Get-LatestPS

using namespace System.Management.Automation.Host

Clear-Host

function Get-LatestPSVersion{
<#
    .SYNOPSIS
        A function to get the Latest Stable Version of PowerShell.
    .DESCRIPTION
        This function web scrapes the GitHub repository of PowerShell and
        parses out the Latest Stable Version of PowerShell.
        This function will return the PowerShell version as a string.

    .EXAMPLE
        Get-LatestPSVersion
#>
    $url = "https://api.github.com/repos/powershell/powershell/releases/latest"
    try{
        $tag = Invoke-RestMethod $url
        return $tag.tag_name
    }catch{
        $_.exception | Write-Warning
        return $null
    }
}

function Download-LatestPSVersion{
<#
    .SYNOPSIS
        A function to download the Lastest Stable Version of PowerShell.
    .DESCRIPTION
        This function web scrapes the GitHub repository of PowerShell and downloads
        the latest stable version.  The download will be saved to Users Downloads folder.
        This function will return the full path string of the downloaded file.

    .EXAMPLE
        Download-LatestPSVersion
#>
    $url = "https://api.github.com/repos/powershell/powershell/releases/latest"
    try{
        $tag = Invoke-RestMethod $url
        $latest = $tag.assets | Where-Object { $_.name -like "*win*x64*.msi" }
        $file = "$HOME\Downloads\$($latest.name)"
        Write-Host $('Dowloading latest release to: ' + $file)
        Invoke-WebRequest $latest.browser_download_url -Out $file
        return $file
    }catch{
        $_.exception | Write-Warning
        return $null
    }
}

function Is-PSCurrent{
<#
    .SYNOPSIS
        A function to determine if the current version of PowerShell is Up To Date.
    .DESCRIPTION
        This fucntion will call another function to get the Latest version of PowerShell, and then
        compare it to the currently installed version.  Returns True or False.

    .EXAMPLE
        Is-PSCurrent
#>
    [version]$current = $PSVersionTable.PSVersion
    $tmp = Get-LatestPSVersion
    if($tmp[0] -eq 'v'){
        [version]$latest = $tmp.split('v')[1]
    }else{
        [version]$latest = $tmp
    }
    if($current -lt $latest){
        return $false
    }else{
        return $true
    }
}

function Get-YesNo{
<#
    .SYNOPSIS
        A function to prompt user for a YES or NO.
    .DESCRIPTION
        This function uses System.Management.Automation.Host to prompt the user for a Yes or No reponse.
        Function returns a boolean value of TRUE or FALSE.

    .PARAMETER Title
        Title of UI
    .PARAMETER Question
        Question or Description of UI

    .EXAMPLE
        $answer = Get-YesNo 'Continue?' 'Do You Wish To Continue?'
#>
    Param ( [Parameter(Mandatory=1)][string]$Title,
            [Parameter(Mandatory=1)][string]$Question
    )
    $answer = $Host.UI.PromptForChoice($Title, $Question, @('&Yes', '&No'), 1)
    if ($answer -eq 0) { return $true }
    return $false
}

if(Is-PSCurrent){
    Write-Host $('PowerShell Is Up To Date: ' + $(Get-LatestPSVersion))
}else{
    if ((Get-YesNo 'Upgrade PowerShell' 'Are you sure you want to Upgrade PowerShell?')) {
        Start-Process (Invoke-Expression Download-LatestPSVersion)
    }else{
        Write-Host 'User Canceled PowerShell Upgrade, PowerShell is Not Up To Date.'
    }
}