"""
Renderers are used to serialize a response into specific media types.

They give us a generic way of being able to handle various media types
on the response, such as JSON encoded data or HTML output.

REST framework also provides an HTML renderer the renders the browsable API.
"""
from __future__ import unicode_literals

import copy
import string
import json
from django import forms
from django.http.multipartparser import parse_header
from django.template import RequestContext, loader, Template
from rest_framework.compat import yaml
from rest_framework.exceptions import ConfigurationError
from rest_framework.settings import api_settings
from rest_framework.request import clone_request
from rest_framework.utils import dict2xml
from rest_framework.utils import encoders
from rest_framework.utils.breadcrumbs import get_breadcrumbs
from rest_framework import VERSION, status
from rest_framework import parsers


class BaseRenderer(object):
    """
    All renderers should extend this class, setting the `media_type`
    and `format` attributes, and override the `.render()` method.
    """

    media_type = None
    format = None

    def render(self, data, accepted_media_type=None, renderer_context=None):
        raise NotImplemented('Renderer class requires .render() to be implemented')


class JSONRenderer(BaseRenderer):
    """
    Renderer which serializes to json.
    """

    media_type = 'application/json'
    format = 'json'
    encoder_class = encoders.JSONEncoder

    def render(self, data, accepted_media_type=None, renderer_context=None):
        """
        Render `obj` into json.
        """
        if data is None:
            return ''

        # If 'indent' is provided in the context, then pretty print the result.
        # E.g. If we're being called by the BrowseableAPIRenderer.
        renderer_context = renderer_context or {}
        indent = renderer_context.get('indent', None)

        if accepted_media_type:
            # If the media type looks like 'application/json; indent=4',
            # then pretty print the result.
            base_media_type, params = parse_header(accepted_media_type.encode('ascii'))
            indent = params.get('indent', indent)
            try:
                indent = max(min(int(indent), 8), 0)
            except (ValueError, TypeError):
                indent = None

        return json.dumps(data, cls=self.encoder_class, indent=indent)


class JSONPRenderer(JSONRenderer):
    """
    Renderer which serializes to json,
    wrapping the json output in a callback function.
    """

    media_type = 'application/javascript'
    format = 'jsonp'
    callback_parameter = 'callback'
    default_callback = 'callback'

    def get_callback(self, renderer_context):
        """
        Determine the name of the callback to wrap around the json output.
        """
        request = renderer_context.get('request', None)
        params = request and request.QUERY_PARAMS or {}
        return params.get(self.callback_parameter, self.default_callback)

    def render(self, data, accepted_media_type=None, renderer_context=None):
        """
        Renders into jsonp, wrapping the json output in a callback function.

        Clients may set the callback function name using a query parameter
        on the URL, for example: ?callback=exampleCallbackName
        """
        renderer_context = renderer_context or {}
        callback = self.get_callback(renderer_context)
        json = super(JSONPRenderer, self).render(data, accepted_media_type,
                                                 renderer_context)
        return "%s(%s);" % (callback, json)


class XMLRenderer(BaseRenderer):
    """
    Renderer which serializes to XML.
    """

    media_type = 'application/xml'
    format = 'xml'

    def render(self, data, accepted_media_type=None, renderer_context=None):
        """
        Renders *obj* into serialized XML.
        """
        if data is None:
            return ''
        return dict2xml(data)


class YAMLRenderer(BaseRenderer):
    """
    Renderer which serializes to YAML.
    """

    media_type = 'application/yaml'
    format = 'yaml'
    encoder = encoders.SafeDumper

    def render(self, data, accepted_media_type=None, renderer_context=None):
        """
        Renders *obj* into serialized YAML.
        """
        if data is None:
            return ''

        return yaml.dump(data, stream=None, Dumper=self.encoder)


class TemplateHTMLRenderer(BaseRenderer):
    """
    An HTML renderer for use with templates.

    The data supplied to the Response object should be a dictionary that will
    be used as context for the template.

    The template name is determined by (in order of preference):

    1. An explicit `.template_name` attribute set on the response.
    2. An explicit `.template_name` attribute set on this class.
    3. The return result of calling `view.get_template_names()`.

