<?php
// Chat routes (client API only):
//   POST /api/chat       — send a chat message to {recipient}
//   GET  /api/chat?since=N — pull all chat messages addressed to me with id > N
//
// Same decrypt-reencrypt hop as messages.php: arrives encrypted with the
// senders client secret, stored at-rest under the inter-tenant key, returned
// re-encrypted with the recipients client secret. Relay sees plaintext only
// during the routing hop.

if (!defined('RELAY_BOOTSTRAPPED')) { http_response_code(404); exit; }

// $clientTenant is set by messages.php earlier in the chain via authClient().
// We re-resolve here to keep this file self-contained.
$clientTenant = $clientTenant ?? authClient($db);

if ($route === '/api/chat' && $method === 'POST') {
    if (!$clientTenant) jsonResponse(['error' => 'unauthorized'], 401);
    $input = json_decode(file_get_contents('php://input'), true) ?: [];
    $encryptedBody = (string)($input['body'] ?? '');
    $recipientName = trim((string)($input['recipient'] ?? ''));
    if ($encryptedBody === '') jsonResponse(['error' => 'body required'], 400);
    if ($recipientName === '') jsonResponse(['error' => 'recipient required'], 400);

    $recipient = getTenantByUsername($db, $recipientName);
    if (!$recipient) jsonResponse(['error' => "no such user: $recipientName"], 404);

    if (empty($clientTenant['secret_encrypted'])) {
        jsonResponse(['error' => 'sender has no client secret set — log into the relay UI and configure one in your account'], 400);
    }
    $senderSecret = masterDecrypt($clientTenant['secret_encrypted'], $MASTER_KEY);
    if (!$senderSecret) jsonResponse(['error' => 'sender secret unavailable'], 500);
    $interKey = getInterTenantKey($db, $MASTER_KEY);
    if (!$interKey) jsonResponse(['error' => 'relay super-shared key not set — admin must complete setup'], 500);

    $plain = clientDecrypt($encryptedBody, $senderSecret);
    if ($plain === '') jsonResponse(['error' => 'body decrypt failed (sender secret mismatch?)'], 400);
    $stored = clientEncrypt($plain, $interKey);

    $db->prepare('INSERT INTO chat_messages (recipient_id, sender_id, sender_username, body) VALUES (:r, :s, :sn, :b)')
        ->execute([
            'r' => $recipient['id'],
            's' => $clientTenant['id'],
            'sn' => $clientTenant['username'],
            'b' => $stored,
        ]);
    jsonResponse(['ok' => true, 'id' => (int)$db->lastInsertId()]);
}

if ($route === '/api/chat' && $method === 'GET') {
    if (!$clientTenant) jsonResponse(['error' => 'unauthorized'], 401);
    if (empty($clientTenant['secret_encrypted'])) {
        jsonResponse(['error' => 'no client secret set — log into the relay UI and configure one in your account'], 400);
    }

    $since = (int)($_GET['since'] ?? 0);
    $stmt = $db->prepare('SELECT id, sender_username, body, created_at FROM chat_messages WHERE recipient_id = :r AND id > :s ORDER BY id ASC LIMIT 500');
    $stmt->execute(['r' => $clientTenant['id'], 's' => $since]);
    $rows = $stmt->fetchAll();

    $interKey = getInterTenantKey($db, $MASTER_KEY);
    if (!$interKey) jsonResponse(['error' => 'relay super-shared key not set'], 500);
    $recipientSecret = masterDecrypt($clientTenant['secret_encrypted'], $MASTER_KEY);
    if (!$recipientSecret) jsonResponse(['error' => 'recipient secret unavailable'], 500);

    $out = [];
    $maxId = $since;
    foreach ($rows as $row) {
        $plain = clientDecrypt($row['body'] ?? '', $interKey);
        $row['body'] = clientEncrypt($plain, $recipientSecret);
        $out[] = $row;
        if ((int)$row['id'] > $maxId) $maxId = (int)$row['id'];
    }
    // Mark fetched so cleanup can prune them sooner if desired. We still
    // keep them around for the 7-day window so a re-poll with since=0
    // backfills history if a client wipes its local cache.
    if ($out) {
        $db->prepare('UPDATE chat_messages SET fetched = 1 WHERE recipient_id = :r AND id <= :m AND fetched = 0')
            ->execute(['r' => $clientTenant['id'], 'm' => $maxId]);
    }
    jsonResponse(['messages' => $out, 'max_id' => $maxId]);
}