public/Set-FrontMatter.ps1
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function Set-FrontMatter { [CmdletBinding()] param ( [Parameter(Mandatory = $true)] [System.IO.FileInfo]$FilePath, [Parameter(Mandatory = $true, ValueFromPipeline = $true)] [PSCustomObject]$FrontMatter, [Parameter(Mandatory = $true)] [ValidateSet('yaml', 'toml', 'json')] [string]$As ) # Read the entire file content as a single string. $content = Get-Content -Path $FilePath -Raw if (-not $content) { throw "File is empty: $FilePath" } # Get the first non-empty line by splitting into lines. $lines = $content -split "\r?\n" $firstNonEmpty = $lines | Where-Object { $_.Trim() -ne '' } | Select-Object -First 1 # Convert the front matter object to the expected string format. $newFrontMatter = switch ($As) { 'yaml' { ConvertTo-YamlFrontMatter -FrontMatter $FrontMatter } 'toml' { ConvertTo-TomlFrontMatter -FrontMatter $FrontMatter } 'json' { ConvertTo-JsonFrontMatter -FrontMatter $FrontMatter } default { throw "Invalid output type: $As" } } # Determine the front matter markers based on the first non-empty line. Switch ($firstNonEmpty) { '---' { $startMarker = '---'; $endMarker = '---' } '+++' { $startMarker = '+++'; $endMarker = '+++' } '{' { $startMarker = '{'; $endMarker = '}' } default { throw "Unknown front matter format: $firstNonEmpty" } } # Build a regex pattern to capture the block from the start marker to the end marker. # The (?ms) flags enable multi-line and single-line modes. $pattern = "(?ms)^" + [regex]::Escape($startMarker) + ".*?" + [regex]::Escape($endMarker) + "\r?\n?" if ($content -match $pattern) { # Replace the first occurrence of the front matter block with the new front matter. $newContent = [regex]::Replace($content, $pattern, $newFrontMatter + "`n", 1) } else { Write-Error 'Unable to locate front matter markers in the file.' return } # Write the updated content back to the file. $newContent | Set-Content -Path $FilePath -Encoding utf8 -NoNewline } |