# Copyright (c) 2014 AnsibleWorks, Inc.
# All Rights Reserved.

# Python
import inspect
import logging
import json

# Django
from django.http import Http404
from django.contrib.auth.models import User
from django.shortcuts import get_object_or_404
from django.template.loader import render_to_string
from django.utils.safestring import mark_safe
from django.utils.timezone import now

# Django REST Framework
from rest_framework.authentication import get_authorization_header
from rest_framework.exceptions import PermissionDenied
from rest_framework import generics
from rest_framework.response import Response
from rest_framework.request import clone_request
from rest_framework import status
from rest_framework import views

# AWX
from awx.main.models import *
from awx.main.utils import *

__all__ = ['APIView', 'GenericAPIView', 'ListAPIView', 'SimpleListAPIView',
           'ListCreateAPIView', 'SubListAPIView', 'SubListCreateAPIView',
           'RetrieveAPIView', 'RetrieveUpdateAPIView',
           'RetrieveDestroyAPIView', 'RetrieveUpdateDestroyAPIView']

logger = logging.getLogger('awx.api.generics')

def get_view_name(cls, suffix=None):
    '''
    Wrapper around REST framework get_view_name() to support get_name() method
    and view_name property on a view class.
    '''
    name = ''
    if hasattr(cls, 'get_name') and callable(cls.get_name):
        name = cls().get_name()
    elif hasattr(cls, 'view_name'):
        if callable(cls.view_name):
            name = cls.view_name()
        else:
            name = cls.view_name
    if name:
        return ('%s %s' % (name, suffix)) if suffix else name
    return views.get_view_name(cls, suffix=None)

def get_view_description(cls, html=False):
    '''
    Wrapper around REST framework get_view_description() to support
    get_description() method and view_description property on a view class.
    '''
    if hasattr(cls, 'get_description') and callable(cls.get_description):
        desc = cls().get_description(html=html)
        cls = type(cls.__name__, (object,), {'__doc__': desc})
    elif hasattr(cls, 'view_description'):
        if callable(cls.view_description):
            view_desc = cls.view_description()
        else:
            view_desc = cls.view_description
        cls = type(cls.__name__, (object,), {'__doc__': view_desc})
    desc = views.get_view_description(cls, html=html)
    if html:
        desc = '<div class="description">%s</div>' % desc
    return mark_safe(desc)

class APIView(views.APIView):

    def initialize_request(self, request, *args, **kwargs):
        '''
        Store the Django REST Framework Request object as an attribute on the
        normal Django request.
        '''
        drf_request = super(APIView, self).initialize_request(request, *args, **kwargs)
        request.drf_request = drf_request
        return drf_request

    def get_authenticate_header(self, request):
        """
        Determine the WWW-Authenticate header to use for 401 responses.  Try to
        use the request header as an indication for which authentication method
        was attempted.
        """
        for authenticator in self.get_authenticators():
            resp_hdr = authenticator.authenticate_header(request)
            if not resp_hdr:
                continue
            req_hdr = get_authorization_header(request)
            if not req_hdr:
                continue
            if resp_hdr.split()[0] and resp_hdr.split()[0] == req_hdr.split()[0]:
                return resp_hdr
        # If it can't be determined from the request, use the last
        # authenticator (should be Basic).
        try:
            return authenticator.authenticate_header(request)
        except NameError:
            pass

    def get_description_context(self):
        return {
            'docstring': type(self).__doc__ or '',
            'new_in_13': getattr(self, 'new_in_13', False),
            'new_in_14': getattr(self, 'new_in_14', False),
            'new_in_145': getattr(self, 'new_in_145', False),
            'new_in_148': getattr(self, 'new_in_148', False),
            'new_in_15': getattr(self, 'new_in_15', False),
        }

    def get_description(self, html=False):
        template_list = []
        for klass in inspect.getmro(type(self)):
            template_basename = camelcase_to_underscore(klass.__name__)
            template_list.append('api/%s.md' % template_basename)
        context = self.get_description_context()
        return render_to_string(template_list, context)

