ecs.py

# Author: Kun Xi <kunxi@kunxi.org>
# License: Python Software Foundation License

"""
A Python wrapper to access Amazon Web Service(AWS) E-Commerce Serive APIs,
based upon pyamazon (http://www.josephson.org/projects/pyamazon/), enhanced
to meet the latest AWS specification(http://www.amazon.com/webservices).

This module defines the following classes:

- `Bag`, a generic container for the python objects
- `listIterator`, a derived class of list
- `pagedIterator`, a page-based iterator using lazy evaluation

Exception classes:

- `AWSException`
- `NoLicenseKey`
- `NoSecretAccessKey`
- `BadLocale`
- `BadOption`
- `ExactParameterRequirement`
- `ExceededMaximumParameterValues`
- `InsufficientParameterValues`
- `InternalError`
- `InvalidEnumeratedParameter`
- `InvalidISO8601Time`
- `InvalidOperationForMarketplace`
- `InvalidOperationParameter`
- `InvalidParameterCombination`
- `InvalidParameterValue`
- `InvalidResponseGroup`
- `InvalidServiceParameter`
- `InvalidSubscriptionId`
- `InvalidXSLTAddress`
- `MaximumParameterRequirement`
- `MinimumParameterRequirement`
- `MissingOperationParameter`
- `MissingParameterCombination`
- `MissingParameters`
- `MissingParameterValueCombination`
- `MissingServiceParameter`
- `ParameterOutOfRange`
- `ParameterRepeatedInRequest`
- `RestrictedParameterValueCombination`
- `XSLTTransformationError`

Functions:

- `setLocale`
- `getLocale`
- `setLicenseKey`
- `getLicenseKey`
- `getVersion`
- `setOptions` 
- `getOptions`
- `buildRequest`
- `buildException`
- `query`
- `rawObject`
- `rawIterator`
- `pagedWrapper`
- `unmarshal`
- `ItemLookup`
- `XMLItemLookup`
- `ItemSearch`
- `XMLItemSearch`
- `SimilarityLookup`
- `XMLSimilarityLookup`
- `ListLookup`
- `XMLListLookup`
- `ListSearch`
- `XMLListSearch`
- `CartCreate`
- `XMLCartCreate`
- `CartAdd`
- `XMLCartAdd`
- `CartGet`
- `XMLCartGet`
- `CartModify`
- `XMLCartModify`
- `CartClear`
- `XMLCartClear`
- `SellerLookup`
- `XMLSellerLookup`
- `SellerListingLookup`
- `XMLSellerListingLookup`
- `SellerListingSearch`
- `XMLSellerListingSearch`
- `CustomerContentSearch`
- `XMLCustomerContentSearch`
- `CustomerContentLookup`
- `XMLCustomerContentLookup`
- `BrowseNodeLookup`
- `XMLBrowseNodeLookup`
- `Help`
- `XMLHelp`
- `TransactionLookup`
- `XMLTransactionLookup`

Accroding to the ECS specification, there are two implementation foo and XMLfoo, for example, `ItemLookup` and `XMLItemLookup`. foo returns a Python object, XMLfoo returns the raw XML file.

How To Use This Module
======================
(See the individual classes, methods, and attributes for details.)

1. Apply for a Amazon Web Service API key from Amazon Web Service:
   https://aws-portal.amazon.com/gp/aws/developer/registration/index.html

2. Import it: ``import pyaws.ecs``

3. Setup the license key: ``ecs.setLicenseKey('YOUR-KEY-FROM-AWS')``
   or you could use the environment variable AMAZON_LICENSE_KEY

   Optional: 
   a) setup other options, like AssociateTag, MerchantID, Validate
   b) export the http_proxy environment variable if you want to use proxy
   c) setup the locale if your locale is not ``us``

4. Send query to the AWS, and manupilate the returned python object.

"""

__author__ = "Kun Xi < kunxi@kunxi.org >"
__version__ = "0.2.0"
__license__ = "Python Software Foundation"
__docformat__ = 'restructuredtext'


import os, urllib, string, hmac, hashlib, sys
from datetime import datetime
from xml.dom import minidom

# python 2.4 compat for hashes
try:
    from hashlib import sha1 as sha
    from hashlib import sha256 as sha256
    
    if sys.version[:3] == "2.4":
        # we are using an hmac that expects a .new() method.
        class Faker:
            def __init__(self, which):
                self.which = which
                self.digest_size = self.which().digest_size
            
            def new(self, *args, **kwargs):
                return self.which(*args, **kwargs)
        
        sha = Faker(sha)
        sha256 = Faker(sha256)

except ImportError:
    import sha
    sha256 = None


# Package-wide variables:
LICENSE_KEY = None
SECRET_ACCESS_KEY = None
LOCALE = "us"
VERSION = "2009-06-01"
OPTIONS = {}


__supportedLocales = {
        None : "ecs.amazonaws.com",  
        "us" : "ecs.amazonaws.com",  
        "uk" : "ecs.amazonaws.co.uk", 
        "de" : "ecs.amazonaws.de", 
        "jp" : "ecs.amazonaws.jp", 
        "fr" : "ecs.amazonaws.fr", 
        "ca" : "ecs.amazonaws.ca", 
    }

