python-piston-mini-client 0.7.2-0ubuntu1 / usr / share / pyshared / piston_mini_client / __init__.py

# -*- coding: utf-8 -*-
# Copyright 2010-2012 Canonical Ltd.  This software is licensed under the
# GNU Lesser General Public License version 3 (see the file LICENSE).

import httplib2

try:
    # ensure we have a version with a fix for
    #  http://code.google.com/p/httplib2/issues/detail?id=38
    # and if not, patch in our own socks with the fix
    from httplib2.socks import PROXY_TYPE_HTTP_NO_TUNNEL
    from httplib2 import socks
except ImportError:
    from piston_mini_client import socks
    httplib2.socks = socks

import json
import os
import socket
import urllib
from datetime import datetime
from functools import wraps
from urlparse import urlparse, urlunparse

from piston_mini_client.failhandlers import (
    APIError,
    ExceptionFailHandler,
    format_request,
    format_response,
    SocketError,
    TimeoutError,
)
from piston_mini_client.consts import (
    DISABLE_SSL_VALIDATION_ENVVAR,
    LOG_FILENAME_ENVVAR,
    TIMEOUT_ENVVAR,
)


class OfflineModeException(Exception):
    pass


# taken from lazr.restfulclients _browser.py file to work around
# the problem that ecryptfs is very unhappy about long filenames
# upstream commented here:
#   http://code.google.com/p/httplib2/issues/detail?id=92
MAXIMUM_CACHE_FILENAME_LENGTH = 143
from httplib2 import _md5, re_url_scheme, re_slash


def safename(filename):
    """Return a filename suitable for the cache.

    Strips dangerous and common characters to create a filename we
    can use to store the cache in.
    """
    # this is a stock httplib2 copy
    try:
        if re_url_scheme.match(filename):
            if isinstance(filename, str):
                filename = filename.decode('utf-8')
                filename = filename.encode('idna')
            else:
                filename = filename.encode('idna')
    except UnicodeError:
        pass
    if isinstance(filename, unicode):
        filename = filename.encode('utf-8')
    filemd5 = _md5(filename).hexdigest()
    filename = re_url_scheme.sub("", filename)
    filename = re_slash.sub(",", filename)

    # This is the part that we changed. In stock httplib2, the
    # filename is trimmed if it's longer than 200 characters, and then
    # a comma and a 32-character md5 sum are appended. This causes
    # problems on eCryptfs filesystems, where the maximum safe
    # filename length is closer to 143 characters.
    #
    # We take a (user-hackable) maximum filename length from
    # RestfulHttp and subtract 33 characters to make room for the comma
    # and the md5 sum.
    #
    # See:
    #  http://code.google.com/p/httplib2/issues/detail?id=92
    #  https://bugs.launchpad.net/bugs/344878
    #  https://bugs.launchpad.net/bugs/545197
    maximum_filename_length = MAXIMUM_CACHE_FILENAME_LENGTH
    maximum_length_before_md5_sum = maximum_filename_length - 32 - 1
    if len(filename) > maximum_length_before_md5_sum:
        filename = filename[:maximum_length_before_md5_sum]
    return ",".join((filename, filemd5))


def returns_json(func):
    """The response data will be deserialized using a simple JSON decoder"""
    @wraps(func)
    def wrapper(*args, **kwargs):
        body = func(*args, **kwargs)
        if not isinstance(body, basestring):
            return body
        return json.loads(body)
    return wrapper


def returns(cls, none_allowed=False):
    """The response data will be deserialized into an instance of ``cls``.

    The provided class should be a descendant of ``PistonResponseObject``,
    or some other class that provides a ``from_response`` method.

    ``none_allowed``, defaulting to ``False``, specifies whether or not
    ``None`` is a valid response. If ``True`` then the api can return ``None``
    instead of a ``PistonResponseObject``.
    """
    def decorator(func):
        @wraps(func)
        def wrapper(self, *args, **kwargs):
            body = func(self, *args, **kwargs)
            if not isinstance(body, basestring):
                return body
            return cls.from_response(body, none_allowed)
        return wrapper
    return decorator


def returns_list_of(cls):
    """The response data will be deserialized into a list of ``cls``.

    The provided class should be a descendant of ``PistonResponseObject``,
    or some other class that provides a ``from_response`` method.
    """
    def decorator(func):
        @wraps(func)
        def wrapper(self, *args, **kwargs):
            body = func(self, *args, **kwargs)
            if not isinstance(body, basestring):
                return body
            data = json.loads(body)
            items = []
            for datum in data:
                items.append(cls.from_dict(datum))
            return items
        return wrapper
    return decorator


class PistonResponseObject(object):
    """Base class for objects that are returned from api calls."""
    @classmethod
    def from_response(cls, body, none_allowed=False):
        data = json.loads(body)
        if none_allowed and data is None:
            return data
        obj = cls.from_dict(data)
        return obj

    @classmethod
    def from_dict(cls, data):
        obj = cls()
        for key, value in data.items():
            setattr(obj, key, value)
        return obj


class PistonSerializable(object):
    """Base class for objects that want to be used as api call arguments.

