Convert-MarkdownToHtml.ps1

<#
.SYNOPSIS
Convert a Markdown file to an HTML file.
.DESCRIPTION
The script converts the specified Markdown file to an HTML file. It shows an overwrite prompt when the HTML already exists.
.PARAMETER MarkdownPath
Specifies the path of an existing .md Markdown file.
.PARAMETER HtmlFilePath
Specifies the path of the output HTML file.
By default, the output HTML file has the same parent directory and base name as the input Markdown file.
.PARAMETER OverWrite
Specifies that the output file should be overriden.
.EXAMPLE
"Here's the link to the [team session](https://fromthetechlab.blogspot.com)." > .\Readme.md
PS> Convert-MarkdownToHtml .\Readme.md
PS> Get-Content .\Readme.html
<p>Here's the link to the <a href="https://fromthetechlab.blogspot.com">team session</a>.</p>
#>
#Requires -Version 6.1
using namespace System.IO
using namespace System.Windows
[CmdletBinding()]
Param (
  [Parameter(Mandatory, Position=0)]
  [ValidatePattern('\.md$')]
  [ValidateScript({Test-Path $_ -PathType Leaf})]
  [string] $MarkdownPath,
  [Parameter(Position=1)]
  [ValidatePattern('\.html?$')]
  [string] $HtmlPath = [Path]::ChangeExtension($MarkdownPath, '.html'),
  [switch] $OverWrite
)

# Handle exceptions when the HTML file already exists or the output path is a directory.
If (Test-Path $HtmlPath -PathType Leaf) {
  If (-not $OverWrite) {
    # Private variable to copy LASTEXITCODE value.
    $Private:LASTEXITCODE = $LASTEXITCODE
    Write-Host ('The file "{0}" already exists.' -f $HtmlPath)
    Write-Host 'Do you want to overwrite it?'
    C:\Windows\System32\choice.exe /C YN /N /M '[Y]es [N]o: '
    # Exit when the user chooses No.
    If ($Global:LASTEXITCODE -eq 2) {
      # Remove impact of choice.exe on LASTEXITCODE.
      $Global:LASTEXITCODE = $Private:LASTEXITCODE
      Return
    }
    # Remove impact of choice.exe on LASTEXITCODE.
    $Global:LASTEXITCODE = $Private:LASTEXITCODE
  }
} ElseIf (Test-Path $HtmlPath) {
  Throw ('"{0}" cannot be overwritten because it is a directory.' -f $HtmlPath)
}
# Conversion from Markdown to HTML.
(ConvertFrom-Markdown $MarkdownPath).Html | Out-File $HtmlPath