#!/usr/bin/perl
use strict;

use DBI;
use Net::SMTP_auth;
use XML::Simple;

my $config_file = $ARGV[0] || "/etc/importantdates.xml";
my $xml = XMLin( $config_file, 'ForceArray' => ['days'] ) or die "what?";

my $dbh = initialize_database( $xml );

my @days_warning = @{ $xml->{'config'}->{'reminders'}->{'days'} };

my $sel_str = q(
        SELECT d_desc, d_date,
                MOD(
                        DAYOFYEAR(
                                CONCAT( YEAR( CURDATE() ), DATE_FORMAT( d_date, '-%m-%d' ) )
                        ) - DAYOFYEAR( CURDATE() ) + 365,
                        365
                ) AS diff
        FROM dates
        HAVING diff <= ?
        ORDER BY diff
);

my $sth = $dbh->prepare( $sel_str );

$sth->execute( max ( @days_warning ) );

while( my ( $d_desc, $d_date, $diff ) = $sth->fetchrow_array() ) {
        my $str = $d_desc;
        foreach ( @days_warning ) {
                if ( $diff == $_ ) {
                        $str .= " in $diff day(s).";
                        send_email( $str, $xml );
                        last;
                }
        }
}

$sth->finish();
$dbh->disconnect();

###### SUBS ######

sub max {
        my $max = $_[0];
        foreach ( @_ ) {
                $max = $_ if ( $_ > $max );
        }
        $max;
}

sub initialize_database {
        my $xml = shift;

        my $username = $xml->{'config'}->{'db'}->{'username'};
        my $password = $xml->{'config'}->{'db'}->{'password'};
        my $database = $xml->{'config'}->{'db'}->{'database'};
        my $hostname = $xml->{'config'}->{'db'}->{'hostname'};

        my $dsn = "DBI:mysql:$database:$hostname";
        my $dbh = DBI->connect( $dsn, $username, $password ) or die "Could not create MySQL connection";
        my $drh = DBI->install_driver("mysql");
        $dbh
}

sub send_email {
        my $content = shift;
        my $xml = shift;

        my $hostname = $xml->{'config'}->{'smtp'}->{'hostname'};
        my $username = $xml->{'config'}->{'smtp'}->{'username'};
        my $password = $xml->{'config'}->{'smtp'}->{'password'};
        my $to = $xml->{'config'}->{'smtp'}->{'to'};
        my $from = $xml->{'config'}->{'smtp'}->{'from'};
        my $subject = $xml->{'config'}->{'smtp'}->{'subject'};

        my $smtp = Net::SMTP_auth->new( $hostname ) or die "Could not create SMTP connection";

        $smtp->auth( 'LOGIN', $username, $password );
        $smtp->mail( $from );

        $smtp->to( $to );

        $smtp->data();

        $smtp->datasend("To: $to\n");
        $smtp->datasend("From: $from\n");
        $smtp->datasend("Subject: $subject\n");
        $smtp->datasend("\n");
        $smtp->datasend( $content . "\n" );

        $smtp->dataend();
        $smtp->quit();
}

##</code><code>##

<?xml version="1.0"?>
<importantdates>
        <config>
                <db>
                        <username>your_db_username</username>
                        <password>your_db_hostname</password>
                        <hostname>yourdb.yourdomain.com</hostname>
                        <database>databasename</database>
                </db>
                <smtp>
                        <hostname>smtp.yourdomain.com</hostname>
                        <username>your_smtp_username</username>
                        <password>your_smtp_password</password>
                        <to>whoisitto@somedomain.com</to>
                        <from>thisisyou@yourdomain.com</from>
                        <subject>Important Date Reminder</subject>
                </smtp>
                <reminders>
                        <!--How often you want reminders.  I want email reminders 7 days before the event, the day before the event, and the day of the event-->
                        <days>0</days>
                        <days>1</days>
                        <days>7</days>
                </reminders>
        </config>
</importantdates>