param(
    [ValidateRange(1, 3600)][int]$HeartbeatSeconds = 10,
    [ValidateRange(0, 3600)][int]$WorkSeconds = 10,
    [ValidateRange(0, 10000)][int]$MaxHeartbeats = 0,
    [string]$OutputRoot
)
$ErrorActionPreference = 'Stop'
$instance = $env:WEBSITE_INSTANCE_ID
if (-not $instance) { $instance = 'local-not-azure' }
$job = $env:WEBJOBS_NAME
if (-not $job) { $job = 'local-demo' }
$type = $env:WEBJOBS_TYPE
if (-not $type) { $type = 'triggered' }
$session = [guid]::NewGuid().ToString('N')
if (-not $OutputRoot) {
    if ($env:WEBSITE_INSTANCE_ID -and $env:HOME) {
        $OutputRoot = Join-Path $env:HOME 'data\webjob-instance-demo'
    } else {
        $OutputRoot = Join-Path ([IO.Path]::GetTempPath()) 'webjob-instance-demo'
    }
}
$safeJob = $job -replace '[^a-zA-Z0-9_-]', '_'
$safeInstance = $instance -replace '[^a-zA-Z0-9_-]', '_'
$directory = Join-Path (Join-Path $OutputRoot $safeJob) $safeInstance
$null = New-Item -ItemType Directory -Path $directory -Force
$logPath = Join-Path $directory "$session.jsonl"
function Write-Record([string]$EventName) {
    $record = [ordered]@{
        utc = [DateTime]::UtcNow.ToString('o')
        event = $EventName
        job = $job
        type = $type
        instance = $instance
        computer = $env:COMPUTERNAME
        processId = $PID
        session = $session
        platformRunId = $env:WEBJOBS_RUN_ID
    }
    $line = $record | ConvertTo-Json -Compress
    Write-Output $line
    # One file per process session: instances never append to the same file.
    Add-Content -LiteralPath $logPath -Value $line -Encoding UTF8
}
function Test-Shutdown {
    return ($env:WEBJOBS_SHUTDOWN_FILE -and
        (Test-Path -LiteralPath $env:WEBJOBS_SHUTDOWN_FILE))
}
function Wait-OrShutdown([int]$Seconds) {
    for ($i = 0; $i -lt $Seconds; $i++) {
        if (Test-Shutdown) { return }
        Start-Sleep -Seconds 1
    }
}
Write-Record 'START'
if ($type -eq 'continuous') {
    $count = 0
    while (-not (Test-Shutdown)) {
        Write-Record 'HEARTBEAT'
        $count++
        # A finite limit is for LOCAL tests only. Azure continuous jobs restart.
        if ($MaxHeartbeats -gt 0 -and $count -ge $MaxHeartbeats) { break }
        Wait-OrShutdown $HeartbeatSeconds
    }
} else {
    # Simulate a short task. This delay is not an exactly-once guarantee.
    Wait-OrShutdown $WorkSeconds
}
if (Test-Shutdown) { Write-Record 'STOP_REQUESTED' }
else { Write-Record 'END' }