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June 27, 2005

Monad and RSS, Part 2

Continuing on with our command-line RSS reader, I first cleaned up my add-feed script:

# add-feed.msh

$regpath = "HKCU:\Software\Microsoft\MshReader"
$feedpath = [System.Uri]$args[0]

# make sure name is a proper URI

if (!$feedpath.IsAbsoluteUri) {
    write-host "Feed name `"$feedpath`" is not a valid URI"
    exit
}

# feed name is domain name

$feedname = $feedpath.Host

# make sure our overall path exists

if (!$(test-path $regpath)) {
    new-item $regpath
}

# create the key for this feed...

$newpath = combine-path $regpath $feedname

new-item $newpath | out-null

# ...and the value for the URI

set-property $newpath -Property "URI" -Type String -Value $feedpath.AbsoluteUri | out-null

# if it worked, then print a message

if ($(test-path $newpath)) {
    write-host "Created feed for `"$($feedpath.OriginalString)`" named `"$feedname`""
}

I now parse the URI by creating a System.Uri (idea courtesy of Keith Farmer) and I store the URI in a value instead of a subkey (the Monad registry provider treats registry values as "properties").

Next, I improved get-feeds.msh. I changed the registry access to reflect the fact that URI is now a value, not a subkey. More importantly, I added another value SeenList which is a REG_MULTI_SZ that stores which entries have already been viewed (I identify them by pubDate, don't know if that is official RSS reader best practice, but it seems to work). I read the REG_MULTI_SZ out of the registry for each feed, check each pubDate to see if it is in SeenList, if it is I skip it, if it isn't I display it and add it to SeenList. At the end I write SeenList back to the registry:

# get-feeds.msh

$regpath = "HKCU:\Software\Microsoft\MshReader"
$feeds = get-childitem $regpath

# loop through all stored feeds

foreach ($f in $feeds) {

    # get the URI for the feed from the registry

    $feedpath = combine-path $regpath $f.MshChildName
    $feeduri = $(get-property $feedpath).URI

    # read the content from $feeduri as XML

    $wc = new-object System.Net.WebClient
    $rssdata = [xml]$wc.DownloadString($feeduri)

    # display title

    write-host $rssdata.rss.channel.title

    # get list of items already seen

    $seenlist = [array]($(get-property $feedpath).SeenList)

    # display title and date of each item

    $rssdata.rss.channel.item |
        foreach-object {
            $seen = $false
            for ($i = 0; $i -lt $seenlist.length; ++$i) {
                if ($seenlist[$i] -eq $_.pubDate) {
                    $seen = $true
                    break
                }
            }
            if (!$seen) {
                write-host "-" $_.title
                write-host "     " $_.pubDate
                if ($seenlist -eq $null) {
                    $seenlist = [array]$_.pubDate
                } else {
                    $seenlist += $_.pubDate
                }
            }
        }

    set-property $feedpath -Property SeenList -Type MultiString -Value $seenlist | out-null
}

It seems to work:

MSH> add-feed "http://www.proudlyserving.com/index.xml"
Created feed for "http://www.proudlyserving.com/index.xml" named "www.proudlyserving.com"
MSH> add-feed "http://radio.weblogs.com/0001011/rss.xml"
Created feed for "http://radio.weblogs.com/0001011/rss.xml" named "radio.weblogs.com"
MSH> get-feeds
Scobleizer: Microsoft Geek Blogger
- SQL Server podcast starts up
     Tue, 28 Jun 2005 02:08:19 GMT
- Blogging food fight breaks out
     Tue, 28 Jun 2005 01:41:00 GMT
...
Proudly Serving My Corporate Masters
- Discovering Objects in Monad
     Sun, 26 Jun 2005 21:24:50 -0800
- Monad and RSS
     Sat, 25 Jun 2005 22:38:53 -0800
...

W00OO00OO00t!! In our next installment, we'll look into how we can display more details about each item (in a nice, user-modifiable, Monad-y way).

Posted by AdamBa at June 27, 2005 10:42 PM

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Comments

Posted by: Larry Osterman at June 28, 2005 06:36 AM

Posted by: Adam Barr at June 28, 2005 10:56 AM

Posted by: Tommy Williams at June 28, 2005 11:19 AM

Posted by: Keith J. Farmer at June 28, 2005 05:44 PM

Posted by: Adam Barr at June 28, 2005 06:48 PM