Implement NIP-17 Private Direct Messages

src/DirectMessageInterface.php

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+<?php
+
+declare(strict_types=1);
+
+namespace swentel\nostr;
+
+interface DirectMessageInterface
+{
+    /**
+     * Send a direct message to a recipient and create a copy for the sender
+     *
+     * @param string $senderPrivkey The sender's private key
+     * @param string $receiverPubkey The receiver's public key
+     * @param string $message The message content
+     * @param array $additionalTags Additional tags to include
+     * @param string|null $replyToId ID of message being replied to (optional)
+     *
+     * @return array An array containing both GiftWraps (receiver and sender copies)
+     */
+    public function sendDirectMessage(
+        string $senderPrivkey,
+        string $receiverPubkey,
+        string $message,
+        array $additionalTags = [],
+        ?string $replyToId = null,
+    ): array;
+
+    /**
+     * Check if a pubkey has published a kind 10050 event with preferred relays
+     *
+     * @param string $pubkey The public key to check
+     * @return bool True if the pubkey has published a kind 10050 event
+     */
+    public function hasPublishedRelayList(string $pubkey): bool;
+
+    /**
+     * Get preferred relays for a pubkey from kind 10050 events
+     *
+     * @param string $pubkey The public key to get relays for
+     * @return array Array of relay URLs
+     */
+    public function getPreferredRelaysForPubkey(string $pubkey): array;
+}

src/Event/Types/DirectMessageEvent.php

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+<?php
+
+declare(strict_types=1);
+
+namespace swentel\nostr\Event\Types;
+
+use swentel\nostr\Event\Event;
+
+class DirectMessageEvent extends Event
+{
+    /**
+     * Construct a Direct Message event (kind 14)
+     */
+    public function __construct()
+    {
+        parent::__construct();
+        $this->setKind(14);
+    }
+
+    /**
+     * Add a recipient to the direct message
+     *
+     * @param string $pubkey The recipient's public key
+     * @param string|null $relayUrl Optional relay URL for the recipient
+     * @return self
+     */
+    public function addRecipient(string $pubkey, ?string $relayUrl = null): self
+    {
+        $tag = ['p', $pubkey];
+        if ($relayUrl !== null) {
+            $tag[] = $relayUrl;
+        }
+
+        $this->addTag($tag);
+        return $this;
+    }
+
+    /**
+     * Set the message as a reply to another message
+     *
+     * @param string $eventId The ID of the message being replied to
+     * @param string|null $relayUrl Optional relay URL where the original message can be found
+     * @return self
+     */
+    public function setAsReplyTo(string $eventId, ?string $relayUrl = null): self
+    {
+        $tag = ['e', $eventId];
+        if ($relayUrl !== null) {
+            $tag[] = $relayUrl;
+        }
+
+        $this->addTag($tag);
+        return $this;
+    }
+
+    /**
+     * Set the sender's public key
+     *
+     * @param string $pubkey The sender's public key
+     * @return self
+     */
+    public function setSenderPubkey(string $pubkey): self
+    {
+        $this->pubkey = $pubkey;
+        return $this;
+    }
+}

