#Requires -Version 5.1
<#
.SYNOPSIS
    Checks CI host drive free space and alerts via Windows Event Log (and optionally a webhook).

.DESCRIPTION
    Intended to run as a scheduled task every 15 minutes (registered by
    Register-CIScheduledTasks.ps1). If the monitored drive is below MinFreeGB,
    writes a Warning entry to the Windows Application Event Log under source
    'CI-DiskAlert' (Event ID 1001) and exits with code 1 so Task Scheduler
    marks the task as failed (visible in Task Scheduler history).

    If WebhookUrl is provided, also POSTs a JSON payload to that URL
    (compatible with Discord and Gitea webhooks — content field only).

    A full drive silently causes vmrun clone to fail with cryptic errors
    (not enough disk space for linked clone delta files). Alert early.

.PARAMETER MinFreeGB
    Alert threshold in GB. Default: 50

.PARAMETER DriveLetter
    Single letter (no colon) of the drive to monitor. Default: F

.PARAMETER WebhookUrl
    Optional Discord/Gitea webhook URL. If empty, only Event Log is written.

.EXAMPLE
    # Manual check
    .\Watch-DiskSpace.ps1 -MinFreeGB 50

    # With Discord webhook
    .\Watch-DiskSpace.ps1 -WebhookUrl "https://discord.com/api/webhooks/..."
#>
[CmdletBinding()]
param(
    [ValidateRange(1, 2000)]
    [int] $MinFreeGB = 50,

    [ValidatePattern('^[A-Za-z]$')]
    [string] $DriveLetter = 'F',

    [string] $WebhookUrl = ''
)

Set-StrictMode -Version Latest
$ErrorActionPreference = 'Continue'

$drive = Get-PSDrive -Name $DriveLetter -ErrorAction SilentlyContinue
if (-not $drive) {
    Write-Warning "[DiskSpace] Drive ${DriveLetter}: not found."
    exit 2
}

$freeGB = [math]::Round($drive.Free / 1GB, 1)
$totalGB = [math]::Round(($drive.Free + $drive.Used) / 1GB, 1)
$pctFree = [math]::Round($freeGB / $totalGB * 100, 0)

if ($freeGB -ge $MinFreeGB) {
    Write-Host "[DiskSpace] Drive ${DriveLetter}: ${freeGB} GB free / ${totalGB} GB (${pctFree}%) — OK (threshold: ${MinFreeGB} GB)"
    exit 0
}

# ── Alert ─────────────────────────────────────────────────────────────────────
$msg = "CI host drive ${DriveLetter}: free space ${freeGB} GB (${pctFree}%) is below " +
       "the ${MinFreeGB} GB threshold. vmrun linked clones may fail silently. " +
       "Run Invoke-RetentionPolicy.ps1 or free disk space manually."

Write-Warning "[DiskSpace] $msg"

# Windows Event Log
$logSource = 'CI-DiskAlert'
try {
    if (-not [System.Diagnostics.EventLog]::SourceExists($logSource)) {
        New-EventLog -LogName Application -Source $logSource -ErrorAction Stop
    }
    Write-EventLog -LogName Application -Source $logSource `
        -EventId 1001 -EntryType Warning -Message $msg
    Write-Host "[DiskSpace] Event Log entry written (Application/$logSource, EventId 1001)."
} catch {
    Write-Warning "[DiskSpace] Could not write Event Log: $_"
}

# Optional webhook (Discord / Gitea)
if ($WebhookUrl) {
    $body = @{ content = ":warning: **CI Disk Alert** — $msg" } | ConvertTo-Json -Compress
    try {
        $null = Invoke-RestMethod -Uri $WebhookUrl -Method Post `
            -Body $body -ContentType 'application/json' -TimeoutSec 10
        Write-Host "[DiskSpace] Webhook notified: $WebhookUrl"
    } catch {
        Write-Warning "[DiskSpace] Webhook POST failed: $_"
    }
}

exit 1   # non-zero → Task Scheduler marks run as failed (visible in history/Event Viewer)