param(
    [string]$ConfigPath = (Join-Path (Split-Path -Parent $PSScriptRoot) 'config.ini'),
    [string]$PickupDirectory,
    [switch]$Send
)

$ErrorActionPreference = 'Stop'
. (Join-Path $PSScriptRoot 'mail-common.ps1')
if ([bool]$Send -eq [bool]$PickupDirectory) {
    throw 'Choose exactly one mode: -Send or -PickupDirectory'
}

$context = Get-MailContext -ConfigPath $ConfigPath
$settings = $context.Settings
foreach ($name in @('SMTP_HOST', 'SMTP_PORT', 'SMTP_USER', 'SMTP_FROM', 'SMTP_REPLY_TO', 'SMTP_TEST_TO')) {
    if (-not $settings.ContainsKey($name) -or -not $settings[$name]) { throw "Missing setting: $name" }
}
if ($settings['SMTP_TLS'] -ne 'on' -or $settings['SMTP_STARTTLS'] -ne 'on') {
    throw 'SMTP_TLS and SMTP_STARTTLS must both be on'
}
$port = 0
if (-not [int]::TryParse($settings['SMTP_PORT'], [ref]$port) -or $port -lt 1 -or $port -gt 65535) {
    throw 'Invalid SMTP_PORT'
}
$testTo = New-Object System.Net.Mail.MailAddress($settings['SMTP_TEST_TO'])
if ($testTo.Address -ne $settings['SMTP_TEST_TO']) { throw 'SMTP_TEST_TO must be a single bare email address' }

$client = $null
$message = $null
$password = $null
$imageStream = $null
try {
    Add-Type -AssemblyName System.Drawing
    $imageStream = New-Object System.IO.MemoryStream
    $bitmap = New-Object System.Drawing.Bitmap(1, 1)
    try {
        $bitmap.SetPixel(0, 0, [System.Drawing.Color]::DarkBlue)
        $bitmap.Save($imageStream, [System.Drawing.Imaging.ImageFormat]::Png)
    }
    finally { $bitmap.Dispose() }
    $imageStream.Position = 0

    $message = New-Object System.Net.Mail.MailMessage
    $message.From = New-Object System.Net.Mail.MailAddress($settings['SMTP_FROM'])
    $null = $message.ReplyToList.Add($settings['SMTP_REPLY_TO'])
    $null = $message.To.Add($testTo)
    $message.Subject = 'MassMailer internal SMTP transport test'
    $message.SubjectEncoding = [System.Text.Encoding]::UTF8
    $html = '<html><body><p>Internal transport test. No marketing campaign was sent.</p>' +
        '<img src="cid:massmailer-test-image" width="1" height="1" alt="Test image"></body></html>'
    $view = [System.Net.Mail.AlternateView]::CreateAlternateViewFromString(
        $html, [System.Text.Encoding]::UTF8, 'text/html')
    $image = New-Object System.Net.Mail.LinkedResource($imageStream, 'image/png')
    $image.ContentId = 'massmailer-test-image'
    $image.TransferEncoding = [System.Net.Mime.TransferEncoding]::Base64
    $null = $view.LinkedResources.Add($image)
    $null = $message.AlternateViews.Add($view)

    $client = New-Object System.Net.Mail.SmtpClient($settings['SMTP_HOST'], $port)
    $client.Timeout = 20000
    if ($Send) {
        $password = Load-SmtpPassword -Context $context
        $client.UseDefaultCredentials = $false
        $client.Credentials = New-Object System.Net.NetworkCredential -ArgumentList @($settings['SMTP_USER'], $password)
        $client.EnableSsl = $true
        $client.Send($message)
        Write-Output "Internal SMTP test accepted for $($testTo.Address). Check that inbox and the received MIME."
    }
    else {
        $pickupPath = [System.IO.Path]::GetFullPath($PickupDirectory)
        if (-not (Test-Path -LiteralPath $pickupPath -PathType Container)) {
            throw "Pickup directory not found: $pickupPath"
        }
        $client.DeliveryMethod = [System.Net.Mail.SmtpDeliveryMethod]::SpecifiedPickupDirectory
        $client.PickupDirectoryLocation = $pickupPath
        $client.Send($message)
        Write-Output "Test MIME written to pickup directory: $pickupPath"
    }
}
finally {
    if ($client) { $client.Dispose() }
    if ($message) { $message.Dispose() }
    if ($imageStream) { $imageStream.Dispose() }
    if ($password) { $password.Dispose() }
}