    def metadata(self, request):
        '''
        Add version number where view was added to Tower.
        '''
        ret = super(APIView, self).metadata(request)
        added_in_version = '1.2'
        for version in ('1.5', '1.4.8', '1.4.5', '1.4', '1.3'):
            if getattr(self, 'new_in_%s' % version.replace('.', ''), False):
                added_in_version = version
                break
        ret['added_in_version'] = added_in_version
        return ret

    def finalize_response(self, request, response, *args, **kwargs):
        if response.status_code >= 400:
            logger.warn("status %s received by user %s attempting to access %s" % (response.status_code, request.user, request.path))
        return super(APIView, self).finalize_response(request, response, *args, **kwargs)


class GenericAPIView(generics.GenericAPIView, APIView):
    # Base class for all model-based views.

    # Subclasses should define:
    #   model = ModelClass
    #   serializer_class = SerializerClass

    def get_serializer(self, *args, **kwargs):
        serializer = super(GenericAPIView, self).get_serializer(*args, **kwargs)
        # Override when called from browsable API to generate raw data form;
        # always remove read only fields from sample raw data.
        if hasattr(self, '_raw_data_form_marker'):
             for name, field in serializer.fields.items():
                if getattr(field, 'read_only', None):
                    del serializer.fields[name]
        return serializer

    def get_queryset(self):
        #if hasattr(self.request.user, 'get_queryset'):
        #    return self.request.user.get_queryset(self.model)
        #else:
        return super(GenericAPIView, self).get_queryset()

    def get_description_context(self):
        # Set instance attributes needed to get serializer metadata.
        if not hasattr(self, 'request'):
            self.request = None
        if not hasattr(self, 'format_kwarg'):
            self.format_kwarg = 'format'
        d = super(GenericAPIView, self).get_description_context()
        d.update({
            'model_verbose_name': unicode(self.model._meta.verbose_name),
            'model_verbose_name_plural': unicode(self.model._meta.verbose_name_plural),
            'serializer_fields': self.get_serializer().metadata(),
        })
        return d

    def metadata(self, request):
        '''
        Add field information for GET requests (so field names/labels are
        available even when we can't POST/PUT).
        '''
        ret = super(GenericAPIView, self).metadata(request)
        actions = ret.get('actions', {})
        # Remove read only fields from PUT/POST data.
        for method in ('POST', 'PUT'):
            fields = actions.get(method, {})
            for field, meta in fields.items():
                if not isinstance(meta, dict):
                    continue
                if meta.get('read_only', False):
                    fields.pop(field)
        if 'GET' in self.allowed_methods:
            cloned_request = clone_request(request, 'GET')
            try:
                # Test global permissions
                self.check_permissions(cloned_request)
                # Test object permissions
                if hasattr(self, 'retrieve'):
                    try:
                        self.get_object()
                    except Http404:
                        # Http404 should be acceptable and the serializer
                        # metadata should be populated. Except this so the
                        # outer "else" clause of the try-except-else block
                        # will be executed.
                        pass
            except (exceptions.APIException, PermissionDenied):
                pass
            else:
                # If user has appropriate permissions for the view, include
                # appropriate metadata about the fields that should be supplied.
                serializer = self.get_serializer()
                actions['GET'] = serializer.metadata()
                if hasattr(serializer, 'get_types'):
                    # Inject the type field choices into GET options as well as on
                    # the metadata itself.
                    if 'type' in actions['GET']:
                        actions['GET']['type']['type'] = 'multiple choice'
                        actions['GET']['type']['choices'] = serializer.get_type_choices()
                    ret['types'] = serializer.get_types()
        if actions:
            ret['actions'] = actions
        if getattr(self, 'search_fields', None):
            ret['search_fields'] = self.search_fields
        return ret

class SimpleListAPIView(generics.ListAPIView, GenericAPIView):

    def get_queryset(self):
        return self.request.user.get_queryset(self.model)

class ListAPIView(generics.ListAPIView, GenericAPIView):
    # Base class for a read-only list view.

