<?php
// Chat routes (client API only):
//   POST /api/chat              — send a chat message to {recipient}
//   GET  /api/chat?since=N      — pull all messages addressed to me (id > N)
//   GET  /api/chat/sent?since=N — pull state updates (delivered/seen) for
//                                  *my* sent messages with id > N. The
//                                  sender uses this to learn read receipts
//                                  without needing a backchannel.
//   POST /api/chat/seen {peer}  — mark every message FROM peer TO me as
//                                  seen. The sender's next /api/chat/sent
//                                  poll picks the new state up.
//
// 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]);
}

// ── GET /api/chat/sent ─────────────────────────────────────────
// Returns the receipt state (fetched/seen) for messages the caller has
// sent. Body is intentionally NOT included — the sender already has the
// plaintext locally; the relay only echoes the state flags so the sender
// can render check / double-check on the right messages.

if ($route === '/api/chat/sent' && $method === 'GET') {
    if (!$clientTenant) jsonResponse(['error' => 'unauthorized'], 401);
    $since = (int)($_GET['since'] ?? 0);
    $stmt = $db->prepare('
        SELECT id, recipient_id, fetched, seen, created_at
        FROM chat_messages
        WHERE sender_id = :s AND id > :since
        ORDER BY id ASC
        LIMIT 1000
    ');
    $stmt->execute(['s' => $clientTenant['id'], 'since' => $since]);
    $rows = $stmt->fetchAll();
    $maxId = $since;
    foreach ($rows as $r) {
        if ((int)$r['id'] > $maxId) $maxId = (int)$r['id'];
    }
    jsonResponse(['receipts' => $rows, 'max_id' => $maxId]);
}

// ── POST /api/chat/seen ────────────────────────────────────────
// Body: { peer: "<sender_username>" }. Marks every message that the
// peer sent to the caller as seen=1. Idempotent — safe to call on
// every thread open.

if ($route === '/api/chat/seen' && $method === 'POST') {
    if (!$clientTenant) jsonResponse(['error' => 'unauthorized'], 401);
    $input = json_decode(file_get_contents('php://input'), true) ?: [];
    $peer = trim((string)($input['peer'] ?? ''));
    if ($peer === '') jsonResponse(['error' => 'peer required'], 400);
    $db->prepare('
        UPDATE chat_messages
        SET seen = 1
        WHERE recipient_id = :r AND sender_username = :p AND seen = 0
    ')->execute(['r' => $clientTenant['id'], 'p' => $peer]);
    jsonResponse(['ok' => true]);
}