# Variables to connect to Entra ID
$ClientId     = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
$TenantId     = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
$ClientSecret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

# Convert the client secret to a secure string
$ClientSecretPass = ConvertTo-SecureString -String $ClientSecret -AsPlainText -Force

# Create a credential object using the client ID and secure string
$ClientSecretCredential = New-Object `
    -TypeName System.Management.Automation.PSCredential `
    -ArgumentList $ClientId, $ClientSecretPass

# Connect to Microsoft Graph with Client Secret
Connect-MgGraph -TenantId $TenantId -ClientSecretCredential $ClientSecretCredential

# Days until expiration
$DaysUntilExpiration = 30

$Now = Get-Date

$Applications = Get-MgApplication -all
$Logs = @()

foreach ($App in $Applications) {
    $AppName = $App.DisplayName
    $AppID   = $App.Id
    $ApplID  = $App.AppId

    $AppCreds = Get-MgApplication -ApplicationId $AppID |
        Select-Object PasswordCredentials, KeyCredentials

    $Secrets = $AppCreds.PasswordCredentials
    $Certs   = $AppCreds.KeyCredentials

    foreach ($Secret in $Secrets) {
        $StartDate  = $Secret.StartDateTime
        $EndDate    = $Secret.EndDateTime
        $SecretName = [string]$Secret.DisplayName

        $Owner     = Get-MgApplicationOwner -ApplicationId $App.Id
        $Username  = $Owner.AdditionalProperties.displayName

        $RemainingDaysCount = ($EndDate - $Now).Days

        if ($RemainingDaysCount -le $DaysUntilExpiration -and $RemainingDaysCount -ge 0) {
            $Logs += [PSCustomObject]@{
                'ApplicationName'        = $AppName
                'ApplicationID'          = $ApplID
                'Expiration Date'        = $EndDate.ToString("dd/MM/yyyy HH:mm:ss")
                'Owner'                  = [string]$Username
            }
        }
    }

    foreach ($Cert in $Certs) {
        $StartDate = $Cert.StartDateTime
        $EndDate   = $Cert.EndDateTime
        $CertName  = $Cert.DisplayName

        $Owner     = Get-MgApplicationOwner -ApplicationId $App.Id
        $Username  = $Owner.AdditionalProperties.displayName

        $RemainingDaysCount = ($EndDate - $Now).Days

        if ($RemainingDaysCount -le $DaysUntilExpiration -and $RemainingDaysCount -ge 0) {
            $Logs += [PSCustomObject]@{
                'ApplicationName'        = $AppName
                'ApplicationID'          = $ApplID
                'Expiration Date'        = $EndDate.ToString("dd/MM/yyyy HH:mm:ss")
                'Owner'                  = [string]$Username
            }
        }
    }
}
 
# Email details
$sender    = "xxxx@ccccc.com"
$recipient = "xxxx@ccccc.com"
$subject   = "Service Principal expiring date report"
$type      = "HTML" 
$save      = "false"

# Html CSS style
$Style = @"
<style>
table { 
    border-collapse: collapse;
}
td, th { 
    border: 1px solid #ddd;
    padding: 8px;
}
th {
    padding-top: 12px;
    padding-bottom: 12px;
    text-align: left;
    background-color: #2864c7;
    color: white;
}
</style>
"@

$body = $Logs | ConvertTo-Html -Property 'ApplicationName','ApplicationID','Expiration Date','Owner' -PreContent "<h3>Service Principal - Expira nos próximos $($DaysUntilExpiration) dias</h3>"  -Head $Style |
        Out-String

$params = @{
    Message           = @{
        Subject       = $subject
        Body          = @{
            ContentType = $type
            Content     = $body
        }
        ToRecipients  = @(
            @{
                EmailAddress = @{
                    Address  = $recipient
                }
            }
        )
    }
    SaveToSentItems = $save
}

# Send message
Send-MgUserMail -UserId $sender -BodyParameter $params