__licenseKeys = (
    (lambda key: key),
    (lambda key: LICENSE_KEY), 
    (lambda key: os.environ.get('AWS_LICENSE_KEY', None)),
    (lambda key: os.environ.get('AWS_ACCESS_KEY_ID', None))
   )

__associateTags = (
    (lambda key: key),
    (lambda key: ASSOCIATE_TAG), 
    (lambda key: os.environ.get('AWS_ASSOCIATE_TAG', None))
   )

__secretAccessKeys = (
    (lambda key: key),
    (lambda key: SECRET_ACCESS_KEY), 
    (lambda key: os.environ.get('AWS_SECRET_ACCESS_KEY', None))
   )



def __buildPlugins():
    """
    Build plugins used in unmarshal
    Return the dict like:
    Operation => { 'isByPassed'=>(...), 'isPivoted'=>(...), 
        'isCollective'=>(...), 'isCollected'=>(...), 
        isPaged=> { key1: (...), key2: (...), ... }  
    """

    """
    ResponseGroups heirachy:
    Parent => children,

    The benefit of this layer is to reduce the redundency, when
    the child ResponseGroup change, it propaged to the parent
    automatically
    """
    rgh = {
        'CustomerFull': ('CustomerInfo', 'CustomerLists', 'CustomerReviews'), 
        'Large': ('Accessories', 'BrowseNodes', 'ListmaniaLists', 'Medium', 'Offers', 'Reviews', 'Similarities', 'Tracks'),
        'ListFull': ('ListInfo', 'ListItems'),
        'ListInfo': ('ListMinimum', ),
        'ListItems': ('ListMinimum', ),
        'Medium': ('EditorialReview', 'Images', 'ItemAttributes', 'OfferSummary', 'Request', 'SalesRank', 'Small'),
        'OfferFull': ('Offers',),
        'Offers': ('OfferSummary',),
        'Variations': ('VariationMinimum', 'VariationSummary')
    }

    """
    ResponseGroup and corresponding plugins:
    ResponseGroup=>(isBypassed, isPivoted, isCollective, isCollected, isPaged)

    isPaged is defined as:
    { kwItems : (kwPage, kwTotalResults, pageSize) }

    - kwItems: string, the tagname of collection
    - kwPage: string, the tagname of page 
    - kwTotalResults: string, the tagname of length 
    - pageSize: constant integer, the size of each page

    CODE DEBT: 
    
    - Do we need to remove the ResponseGroup in rgh.keys()? At least, Medium does not
    introduce any new attributes.

    """
    rgps = {
        'Accessories': ((), (), ('Accessories',), ('Accessory',), {}), 
        'AlternateVersions': ((), (), (), (), {}), 
        'BrowseNodeInfo': ((), (), ('Children', 'Ancestors'), ('BrowseNode',), {}),
        'BrowseNodes': ((), (), ('Children', 'Ancestors', 'BrowseNodes'), ('BrowseNode',), {}),
        'Cart': ((), (), (), (), {}),
        'CartNewReleases': ((), (), (), (), {}),
        'CartTopSellers': ((), (), (), (), {}),
        'CartSimilarities': ((), (), (), (), {}),
        'Collections': ((), (), (), (), {}),
        'CustomerFull': ((), (), (), (), {}),
        'CustomerInfo': ((), (), ('Customers',), ('Customer',), {}),
        'CustomerLists': ((), (), ('Customers',), ('Customer',), {}),
        'CustomerReviews': ((), (), ('Customers',),('Customer', 'Review'), 
            {'CustomerReviews': ('ReviewPage', 'TotalReviews', 10)}),
        'EditorialReview': ((), (), ('EditorialReviews',), ('EditorialReview',), {}),
        'Help': ((), (), ('RequiredParameters', 'AvailableParameters',
            'DefaultResponseGroups', 'AvailableResponseGroups'),
             ('Parameter', 'ResponseGroup'), {}),
        'Images': ((), (), ('ImageSets',), ('ImageSet',), {}),
        'ItemAttributes': ((), ('ItemAttributes',), (), (), {}),
        'ItemIds': ((), (), (), (), {}),
        'ItemLookup.Small': ((), ('ItemAttributes',), (), ('Item',), 
            {'Items': ('OfferPage', 'TotalResults', 10) }),
        'ItemSearch.Small': ((), ('ItemAttributes',), (), ('Item',), 
            {'Items': ('ItemPage', 'TotalResults', 10) }),
        'Large': ((), (), (), (), {}),
        'ListFull': ((), (), (), (), {}),
        'ListInfo': ((), (), (), (), {}),
        'ListItems': ((), (), (), (), {}),
        'ListmaniaLists': ((), (), ('ListmaniaLists', ), ('ListmaniaList',), {}),
        'ListMinimum': ((), (), (), (), {}),
        'Medium': ((), (), (), (), {}),
        'MerchantItemAttributes': ((), (), (), (), {}),
        'NewReleases': ((), (), ('NewReleases',), ('NewRelease',), {}),
        'OfferFull': ((), (), (), (), {}),
        'OfferListings': ((), (), (), (), {}),
        'Offers': ((), (), (), ('Offer',), {'Offers': ('OfferPage', 'TotalOffers', 10)}),
        'OfferSummary': ((), (), (), (), {}),
        'Request': (('Request',), (), (), (), {}),
        'Reviews': ((), (), (),('Review',), 
            {'CustomerReviews': ('ReviewPage', 'TotalReviews', 10)}),
        'SalesRank': ((), (), (), (), {}),
        'SearchBins': ((), (), ('SearchBinSets',), ('SearchBinSet',), {}),
        'Seller': ((), (), (), (), {}),
        'SellerListing': ((), (), (), (), {}),
        'Similarities': ((), (), ('SimilarProducts',), ('SimilarProduct',), {}),
        'Small': ((), (), (), (), {}),
        'Subjects': ((), (), ('Subjects',), ('Subject',), {}),
        'TopSellers': ((), (), ('TopSellers',), ('TopSeller',), {}),
        'Tracks': ((), (), (), (), {}),
        'TransactionDetails': ((), (), ('Transactions', 'TransactionItems', 'Shipments'),
            ('Transaction', 'TransactionItem', 'Shipment'), {}),
        'Variations': ((), (), (), (), {}),
        'VariationMinimum': ((), (), ('Variations',), ('Variation',), {}),
        'VariationImages': ((), (), (), (), {}),
        'VariationSummary':((), (), (), (), {}) 
    }
    
