#!/usr/bin/python

from xml.dom import minidom, Node
import urllib
import time
import datetime
import hashlib
import base64
import hmac

class PyMazonError(Exception):
    """Holds information about an error that occured during a pymazon request"""
    def __init__(self, messages):
        self.__message = '\n'.join(messages)

    def __get_message(self):
        return self.__message

    def __str__(self):
        return repr(self.__message)

    message = property(fget=__get_message)


class PyMazonBook:
    """Stores information about a book retrieved via PyMazon."""
    def __init__(self, title, authors, publisher, year, isbn10, isbn13, edition):
        self.__title = title
        self.__authors = authors
        self.__publisher = publisher
        self.__year = year 
        self.__isbn10 = isbn10
        self.__isbn13 = isbn13
        self.__edition = edition

    def __str__(self):
        return 'Title:     ' + self.title + '\n' + \
               'Author(s): ' + ', '.join(self.authors) + '\n' \
                 'Publisher: ' + self.publisher + '\n' + \
                 'Year:      ' + self.year + '\n' + \
                 'ISBN-10:   ' + self.isbn10 + '\n' + \
                 'ISBN-13:   ' + self.isbn13 + '\n' + \
                 'Edition:   ' + self.edition

    def __get_title(self):
        return self.__title

    def __get_authors(self):
        return self.__authors
    
    def __get_publisher(self):
        return self.__publisher

    def __get_year(self):
        return self.__year

    def __get_isbn10(self):
        return self.__isbn10

    def __get_isbn13(self):
        return self.__isbn13

    def __get_edition(self):
        return self.__edition

    title = property(fget=__get_title)
    authors = property(fget=__get_authors)
    publisher = property(fget=__get_publisher)
    year = property(fget=__get_year)
    isbn10 = property(fget=__get_isbn10)
    isbn13 = property(fget=__get_isbn13)
    edition = property(fget=__get_edition)


class PyMazon:
    """A method of looking up book information on Amazon."""
    def __init__(self, accesskey, secretkey):
        self.__key = accesskey
        self.__secret = secretkey
        self.__last_query_time = 0

    def __form_request(self, isbn):
        content = {}
        dstamp = datetime.datetime.utcfromtimestamp(time.time())
        content['Timestamp'] = dstamp.strftime('%Y-%m-%dT%H:%M:%S.000Z')
        content['Service'] = 'AWSECommerceService'
        content['Version'] = '2008-08-19'
        content['Operation'] = 'ItemLookup'
        content['ResponseGroup'] = 'ItemAttributes'
        content['IdType'] = 'ISBN'
        content['SearchIndex'] = 'Books'
        content['ItemId'] = isbn
        content['AWSAccessKeyId'] = self.__key

        URI_String = []

        for key, value in sorted(content.items()):
            URI_String.append('%s=%s' % (key, urllib.quote(value)))

        req = '&'.join(URI_String)
        to_sign_req = 'GET\necs.amazonaws.com\n/onca/xml\n' + req

        h = hmac.new(self.__secret, to_sign_req, hashlib.sha256)
        sig = base64.b64encode(h.digest())
        req += '&Signature=%s' % urllib.quote(sig)

        return 'http://ecs.amazonaws.com/onca/xml?' + req

    def __elements_text(self, element, name):
        result = []
        matching = element.getElementsByTagName(name)
        for match in matching:
            if len(match.childNodes) != 1:
                continue
            child = match.firstChild
            if child.nodeType != Node.TEXT_NODE:
                continue
            result.append(child.nodeValue.strip())
        return result

    def __format_errors(self, errors):
        error_list = []
        for error in errors:
            error_list.extend(self.__elements_text(error, 'Message'))
        return error_list

    def __extract_single(self, element, name):
        matches = self.__elements_text(element, name)
        if len(matches) == 0:
            return ''
        return matches[0]

    def lookup(self, isbn):
        file = urllib.urlretrieve(self.__form_request(isbn))[0]
        xmldoc = minidom.parse(file)

        cur_time = time.time()
        while cur_time - self.__last_query_time < 1.0:
            sleep(cur_time - self.__last_query_time)
            cur_time = time.time()
        self.__last_query_time = cur_time

        errors = xmldoc.getElementsByTagName('Errors')
        if len(errors) != 0:
            raise PyMazonError, self.__format_errors(errors)

        title = self.__extract_single(xmldoc, 'Title')
        authors = self.__elements_text(xmldoc, 'Author')
        publisher = self.__extract_single(xmldoc, 'Publisher')
        year = self.__extract_single(xmldoc, 'PublicationDate')[0:4]
        isbn10 = self.__extract_single(xmldoc, 'ISBN')
        isbn13 = self.__extract_single(xmldoc, 'EAN')
        edition = self.__extract_single(xmldoc, 'Edition')
        
        return PyMazonBook(title, authors, publisher, year, isbn10, isbn13, edition)