ImprovedRSSFeed.ps1

$dir="$(Split-Path -Parent $MyInvocation.MyCommand.Definition)"
$MyOPMLFile= "$dir\simple-talk.opml" #change this to the name of your OPML file
$MyListOfArticles="$dir\LatestStories.XML"
$OldListOfArticles="$dir\NotSoLatestStories.XML"
$MyXSLTTemplate="$dir\FeedItemToGridTransformer.xsl"
$MyHTMLFile="$dir\DBW.HTML"

$DaysBack=[int]-20 #the number of days back you want articles from

function truncate([string]$value, [int]$MaxLength)
{#can you believe there is no powershell built-in way of doing this?
    if ($value.Length -gt $MaxLength) { $value.Substring(0, $MaxLength) }
    else { $value }
}

function ConvertDateFromRFC822([string]$RFC822Data)
{
switch -regex ($RFC822Data)
{
   ( '(^.*)UT' )  { $matches[1]+ 'GMT'     ; break }
   ( '(^.*)EST' )  { $matches[1]+ '-05:00' ; break }
   ( '(^.*)EDT' )  { $matches[1]+ '-04:00' ; break }
   ( '(^.*)CST' )  { $matches[1]+ '-06:00' ; break }
   ( '(^.*)CDT' )  { $matches[1]+ '-05:00' ; break }
   ( '(^.*)MST' )  { $matches[1]+ '-07:00' ; break }
   ( '(^.*)MDT' )  { $matches[1]+ '-06:00' ; break }
   ( '(^.*)PST' )  { $matches[1]+ '-08:00' ; break }
   ( '(^.*)PDT' )  { $matches[1]+ '-07:00' ; break }
   ( '(^.*)Z' )    { $matches[1]+ 'GMT'    ; break }
   ( '(^.*)A' )    { $matches[1]+ '-01:00' ; break }
   ( '(^.*)M' )    { $matches[1]+ '-12:00' ; break }
   ( '(^.*)N' )    { $matches[1]+ '+01:00' ; break }
   ( '(^.*)Y' )    { $matches[1]+ '+12:00' ; break }
      default         { $_ }
}

}

[xml]$opml= Get-Content $MyOPMLFile # grab the OPML file of feeds
[xml]$Output=$opml.opml.body.outline.outline | 
   select @{name="Title"; Expression={$_.title}},
			 @{name="Feed"; Expression={$_.xmlUrl}},
			 @{name="PageURL"; Expression={$_.htmlUrl}},
            @{name="Color"; Expression={$_.color}},
          @{name="Publication"; Expression={$_.ParentNode.text}} |
foreach-object { 
	$successful=$true #assume the best
	try {
      Invoke-WebRequest $_.Feed -outfile '.\tempXML'
      [xml]$xml = Get-Content '.\tempXML'}
		catch{$successful=$false} #filter out 404s, malformed items  and bad links
   $Publication=$_.Publication
	$Stream=$_.Title
	$PageURL=$_.PageURL
	$FeedName=$xml.rss.channel.title #makes sure there is something in it
    $Color=$_.Color
	If ($successful)
	 {
    $xml.rss.channel.item | # flag if an error happened

<# Each <item> within a feed represents an article. The <item> must include at least the following elements:
    <link>: The canonical URL for the article.
    <content:encoded>: The full HTML content of the article.
But you are also likely to find ..
    <title>: The article's headline. If it isn't there, you'd need to find it in the content
    <pubDate>: The date of the article's publication, in RFC822 format.
    <description>: A short, summary or abstract of the article.
    <dc:creator>: Name of the person who wrote the article. 
    <media:content> and <media:group>: URLs and metadata for image, video, and audio assets. 
#>
     Select @{name="Feed"; Expression={$FeedName}}, 
		@{name="Title"; Expression = {try {$_.title} catch {'Unknown title'}}}, 
      @{name="Description"; # this isn't manatory, but you can get the content
         Expression ={ &{try { if ($_.SelectSingleNode('description') -eq $null) 
                                 { truncate ($_.encoded.'#cdata-section' -replace "<.*?>") 500} 
                            elseif ( $_.description.ToString() -eq 'description') 
                                 {truncate ($_.description.'#cdata-section'  -replace "<.*?>") 500 } 
                            else {truncate ($_.description  -replace "<.*?>") 500 }} 
                      catch {'error'}} -replace '&amp;#8217;', '&apos;'},
      @{name="Publication"; Expression={$Publication}},
      @{name="Stream"; Expression={$Stream}},
      @{name="PageURL"; Expression={$PageURL}},
      @{name="PubDate"; Expression = {try {get-date (ConvertDateFromRFC822($_.PubDate))} # force it into a PS date  
                                       catch {Get-Date '01 January 2006 00:00:00'}}}, 
      @{name="Color"; Expression={$Color}},
      @{name="author"; Expression = {try {if ( $_.author.length -eq 0) {$_.creator} 
                                           else {$_.author}} 
                                      catch{'Unknown Author'}}},
      @{name="Ago"; Expression={switch ($([datetime]::Now - $(get-date (ConvertDateFromRFC822 ($_.PubDate))) ).Days)
		    { 
		        0 {"Today"} 
				  1 {"Yesterday"} 
		        default {"$_ days ago"}
		    }}},
        link | #we already checked for a link!
			 where-object {$_.Pubdate -gt  (Get-Date).AddDays($DaysBack)} #select only the young ones
				# we only get the fresh news from the last couple of days.
    }
  else #we couldn't get the feed so write error
	{
	write-error " $_ didn't respond" #this will be logged in the working system
   }
  }|sort-object PubDate -descending |ConvertTo-XML #sort by date and convert to XML

$Output.Save($MyListOfArticles) #save the list of articles ready for processing

if (!(Test-Path  $OldListOfArticles)) {'' > $OldListOfArticles}
if (Test-Path  $MyListOfArticles) {
	if (diff (ls $MyListOfArticles) (ls $OldListOfArticles) -Property Length) { 
	 #not equal
		$xslt = New-Object System.Xml.Xsl.XslCompiledTransform #crank up the net library to do the job
		$xslt.Load($MyXSLTTemplate) #heave in the template
		$xslt.Transform($MyListOfArticles, $MyHTMLFile) #and create the HTML
		Copy-Item $MyListOfArticles $OldListOfArticles -force
		"saved $MyListOfArticles to $MyHTMLFile"
  }
}
'All done, master'