    Children classes should at least redefine ``_atts`` to state the list of
    attributes that will be serialized into each request.
    """
    _atts = ()

    def __init__(self, **kwargs):
        for (key, value) in kwargs.items():
            setattr(self, key, value)

    def as_serializable(self):
        """Return a serializable representation of this object."""
        data = {}
        for att in self._atts:
            if not hasattr(self, att):
                raise ValueError("Attempted to serialize attribute '%s'"
                    % att)
            data[att] = getattr(self, att)
        return data

    def _as_serializable(self):
        """_as_serializable is deprecated; use as_serializable() instead."""
        import warnings
        warnings.warn("_as_serializable is deprecated; "
                      "use as_serializable instead", DeprecationWarning)
        return self.as_serializable()


class PistonAPI(object):
    """This class provides methods to make http requests slightly easier.

    It's a wrapper around ``httplib2`` to allow for a bit of state to
    be stored (like the service root) so that you don't need to repeat
    yourself as much.

    It's not intended to be used directly.  Children classes should implement
    methods that actually call out to the api methods.

    When you define your API's methods you'll
    want to just call out to the ``_get``, ``_post``, ``_put`` or ``_delete``
    methods provided by this class.
    """
    SUPPORTED_SCHEMAS = ("http", "https")
    default_service_root = ''
    default_content_type = 'application/json'
    default_timeout = None
    fail_handler = ExceptionFailHandler
    extra_headers = None
    serializers = None

    def __init__(self, service_root=None, cachedir=None, auth=None,
                 offline_mode=False, disable_ssl_validation=False,
                 log_filename=None, timeout=None):
        """Initialize a ``PistonAPI``.

        ``service_root`` is the url to the server's service root.
        Children classes can provide a ``default_service_root`` class
        attribute that will be used if ``service_root`` is ``None``.

        ``cachedir`` will be used as ``httplib2``'s cache directory if
        provided.

        ``auth`` can be an instance of ``BasicAuthorizer`` or
        ``OAuthAuthorizer`` or any object that provides a ``sign_request``
        method.  If ``auth`` is ``None`` you'll only be able to make public
        API calls.  See :ref:`authentication` for details.

        ``disable_ssl_validation`` will skip server SSL certificate
        validation when using secure connections.  ``httplib2`` < 0.7.0
        doesn't support certificate validation anyway, so if you're using an
        older ``httplib2`` this will have no effect.

        ``offline_mode`` will not touch the network.  In this case only cached
        results will be available.

        If you pass in a ``log_filename``, all requests and responses
        including headers will be logged to this file.

        ``timeout`` will be used as a socket timeout for all calls this
        instance makes.  To explicitly set no timeout, set timeout=0.  The
        default timeout=None will first check for an environment variable
        ``PISTON_MINI_CLIENT_DEFAULT_TIMEOUT`` and try to use that. If this
        environment variable is not found or it is an invalid float, the
        class's ``default_timeout`` will be used.  Finally, if the class's
        default is also None, Python's default timeout for sockets will be
        used.  All these should be in seconds.
        """
        if service_root is None:
            service_root = self.default_service_root
        if not service_root:
            raise ValueError("No service_root provided, and no default found")
        parsed_service_root = urlparse(service_root)
        scheme = parsed_service_root.scheme
        if scheme not in self.SUPPORTED_SCHEMAS:
            raise ValueError("service_root's scheme must be http or https")
        self._service_root = service_root
        self._parsed_service_root = list(parsed_service_root)
        if cachedir:
            self._httplib2_cache = httplib2.FileCache(cachedir, safe=safename)
        else:
            self._httplib2_cache = None
        self._auth = auth
        self._offline_mode = offline_mode
        self._disable_ssl_validation = disable_ssl_validation
        if timeout is None:
            try:
                timeout = float(os.environ.get(TIMEOUT_ENVVAR))
            except (TypeError, ValueError):
                timeout = self.default_timeout
        self._timeout = timeout
        # create one httplib2.Http object per scheme so that we can
        # have per-scheme proxy settings (see also Issue 26
        #   http://code.google.com/p/httplib2/issues/detail?id=26)
        self._http = {}
        for scheme in self.SUPPORTED_SCHEMAS:
            self._http[scheme] = self._get_http_obj_for_scheme(scheme)
        if self.serializers is None:
            self.serializers = {}
        if log_filename is None:
            log_filename = os.environ.get(LOG_FILENAME_ENVVAR)
        self.log_filename = log_filename

