Get-AbsoluteURLFromRelative.ps1

function Get-AbsoluteURLFromRelative {
    #region FunctionHeader #####################################################
    # This functions takes a potentially relative URL (/etc/foo.html) and turns it
    # into an absolute URL if it is, in fact, a relative URL. If the URL is an
    # absolute URL, then the function simply returns the absolute URL.
    #
    # The function takes two positional arguments.
    #
    # The first argument is a string containing the base URL (i.e., the parent URL)
    # from which the second URL is derived
    #
    # The second argument is a string containing the (potentially) relative URL.
    #
    # The function returns a string that represents the absolute URL.
    #
    # Example 1:
    # $strURLBase = 'http://foo.net/stuff/index.html'
    # $strURLRelative = '/downloads/list.txt'
    # $strURLAbsolute = Get-AbsoluteURLFromRelative $strURLBase $strURLRelative
    # # $strURLAbsolute is 'http://foo.net/downloads/list.txt'
    #
    # Example 2:
    # $strURLBase = 'http://foo.net/stuff/index.html'
    # $strURLRelative = 'downloads/list.txt'
    # $strURLAbsolute = Get-AbsoluteURLFromRelative $strURLBase $strURLRelative
    # # $strURLAbsolute is 'http://foo.net/stuff/downloads/list.txt'
    #
    # Example 3:
    # $strURLBase = 'http://foo.net/stuff/index.html'
    # $strURLRelative = 'http://foo.net/stuff/downloads/list.txt'
    # $strURLAbsolute = Get-AbsoluteURLFromRelative $strURLBase $strURLRelative
    # # $strURLAbsolute is 'http://foo.net/stuff/downloads/list.txt'
    #
    # Version 1.0.20241110.0
    #endregion FunctionHeader #####################################################

    #region License ################################################################
    # Copyright (c) 2024 Frank Lesniak
    #
    # Permission is hereby granted, free of charge, to any person obtaining a copy of
    # this software and associated documentation files (the "Software"), to deal in the
    # Software without restriction, including without limitation the rights to use,
    # copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
    # Software, and to permit persons to whom the Software is furnished to do so,
    # subject to the following conditions:
    #
    # The above copyright notice and this permission notice shall be included in all
    # copies or substantial portions of the Software.
    #
    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
    # FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
    # COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
    # AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
    # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    #endregion License ################################################################

    #region Acknowledgements #######################################################
    # Note: this function is converted from
    # https://stackoverflow.com/a/34603567/2134110
    # Thanks to Vikash Rathee for pointing me in the right direction
    #endregion Acknowledgements #######################################################

    #region DownloadLocationNotice #########################################
    # The most up-to-date version of this script can be found on the author's
    # GitHub repository at:
    # https://github.com/franklesniak/PowerShell_Resources
    #endregion DownloadLocationNotice #########################################

    $strURLBase = $args[0]
    $strURLRelative = $args[1]

    $uriKindRelativeOrAbsolute = [System.UriKind]::RelativeOrAbsolute
    $uriWorking = New-Object -TypeName 'System.Uri' -ArgumentList @($strURLRelative, $uriKindRelativeOrAbsolute)
    if ($uriWorking.IsAbsoluteUri -ne $true) {
        $uriBase = New-Object -TypeName 'System.Uri' -ArgumentList @($strURLBase)
        $uriWorking = New-Object -TypeName 'System.Uri' -ArgumentList @($uriBase, $strURLRelative)
    }
    return ($uriWorking.ToString())
}