checkhealth-task-control.ps1

# ------------------------------------------------------------------------------

# Leopard Systems ? (2017)
# contributors: Adam Laing

# note: requires powershell 2.0 or later

set-strictmode -version 'latest'
$erroractionpreference = 'stop'

# ------------------------------------------------------------------------------

add-type -assemblyname 'system.windows.forms'
add-type -assemblyname 'presentationframework'
add-type -assemblyname 'windowsformsintegration'
set-variable taskname -option constant -value 'checkhealth'
set-variable rootdir -option constant `
	-value ([io.path]::getdirectoryname($script:myinvocation.mycommand.path))

$taskinfo = $null

function entrypoint {
	# must run with -sta
	enforce ([threading.thread]::currentthread.getapartmentstate() `
		-eq [threading.apartmentstate]::sta)

	[windows.forms.application]::enablevisualstyles()
	[windows.forms.application]::run((create-main-form))
}

function create-main-form {
	$mf = new-object windows.forms.form
	$mf.text = 'Server Health Monitor'
	$mf.showicon = $false

	# status info
	# buttons:
	# 	enable/disable 
	# 	pause
	# 	refresh

	$xamlsrc = @'
		<Window
			xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
			xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
			xmlns:wf="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
		>
			<WindowsFormsHost>
				<wf:MaskedTextBox x:Name="mtbDate" Mask="00/00/0000"/>
			</WindowsFormsHost>
		</Window>
'@ # picky syntax - no space before this token

	# put the xaml in the form
	$mf.controls.add(
		[windows.markup.xamlreader]::parse($xamlsrc).content.child)

	update-main-form $mf
	$mf.add_shown({main-form-onshown $mf}.getnewclosure())

	return $mf
}

function main-form-onshown($mf) {
	$taskinfo = $(try {checkhealth-task-info $taskname} catch {
		throw xcep "failed to get info for task '$taskname'" $_})

	log "checkhealth var path: `"$($taskinfo.varpath)`""

	update-main-form $mf

	pause-checkhealth-task (new-object timespan(1, 0, 0)) # 1 hour
}

function update-main-form($mf) {
	#
}

function pause-checkhealth-task($duration) {
	enforce ($duration -is [timespan])
	enforce ($duration.ticks -gt 0)
	log "pausing task for duration: $duration ..."

	$pauseuntil = (get-date).add($duration)

	# write the pause details into the checkhealth var file
	with-task-stopped $taskinfo.taskobj {
		$vardoc = read-checkhealth-state-file $taskinfo.varpath
		$vardoc.selectsinglenode('/*').`
			setattribute('pause-until', "$($pauseuntil.ticks)")
		$vardoc.save($taskinfo.varpath)
	}

	log '... done'
}

function with-task-stopped($taskobj, $fn) {
	enforce ($taskobj -is [__comobject])
	enforce ($fn -is [scriptblock])

	$wasenabled = $taskobj.enabled
	$taskobj.stop(0)
	$taskobj.enabled = $false
	trap {$taskobj.enabled = $wasenabled}

	& $fn

	$taskobj.enabled = $wasenabled
}

function read-checkhealth-state-file($path) {
	# or create a new xml document if the file doesn't exist
	# should only use inside a 'with-task-stopped' block
	try {
		if (test-path -literalpath $path -pathtype 'leaf') {
			return slurp-xml $path
		} else {
			$d = new-object xml.xmldocument
			$d.loadxml('<var/>')
			return $d
		}
	} catch {
		throw xcep "failed to read state file `"$path`"" $_
	}
}

function checkhealth-task-info($taskname) {
	# find the checkhealth scheduled task and script dir
	$s = new-object -comobject 'schedule.service'
	$s.connect()
	$task = enforce (
		$s.getfolder('\').gettasks(0) | ? {$_.name -eq $taskname})
	$xs = $task.definition.actions
	[void] (enforce ($xs.count -eq 1))
	[void] (enforce ($xs.item(1).type -eq 0)) # TASK_ACTION_EXEC
	$dir = [io.path]::getdirectoryname($xs.item(1).path)
	[void] (enforce (test-path -literalpath $dir -pathtype 'container'))

	return @{
		taskobj = $task;
		scriptdir = $dir;
		varpath = (join-path $dir 'var.xml');}
}

function slurp-xml($filepath) {
	$cfgxml = new-object xml.xmldocument
	$r = new-object xml.xmltextreader($filepath)
	$cfgxml.load($r)
	$r.close()
	return $cfgxml
}

function log($msg) {
	[void] (write-host -nonewline -object "$msg `r`n")
}

function enforce($cond) {
	# [intptr]::zero is a truthy value apparently
	# so explicit test for 0
	if (!$cond -or ($cond -eq 0)) {
		throw xcep (
			'enforcement failed @ line {0}' -f $myinvocation.scriptlinenumber)}
	return $cond
}

function xcep($msg, $innerx) {
	if ($innerx -is [management.automation.errorrecord]) {
		$innerx = $innerx.exception}
	new-object applicationexception($msg, $innerx)
}

# ------------------------------------------------------------------------------

[void] (entrypoint)

# ------------------------------------------------------------------------------

<#

	$(# need the task enabled to do anything
		$s = $taskinfo.taskobj.definition.settings
		if (!$s.enabled) {
			$answer = [windows.forms.messagebox]::show(
				"Task '$taskname' is disabled. Enable it now?", # message
				'', # title
				[windows.forms.messageboxbuttons]::yesno,
				[windows.forms.messageboxicon]::exclamation,
				[windows.forms.messageboxdefaultbutton]::button2,
				0)
			if ($answer -eq [windows.forms.dialogresult]::yes) {
				$s.enabled = $true
				log "task '$taskname' enabled"
			} else {
				log "task '$taskname' not enabled, terminating"
				[windows.forms.application]::exit()
			}
		}
	)













































#>

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