# Utility module for using Amazon's XML services.
# Adam Sampson <ats@offog.org>
import os, urllib, xml.dom.minidom, time, hmac, hashlib, lxml.html, re
import subprocess
import urllib2
from lxml import etree
from offog import die, warn
def get_token():
	"""Return (token, secret_key, associate_tag)."""
	f = open(os.environ["HOME"] + "/.amazon_token")
	fields = f.read().strip().split()
	f.close()
	return (fields[0], fields[1], fields[2])
def call(args):
	"""Call an Amazon API with the given args, returning an
	xml.dom.minidom-parsed version of the response."""
	(token, secret_key, associate_tag) = get_token()
	all_args = {}
	all_args.update(args)
	all_args["Service"] = "AWSECommerceService"
	all_args["SubscriptionId"] = token
	all_args["AssociateTag"] = associate_tag
	all_args["Timestamp"] = time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
	def aquote(s):
		return urllib.quote(s, "~")
	uri_args = [(aquote(k) + "=" + aquote(v)).encode("UTF-8")
	 for k, v in all_args.items()]
	uri_args.sort()
	uri_host = "webservices.amazon.co.uk"
	uri_path = "/onca/xml"
	uri_query = "&".join(uri_args)
	uri = "https://%s%s?%s" % (uri_host, uri_path, uri_query)
	sign_data = chr(10).join(["GET", uri_host, uri_path, uri_query])
	signature = hmac.new(secret_key, sign_data, hashlib.sha256).digest()
	uri += "&Signature=" + aquote(signature.encode("base64").strip())
	f = urllib.urlopen(uri)
	data = xml.dom.minidom.parse(f)
	f.close()
	return data
def isbn_to_asin(isbn):
	if len(isbn) == 10:
		return isbn
	elif len(isbn) == 13 and isbn.startswith("978"):
		# Convert to ISBN-10.
		# See: https://en.wikipedia.org/wiki/ISBN
		csum = 0
		for i, c in enumerate(isbn[3:-1]):
			csum += int(c) * (10 - i)
		x = isbn[3:-1] + "0123456789X0"[11 - (csum % 11)]
		return x
	else:
		raise ValueError("Bad ISBN: " + isbn)
def item_url(asin):
	"""Return the URL for an item."""
	return "https://www.amazon.co.uk/dp/" + asin
def get_text(node):
	"""Return the contents of the first text node encountered in a minidom
	subtree."""
	for cn in node.childNodes:
		if cn.nodeType == node.TEXT_NODE:
			return cn.data
	return None
def get_wishlist_items(wishlist_id):
	"""Return a dictionary mapping item IDs to titles from the given
	wishlist."""
	# Amazon used to have an API call for this (ListLookup), but it
	# disappeared some time in 2010...
	# And in 2016 it stopped accepting requests without a fake User-Agent.
	# And in 2017 it turned into some horrific AJAX disaster.
	url = "https://www.amazon.co.uk/hz/wishlist/ls/%s?type=wishlist&filter=all&sort=default" % wishlist_id
	items = {}
	while True:
		print "Fetching", url
		request = urllib2.Request(url)
		request.add_header("User-Agent", "User-Agent: Mozilla/5.0 (X11; Linux.x86_64; rv:48.0) Gecko/20100101 Firefox/48.0")
		f = urllib2.urlopen(request)
		page = lxml.html.parse(f).getroot()
		f.close()
		page.make_links_absolute(url)
		found_any = False
		for anchor in page.cssselect("a.a-link-normal"):
			aid = anchor.get("id", "")
			if not aid.startswith("itemName_"):
				continue
			m = re.search(r'/dp/([^\?/]+)', anchor.get("href", ""))
			if m is not None:
				items[m.group(1)] = anchor.get("title")
				found_any = True
		# Find the next page.
		for anchor in page.cssselect("a.wl-see-more"):
			if anchor.text_content().find("See More") != -1:
				url = anchor.get("href")
				break
		else:
			# No more pages.
			break
		if not found_any:
			die("No items found")
	return items
def load_hux_wishlist(filename):
	"""Parse a hux file containing wishlist items for ones that Amazon can
	find. (This is the source for the wishlist on my web site.)
	Return a dict mapping item IDs to titles."""
	items = {}
	f = subprocess.Popen(["hux", filename], stdout=subprocess.PIPE).stdout
	wishlist = etree.parse(f).getroot()
	f.close()
	for tag in ("isbn", "amazon", "amazonde", "amazonus"):
		for el in wishlist.iter(tag=tag):
			if tag == "isbn":
				asin = isbn_to_asin(el.text)
				if asin != el.text:
					warn("ISBN ", el.text,
					 " should be ", asin)
			else:
				asin = el.text
			items[asin] = el.getparent().find("title").text
	return items
if __name__ == "__main__":
	assert isbn_to_asin("0356511081") == "0356511081"
	assert isbn_to_asin("9780099449256") == "0099449250"
	assert isbn_to_asin("9780356511085") == "0356511081"
	assert isbn_to_asin("9780356511689") == "0356511685"
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