Set-StrictMode -Version Latest

function Get-CampaignLaSessionProcessCorrelations {
    [CmdletBinding()]
    param()

    $matches = [Collections.Generic.List[object]]::new()
    if ($IsWindows) {
        $pattern = '(?i)(?:^|\s)(?:--config|--session-config)\s+(?:"([^"]+)"|(\S+))'
        foreach ($candidate in @(Get-CimInstance Win32_Process -ErrorAction Stop)) {
            $commandLine = [string]$candidate.CommandLine
            if ([string]::IsNullOrWhiteSpace($commandLine)) { continue }
            foreach ($match in [Text.RegularExpressions.Regex]::Matches(
                         $commandLine,
                         $pattern)) {
                $value = if ($match.Groups[1].Success) {
                    $match.Groups[1].Value
                } else { $match.Groups[2].Value }
                if ([IO.Path]::IsPathFullyQualified($value)) {
                    $matches.Add([pscustomobject]@{
                        ProcessId = [int]$candidate.ProcessId
                        SessionConfigPath = [IO.Path]::GetFullPath($value)
                    })
                }
            }
        }
    }
    elseif ($IsLinux) {
        foreach ($directory in [IO.Directory]::EnumerateDirectories('/proc')) {
            $leaf = [IO.Path]::GetFileName($directory)
            $processId = 0
            if (-not [int]::TryParse(
                    $leaf,
                    [Globalization.NumberStyles]::None,
                    [Globalization.CultureInfo]::InvariantCulture,
                    [ref]$processId)) {
                continue
            }
            try {
                $bytes = [IO.File]::ReadAllBytes((Join-Path $directory 'cmdline'))
                if ($bytes.Length -eq 0) { continue }
                $arguments = @([Text.Encoding]::UTF8.GetString($bytes).Split(
                    [char]0,
                    [StringSplitOptions]::RemoveEmptyEntries))
                for ($index = 0; $index + 1 -lt $arguments.Count; $index++) {
                    if ($arguments[$index] -cin @('--config', '--session-config') -and
                        [IO.Path]::IsPathFullyQualified($arguments[$index + 1])) {
                        $matches.Add([pscustomobject]@{
                            ProcessId = $processId
                            SessionConfigPath = [IO.Path]::GetFullPath(
                                $arguments[$index + 1])
                        })
                    }
                }
            }
            catch [IO.IOException] {
                # A process may exit between /proc enumeration and cmdline read.
            }
            catch [UnauthorizedAccessException] {
                # Other-user processes cannot be the owner-readable gate child.
            }
        }
    }
    else {
        throw 'Campaign LA process correlation supports Windows and Linux only.'
    }

    return @($matches)
}

function Get-CampaignLaCorrelatedProcessIds {
    [CmdletBinding()]
    param([Parameter(Mandatory = $true)][string]$SessionConfigPath)

    if (-not [IO.Path]::IsPathFullyQualified($SessionConfigPath)) {
        throw 'Session-config correlation requires an absolute path.'
    }
    $SessionConfigPath = [IO.Path]::GetFullPath($SessionConfigPath)
    $comparison = if ($IsWindows) {
        [StringComparison]::OrdinalIgnoreCase
    } else { [StringComparison]::Ordinal }
    $matches = [Collections.Generic.HashSet[int]]::new()
    foreach ($candidate in @(Get-CampaignLaSessionProcessCorrelations)) {
        if ([string]::Equals(
                $candidate.SessionConfigPath,
                $SessionConfigPath,
                $comparison)) {
            $null = $matches.Add([int]$candidate.ProcessId)
        }
    }

    return @($matches | Sort-Object)
}