from django.utils import simplejson

import cgi

class JSONFilter(object):

    def __init__(self, app, mime_type='text/x-json'):

        self.app = app

        self.mime_type = mime_type

    def __call__(self, environ, start_response):

        # Read JSON POST input to jsonfilter.json if matching mime type

        response = {'status': '200 OK', 'headers': []}

        def json_start_response(status, headers):

            response['status'] = status

            response['headers'].extend(headers)

        environ['jsonfilter.mime_type'] = self.mime_type

        if environ.get('REQUEST_METHOD', '') == 'POST':

            if environ.get('CONTENT_TYPE', '') == self.mime_type:

                args = [_ for _ in [environ.get('CONTENT_LENGTH')] if _]

                data = environ['wsgi.input'].read(*map(int, args))

                environ['jsonfilter.json'] = simplejson.loads(data)

        res = simplejson.dumps(self.app(environ, json_start_response))

        jsonp = cgi.parse_qs(environ.get('QUERY_STRING', '')).get('jsonp')

        if jsonp:

            content_type = 'text/javascript'

            res = ''.join(jsonp + ['(', res, ')'])

        elif 'Opera' in environ.get('HTTP_USER_AGENT', ''):

            # Opera has bunk XMLHttpRequest support for most mime types

            content_type = 'text/plain'

        else:

            content_type = self.mime_type

        headers = [

            ('Content-type', content_type),

            ('Content-length', len(res)),

        ]

        headers.extend(response['headers'])

        start_response(response['status'], headers)

        return [res]

def factory(app, global_conf, **kw):

    return JSONFilter(app, **kw)