    For example:
        data = {'users': User.objects.all()}
        return Response(data, template_name='users.html')

    For pre-rendered HTML, see StaticHTMLRenderer.
    """

    media_type = 'text/html'
    format = 'html'
    template_name = None
    exception_template_names = [
        '%(status_code)s.html',
        'api_exception.html'
    ]

    def render(self, data, accepted_media_type=None, renderer_context=None):
        """
        Renders data to HTML, using Django's standard template rendering.

        The template name is determined by (in order of preference):

        1. An explicit .template_name set on the response.
        2. An explicit .template_name set on this class.
        3. The return result of calling view.get_template_names().
        """
        renderer_context = renderer_context or {}
        view = renderer_context['view']
        request = renderer_context['request']
        response = renderer_context['response']

        if response.exception:
            template = self.get_exception_template(response)
        else:
            template_names = self.get_template_names(response, view)
            template = self.resolve_template(template_names)

        context = self.resolve_context(data, request, response)
        return template.render(context)

    def resolve_template(self, template_names):
        return loader.select_template(template_names)

    def resolve_context(self, data, request, response):
        if response.exception:
            data['status_code'] = response.status_code
        return RequestContext(request, data)

    def get_template_names(self, response, view):
        if response.template_name:
            return [response.template_name]
        elif self.template_name:
            return [self.template_name]
        elif hasattr(view, 'get_template_names'):
            return view.get_template_names()
        raise ConfigurationError('Returned a template response with no template_name')

    def get_exception_template(self, response):
        template_names = [name % {'status_code': response.status_code}
                          for name in self.exception_template_names]

        try:
            # Try to find an appropriate error template
            return self.resolve_template(template_names)
        except Exception:
            # Fall back to using eg '404 Not Found'
            return Template('%d %s' % (response.status_code,
                                       response.status_text.title()))


# Note, subclass TemplateHTMLRenderer simply for the exception behavior
class StaticHTMLRenderer(TemplateHTMLRenderer):
    """
    An HTML renderer class that simply returns pre-rendered HTML.

    The data supplied to the Response object should be a string representing
    the pre-rendered HTML content.

    For example:
        data = '<html><body>example</body></html>'
        return Response(data)

    For template rendered HTML, see TemplateHTMLRenderer.
    """
    media_type = 'text/html'
    format = 'html'

    def render(self, data, accepted_media_type=None, renderer_context=None):
        renderer_context = renderer_context or {}
        response = renderer_context['response']

        if response and response.exception:
            request = renderer_context['request']
            template = self.get_exception_template(response)
            context = self.resolve_context(data, request, response)
            return template.render(context)

        return data


class BrowsableAPIRenderer(BaseRenderer):
    """
    HTML renderer used to self-document the API.
    """
    media_type = 'text/html'
    format = 'api'
    template = 'rest_framework/api.html'

    def get_default_renderer(self, view):
        """
        Return an instance of the first valid renderer.
        (Don't use another documenting renderer.)
        """
        renderers = [renderer for renderer in view.renderer_classes
                     if not issubclass(renderer, BrowsableAPIRenderer)]
        if not renderers:
            return None
        return renderers[0]()

    def get_content(self, renderer, data,
                    accepted_media_type, renderer_context):
        """
        Get the content as if it had been rendered by the default
        non-documenting renderer.
        """
        if not renderer:
            return '[No renderers were found]'

        renderer_context['indent'] = 4
        content = renderer.render(data, accepted_media_type, renderer_context)

        if not all(char in string.printable for char in content):
            return '[%d bytes of binary content]'

        return content

    def show_form_for_method(self, view, method, request, obj):
        """
        Returns True if a form should be shown for this method.
        """
        if not method in view.allowed_methods:
            return  # Not a valid method

        if not api_settings.FORM_METHOD_OVERRIDE:
            return  # Cannot use form overloading

        request = clone_request(request, method)
        try:
            if not view.has_permission(request, obj):
                return  # Don't have permission
        except Exception:
            return  # Don't have permission and exception explicitly raise
        return True

    def serializer_to_form_fields(self, serializer):
        fields = {}
        for k, v in serializer.get_fields().items():
            if getattr(v, 'read_only', True):
                continue

            kwargs = {}
            kwargs['required'] = v.required

            #if getattr(v, 'queryset', None):
            #    kwargs['queryset'] = v.queryset

            if getattr(v, 'choices', None) is not None:
                kwargs['choices'] = v.choices

            if getattr(v, 'regex', None) is not None:
                kwargs['regex'] = v.regex

            if getattr(v, 'widget', None):
                widget = copy.deepcopy(v.widget)
                kwargs['widget'] = widget