    def _get_http_obj_for_scheme(self, scheme):
        proxy_info = self._get_proxy_info(scheme)
        http = None
        if (self._disable_ssl_validation or
            os.environ.get(DISABLE_SSL_VALIDATION_ENVVAR)):
            try:
                http = httplib2.Http(
                    cache=self._httplib2_cache,
                    timeout=self._timeout,
                    disable_ssl_certificate_validation=True,
                    proxy_info=proxy_info)
            except TypeError:
                # httplib2 < 0.7.0 doesn't support cert validation anyway
                pass
        if http is None:
            http = httplib2.Http(cache=self._httplib2_cache,
                timeout=self._timeout, proxy_info=proxy_info)
        return http

    def _get_proxy_info(self, scheme):
        envvar = "%s_proxy" % scheme
        if envvar in os.environ:
            url = urlparse(os.environ[envvar])
            user_pass, sep, host_and_port = url.netloc.rpartition("@")
            user, sep, passw = user_pass.partition(":")
            host, sep, port = host_and_port.partition(":")
            if port:
                port = int(port)
            proxy_type = socks.PROXY_TYPE_HTTP
            if scheme == "http":
                # this will not require the CONNECT acl from squid and
                # is good enough for http connections
                proxy_type = socks.PROXY_TYPE_HTTP_NO_TUNNEL
            proxy_info = httplib2.ProxyInfo(
                proxy_type=proxy_type,
                proxy_host=host,
                proxy_port=port or 8080,
                proxy_user=user or None,
                proxy_pass=passw or None)
            return proxy_info
        return None

    def _get(self, path, args=None, scheme=None, extra_headers=None):
        """Perform an HTTP GET request.

        The provided ``path`` is appended to this resource's ``_service_root``
        attribute to obtain the absolute URL that will be requested.

        If provided, ``args`` should be a dict specifying additional GET
        arguments that will be encoded on to the end of the url.

        ``scheme`` must be one of *http* or *https*, and will determine the
        scheme used for this particular request.  If not provided the
        service_root's scheme will be used.

        ``extra_headers`` is an optional dictionary of header key/values that
        will be added to the http request.
        """
        if args is not None:
            if '?' in path:
                path += '&'
            else:
                path += '?'
            path += urllib.urlencode(args)
        headers = self._prepare_headers(extra_headers=extra_headers)
        return self._request(path, method='GET', scheme=scheme,
            headers=headers)

    def _post(self, path, data=None, content_type=None, scheme=None,
        extra_headers=None):
        """Perform an HTTP POST request.

        The provided ``path`` is appended to this api's ``_service_root``
        attribute to obtain the absolute URL that will be requested.  ``data``
        should be:

         - A string, in which case it will be used directly as the request's
           body, or
         - A ``list``, ``dict``, ``int``, ``bool`` or ``PistonSerializable``
           (something with an ``as_serializable`` method) or even ``None``,
           in which case it will be serialized into a string according to
           ``content_type``.

        If ``content_type`` is ``None``, ``self.default_content_type`` will
        be used.

        ``scheme`` must be one of *http* or *https*, and will determine the
        scheme used for this particular request.  If not provided the
        service_root's scheme will be used.

        ``extra_headers`` is an optional dictionary of header key/values that
        will be added to the http request.
        """
        body, headers = self._prepare_request(data, content_type,
            extra_headers=extra_headers)
        return self._request(path, method='POST', body=body,
            headers=headers, scheme=scheme)

    def _put(self, path, data=None, content_type=None, scheme=None,
        extra_headers=None):
        """Perform an HTTP PUT request.

        The provided ``path`` is appended to this api's ``_service_root``
        attribute to obtain the absolute URL that will be requested.  ``data``
        should be:

         - A string, in which case it will be used directly as the request's
           body, or
         - A ``list``, ``dict``, ``int``, ``bool`` or ``PistonSerializable``
           (something with an ``as_serializable`` method) or even ``None``,
           in which case it will be serialized into a string according to
           ``content_type``.

        If ``content_type`` is ``None``, ``self.default_content_type`` will be
        used.

        ``scheme`` must be one of *http* or *https*, and will determine the
        scheme used for this particular request.  If not provided the
        service_root's scheme will be used.

        ``extra_headers`` is an optional dictionary of header key/values that
        will be added to the http request.
        """
        body, headers = self._prepare_request(data, content_type,
            extra_headers=extra_headers)
        return self._request(path, method='PUT', body=body,
            headers=headers, scheme=scheme)

    def _delete(self, path, scheme=None, extra_headers=None):
        """Perform an HTTP DELETE request.