    def get_queryset(self):
        return self.request.user.get_queryset(self.model)

    def get_description_context(self):
        opts = self.model._meta
        if 'username' in opts.get_all_field_names():
            order_field = 'username'
        else:
            order_field = 'name'
        d = super(ListAPIView, self).get_description_context()
        d.update({
            'order_field': order_field,
        })
        return d

    @property
    def search_fields(self):
        fields = []
        for field in self.model._meta.fields:
            if field.name in ('username', 'first_name', 'last_name', 'email',
                              'name', 'description', 'email'):
                fields.append(field.name)
        return fields

class ListCreateAPIView(ListAPIView, generics.ListCreateAPIView):
    # Base class for a list view that allows creating new objects.
    pass

class SubListAPIView(ListAPIView):
    # Base class for a read-only sublist view.

    # Subclasses should define at least:
    #   model = ModelClass
    #   serializer_class = SerializerClass
    #   parent_model = ModelClass
    #   relationship = 'rel_name_from_parent_to_model'
    # And optionally (user must have given access permission on parent object
    # to view sublist):
    #   parent_access = 'read'

    def get_description_context(self):
        d = super(SubListAPIView, self).get_description_context()
        d.update({
            'parent_model_verbose_name': unicode(self.parent_model._meta.verbose_name),
            'parent_model_verbose_name_plural': unicode(self.parent_model._meta.verbose_name_plural),
        })
        return d

    def get_parent_object(self):
        parent_filter = {
            self.lookup_field: self.kwargs.get(self.lookup_field, None),
        }
        return get_object_or_404(self.parent_model, **parent_filter)

    def check_parent_access(self, parent=None):
        parent = parent or self.get_parent_object()
        parent_access = getattr(self, 'parent_access', 'read')
        if parent_access in ('read', 'delete'):
            args = (self.parent_model, parent_access, parent)
        else:
            args = (self.parent_model, parent_access, parent, None)
        if not self.request.user.can_access(*args):
            raise PermissionDenied()

    def get_queryset(self):
        parent = self.get_parent_object()
        self.check_parent_access(parent)
        qs = self.request.user.get_queryset(self.model).distinct()
        sublist_qs = getattr(parent, self.relationship).distinct()
        return qs & sublist_qs

class SubListCreateAPIView(SubListAPIView, ListCreateAPIView):
    # Base class for a sublist view that allows for creating subobjects and
    # attaching/detaching them from the parent.

    # In addition to SubListAPIView properties, subclasses may define (if the
    # sub_obj requires a foreign key to the parent):
    #   parent_key = 'field_on_model_referring_to_parent'

    def get_description_context(self):
        d = super(SubListCreateAPIView, self).get_description_context()
        d.update({
            'parent_key': getattr(self, 'parent_key', None),
        })
        return d

    def create(self, request, *args, **kwargs):
        # If the object ID was not specified, it probably doesn't exist in the
        # DB yet. We want to see if we can create it.  The URL may choose to
        # inject it's primary key into the object because we are posting to a
        # subcollection. Use all the normal access control mechanisms.

        # Make a copy of the data provided (since it's readonly) in order to
        # inject additional data.
        if hasattr(request.DATA, 'dict'):
            data = request.DATA.dict()
        else:
            data = request.DATA

        # add the parent key to the post data using the pk from the URL
        parent_key = getattr(self, 'parent_key', None)
        if parent_key:
            data[parent_key] = self.kwargs['pk']

        # attempt to deserialize the object
        serializer = self.serializer_class(data=data)
        if not serializer.is_valid():
            return Response(serializer.errors,
                            status=status.HTTP_400_BAD_REQUEST)

        # Verify we have permission to add the object as given.
        if not request.user.can_access(self.model, 'add', serializer.init_data):
            raise PermissionDenied()

