# 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
from offog import die

def get_token():
	"""Return (token, secret_key)."""
	f = open(os.environ["HOME"] + "/.amazon_token")
	fields = f.read().strip().split()
	f.close()
	return (fields[0], fields[1])

def call(args):
	"""Call an Amazon API with the given args, returning an
	xml.dom.minidom-parsed version of the response."""

	(token, secret_key) = get_token()

	all_args = {}
	all_args.update(args)
	all_args["Service"] = "AWSECommerceService"
	all_args["SubscriptionId"] = token
	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 = "http://%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 item_url(asin):
	"""Return the URL for an item."""
	return "http://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."""

	items = {}
	page_num = 1
	last_page = False
	while not last_page:
		# Amazon used to have an API call for this (ListLookup), but it
		# disappeared some time in 2010...
		url = "http://www.amazon.co.uk/registry/wishlist/%s/?_encoding=UTF8&filter=all&sort=date-added&layout=compact&reveal=all&page=%d" % (wishlist_id, page_num)
		page = lxml.html.parse(url).getroot()
		page.make_links_absolute(url)

		sortbar = page.cssselect(".sortbarText")
		if len(sortbar) == 0:
			die("No sortbarText found")
		m = re.search(r'Page (\d+) of (\d+)', sortbar[0].text_content())
		if m is None:
			die("No 'Page x of y' found")
		if int(m.group(1)) == int(m.group(2)):
			last_page = True

		found_any = False
		for anchor in page.cssselect(".compact-items a"):
			m = re.search(r'/dp/([^/]+)', anchor.get("href"))
			if m is not None:
				items[m.group(1)] = anchor.text_content()
				found_any = True

		if not found_any:
			die("No items found")

		page_num += 1

	return items