<?php
/**
 * VC Gateway Helpers
 *
 * Shared functions for the VC Gateway module.
 * Handles visitor authentication, rate limiting, and invite link validation.
 */

require_once __DIR__ . '/../../helpers.php';

// Rate limit: max messages per window
define('VCGW_RATE_LIMIT_MAX', 10);         // 10 messages
define('VCGW_RATE_LIMIT_WINDOW_SEC', 300); // per 5-minute window

/**
 * Authenticate a visitor via X-Visitor-Token header.
 * Returns the visitor row (with invite link data) or aborts with 401.
 */
function requireVisitorAuth(): array {
    $token = headerValue('X-Visitor-Token');
    if (empty($token)) {
        jsonResponse(['OK' => false, 'ERROR' => 'visitor_token_required'], 401);
    }

    $visitor = queryOne(
        "SELECT v.*, il.Token AS InviteToken, il.AllowedChannels, il.HostAddress,
                il.IsRevoked AS InviteRevoked, il.ExpiresAt AS InviteExpiresAt
         FROM Hub_Visitors v
         JOIN Hub_InviteLinks il ON il.ID = v.InviteLinkID
         WHERE v.VisitorToken = ?
         LIMIT 1",
        [$token]
    );

    if (!$visitor) {
        jsonResponse(['OK' => false, 'ERROR' => 'invalid_visitor_token'], 401);
    }

    // Check if the underlying invite link is still valid
    if ($visitor['InviteRevoked']) {
        jsonResponse(['OK' => false, 'ERROR' => 'invite_revoked'], 403);
    }

    if ($visitor['InviteExpiresAt'] && strtotime($visitor['InviteExpiresAt']) < time()) {
        jsonResponse(['OK' => false, 'ERROR' => 'invite_expired'], 403);
    }

    // Update last active
    queryTimed("UPDATE Hub_Visitors SET LastActiveAt = NOW() WHERE ID = ?", [$visitor['ID']]);

    return $visitor;
}

/**
 * Get the allowed channel IDs for a visitor.
 */
function getVisitorAllowedChannels(array $visitor): array {
    $channels = json_decode($visitor['AllowedChannels'], true);
    return is_array($channels) ? array_map('intval', $channels) : [];
}

/**
 * Check if a visitor can read a specific channel.
 */
function visitorCanReadChannel(array $visitor, int $channelId): bool {
    $allowed = getVisitorAllowedChannels($visitor);
    return in_array($channelId, $allowed, true);
}

/**
 * Check rate limit for a visitor. Aborts with 429 if exceeded.
 */
function checkVisitorRateLimit(int $visitorId): void {
    // Current window start (rounded to 5-min intervals)
    $windowSec = VCGW_RATE_LIMIT_WINDOW_SEC;
    $windowStart = date('Y-m-d H:i:s', (int)(floor(time() / $windowSec) * $windowSec));

    $row = queryOne(
        "SELECT MessageCount FROM Hub_VisitorRateLimit
         WHERE VisitorID = ? AND WindowStart = ?",
        [$visitorId, $windowStart]
    );

    $currentCount = $row ? (int)$row['MessageCount'] : 0;

    if ($currentCount >= VCGW_RATE_LIMIT_MAX) {
        $resetAt = (int)(floor(time() / $windowSec) * $windowSec) + $windowSec;
        jsonResponse([
            'OK' => false,
            'ERROR' => 'rate_limit_exceeded',
            'Limit' => VCGW_RATE_LIMIT_MAX,
            'WindowSeconds' => $windowSec,
            'ResetsAt' => toISO8601(date('Y-m-d H:i:s', $resetAt)),
        ], 429);
    }

    // Upsert the count
    queryTimed(
        "INSERT INTO Hub_VisitorRateLimit (VisitorID, WindowStart, MessageCount)
         VALUES (?, ?, 1)
         ON DUPLICATE KEY UPDATE MessageCount = MessageCount + 1",
        [$visitorId, $windowStart]
    );
}

/**
 * Require that the caller is a Sprinter agent (via X-Agent-Address header).
 * Returns the agent address string.
 */
function requireAgentAuth(): string {
    $address = headerValue('X-Agent-Address');
    if (empty($address)) {
        jsonResponse(['OK' => false, 'ERROR' => 'agent_address_required'], 401);
    }

    // Verify the agent exists in Sprinter_Agents
    $agent = queryOne(
        "SELECT ID, FullAddress FROM Sprinter_Agents WHERE FullAddress = ? AND IsActive = 1 LIMIT 1",
        [$address]
    );

    if (!$agent) {
        jsonResponse(['OK' => false, 'ERROR' => 'agent_not_found'], 401);
    }

    return $agent['FullAddress'];
}