"""
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.http import QueryDict
from django.http.multipartparser import MultiPartParser as DjangoMultiPartParser
from django.http.multipartparser import MultiPartParserError
from rest_framework.compat import yaml, etree
from rest_framework.exceptions import ParseError
from rest_framework.compat import six
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'

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Returns a 2-tuple of `(data, files)`.

        `data` will be an object which is the parsed content of the response.
        `files` will always be `None`.
        """
        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):
        """
        Returns a 2-tuple of `(data, files)`.

        `data` will be an object which is the parsed content of the response.
        `files` will always be `None`.
        """
        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.u(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):
        """
        Returns a 2-tuple of `(data, files)`.

        `data` will be a :class:`QueryDict` containing all the form parameters.
        `files` will always be :const:`None`.
        """
        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):
        """
        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
        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' % six.u(exc))


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

    media_type = 'application/xml'

    def parse(self, stream, media_type=None, parser_context=None):
        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.u(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