Horde iMIP

horde/imip is the iMIP (RFC 6047) transport layer for sending and parsing MIME-encapsulated iTIP messages. It bridges horde/itip's decision engine to actual email delivery by listening for PSR-14 scheduling events and constructing RFC-compliant text/calendar MIME messages.

Installation

composer require horde/imip

Requires PHP 8.1+.

Architecture

Design Principles

• Listener-based — plugs into any PSR-14 dispatcher, no tight coupling
• Pure PSR-4 — no legacy PSR-0 code, fully typed, readonly value objects
• Builds on modern horde/mime — uses Horde\Mime\Part, PartBuilder, MessageRenderer
• Sends via modern horde/mail — uses Horde\Mail\Transport\Transport interface
• Bidirectional — sends outbound iTIP and parses inbound iMIP messages

Components

Class	Purpose
ImipSendingListener	PSR-14 listener: handles *Sending events, builds and sends MIME
MessageBuilder	Constructs ComposedMessage from VCalendar + sender/recipient info
ImipParsingService	Extracts ItipMessage from incoming MIME Part tree
SenderIdentity	Interface describing the sender (email, name, reply-to)
SimpleSenderIdentity	Value-object implementation of SenderIdentity
ImipOptions	Configuration: charset, prodId, multipart preference

Outbound Flow

horde/itip ItipProcessor
    │
    │ App applies ItipResult, then dispatches PSR-14 event
    ▼
PSR-14 EventDispatcher
    │
    ▼
ImipSendingListener
    │  - receives InvitationSending / ReplySending / CancellationSending
    │  - iterates result->actions (SendRequest, SendReply, SendCancel)
    │  - calls MessageBuilder::build() for each recipient
    │  - renders via MessageRenderer and sends via Transport
    ▼
Horde\Mail\Transport\Transport::send()

Inbound Flow

Incoming email (raw MIME)
    │
    │ Application parses with Horde\Mime\MimeParser
    ▼
Horde\Mime\Part tree
    │
    ▼
ImipParsingService::parse($part, $actorEmail)
    │  - finds text/calendar part (recursive search)
    │  - parses iCalendar via horde/icalendar
    │  - wraps as ItipMessage
    ▼
ItipMessage → feed into ItipProcessor::process()

Boundaries

This library is responsible for:

• Constructing RFC 6047 MIME messages from VCalendar objects
• Sending iMIP messages via Horde\Mail\Transport\Transport
• Listening for PSR-14 scheduling events dispatched after iTIP processing
• Parsing inbound MIME messages to extract ItipMessage

This library is not responsible for:

• iTIP logic (accept/reject, SEQUENCE handling, conflict detection) — see horde/itip
• iCalendar parsing/writing — see horde/icalendar
• Mail transport implementation (SMTP, sendmail, etc.) — see horde/mail
• MIME structure parsing beyond finding the text/calendar part — see horde/mime
• Event dispatching — the application calls $dispatcher->dispatch()

Collaboration Partners

Package	Relationship
horde/itip	Provides ItipMessage, ItipResult, SendReply/Request/Cancel actions, and PSR-14 event types
horde/icalendar	Provides VCalendar, Writer for serialization, Reader/AbstractComponent for parsing
horde/mime	Provides Part, PartBuilder, MessageBuilder, MessageRenderer, MimeParser
horde/mail	Provides Transport interface, AddressList, Address, MockTransport for testing
horde/eventdispatcher	PSR-14 dispatcher that routes events to this listener

Usage

Sending (Outbound iMIP)

use Horde\Imip\ImipSendingListener;
use Horde\Imip\MessageBuilder;
use Horde\Imip\SimpleSenderIdentity;
use Horde\Mail\Transport\SmtpTransport;

// Configure
$sender = new SimpleSenderIdentity(
    email: 'calendar@example.com',
    commonName: 'Calendar System',
);
$builder = new MessageBuilder();
$transport = new SmtpTransport(/* config */);

// Register listener with your PSR-14 provider
$listener = new ImipSendingListener($builder, $sender, $transport);
$provider->addListener(ItipEvent::class, $listener);

// After processing iTIP, dispatch the event — listener sends automatically
$result = $processor->process($message);
// ... apply changes ...
$dispatcher->dispatch(new ReplySending($message, $result));

Parsing (Inbound iMIP)

use Horde\Imip\ImipParsingService;
use Horde\Mime\MimeParser;

$service = new ImipParsingService();

// Parse raw email into a Part tree
$part = MimeParser::parse($rawMimeMessage);

// Extract ItipMessage (returns null if no text/calendar part)
$itipMessage = $service->parse($part, 'sender@example.com');

if ($itipMessage !== null) {
    $result = $processor->process($itipMessage);
    // ... handle result ...
}

Custom Sender Identity

Implement SenderIdentity for integration with your application's identity system:

use Horde\Imip\SenderIdentity;

class HordeIdentityAdapter implements SenderIdentity
{
    public function __construct(private MyIdentityService $identities) {}

    public function getEmail(): string { return $this->identities->getDefault()->email; }
    public function getCommonName(): string { return $this->identities->getDefault()->fullname; }
    public function getFrom(): string { return sprintf('%s <%s>', $this->getCommonName(), $this->getEmail()); }
    public function getReplyTo(): ?string { return $this->identities->getDefault()->replyTo; }
}

Upgrading

This is a new package — there is no legacy Horde_Imip to upgrade from. The iMIP transport logic was previously embedded in horde/itip's Horde_Itip_Response* classes (PSR-0 lib/). Those classes remain frozen in horde/itip for backward compatibility but are not used by this package.

See horde/itip's doc/UPGRADING.md for guidance on migrating from the legacy combined itip+imip API.

License

LGPL-2.1 — see LICENSE.