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renderers.py
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renderers.py
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# Copyright (C) 2015 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU Affero General Public License version 3, or any later version
# See top-level LICENSE file for more information
import yaml
from flask import make_response, request
from flask.ext.api import renderers, parsers
from flask_api.mediatypes import MediaType
from swh.web.ui import utils
class SWHFilterRenderer():
"""Base renderer for swh's common behavior.
"""
def filter_by_fields(self, data):
fields = request.args.get('fields')
if fields:
fields = set(fields.split(','))
data = utils.filter_field_keys(data, fields)
return data
class PlainRenderer(renderers.BaseRenderer):
"""Renderer for plain/text, do nothing but send the data as is.
"""
media_type = 'text/plain'
def render(self, data, media_type, **options):
return data
class YAMLRenderer(renderers.BaseRenderer, SWHFilterRenderer):
"""Renderer for application/yaml.
Orchestrate from python data structure to yaml.
"""
media_type = 'application/yaml'
def render(self, data, media_type, **options):
data = self.filter_by_fields(data)
return yaml.dump(data, encoding=self.charset)
class JSONPEnricher():
"""JSONP rendering.
Defines a jsonp function that extracts a potential 'callback'
request parameter holding the function name and wraps the data
inside a call to such function
e.g:
GET /blah/foo/bar renders: {'output': 'wrapped'}
GET /blah/foo/bar?callback=fn renders: fn({'output': 'wrapped'})
"""
def enrich(self, data):
jsonp = request.args.get('callback')
if jsonp:
return '%s(%s)' % (jsonp, data)
return data
class SWHJSONRenderer(renderers.JSONRenderer,
SWHFilterRenderer,
JSONPEnricher):
"""Renderer for application/json.
Serializes in json the data and returns it.
Also deals with jsonp. If callback is found in request parameter,
wrap the result as a function with name the value of the parameter
query 'callback'.
"""
def render(self, data, media_type, **options):
data = self.filter_by_fields(data)
res = super().render(data, media_type, **options)
return self.enrich(res)
RENDERERS = [
'swh.web.ui.renderers.SWHJSONRenderer',
'flask.ext.api.renderers.BrowsableAPIRenderer',
'flask.ext.api.parsers.URLEncodedParser',
'swh.web.ui.renderers.YAMLRenderer',
'swh.web.ui.renderers.PlainRenderer',
]
RENDERERS_INSTANCE = [
SWHJSONRenderer(),
renderers.BrowsableAPIRenderer(),
parsers.URLEncodedParser(),
YAMLRenderer(),
]
RENDERERS_BY_TYPE = {
r.media_type: r
for r in RENDERERS_INSTANCE
}
def error_response(default_error_msg, error_code, error):
"""Private function to create a custom error response.
"""
# if nothing is requested by client, use json
default_application_type = 'application/json'
accept_type = request.headers.get('Accept', default_application_type)
renderer = RENDERERS_BY_TYPE.get(
accept_type,
RENDERERS_BY_TYPE[default_application_type])
# for edge cases, use the elected renderer's media type
accept_type = renderer.media_type
response = make_response(default_error_msg, error_code)
response.headers['Content-Type'] = accept_type
response.data = renderer.render({"error": str(error)},
media_type=MediaType(accept_type),
status=error_code,
headers={'Content-Type': accept_type})
return response

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