src/Event/Types/FileMessageEvent.php

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+<?php
+
+declare(strict_types=1);
+
+namespace swentel\nostr\Event\Types;
+
+use swentel\nostr\Event\Event;
+
+class FileMessageEvent extends Event
+{
+    /**
+     * Construct a File Message event (kind 15)
+     */
+    public function __construct()
+    {
+        parent::__construct();
+        $this->setKind(15);
+    }
+
+    /**
+     * Add a recipient to the file message
+     *
+     * @param string $pubkey The recipient's public key
+     * @param string|null $relayUrl Optional relay URL for the recipient
+     * @return self
+     */
+    public function addRecipient(string $pubkey, ?string $relayUrl = null): self
+    {
+        $tag = ['p', $pubkey];
+        if ($relayUrl !== null) {
+            $tag[] = $relayUrl;
+        }
+
+        $this->addTag($tag);
+        return $this;
+    }
+
+    /**
+     * Set the file type
+     *
+     * @param string $mimeType The file MIME type
+     * @return self
+     */
+    public function setFileType(string $mimeType): self
+    {
+        $this->addTag(['file-type', $mimeType]);
+        return $this;
+    }
+
+    /**
+     * Set the encryption algorithm
+     *
+     * @param string $algorithm The encryption algorithm used
+     * @return self
+     */
+    public function setEncryptionAlgorithm(string $algorithm): self
+    {
+        $this->addTag(['encryption-algorithm', $algorithm]);
+        return $this;
+    }
+
+    /**
+     * Set the decryption key
+     *
+     * @param string $key The decryption key
+     * @return self
+     */
+    public function setDecryptionKey(string $key): self
+    {
+        $this->addTag(['decryption-key', $key]);
+        return $this;
+    }
+
+    /**
+     * Set the decryption nonce
+     *
+     * @param string $nonce The decryption nonce
+     * @return self
+     */
+    public function setDecryptionNonce(string $nonce): self
+    {
+        $this->addTag(['decryption-nonce', $nonce]);
+        return $this;
+    }
+
+    /**
+     * Set the file hash
+     *
+     * @param string $hash The SHA-256 hexencoded string of the file
+     * @return self
+     */
+    public function setFileHash(string $hash): self
+    {
+        $this->addTag(['x', $hash]);
+        return $this;
+    }
+
+    /**
+     * Set the file URL in the content
+     *
+     * @param string $url URL where the file can be downloaded
+     * @return self
+     */
+    public function setFileUrl(string $url): self
+    {
+        $this->setContent($url);
+        return $this;
+    }
+}