            if getattr(v, 'default', None) is not None:
                kwargs['initial'] = v.default

            kwargs['label'] = k

            fields[k] = v.form_field_class(**kwargs)

        return fields

    def get_form(self, view, method, request):
        """
        Get a form, possibly bound to either the input or output data.
        In the absence on of the Resource having an associated form then
        provide a form that can be used to submit arbitrary content.
        """
        obj = getattr(view, 'object', None)
        if not self.show_form_for_method(view, method, request, obj):
            return

        if method == 'DELETE' or method == 'OPTIONS':
            return True  # Don't actually need to return a form

        if not getattr(view, 'get_serializer', None) or not parsers.FormParser in view.parser_classes:
            media_types = [parser.media_type for parser in view.parser_classes]
            return self.get_generic_content_form(media_types)

        serializer = view.get_serializer(instance=obj)
        fields = self.serializer_to_form_fields(serializer)

        # Creating an on the fly form see:
        # http://stackoverflow.com/questions/3915024/dynamically-creating-classes-python
        OnTheFlyForm = type(str("OnTheFlyForm"), (forms.Form,), fields)
        data = (obj is not None) and serializer.data or None
        form_instance = OnTheFlyForm(data)
        return form_instance

    def get_generic_content_form(self, media_types):
        """
        Returns a form that allows for arbitrary content types to be tunneled
        via standard HTML forms.
        (Which are typically application/x-www-form-urlencoded)
        """

        # If we're not using content overloading there's no point in supplying a generic form,
        # as the view won't treat the form's value as the content of the request.
        if not (api_settings.FORM_CONTENT_OVERRIDE
                and api_settings.FORM_CONTENTTYPE_OVERRIDE):
            return None

        content_type_field = api_settings.FORM_CONTENTTYPE_OVERRIDE
        content_field = api_settings.FORM_CONTENT_OVERRIDE
        choices = [(media_type, media_type) for media_type in media_types]
        initial = media_types[0]

        # NB. http://jacobian.org/writing/dynamic-form-generation/
        class GenericContentForm(forms.Form):
            def __init__(self):
                super(GenericContentForm, self).__init__()

                self.fields[content_type_field] = forms.ChoiceField(
                    label='Content Type',
                    choices=choices,
                    initial=initial
                )
                self.fields[content_field] = forms.CharField(
                    label='Content',
                    widget=forms.Textarea
                )

        return GenericContentForm()

    def get_name(self, view):
        try:
            return view.get_name()
        except AttributeError:
            return view.__doc__

    def get_description(self, view):
        try:
            return view.get_description(html=True)
        except AttributeError:
            return view.__doc__

    def render(self, data, accepted_media_type=None, renderer_context=None):
        """
        Renders *obj* using the :attr:`template` set on the class.

        The context used in the template contains all the information
        needed to self-document the response to this request.
        """
        accepted_media_type = accepted_media_type or ''
        renderer_context = renderer_context or {}

        view = renderer_context['view']
        request = renderer_context['request']
        response = renderer_context['response']

        renderer = self.get_default_renderer(view)
        content = self.get_content(renderer, data, accepted_media_type, renderer_context)

        put_form = self.get_form(view, 'PUT', request)
        post_form = self.get_form(view, 'POST', request)
        delete_form = self.get_form(view, 'DELETE', request)
        options_form = self.get_form(view, 'OPTIONS', request)

        name = self.get_name(view)
        description = self.get_description(view)
        breadcrumb_list = get_breadcrumbs(request.path)

        template = loader.get_template(self.template)
        context = RequestContext(request, {
            'content': content,
            'view': view,
            'request': request,
            'response': response,
            'description': description,
            'name': name,
            'version': VERSION,
            'breadcrumblist': breadcrumb_list,
            'allowed_methods': view.allowed_methods,
            'available_formats': [renderer.format for renderer in view.renderer_classes],
            'put_form': put_form,
            'post_form': post_form,
            'delete_form': delete_form,
            'options_form': options_form,
            'api_settings': api_settings
        })

        ret = template.render(context)

        # Munge DELETE Response code to allow us to return content
        # (Do this *after* we've rendered the template so that we include
        # the normal deletion response code in the output)
        if response.status_code == status.HTTP_204_NO_CONTENT:
            response.status_code = status.HTTP_200_OK

        return ret