# Set-FmsHostsEntry.ps1 - idempotently pin FMS host in C:\Windows\System32\drivers\etc\hosts.
#
# Why pinned:
#   eDNC's FMS prescan (CPreScan::Initialise_Sockets in DncMain.exe and
#   CDoPersonnel::InitializeSocket in DNCdll.dll) resolves the FMS host
#   via MFC CSocket, which calls inet_addr first then gethostbyname. The
#   legacy WinSock1 resolver path fails on the GE corporate network for
#   wjfms3.ae.ge.com (modern getaddrinfo path used by PowerShell works
#   fine, but eDNC does not use it). Hosts file entry is consulted by
#   gethostbyname before any DNS query, so the pin short-circuits the
#   broken legacy path.
#
# Idempotent: adds line if missing, leaves it alone if already present.
# Safe to run every cycle (DetectionMethod=Always in manifest).

$ErrorActionPreference = 'Stop'

$hostsPath = Join-Path $env:windir 'System32\drivers\etc\hosts'
$ip        = '10.233.112.158'
$fqdn      = 'WJFMS3.AE.GE.COM'
$line      = "$ip`t$fqdn"

if (-not (Test-Path $hostsPath)) {
    Write-Host "hosts file not found at $hostsPath - aborting"
    exit 1
}

$content = Get-Content -LiteralPath $hostsPath -ErrorAction Stop

# Match any non-comment line that maps either the IP or the FQDN.
# Drops stale or wrong mappings of the same FQDN/IP, then appends the canonical pin.
$pattern = '(?i)^\s*[^#\s]+\s+\S*' + [regex]::Escape($fqdn) + '\b|^\s*' + [regex]::Escape($ip) + '\s'
$existing  = $content | Where-Object { $_ -match $pattern }
$canonical = ($existing | Where-Object { $_ -match "^\s*$([regex]::Escape($ip))\s+$([regex]::Escape($fqdn))\s*$" })

if ($canonical -and $existing.Count -eq @($canonical).Count) {
    # Already pinned correctly. No change.
    exit 0
}

# Either no entry, or an entry exists with wrong IP/FQDN/casing/whitespace. Rewrite.
$kept = $content | Where-Object { $_ -notmatch $pattern }
$new  = @($kept) + $line
Set-Content -LiteralPath $hostsPath -Value $new -Encoding ascii -ErrorAction Stop
Write-Host "Wrote FMS hosts pin: $line"
exit 0