#Requires -Version 5.1

<#
.SYNOPSIS
Gets user logon, logoff, lock, and unlock activity from the Windows Security log.

.EXAMPLE
$Start = '2026-07-03T00:00:00Z'
$End = '2026-07-06T00:00:00Z'
.\Get-UserLogonActivity.ps1

.EXAMPLE
.\Get-UserLogonActivity.ps1
#>

$StartVariable = Get-Variable -Name Start -ErrorAction SilentlyContinue
$EndVariable = Get-Variable -Name End -ErrorAction SilentlyContinue
$UseDateRange = ($null -ne $StartVariable -and $null -ne $EndVariable)

If (($null -ne $StartVariable) -xor ($null -ne $EndVariable)) {
    Write-Error '$Start and $End must either both be defined or both be omitted. If omitted, the script returns the latest 15 activity events.'
    Exit 1
}

Function ConvertTo-ActivityDateTime {
    Param(
        [Parameter(Mandatory=$true)]
        [AllowNull()]
        [object]$Value,

        [Parameter(Mandatory=$true)]
        [string]$ParameterName
    )

    If ($Value -is [DateTimeOffset]) {
        Return $Value
    }

    If ($Value -is [DateTime]) {
        Return [DateTimeOffset]$Value
    }

    $TrimmedValue = ([string]$Value).Trim()
    $Culture = [Globalization.CultureInfo]::InvariantCulture
    $ParsedDateTime = [DateTimeOffset]::MinValue

    $UtcFormats = [string[]]@(
        "yyyy-MM-dd'T'HH:mm:ss'Z'",
        "yyyy-MM-dd'T'HH:mm:ss.FFFFFFF'Z'"
    )

    $OffsetFormats = [string[]]@(
        "yyyy-MM-dd'T'HH:mm:sszzz",
        "yyyy-MM-dd'T'HH:mm:ss.FFFFFFFzzz"
    )

    $LocalFormats = [string[]]@(
        "yyyy-MM-dd'T'HH:mm:ss",
        "yyyy-MM-dd'T'HH:mm:ss.FFFFFFF",
        "yyyy-MM-dd HH:mm:ss",
        "yyyy-MM-dd",
        "MM/dd/yyyy HH:mm:ss",
        "MM/dd/yyyy"
    )

    $UtcStyles = [Globalization.DateTimeStyles]::AllowWhiteSpaces -bor [Globalization.DateTimeStyles]::AssumeUniversal -bor [Globalization.DateTimeStyles]::AdjustToUniversal
    $LocalStyles = [Globalization.DateTimeStyles]::AllowWhiteSpaces -bor [Globalization.DateTimeStyles]::AssumeLocal

    If ([DateTimeOffset]::TryParseExact($TrimmedValue, $UtcFormats, $Culture, $UtcStyles, [ref]$ParsedDateTime)) {
        Return $ParsedDateTime
    }

    If ([DateTimeOffset]::TryParseExact($TrimmedValue, $OffsetFormats, $Culture, [Globalization.DateTimeStyles]::AllowWhiteSpaces, [ref]$ParsedDateTime)) {
        Return $ParsedDateTime
    }

    If ([DateTimeOffset]::TryParseExact($TrimmedValue, $LocalFormats, $Culture, $LocalStyles, [ref]$ParsedDateTime)) {
        Return $ParsedDateTime
    }

    If ([DateTimeOffset]::TryParse($TrimmedValue, $Culture, $LocalStyles, [ref]$ParsedDateTime)) {
        Return $ParsedDateTime
    }

    Throw "Invalid -${ParameterName} datetime '${Value}'. Use ISO 8601 UTC format: yyyy-MM-ddTHH:mm:ssZ. Example: 2026-07-03T00:00:00Z"
}

Function Get-EventDataValue {
    Param(
        [Parameter(Mandatory=$true)]
        [xml]$EventXml,

        [Parameter(Mandatory=$true)]
        [string]$Name
    )

    $Data = $EventXml.Event.EventData.Data | Where-Object { $_.Name -eq $Name } | Select-Object -First 1
    If ($null -eq $Data) { Return $null }

    Return [string]$Data.'#text'
}

Function Get-EventDataValueFromList {
    Param(
        [Parameter(Mandatory=$true)]
        [xml]$EventXml,

        [Parameter(Mandatory=$true)]
        [string[]]$Names
    )

    ForEach ($Name in $Names) {
        $Value = Get-EventDataValue -EventXml $EventXml -Name $Name
        If (-not [string]::IsNullOrWhiteSpace($Value) -and $Value -ne '-') {
            Return $Value
        }
    }

    Return $null
}

Function Test-UserLogonActivityUser {
    Param(
        [AllowNull()]
        [string]$UserName
    )

    If ([string]::IsNullOrWhiteSpace($UserName)) { Return $false }
    If ($UserName -eq '-') { Return $false }
    If ($UserName.EndsWith('$')) { Return $false }
    If ($UserName -in @('ANONYMOUS LOGON', 'LOCAL SERVICE', 'NETWORK SERVICE', 'SYSTEM')) { Return $false }
    If ($UserName -match '^(DWM|UMFD)-\d+$') { Return $false }

    Return $true
}

Function Format-UserName {
    Param(
        [AllowNull()]
        [string]$DomainName,