        The provided ``path`` is appended to this resource's ``_service_root``
        attribute to obtain the absolute URL that will be requested.

        ``scheme`` must be one of *http* or *https*, and will determine the
        scheme used for this particular request.  If not provided the
        service_root's scheme will be used.

        ``extra_headers`` is an optional dictionary of header key/values that
        will be added to the http request.
        """
        headers = self._prepare_headers(extra_headers=extra_headers)
        return self._request(path, method='DELETE', scheme=scheme,
            headers=headers)

    def _prepare_request(self, data=None, content_type=None,
        extra_headers=None):
        """Put together a set of headers and a body for a request.

        If ``content_type`` is not provided, ``self.default_content_type``
        will be assumed.

        You probably never need to call this method directly.
        """
        if content_type is None:
            content_type = self.default_content_type
        body = self._prepare_body(data, content_type)
        headers = self._prepare_headers(content_type, extra_headers)
        return body, headers

    def _prepare_headers(self, content_type=None, extra_headers=None):
        """Put together and return a complete set of headers.

        If ``content_type`` is provided, it will be added as
        the Content-type header.

        Any provided ``extra_headers`` will be added last.

        You probably never need to call this method directly.
        """
        headers = {}
        if content_type:
            headers['Content-type'] = content_type
        if self.extra_headers is not None:
            headers.update(self.extra_headers)
        if extra_headers is not None:
            headers.update(extra_headers)
        return headers

    def _prepare_body(self, data=None, content_type=None):
        """Serialize data into a request body.

        ``data`` will be serialized into a string, according to
        ``content_type``.

        You probably never need to call this method directly.
        """
        body = data
        if not isinstance(data, basestring):
            serializer = self._get_serializer(content_type)
            body = serializer.serialize(data)
        return body

    def _request(self, path, method, body='', headers=None, scheme=None):
        """Perform an HTTP request.

        You probably want to call one of the ``_get``, ``_post``, ``_put``
        methods instead.
        """
        if headers is None:
            headers = {}
        if scheme not in [None, 'http', 'https']:
            raise ValueError('Invalid scheme %s' % scheme)
        url = self._path2url(path, scheme=scheme)

        # in offline mode either get it from the cache or return None
        if self._offline_mode:
            if method in ('POST', 'PUT'):
                err = "method '%s' not allowed in offline-mode" % method
                raise OfflineModeException(err)
            return self._get_from_cache(url)

        if scheme is None:
            scheme = urlparse(url).scheme

        if self._auth:
            self._auth.sign_request(url, method, body, headers)
        if self.log_filename:
            self._dump_request(url, method, body, headers)
        try:
            response, response_body = self._http[scheme].request(url,
                method=method, body=body, headers=headers)
        except AttributeError, e:
            # Special case out httplib2's way of telling us unable to connect
            if e.args[0] == "'NoneType' object has no attribute 'makefile'":
                raise APIError('Unable to connect to %s' % self._service_root)
            else:
                raise
        except socket.timeout, e:
            raise TimeoutError('Timed out attempting to connect to %s' %
                self._service_root)
        except (socket.gaierror, socket.error), e:
            raise SocketError('connecting to %s: %s' % (self._service_root,
                e.message))
        if self.log_filename:
            self._dump_response(response, response_body)
        handler = self.fail_handler(url, method, body, headers)
        body = handler.handle(response, response_body)
        return body

    def _dump_request(self, url, method, body, headers):
        try:
            with open(self.log_filename, 'a') as f:
                f.write("{0}: {1}".format(datetime.now(),
                    format_request(url, method, body, headers)))
        except IOError:
            pass

    def _dump_response(self, response, body):
        try:
            with open(self.log_filename, 'a') as f:
                f.write("{0}: {1}".format(datetime.now(),
                    format_response(response, body)))
        except IOError:
            pass

    def _get_from_cache(self, url):
        """ get a given url from the cachedir even if its expired
            or return None if no data is available
        """
        scheme = urlparse(url).scheme
        if self._http[scheme].cache:
            cached_value = self._http[scheme].cache.get(
                httplib2.urlnorm(url)[-1])
            if cached_value:
                info, content = cached_value.split('\r\n\r\n', 1)
                return content

    def _path2url(self, path, scheme=None):
        if scheme is None:
            service_root = self._service_root
        else:
            parts = [scheme] + self._parsed_service_root[1:]
            service_root = urlunparse(parts)
        return service_root.strip('/') + '/' + path.lstrip('/')

    def _get_serializer(self, content_type=None):
        # Import here to avoid a circular import
        from piston_mini_client.serializers import get_serializer
        if content_type is None:
            content_type = self.default_content_type
        default_serializer = get_serializer(content_type)
        return self.serializers.get(content_type, default_serializer)