    """
    Operation=>ResponseGroups 
    """
    orgs = {
        'BrowseNodeLookup': ('Request', 'BrowseNodeInfo', 'NewReleases', 'TopSellers'),
        'CartAdd': ('Cart', 'Request', 'CartSimilarities', 'CartTopSellers', 'NewReleases'),
        'CartClear': ('Cart', 'Request'),
        'CartCreate': ('Cart', 'Request', 'CartSimilarities', 'CartTopSellers', 'CartNewReleases'),
        'CartGet': ('Cart', 'Request', 'CartSimilarities', 'CartTopSellers', 'CartNewReleases'),
        'CartModify': ('Cart', 'Request', 'CartSimilarities', 'CartTopSellers', 'CartNewReleases'),
        'CustomerContentLookup': ('Request', 'CustomerInfo', 'CustomerReviews', 'CustomerLists', 'CustomerFull'),
        'CustomerContentSearch': ('Request', 'CustomerInfo'),
        'Help': ('Request', 'Help'),
        'ItemLookup': ('Request', 'ItemLookup.Small', 'Accessories', 'BrowseNodes', 'EditorialReview', 'Images', 'ItemAttributes', 'ItemIds', 'Large', 'ListmaniaLists', 'Medium', 'MerchantItemAttributes', 'OfferFull', 'Offers', 'OfferSummary', 'Reviews', 'SalesRank', 'Similarities', 'Subjects', 'Tracks', 'VariationImages', 'VariationMinimum', 'Variations', 'VariationSummary'),
        'ItemSearch': ('Request', 'ItemSearch.Small', 'Accessories', 'BrowseNodes', 'EditorialReview', 'ItemAttributes', 'ItemIds', 'Large', 'ListmaniaLists', 'Medium', 'MerchantItemAttributes', 'OfferFull', 'Offers', 'OfferSummary', 'Reviews', 'SalesRank', 'SearchBins', 'Similarities', 'Subjects', 'Tracks', 'VariationMinimum', 'Variations', 'VariationSummary'),
        'ListLookup': ('Request', 'ListInfo', 'Accessories', 'BrowseNodes', 'EditorialReview', 'Images', 'ItemAttributes', 'ItemIds', 'Large', 'ListFull', 'ListItems', 'ListmaniaLists', 'Medium', 'Offers', 'OfferSummary', 'Reviews', 'SalesRank', 'Similarities', 'Subjects', 'Tracks', 'VariationMinimum', 'Variations', 'VariationSummary'),
        'ListSearch': ('Request', 'ListInfo', 'ListMinimum'),
        'SellerListingLookup': ('Request', 'SellerListing'),
        'SellerListingSearch': ('Request', 'SellerListing'),
        'SellerLookup': ('Request', 'Seller'),
        'SimilarityLookup': ('Request', 'Small', 'Accessories', 'BrowseNodes', 'EditorialReview', 'Images', 'ItemAttributes', 'ItemIds', 'Large', 'ListmaniaLists', 'Medium', 'Offers', 'OfferSummary', 'Reviews', 'SalesRank', 'Similarities', 'Tracks', 'VariationMinimum', 'Variations', 'VariationSummary'),
        'TransactionLookup':('Request', 'TransactionDetails') 
    }
    
    def collapse(responseGroups):
        l = []
        for x in responseGroups:
            l.append(x)
            if x in rgh.keys():
                l.extend( collapse(rgh[x]) )
        return l


    def mergePlugins(responseGroups, index):
        #return reduce(lambda x, y: x.update(set(rgps[y][index])), responseGroups, set()) 
        # this magic reduce does not work, using the primary implementation first.
        # CODEDEBT: magic number !
        if index == 4:
            s = dict()
        else:
            s = set()

        map(lambda x: s.update(rgps[x][index]), responseGroups)
        return s
            
    def unionPlugins(responseGroups):
        return dict( [ (key, mergePlugins(collapse(responseGroups), index)) for index, key in enumerate(['isBypassed', 'isPivoted', 'isCollective', 'isCollected', 'isPaged']) ])

    return dict( [ (k, unionPlugins(v)) for k, v in orgs.items() ] )
    

