#!/usr/local/bin/perl

=head1 NAME

wishlist - look for cheap stuff on your Amazon wishlist

=head1 SYNOPSIS

    wishlist --token=MYAMAZONTOKEN --wishlist=WISHLISTID --email=god@heaven.mil

=head1 DESCRIPTION

If you maintain an amazon wishlist, and don't mind buying used books
C<wishlist> will go to amazon and look for cheap copies of things you
want and email you if cheap stuff is found. The idea is that you put 
a call to wishlist in your crontab to run every hour looking for bargains.
When a bargain appears you'll get an email letting you know what's 
available.

C<wishlist> uses Amazons Web Services so you'll need to get a token, which
takes just a second, and is absolutely free.

Once you've got a token, you need to figure out what your wishlist ID
is. The easiest way to do this is to search for your own wishlist, and
look at the URL that links to it. For example mine looks like:

    http://www.amazon.com/gp/registry/registry.html/102-0255529-0382518?%5Fencoding=UTF8&id=F1K2C8DXQGOE

The id=F1K2C8DXQGOE identifies my wishlist ID. With these two pieces of
informaton you can run wishlist if you supply an email address to send
the notifications to. 

You can change the limits by which something is regarded as 'cheap' with 
the remining optiond detailed below. 

=head1 OPTIONS

=head2 --token

Your Amazon Web Services token. 

=head2 --wishlist 

The ID for your wishlist.

=head2 --email

The email address to send notifications.

=head2 --sale

A decimal percentage indicating what you consider cheap off the list price.
Defaults to .50 which means if an item is available for less than 50% of the
list price it qualifies as as a bargain. 

=head2 --cheap

If an item is less than this it qualifies as a bargain. Default is 5, which
means that if an item is available for less than $5.00 you'll get an email.

=head2 --window

Time window (days) in which you don't want to be renotified. Defaults to 3. 
This means if an item is cheap you won't get notified about it again for 
three days. 

=head1 AUTHORS

=over 4

=item * Ed Summers <ehs@pobox.com>

=back

=cut

use strict;
use LWP::Simple;
use XML::Simple;
use File::Copy;
use Mail::Send;
use Getopt::Long;
use Pod::Usage qw( pod2usage );

my $tmpDir = '/tmp';

## wishlist and directory options
my ( $token, $wishlist, $email, $salePercent, $cheap, $notifyPeriod ) = @_;
GetOptions( 
    'token:s'       => \$token,
    'wishlist:s'    => \$wishlist,
    'email:s'	    => \$email,
    'sale:s'        => \$salePercent,
    'cheap:s'       => \$cheap,
    'window:i'      => \$notifyPeriod
);

if ( ! $wishlist or ! $token or ! $email ) {
    pod2usage( { -verbose => 3 } );
}

## alerts when item drops below this percentage of list
my $salePercent = .50 if ! $salePercent; 

## alerts when item is below this price
my $cheap = 5 if ! $cheap;

## no repeat alert within this amount of days
my $notifyPeriod = 3 if ! $notifyPeriod;

## build the amazon web services url 
my $host = 'xml.amazon.com';
my $path = 'onca/xml2';
my $query = 
    "t=webservices-20" .
    "&dev-t=$token" . 
    "&type=heavy" .
    "&f=xml" .
    "&WishlistSearch=$wishlist";

## fetch the XML
my $wishlist = XMLin( get( "http://$host/$path?$query" ) );

## cycle through items, and look for good stuff
foreach my $item (@{ $wishlist->{ Details } } ) {

    my $listPrice   = $item->{ ListPrice };
    my $amazonPrice = $item->{ OurPrice };
    my $usedPrice   = $item->{ UsedPrice };

    ## strip of dollar sign so we can use as numbers
    map { s/\$// } ($usedPrice,$amazonPrice,$listPrice);

    ## if a used copy is significantly cheaper
    if ( $usedPrice and $amazonPrice and 
	( ($usedPrice/$listPrice) <= $salePercent ) ) {
	email( $email, $item );
    }

    ## or amazon has it on sale
    elsif ( $amazonPrice and $listPrice and
	( ($amazonPrice/$listPrice) <= $salePercent ) ) {
	email( $email, $item );
    }

    ## or if it's just plain cheap
    elsif ( $amazonPrice and $usedPrice and
	( $amazonPrice <= $cheap or $usedPrice <= $cheap ) ) {
	email( $email, $item );
    }

}

## fire off notification email

sub email {

    my ($email,$item) = @_;

    ## create a file that will be used to indicate we've seen this sale item 
    ## and how much it cost
    my ($isbn) = ( $item->{ Isbn } =~ tr/0-9//dc );
    my $bookfile = "$tmpDir/amazon_" . $item->{ Isbn };

    ## don't email if we've seen this book before in the past N days
    return() if ( -f $bookfile and -M $bookfile <= $notifyPeriod );

    ## touch the file to indicate we're emailing now
    system( 'touch', $bookfile ); 

    my $msg = new Mail::Send;
    $msg->to( $email);
    $msg->subject( "sale: " . $item->{ ProductName } );
    my $fh = $msg->open();
    $item =~ s{</?.*?>}{}g;
    print $fh 
	"title: ",	$item->{ ProductName }, "\n",
	"url: ",	$item->{ url }, "\n",
	"list: ",	$item->{ ListPrice }, "\n",
	"amazon: ",	$item->{ OurPrice }, "\n",
	"used: ",	$item->{ UsedPrice }, "\n\n";
    $fh->close();

}