src/Examples/nip17-private-direct-messages.php

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+<?php
+
+declare(strict_types=1);
+
+use swentel\nostr\Key\Key;
+use swentel\nostr\Nip17\DirectMessage;
+use swentel\nostr\Nip59\GiftWrapService;
+use swentel\nostr\Sign\Sign;
+
+require __DIR__ . '/../../vendor/autoload.php';
+
+// Set up keys for Alice and Bob
+$key = new Key();
+$sign = new Sign();
+$giftWrapService = new GiftWrapService($key, $sign);
+
+try {
+    // Alice's private and public keys
+    $alicePrivKey = '0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef';
+    $alicePubKey = $key->getPublicKey($alicePrivKey);
+    print "Alice's public key: " . $alicePubKey . PHP_EOL;
+
+    // Bob's private and public keys
+    $bobPrivKey = 'fedcba9876543210fedcba9876543210fedcba9876543210fedcba9876543210';
+    $bobPubKey = $key->getPublicKey($bobPrivKey);
+    print "Bob's public key: " . $bobPubKey . PHP_EOL;
+
+    // Create DirectMessage service
+    $directMessage = new DirectMessage($giftWrapService, $key);
+
+    print PHP_EOL . "===== SENDING A PRIVATE DIRECT MESSAGE =====" . PHP_EOL;
+
+    // Message from Alice to Bob
+    $messageText = "Hey Bob, this is a private message that only you can read!";
+    print "Alice is sending message to Bob: '" . $messageText . "'" . PHP_EOL;
+
+    // Send the direct message, creating gift wraps for both sender and receiver
+    $result = $directMessage->sendDirectMessage(
+        $alicePrivKey,
+        $bobPubKey,
+        $messageText,
+    );
+
+    // Display information about the created gift wraps
+    print PHP_EOL . "Two gift wraps were created:" . PHP_EOL;
+    print "1. Receiver gift wrap (for Bob):" . PHP_EOL;
+    print "   - Kind: " . $result['receiver']->getKind() . PHP_EOL;
+    print "   - ID: " . $result['receiver']->getId() . PHP_EOL;
+
+    print PHP_EOL . "2. Sender gift wrap (for Alice):" . PHP_EOL;
+    print "   - Kind: " . $result['sender']->getKind() . PHP_EOL;
+    print "   - ID: " . $result['sender']->getId() . PHP_EOL;
+
+    print PHP_EOL . "===== PUBLISHING GIFT WRAPS TO RELAYS =====" . PHP_EOL;
+
+    // Normally, you would get the relay list from the NIP-10050 event
+    // but for this example, we'll use hardcoded relay URLs
+    print "Publishing to receiver's relay: wss://relay.example.com" . PHP_EOL;
+
+    // In a real implementation, you would publish to relays from the result
+    // $receiverRelays = $result['receiver_relays'];
+    // $senderRelays = $result['sender_relays'];
+
+    print PHP_EOL . "===== SIMULATING GIFT WRAP RECEPTION AND DECRYPTION =====" . PHP_EOL;
+
+    // Simulate Bob receiving the gift wrap
+    print "Bob received a gift wrap with ID: " . $result['receiver']->getId() . PHP_EOL;
+
+    // In a real scenario, Bob would look for gift wraps addressed to him (p tag with his pubkey)
+    // For this example, we'll just use the gift wrap we already created
+
+    // Using the new static decryptDirectMessage helper method
+    print "Bob is decrypting the message using his private key and Alice's public key..." . PHP_EOL;
+    $decryptedEvent = DirectMessage::decryptDirectMessage(
+        $result['receiver'],  // The gift wrap to decrypt
+        $bobPrivKey,          // Bob's private key
+        true,                  // Verify the gift wrap is addressed to Bob
+    );
+
+    if ($decryptedEvent) {
+        print "Decryption successful!" . PHP_EOL;
+
+        print PHP_EOL . "===== DECRYPTED MESSAGE DETAILS =====" . PHP_EOL;
+        print "Message kind: " . $decryptedEvent['kind'] . PHP_EOL;
+        print "Message content: '" . $decryptedEvent['content'] . "'" . PHP_EOL;
+
+        // Get the p tags to identify the participants
+        $tags = $decryptedEvent['tags'] ?? [];
+        $participants = [];
+
+        foreach ($tags as $tag) {
+            if ($tag[0] === 'p') {
+                $participants[] = $tag[1];
+            }
+        }
+
+        print "Participants: " . implode(', ', $participants) . PHP_EOL;
+
+        // Bob can now reply to Alice using the same process
+        print PHP_EOL . "===== BOB REPLYING TO ALICE =====" . PHP_EOL;
+
+        // Create a reply message
+        $replyText = "Hey Alice, thanks for your message! This is a private reply.";
+        print "Bob is sending reply to Alice: '" . $replyText . "'" . PHP_EOL;
+
+        // Use the ID of the original message for reply
+        $originalMessageId = $decryptedEvent['id'] ?? null;
+
+        // Send the reply as a direct message
+        $replyResult = $directMessage->sendDirectMessage(
+            $bobPrivKey,
+            $alicePubKey,
+            $replyText,
+            [],
+            $originalMessageId,  // Set as reply to the original message
+        );
+
+        print PHP_EOL . "Reply gift wrap created with ID: " . $replyResult['receiver']->getId() . PHP_EOL;
+
+        // Alice can now decrypt Bob's reply
+        print PHP_EOL . "===== ALICE DECRYPTING BOB'S REPLY =====" . PHP_EOL;
+        print "Alice received a gift wrap with ID: " . $replyResult['receiver']->getId() . PHP_EOL;
+
+        $decryptedReply = DirectMessage::decryptDirectMessage(
+            $replyResult['receiver'],  // The gift wrap to decrypt
+            $alicePrivKey,             // Alice's private key
+            true,                       // Verify the gift wrap is addressed to Alice
+        );
+
+        if ($decryptedReply) {
+            print "Alice successfully decrypted Bob's reply!" . PHP_EOL;
+            print "Reply content: '" . $decryptedReply['content'] . "'" . PHP_EOL;
+
+            // Check if it's a reply to the original message
+            $isReply = false;
+            foreach ($decryptedReply['tags'] as $tag) {
+                if ($tag[0] === 'e' && isset($tag[1]) && $tag[1] === $decryptedEvent['id']) {
+                    $isReply = true;
+                    break;
+                }
+            }
+
+            if ($isReply) {
+                print "This is a reply to Alice's original message." . PHP_EOL;
+            }
+        } else {
+            print "Alice could not decrypt the message." . PHP_EOL;
+        }
+    } else {
+        print "Decryption failed! The message might not be for Bob or the encryption keys don't match." . PHP_EOL;
+    }
+
+} catch (Exception $e) {
+    print 'Exception: ' . $e->getMessage() . PHP_EOL;
+}