__plugins = __buildPlugins()

# Wrapper class for ECS
class Bag : 
    """A generic container for the python objects"""
    def __repr__(self):
        return '<Bag instance: ' + self.__dict__.__repr__() + '>'
    


def rawObject(XMLSearch, arguments, kwItem, plugins=None):
    """Return simple object from `unmarshal`"""
    dom = XMLSearch(** arguments)
    return unmarshal(XMLSearch, arguments, dom.getElementsByTagName(kwItem).item(0), plugins) 

def rawIterator(XMLSearch, arguments, kwItems, plugins=None):
    """Return list of objects from `unmarshal`"""
    dom = XMLSearch(** arguments)
    return unmarshal(XMLSearch, arguments, dom.getElementsByTagName(kwItems).item(0), plugins, listIterator())


class listIterator(list):
    """List with extended attributes"""
    pass


def pagedWrapper(XMLSearch, arguments, keywords, plugins):
    """Wrapper of pagedIterator
    Parameters:

    - `XMLSearch`: a function, the query to get the DOM
    - `arguments`: a dictionary, `XMLSearch`'s arguments
    - `keywords`: a tuple, (kwItems, (kwPage, kwTotalResults, pageSize) )
    - `plugins`: a dictionary, collection of plugged objects
    
    Note: it is possible to have more than one pagedIterators
    in plugins, but only one pagedIterator is returned in
    pagedWrapper. 
    """

    return pagedIterator(XMLSearch, arguments, keywords,
        XMLSearch(** arguments).getElementsByTagName(keywords[0]).item(0),
        plugins)
    
class pagedIterator:
    """
    A page-based iterator using lazy evaluation.
    In some service, such as ItemSearch, AWS returns the result based on
    pages, the pagedIterator keeps track of the current page, and send
    the request only if necessary.

    Bugs: 

    - list slicing is still missing.
    """

    def __init__(self, XMLSearch, arguments, keywords, element, plugins):
        """
        Initialize a `pagedIterator` object.
        Parameters:

        - `XMLSearch`: a function, the query to get the DOM
        - `arguments`: a dictionary, `XMLSearch`'s arguments
        - `keywords`: a tuple, (kwItems, (kwPage, kwTotalResults, pageSize) )
        - `element`: a DOM element, the root of the collection
        - `plugins`: a dictionary, collection of plugged objects
        """
        kwItems, (kwPage, kwTotalResults, pageSize) = keywords

        self.__search = XMLSearch 
        self.__arguments = arguments 
        self.__plugins = plugins
        self.__keywords ={'Items':kwItems, 'Page':kwPage}
        self.__page = arguments[kwPage] or 1
            
        """Current page"""
        self.__index = 0
        """Current index"""
        self.__pageSize = pageSize

        self.__items = unmarshal(XMLSearch, arguments, element, plugins, listIterator())
        """Cached items"""
        try:
            self.__len = int(element.getElementsByTagName(kwTotalResults).item(0).firstChild.data)
        except AttributeError, e:
            self.__len = len(self.__items)

    def __len__(self):
        return self.__len

    def __iter__(self):
        return self

    def next(self):
        if self.__index < self.__len:
            self.__index = self.__index + 1
            return self.__getitem__(self.__index-1)
        else:
            raise StopIteration

    def __getitem__(self, key):
        num = int(key)
        if num >= self.__len:
            raise IndexError

        page = num / self.__pageSize + 1
        index = num % self.__pageSize
        if page != self.__page:
            self.__arguments[self.__keywords['Page']] = page
            dom = self.__search(** self.__arguments)
            self.__items = unmarshal(self.__search, self.__arguments, dom.getElementsByTagName(self.__keywords['Items']).item(0), self.__plugins, listIterator())
            self.__page = page

        return self.__items[index]


# Exception classes
class AWSException(Exception) : pass
class NoLicenseKey(AWSException) : pass
class NoAssociateTag(AWSException): pass
class NoSecretAccessKey(AWSException) : pass
class BadLocale(AWSException) : pass
class BadOption(AWSException): pass
# Runtime exception
class ExactParameterRequirement(AWSException): pass
class ExceededMaximumParameterValues(AWSException): pass
class InsufficientParameterValues(AWSException): pass
class InternalError(AWSException): pass
class InvalidEnumeratedParameter(AWSException): pass
class InvalidISO8601Time(AWSException): pass
class InvalidOperationForMarketplace(AWSException): pass
class InvalidOperationParameter(AWSException): pass
class InvalidParameterCombination(AWSException): pass
class InvalidParameterValue(AWSException): pass
class InvalidResponseGroup(AWSException): pass
class InvalidServiceParameter(AWSException): pass
class InvalidSubscriptionId(AWSException): pass
class InvalidXSLTAddress(AWSException): pass
class MaximumParameterRequirement(AWSException): pass
class MinimumParameterRequirement(AWSException): pass
class MissingOperationParameter(AWSException): pass
class MissingParameterCombination(AWSException): pass
class MissingParameters(AWSException): pass
class MissingParameterValueCombination(AWSException): pass
class MissingServiceParameter(AWSException): pass
class ParameterOutOfRange(AWSException): pass
class ParameterRepeatedInRequest(AWSException): pass
class RestrictedParameterValueCombination(AWSException): pass
class XSLTTransformationError(AWSException): pass


