few fixes and new func IsURL

Tools.ps1

@@ -169,15 +169,15 @@ Function Get-Version {
 # Determines whether a URL is valid
 Function IsURLValid {
     param([Parameter(Mandatory=$true,ValueFromPipeline=$true)][string]$URL)
-    Try {
-        $HTTPRequest = [System.Net.WebRequest]::Create($URL)
-        $HTTPResponse = $HTTPRequest.GetResponse()
-        $HTTPStatus = [int]$HTTPResponse.StatusCode
-        $HTTPResponse.Close()
-    }
-    Catch { }
-    If ($HTTPStatus -ne 404) { Return $true }
-    Else { Return $false }
+    Try { $status = [System.Net.WebRequest]::Create($URL).GetResponse().StatusCode }
+    Catch { Write-Error $_.Exception.Message ; Return $false }
+    If ( $status -eq 404 ) { Return $false }
+    Return $true
+}
+
+Function IsURL {
+    param([Parameter(Mandatory=$true,ValueFromPipeline=$true)][string]$Value)
+    Return $value -match "https?:\/\/"
 }
 
 # Downloads a file from a URL
@@ -186,21 +186,19 @@ Function Download-File {
         [Parameter(Mandatory=$true,ValueFromPipeline=$true)][string]$URL,
         [Parameter(Mandatory=$false,ValueFromPipeline=$false)][string]$File
     )
-    If ( !($File) ) { $File = '{0}{1}' -f (Get-TempPath), (Split-Path $URL -Leaf) }
-    $URL = Get-AbsoluteURI -URL $URL
-    If ( IsURLValid $URL ) { 
-        If ( Test-Path $File ) {
-            Write-Output "Deleting existing file: ""${File}"""
-            Try { Remove-Item $File -Force }
-            Catch { Write-Error $_.Exception.Message }
-        }
-        Write-Output "Downloading ""${URL}"" to ""${File}"""
-        Try { (New-Object System.Net.WebClient).DownloadFile($URL,$File) }
-        Catch { Write-Error $_.Exception.Message }
-        If ( Test-Path "${File}" ) { Return "${File}" }
-        Else { Write-Output "Downloaded file does not exist at ""${File}""" ; Return $false }
+    $URI = Get-AbsoluteURI -URL $URL
+    If ( $null -eq $URI ) { Return }
+    If ( [string]::IsNullOrEmpty($File) ) { $File = '{0}{1}' -f (Get-TempPath), (Split-Path $URL -Leaf) }
+    If ( Test-Path $File ) {
+        Write-Output "Deleting existing file: ""${File}"""
+        Try { Remove-Item $File -Force }
+        Catch { Write-Error $_.Exception.Message ; Return }
     }
-    Else { Write-Output "URL is not valid or file cannot be reached: ${URL}" }
+    Write-Output "Downloading ""${URI}"" to ""${File}"""
+    Try { (New-Object System.Net.WebClient).DownloadFile($URI,$File) }
+    Catch { Write-Error $_.Exception.Message ; Return }
+    If ( Test-Path "${File}" ) { Return "${File}" }
+    Else { Write-Output "Downloaded file does not exist at ""${File}""" ; Return }
 }
 
 # Install a program from a provided path
@@ -822,6 +820,7 @@ Function ZeroPad-Decimal {
 # Function to follow a URL and return the absolute URI of the result (whether redirected or not)
 Function Get-AbsoluteURI {
     param([string]$URL)
+    If ( !(IsURLValid $URL) ) { Return }
     Return [System.Net.HttpWebRequest]::Create($URL).GetResponse().ResponseUri.AbsoluteUri
 }