        [Parameter(Mandatory=$true)]
        [string]$UserName
    )

    If ([string]::IsNullOrWhiteSpace($DomainName) -or $DomainName -eq '-') {
        Return $UserName
    }

    Return "${DomainName}\${UserName}"
}

Function Get-UserLogonActivitySecurityLogAccessError {
    Try {
        Get-WinEvent -ListLog Security -ErrorAction Stop | Out-Null
        Return $null
    }
    Catch {
        Return "Unable to read the Windows Security event log. Run PowerShell as administrator if access is denied. $($_.Exception.Message)"
    }
}

Function ConvertTo-UserLogonActivity {
    Param(
        [Parameter(Mandatory=$true)]
        [object]$Event
    )

    $EventXml = [xml]$Event.ToXml()
    $UserName = Get-EventDataValueFromList -EventXml $EventXml -Names @('TargetUserName', 'SubjectUserName')
    $DomainName = Get-EventDataValueFromList -EventXml $EventXml -Names @('TargetDomainName', 'SubjectDomainName')
    $LogonType = Get-EventDataValue -EventXml $EventXml -Name 'LogonType'
    $Activity = $null

    Switch ($Event.Id) {
        4624 {
            Switch ($LogonType) {
                '2' { $Activity = 'logon' }
                '7' { $Activity = 'unlock' }
                '10' { $Activity = 'logon' }
                '11' { $Activity = 'logon' }
                Default { Return $null }
            }
        }
        4634 {
            If ($LogonType -notin @('2', '7', '10', '11')) { Return $null }
            $Activity = 'logoff'
        }
        4647 {
            $Activity = 'logoff'
        }
        4800 {
            $Activity = 'lock'
        }
        4801 {
            $Activity = 'unlock'
        }
        Default {
            Return $null
        }
    }

    If (-not (Test-UserLogonActivityUser -UserName $UserName)) { Return $null }

    $EventTime = $Event.TimeCreated

    [PSCustomObject]@{
        Date = $EventTime.ToString('yyyy-MM-dd')
        Time = $EventTime.ToString('HH:mm:ss')
        User = Format-UserName -DomainName $DomainName -UserName $UserName
        Activity = $Activity
    }
}

$SecurityLogAccessError = Get-UserLogonActivitySecurityLogAccessError
If (-not [string]::IsNullOrWhiteSpace($SecurityLogAccessError)) {
    Write-Error $SecurityLogAccessError
    Exit 1
}

$Filter = @{
    LogName = 'Security'
    Id = @(4624, 4634, 4647, 4800, 4801)
}

If ($UseDateRange) {
    Try {
        $StartDateTime = ConvertTo-ActivityDateTime -Value $Start -ParameterName 'Start'
        $EndDateTime = ConvertTo-ActivityDateTime -Value $End -ParameterName 'End'
    }
    Catch {
        Write-Error $_.Exception.Message
        Exit 1
    }

    If ($EndDateTime -le $StartDateTime) {
        Write-Error "-End must be later than -Start."
        Exit 1
    }

    $Filter.StartTime = $StartDateTime.LocalDateTime
    $Filter.EndTime = $EndDateTime.LocalDateTime

    Try {
        $Events = Get-WinEvent -FilterHashtable $Filter -ErrorAction Stop
    }
    Catch {
        If ($_.FullyQualifiedErrorId -like '*NoMatchingEventsFound*' -or $_.Exception.Message -like '*No events were found*') {
            $Events = @()
        }
        Else {
            Write-Error "Unable to read the Windows Security event log. Run PowerShell as administrator if access is denied. $($_.Exception.Message)"
            Exit 1
        }
    }

    ForEach ($Event in ($Events | Sort-Object -Property TimeCreated)) {
        ConvertTo-UserLogonActivity -Event $Event
    }
}
Else {
    $ActivityLimit = 15
    $SearchLimit = 200
    $MaxSearchLimit = 10000
    $ActivityEvents = New-Object System.Collections.Generic.List[object]

    Do {
        $ActivityEvents.Clear()

        Try {
            $Events = Get-WinEvent -FilterHashtable $Filter -MaxEvents $SearchLimit -ErrorAction Stop
        }
        Catch {
            If ($_.FullyQualifiedErrorId -like '*NoMatchingEventsFound*' -or $_.Exception.Message -like '*No events were found*') {
                $Events = @()
            }
            Else {
                Write-Error "Unable to read the Windows Security event log. Run PowerShell as administrator if access is denied. $($_.Exception.Message)"
                Exit 1
            }
        }

        ForEach ($Event in $Events) {
            $ActivityEvent = ConvertTo-UserLogonActivity -Event $Event

            If ($null -ne $ActivityEvent) {
                $ActivityEvents.Add($ActivityEvent)
            }

            If ($ActivityEvents.Count -ge $ActivityLimit) {
                Break
            }
        }

        If ($ActivityEvents.Count -ge $ActivityLimit -or $Events.Count -lt $SearchLimit -or $SearchLimit -ge $MaxSearchLimit) {
            Break
        }

        $SearchLimit = [Math]::Min(($SearchLimit * 2), $MaxSearchLimit)
    } While ($true)

    $ActivityEvents | Select-Object -First $ActivityLimit
}