# Utilities functions
def setLocale(locale):
    """Set the locale
    if unsupported locale is set, BadLocale is raised."""
    global LOCALE
    if not __supportedLocales.has_key(locale):
        raise BadLocale, ("Unsupported locale. Locale must be one of: %s" %
            ', '.join([x for x in __supportedLocales.keys() if x]))
    LOCALE = locale


def getLocale():
    """Get the locale"""
    return LOCALE


def setAssociateTag(associate_tag=None):
    """Set AWS Associate Tag Required since Oct 2011
        AWS won't let you search without an associate tag
        """

    global ASSOCIATE_TAG
    for get in __associateTags:
        rc = get(associate_tag)
        if rc: 
            ASSOCIATE_TAG = rc;
            return;
    raise NoAssociateTag, ("Please get an associate tag from  http://www.amazon.com/webservices")

def getAssociateTag():
    """Get Associate Tag;
    if no associate tag is known, NoAssociateTag is raised.
    """
    if not ASSOCIATE_TAG:
        setAssociateTag()
    return ASSOCIATE_TAG

def setLicenseKey(license_key=None):
    """Set AWS license key.
    If license_key is not specified, the license key is set using the
    environment variable: AMAZON_LICENSE_KEY; if no license key is 
    set, NoLicenseKey exception is raised."""
    
    global LICENSE_KEY
    for get in __licenseKeys:
        rc = get(license_key)
        if rc: 
            LICENSE_KEY = rc;
            return;
    raise NoLicenseKey, ("Please get the license key from  http://www.amazon.com/webservices")


def getLicenseKey():
    """Get license key.
    If no license key is specified,  NoLicenseKey is raised."""

    if not LICENSE_KEY:
        setLicenseKey()
    return LICENSE_KEY

def setSecretAccessKey(secret_access_key=None):
    """Sets your secret AWS key.
    If secret_access_key is not specified, we look for the 
    environment variable: AMAZON_SECRET_ACCESS_KEY.  
    Raises NoSecretAccessKey if we can't get it to work."""
    
    global SECRET_ACCESS_KEY
    for get in __secretAccessKeys:
        rc = get(secret_access_key)
        if rc: 
            SECRET_ACCESS_KEY = rc;
            return;
    raise NoSecretAccessKey, ("Please get your secret key from  http://www.amazon.com/webservices")

def getSecretAccessKey():
    """Get the secret access key.
    If no key is specified,  NoSecretAccessKey is raised."""

    if not SECRET_ACCESS_KEY:
        setSecretAccessKey()
    return SECRET_ACCESS_KEY

def getVersion():
    """Get the version of ECS specification"""
    return VERSION
    

def setOptions(options):
    """
    Set the general optional parameter, available options are:
    - AssociateTag
    - MerchantID
    - Version
    - Validate
    """
    
    if set(options.keys()).issubset( set(['AssociateTag', 'MerchantID', 'Validate']) ):
        global OPTIONS
        OPTIONS.update(options)
    else:
        raise BadOption, ('Unsupported option')

        
def getOptions():
    """Get options"""
    return OPTIONS 

def buildSignature(netloc,query_string):
    secret_key = getSecretAccessKey()
    string_to_sign = 'GET\n%s\n%s\n%s' % (netloc,'/onca/xml',query_string)
    
    return urllib.quote_plus(hmac.new(secret_key,string_to_sign,sha256).digest().encode('base64').strip())

def buildQuery(argv):
    # 1. Filter any key set to 'None'
    # 2. Sort the dict by key
    # 3. Quote everything and build the query string
    query_string = "&".join("%s=%s" % (k, urllib.quote(str(argv[k]))) for (k) in sorted(argv.keys()) if argv[k])

    netloc = __supportedLocales[getLocale()]
    signature = buildSignature(netloc, query_string)
    return 'http://' + netloc + '/onca/xml?' + query_string + '&Signature=' + signature

def buildRequest(argv):
    """Adds some standard keys (like Timestamp and Version) to the request,
    then builds and returns the request-url."""

    if not argv['AWSAccessKeyId']:
        argv['AWSAccessKeyId'] = getLicenseKey()
    if not argv['AssociateTag']:
        argv['AssociateTag'] = getAssociateTag()
        
    argv.update(getOptions())
    argv.update({'Service':'AWSECommerceService',
                 'Timestamp':datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%SZ'),
                 'Version':VERSION})

    return buildQuery(argv)

def buildException(els):
    """Build the exception from the returned DOM node
    Note: only the first exception is raised."""

    error = els[0]
    class_name = error.childNodes[0].firstChild.data[4:]
    msg = error.childNodes[1].firstChild.data 

    e = globals()[ class_name ](msg)
    return e


def query(url):
    """Send the query url and return the DOM
    Exception is raised if there are errors"""
    u = urllib.FancyURLopener()
    usock = u.open(url)
    dom = minidom.parse(usock)
    usock.close()

    errors = dom.getElementsByTagName('Error')
    if errors:
        e = buildException(errors)
        raise e
    return dom


def unmarshal(XMLSearch, arguments, element, plugins=None, rc=None):
    """Return the `Bag` / `listIterator` object with attributes 
    populated using DOM element.
    