        # save the object through the serializer, reload and returned the saved
        # object deserialized
        obj = serializer.save()
        serializer = self.serializer_class(obj)

        return Response(serializer.data, status=status.HTTP_201_CREATED)

    def attach(self, request, *args, **kwargs):
        created = False
        parent = self.get_parent_object()
        relationship = getattr(parent, self.relationship)
        sub_id = request.DATA.get('id', None)
        data = request.DATA

        # Create the sub object if an ID is not provided.
        if not sub_id:
            response = self.create(request, *args, **kwargs)
            if response.status_code != status.HTTP_201_CREATED:
                return response
            sub_id = response.data['id']
            data = response.data
            try:
                location = response['Location']
            except KeyError:
                location = None
            created = True

        # Retrive the sub object (whether created or by ID).
        sub = get_object_or_400(self.model, pk=sub_id)
            
        # Verify we have permission to attach.
        if not request.user.can_access(self.parent_model, 'attach', parent, sub,
                                       self.relationship, data,
                                       skip_sub_obj_read_check=created):
            raise PermissionDenied()

        # Attach the object to the collection.
        if sub not in relationship.all():
            relationship.add(sub)

        if created:
            headers = {}
            if location:
                headers['Location'] = location
            return Response(data, status=status.HTTP_201_CREATED, headers=headers)
        else:
            return Response(status=status.HTTP_204_NO_CONTENT)

    def unattach(self, request, *args, **kwargs):
        sub_id = request.DATA.get('id', None)
        if not sub_id:
            data = dict(msg='"id" is required to disassociate')
            return Response(data, status=status.HTTP_400_BAD_REQUEST)

        parent = self.get_parent_object()
        parent_key = getattr(self, 'parent_key', None)
        relationship = getattr(parent, self.relationship)
        sub = get_object_or_400(self.model, pk=sub_id)

        if not request.user.can_access(self.parent_model, 'unattach', parent,
                                       sub, self.relationship):
            raise PermissionDenied()

        if parent_key:
            # sub object has a ForeignKey to the parent, so we can't remove it
            # from the set, only mark it as inactive.
            sub.mark_inactive()
        else:
            relationship.remove(sub)

        return Response(status=status.HTTP_204_NO_CONTENT)

    def post(self, request, *args, **kwargs):
        if not isinstance(request.DATA, dict):
            return Response('invalid type for post data',
                            status=status.HTTP_400_BAD_REQUEST)
        if 'disassociate' in request.DATA:
            return self.unattach(request, *args, **kwargs)
        else:
            return self.attach(request, *args, **kwargs)

class RetrieveAPIView(generics.RetrieveAPIView, GenericAPIView):
    pass

class RetrieveUpdateAPIView(RetrieveAPIView, generics.RetrieveUpdateAPIView):

    def pre_save(self, obj):
        super(RetrieveUpdateAPIView, self).pre_save(obj)

    def update(self, request, *args, **kwargs):
        self.update_filter(request, *args, **kwargs)
        return super(RetrieveUpdateAPIView, self).update(request, *args, **kwargs)

    def update_filter(self, request, *args, **kwargs):
        ''' scrub any fields the user cannot/should not put/patch, based on user context.  This runs after read-only serialization filtering '''
        pass

class RetrieveDestroyAPIView(RetrieveAPIView, generics.RetrieveDestroyAPIView):

    def destroy(self, request, *args, **kwargs):
        # somewhat lame that delete has to call it's own permissions check
        obj = self.get_object()
        # FIXME: Why isn't the active check being caught earlier by RBAC?
        if getattr(obj, 'active', True) == False:
            raise Http404()
        if getattr(obj, 'is_active', True) == False:
            raise Http404()
        if not request.user.can_access(self.model, 'delete', obj):
            raise PermissionDenied()
        if hasattr(obj, 'mark_inactive'):
            obj.mark_inactive()
        else:
            raise NotImplementedError('destroy() not implemented yet for %s' % obj)
        return Response(status=status.HTTP_204_NO_CONTENT)

class RetrieveUpdateDestroyAPIView(RetrieveUpdateAPIView, RetrieveDestroyAPIView):
    pass