Friday, April 6, 2007

Amazon links in Ruby

As I mentioned in an earlier post, I read a lot, and I want to be able to comment on the books I like, with links to a page about the book on my preferred book seller, Amazon. I also have an associates account with Amazon and I'd like to include that in the link, even though the last time I made any money from that was about 2001! Making the links has, frankly, been a pain the butt, but I finally dusted off my Ruby and used Amazon Web Services (AWS) to make this easier.

First I tried Ruby/Amazon, but this seemed to be using an old version of the AWS and I couldn't figure out how to do an ISBN based lookup, and I eventually abandoned it. In hindsight I should have done this earlier - the functionality I need was pretty easy to write directly in Ruby, and only the latest version of AWS seems to handle both 10 and 13 digit ISBNs correctly.

So here's my code:

require 'rubygems'
require 'hpricot'
require 'open-uri'

isbn = ARGV[0]

ASSOCIATES_TAG = 'cogentconsult-20'

site = '' +
'&AWSAccessKeyId=' + ACCESS_KEY +
'&AssociateTag=' + ASSOCIATES_TAG +
'&Operation=ItemLookup' +
'&ResponseGroup=ItemAttributes,Images' +
'&IdType=ISBN' +
'&SearchIndex=Books' +
'&ItemId=' + isbn

doc = Hpricot(open(site))

author ="author").inner_html
title ="title").inner_html
detail_page ="detailpageurl").inner_html
image ="smallimage/url").inner_html

puts ''

html = "<a href='#{detail_page}'><img src='#{image}' alt='#{title}'></a><a href='#{detail_page}'>#{title}</a> by #{author}"

puts html

Open-uri made the http access a piece of cake - definitely use this instead of Net::HTTP - and Hpricot was equally adept at giving me just the parts of the returned XML that I needed.

I can run this at the command line using "ruby booklink.rb someISBN" and I get the html for both an image link and a text link, that I can then paste into my web pages and edit ass appropriate. Hopefully I'll now be less reluctant to write about the books I've read.

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