(exc))
        data = self._xml_convert(tree.getroot())

        return data

    def _xml_convert(self, element):
        """
        convert the xml `element` into the corresponding python object
        """

        children = list(element)

        if len(children) == 0:
            return self._type_convert(element.text)
        else:
            # if the fist child tag is list-item means all children are list-item
            if children[0].tag == "list-item":
                data = []
                for child in children:
                    data.append(self._xml_convert(child))
            else:
                data = {}
                for child in children:
                    data[child.tag] = self._xml_convert(child)

            return data

    def _type_convert(self, value):
        """
        Converts the value returned by the XMl parse into the equivalent
        Python type
        """
        if value is None:
            return value

        try:
            return datetime.datetime.strptime(value, '%Y-%m-%d %H:%M:%S')
        except ValueError:
            pass

        try:
            return int(value)
        except ValueError:
            pass

        try:
            return decimal.Decimal(value)
        except decimal.InvalidOperation:
            pass

        return value


class FileUploadParser(BaseParser):
    """
    Parser for file upload data.
    """
    media_type = '*/*'

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Treats the incoming bytestream as a raw file upload and returns
        a `DateAndFiles` object.

        `.data` will be None (we expect request body to be a file content).
        `.files` will be a `QueryDict` containing one 'file' element.
        """

        parser_context = parser_context or {}
        request = parser_context['request']
        encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
        meta = request.META
        upload_handlers = request.upload_handlers
        filename = self.get_filename(stream, media_type, parser_context)

        # Note that this code is extracted from Django's handling of
        # file uploads in MultiPartParser.
        content_type = meta.get('HTTP_CONTENT_TYPE',
                                meta.get('CONTENT_TYPE', ''))
        try:
            content_length = int(meta.get('HTTP_CONTENT_LENGTH',
                                          meta.get('CONTENT_LENGTH', 0)))
        except (ValueError, TypeError):
            content_length = None

        # See if the handler will want to take care of the parsing.
        for handler in upload_handlers:
            result = handler.handle_raw_input(None,
                                              meta,
                                              content_length,
                                              None,
                                              encoding)
            if result is not None:
                return DataAndFiles(None, {'file': result[1]})

        # This is the standard case.
        possible_sizes = [x.chunk_size for x in upload_handlers if x.chunk_size]
        chunk_size = min([2 ** 31 - 4] + possible_sizes)
        chunks = ChunkIter(stream, chunk_size)
        counters = [0] * len(upload_handlers)

        for handler in upload_handlers:
            try:
                handler.new_file(None, filename, content_type,
                                 content_length, encoding)
            except StopFutureHandlers:
                break

        for chunk in chunks:
            for i, handler in enumerate(upload_handlers):
                chunk_length = len(chunk)
                chunk = handler.receive_data_chunk(chunk, counters[i])
                counters[i] += chunk_length
                if chunk is None:
                    break

        for i, handler in enumerate(upload_handlers):
            file_obj = handler.file_complete(counters[i])
            if file_obj:
                return DataAndFiles(None, {'file': file_obj})
        raise ParseError("FileUpload parse error - "
                         "none of upload handlers can handle the stream")

    def get_filename(self, stream, media_type, parser_context):
        """
        Detects the uploaded file name. First searches a 'filename' url kwarg.
        Then tries to parse Content-Disposition header.
        """
        try:
            return parser_context['kwargs']['filename']
        except KeyError:
            pass

        try:
            meta = parser_context['request'].META
            disposition = parse_header(meta['HTTP_CONTENT_DISPOSITION'])
            return disposition[1]['filename']
        except (AttributeError, KeyError):
            pass