    Parameters:

    - `XMLSearch`: callback function, used when construct pagedIterator
    - `arguments`: arguments of `XMLSearch`
    - `element`: DOM object, the DOM element interested in
    - `plugins`: a dictionary, collection of plugged objects to fine-tune
      the object attributes
    - `rc`: Bag object, parent object

    This core function is inspired by Mark Pilgrim (f8dy@diveintomark.org)
    with some enhancement. Each node.tagName is evalued by plugins' callback
    functions:
        
    - if tagname in plugins['isBypassed']
        this elment is ignored
    - if tagname in plugins['isPivoted'] 
        this children of this elment is moved to grandparents
        this object is ignored.
    - if tagname in plugins['isCollective'] 
        this elment is mapped to []
    - if tagname in plugins['isCollected'] 
        this children of elment is appended to grandparent
        this object is ignored.
    - if tagname in plugins['isPaged'].keys():
        this pagedIterator is constructed for the object

    CODE DEBT:
    
    - Use optimal search for optimization if necessary
    """

    if(rc == None):
        rc = Bag()
    
    childElements = [e for e in element.childNodes if isinstance(e, minidom.Element)]

    if childElements:
        for child in childElements:
            key = child.tagName
            if hasattr(rc, key):
                attr = getattr(rc, key)
                if type(attr) <> type([]):
                    setattr(rc, key, [attr])
                setattr(rc, key, getattr(rc, key) + [unmarshal(XMLSearch, arguments, child, plugins)])
            elif isinstance(child, minidom.Element):
                if child.tagName in plugins['isCollected']:
                    rc.append(unmarshal(XMLSearch, arguments, child, plugins))
                elif child.tagName in plugins['isCollective']:
                    setattr(rc, key, unmarshal(XMLSearch, arguments, child, plugins, listIterator([])))
                elif child.tagName in plugins['isPaged'].keys():
                    setattr(rc, key, pagedIterator(XMLSearch, arguments, (child.tagName, plugins['isPaged'][child.tagName]), child, plugins))
                elif child.tagName in plugins['isPivoted']:
                    unmarshal(XMLSearch, arguments, child, plugins, rc)
                elif child.tagName in plugins['isBypassed']:
                    continue
                else:
                    setattr(rc, key, unmarshal(XMLSearch, arguments, child, plugins))
    else:
        rc = "".join([e.data for e in element.childNodes if isinstance(e, minidom.Text)])
    return rc


    
# User interfaces

def ItemLookup(ItemId, IdType=None, SearchIndex=None, MerchantId=None, Condition=None, DeliveryMethod=None, ISPUPostalCode=None, OfferPage=None, ReviewPage=None, ReviewSort=None, VariationPage=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None): 
    '''ItemLookup in ECS'''
    return pagedWrapper(XMLItemLookup, vars(), 
        ('Items', __plugins['ItemLookup']['isPaged']['Items']), __plugins['ItemLookup'])

    
def XMLItemLookup(ItemId, IdType=None, SearchIndex=None, MerchantId=None, Condition=None, DeliveryMethod=None, ISPUPostalCode=None, OfferPage=None, ReviewPage=None, ReviewSort=None, VariationPage=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None): 
    '''DOM representation of ItemLookup in ECS'''

    Operation = "ItemLookup"
    return query(buildRequest(vars()))


def ItemSearch(Keywords, SearchIndex="Blended", Availability=None, Title=None, Power=None, BrowseNode=None, Artist=None, Author=None, Actor=None, Director=None, AudienceRating=None, Manufacturer=None, MusicLabel=None, Composer=None, Publisher=None, Brand=None, Conductor=None, Orchestra=None, TextStream=None, ItemPage=None, OfferPage=None, ReviewPage=None, Sort=None, City=None, Cuisine=None, Neighborhood=None, MinimumPrice=None, MaximumPrice=None, MerchantId=None, Condition=None, DeliveryMethod=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):  
    '''ItemSearch in ECS'''

    return pagedWrapper(XMLItemSearch, vars(), 
        ('Items', __plugins['ItemSearch']['isPaged']['Items']), __plugins['ItemSearch'])


def XMLItemSearch(Keywords, SearchIndex="Blended", Availability=None, Title=None, Power=None, BrowseNode=None, Artist=None, Author=None, Actor=None, Director=None, AudienceRating=None, Manufacturer=None, MusicLabel=None, Composer=None, Publisher=None, Brand=None, Conductor=None, Orchestra=None, TextStream=None, ItemPage=None, OfferPage=None, ReviewPage=None, Sort=None, City=None, Cuisine=None, Neighborhood=None, MinimumPrice=None, MaximumPrice=None, MerchantId=None, Condition=None, DeliveryMethod=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):  
    '''DOM representation of ItemSearch in ECS'''

