import yaml

from rest_framework.compat import coreapi, urlparse
from rest_framework.schemas import SchemaGenerator
from rest_framework_swagger import renderers
from rest_framework.response import Response
from rest_framework.views import APIView
from rest_framework import exceptions
from rest_framework.permissions import AllowAny


class CustomSchemaGenerator(SchemaGenerator):
    def get_link(self, path, method, view):
        """
        __doc__ in yaml format, eg:

        desc: the desc of this api.
        parameters:
        - name: mobile
          desc: the mobile number
          type: string
          required: true
          location: query
        - name: promotion
          desc: the activity id
          type: int
          required: true
          location: form
        """
        fields = self.get_path_fields(path, method, view)
        yaml_doc = None
        func = getattr(view, view.action) if getattr(view, 'action', None) else None
        if func and func.__doc__:
            try:
                yaml_doc = yaml.load(func.__doc__)
            except:
                yaml_doc = None
        if yaml_doc and 'desc' in yaml_doc:
            desc = yaml_doc.get('desc', '')
            _method_desc = desc
            params = yaml_doc.get('parameters', [])
            for i in params:
                _name = i.get('name')
                _desc = i.get('desc')
                _required = i.get('required', True)
                _type = i.get('type', 'string')
                _location = i.get('location', 'query')
                f = coreapi.Field(
                    name=_name,
                    location=_location,
                    required=_required,
                    description=_desc,
                    type=_type
                )
                fields.append(f)
        else:
            _method_desc = func.__doc__ if func and func.__doc__ else ''
            fields += self.get_serializer_fields(path, method, view)
        fields += self.get_pagination_fields(path, method, view)
        fields += self.get_filter_fields(path, method, view)

        if fields and any([field.location in ('form', 'body') for field in fields]):
            encoding = self.get_encoding(path, method, view)
        else:
            encoding = None

        if self.url and path.startswith('/'):
            path = path[1:]

        return coreapi.Link(
            url=urlparse.urljoin(self.url, path),
            action=method.lower(),
            encoding=encoding,
            fields=fields,
            description=_method_desc
        )


def get_swagger_view(title=None, url=None, patterns=None, urlconf=None):
    """
    Return schema view which renders Swagger/OpenAPI.
    """
    class SwaggerSchemaView(APIView):
        _ignore_model_permissions = True
        exclude_from_schema = True
        permission_classes = [AllowAny]
        renderer_classes = [
            renderers.JSONRenderer,
            renderers.OpenAPIRenderer,
            renderers.SwaggerUIRenderer
        ]

        def get(self, request):
            generator = CustomSchemaGenerator(
                title=title,
                url=url,
                patterns=patterns,
                urlconf=urlconf
            )
            schema = generator.get_schema(request=request)

            if not schema:
                raise exceptions.ValidationError(
                    'The schema generator did not return a schema Document'
                )

            return Response(schema)

    return SwaggerSchemaView.as_view()