    Operation = "ItemSearch"
    return query(buildRequest(vars()))


def SimilarityLookup(ItemId, SimilarityType=None, MerchantId=None, Condition=None, DeliveryMethod=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):  
    '''SimilarityLookup in ECS'''

    argv = vars()
    plugins = {
        'isBypassed': (), 
        'isPivoted': ('ItemAttributes',),
        'isCollective': ('Items',),
        'isCollected': ('Item',),
        'isPaged': {}
    }
    return rawIterator(XMLSimilarityLookup, argv, 'Items', plugins)


def XMLSimilarityLookup(ItemId, SimilarityType=None, MerchantId=None, Condition=None, DeliveryMethod=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):  
    '''DOM representation of SimilarityLookup in ECS'''

    Operation = "SimilarityLookup"
    return query(buildRequest(vars()))


# List Operations

def ListLookup(ListType, ListId, ProductPage=None, ProductGroup=None, Sort=None, MerchantId=None, Condition=None, DeliveryMethod=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):  
    '''ListLookup in ECS'''

    argv = vars()
    plugins = {
        'isBypassed': (), 
        'isPivoted': ('ItemAttributes',),
        'isCollective': ('Lists',), 
        'isCollected': ('List',),
        'isPaged' : { 'Lists': ('ProductPage', 'TotalResults', 10) }
    }
    return pagedWrapper(XMLListLookup, argv, 
        ('Lists', plugins['isPaged']['Lists']), plugins)


def XMLListLookup(ListType, ListId, ProductPage=None, ProductGroup=None, Sort=None, MerchantId=None, Condition=None, DeliveryMethod=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):  
    '''DOM representation of ListLookup in ECS'''

    Operation = "ListLookup"
    return query(buildRequest(vars()))


def ListSearch(ListType, Name=None, FirstName=None, LastName=None, Email=None, City=None, State=None, ListPage=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''ListSearch in ECS'''

    argv = vars()
    plugins = {
        'isBypassed': (), 
        'isPivoted': ('ItemAttributes',),
        'isCollective': ('Lists',), 
        'isCollected': ('List',),
        'isPaged' : { 'Lists': ('ListPage', 'TotalResults', 10) }
    }
    return pagedWrapper(XMLListSearch, argv, 
        ('Lists', plugins['isPaged']['Lists']), plugins)


def XMLListSearch(ListType, Name=None, FirstName=None, LastName=None, Email=None, City=None, State=None, ListPage=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of ListSearch in ECS'''

    Operation = "ListSearch"
    return query(buildRequest(vars()))


#Remote Shopping Cart Operations
def CartCreate(Items, Quantities, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CartCreate in ECS'''

    return __cartOperation(XMLCartCreate, vars())


def XMLCartCreate(Items, Quantities, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CartCreate in ECS'''

    Operation = "CartCreate"
    argv = vars()
    for x in ('Items', 'Quantities'):
        del argv[x]

    __fromListToItems(argv, Items, 'ASIN', Quantities)
    return query(buildRequest(argv))


def CartAdd(Cart, Items, Quantities, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CartAdd in ECS'''

    return __cartOperation(XMLCartAdd, vars())


def XMLCartAdd(Cart, Items, Quantities, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CartAdd in ECS'''

    Operation = "CartAdd"
    CartId = Cart.CartId
    HMAC = Cart.HMAC
    argv = vars()
    for x in ('Items', 'Cart', 'Quantities'):
        del argv[x]

    __fromListToItems(argv, Items, 'ASIN', Quantities)
    return query(buildRequest(argv))


def CartGet(Cart, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CartGet in ECS'''
    return __cartOperation(XMLCartGet, vars())


def XMLCartGet(Cart, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CartGet in ECS'''

    Operation = "CartGet"
    CartId = Cart.CartId
    HMAC = Cart.HMAC
    argv = vars()
    del argv['Cart']
    return query(buildRequest(argv))


def CartModify(Cart, Items, Actions, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CartModify in ECS'''

    return __cartOperation(XMLCartModify, vars())


def XMLCartModify(Cart, Items, Actions, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CartModify in ECS'''
    Operation = "CartModify"
    CartId = Cart.CartId
    HMAC = Cart.HMAC
    argv = vars()
    for x in ('Cart', 'Items', 'Actions'):
        del argv[x]

    __fromListToItems(argv, Items, 'CartItemId', Actions)
    return query(buildRequest(argv))

    
def CartClear(Cart, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CartClear in ECS'''
    return __cartOperation(XMLCartClear, vars())


def XMLCartClear(Cart, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CartClear in ECS'''

    Operation = "CartClear"
    CartId = Cart.CartId
    HMAC = Cart.HMAC
    argv = vars()
    del argv['Cart']

    return query(buildRequest(argv))


def __fromListToItems(argv, items, id, actions):
    '''Convert list to AWS REST arguments'''

    for i in range(len(items)):
        argv["Item.%d.%s" % (i+1, id)] = getattr(items[i], id);
        action = actions[i]
        if isinstance(action, int):
            argv["Item.%d.Quantity" % (i+1)] = action
        else:
            argv["Item.%d.Action" % (i+1)] = action


def __cartOperation(XMLSearch, arguments):
    '''Generic cart operation'''

    plugins = {
        'isBypassed': ('Request',),
        'isPivoted': (), 
        'isCollective': ('CartItems', 'SavedForLaterItems'),
        'isCollected': ('CartItem', 'SavedForLaterItem'),
        'isPaged': {}
    }
    return rawObject(XMLSearch, arguments, 'Cart', plugins)


# Seller Operation
def SellerLookup(Sellers, FeedbackPage=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''SellerLookup in AWS'''

    argv = vars()
    plugins = {
        'isBypassed': ('Request',),
        'isPivoted': (), 
        'isCollective': ('Sellers',),
        'isCollected': ('Seller',),
        'isPaged': {}
    }
    return rawIterator(XMLSellerLookup, argv, 'Sellers', plugins)


def XMLSellerLookup(Sellers, FeedbackPage=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of SellerLookup in AWS'''

    Operation = "SellerLookup"
    SellerId = ",".join(Sellers)
    argv = vars()
    del argv['Sellers']
    return query(buildRequest(argv))


def SellerListingLookup(SellerId, Id, IdType="Listing", ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''SellerListingLookup in AWS

    Notice: although the repsonse includes TotalPage, TotalResults, 
    there is no ListingPage in the request, so we have to use rawIterator
    instead of pagedIterator. Hope Amazaon would fix this inconsistance'''
    
    argv = vars()
    plugins = {
        'isBypassed': ('Request',),
        'isPivoted': (), 
        'isCollective': ('SellerListings',), 
        'isCollected': ('SellerListing',),
        'isPaged': {}
    }
    return rawIterator(XMLSellerListingLookup, argv, "SellerListings", plugins)


def XMLSellerListingLookup(SellerId, Id, IdType="Listing", ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of SellerListingLookup in AWS'''

    Operation = "SellerListingLookup"
    return query(buildRequest(vars()))


def SellerListingSearch(SellerId, Title=None, Sort=None, ListingPage=None, OfferStatus=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''SellerListingSearch in AWS'''

    argv = vars()
    plugins = {
        'isBypassed': ('Request',),
        'isPivoted': (), 
        'isCollective': ('SellerListings',), 
        'isCollected': ('SellerListing',),
        'isPaged' : { 'SellerListings': ('ListingPage', 'TotalResults', 10) }
    }
    return pagedWrapper(XMLSellerListingSearch, argv, 
        ('SellerListings', plugins['isPaged']['SellerListings']), plugins)


def XMLSellerListingSearch(SellerId, Title=None, Sort=None, ListingPage=None, OfferStatus=None, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of SellerListingSearch in AWS'''

    Operation = "SellerListingSearch"
    return query(buildRequest(vars()))


def CustomerContentSearch(Name=None, Email=None, CustomerPage=1, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CustomerContentSearch in AWS'''

    return rawIterator(XMLCustomerContentSearch, vars(), 'Customers', __plugins['CustomerContentSearch'])


def XMLCustomerContentSearch(Name=None, Email=None, CustomerPage=1, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CustomerContentSearch in AWS'''

    Operation = "CustomerContentSearch"
    argv = vars()
    for x in ('Name', 'Email'):
        if not argv[x]:
            del argv[x]
    return query(buildRequest(argv))


def CustomerContentLookup(CustomerId, ReviewPage=1, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''CustomerContentLookup in AWS'''

    argv = vars()
    plugins = {
        'isBypassed': ('Request',),
        'isPivoted': (), 
        'isCollective': ('Customers',),
        'isCollected': ('Customer',),

    }
    return rawIterator(XMLCustomerContentLookup, argv, 'Customers', __plugins['CustomerContentLookup'])


def XMLCustomerContentLookup(CustomerId, ReviewPage=1, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of CustomerContentLookup in AWS'''

    Operation = "CustomerContentLookup"
    return query(buildRequest(vars()))


# BrowseNode
def BrowseNodeLookup(BrowseNodeId, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    """
    BrowseNodeLookup in AWS 
    """
    return rawIterator(XMLBrowseNodeLookup, vars(), 'BrowseNodes', __plugins['BrowseNodeLookup'])


def XMLBrowseNodeLookup(BrowseNodeId, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of BrowseNodeLookup in AWS'''
    
    Operation = "BrowseNodeLookup"
    return query(buildRequest(vars()))


# Help
def Help(HelpType, About, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''Help in AWS'''
    return rawObject(XMLHelp, vars(), 'Information', __plugins['Help'])


def XMLHelp(HelpType, About, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of Help in AWS'''

    Operation = "Help"
    return query(buildRequest(vars()))


# Transaction
def TransactionLookup(TransactionId, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''TransactionLookup in AWS'''
    return rawIterator(XMLTransactionLookup, vars(), 'Transactions', __plugins['TransactionLookup'])
    

def XMLTransactionLookup(TransactionId, ResponseGroup=None, AWSAccessKeyId=None, AssociateTag=None):
    '''DOM representation of TransactionLookup in AWS'''

    Operation = "TransactionLookup"
    return query(buildRequest(vars()))



if __name__ == "__main__" :
    setLicenseKey("1MGVS72Y8JF7EC7JDZG2")
    ItemSearch('XML Python', SearchIndex='Books', MerchantId='All', ResponseGroup='OfferFull')
    import pdb
    pdb.set_trace()