<?php

namespace App\Services;

final class SecurityHeadersService
{
    public function buildHeaders(?bool $isHttps = null): array
    {
        $isHttps = $isHttps ?? $this->isHttpsRequest();

        $headers = [
            'Content-Security-Policy' => $this->buildContentSecurityPolicy($isHttps),
            'Referrer-Policy' => 'strict-origin-when-cross-origin',
            'Permissions-Policy' => 'accelerometer=(), autoplay=(), camera=(), display-capture=(), geolocation=(), gyroscope=(), magnetometer=(), microphone=(), payment=(), usb=()',
            'Cross-Origin-Opener-Policy' => 'same-origin',
            'Cross-Origin-Resource-Policy' => 'same-origin',
            'Origin-Agent-Cluster' => '?1',
            'X-Content-Type-Options' => 'nosniff',
            'X-Frame-Options' => 'SAMEORIGIN',
            'X-Permitted-Cross-Domain-Policies' => 'none',
        ];

        if ($isHttps) {
            $headers['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains';
        }

        return $headers;
    }

    public function send(array $overrides = [], ?bool $isHttps = null): void
    {
        if (headers_sent()) {
            return;
        }

        $headers = $this->buildHeaders($isHttps);

        foreach ($overrides as $name => $value) {
            if (!is_string($name) || trim($name) === '') {
                continue;
            }

            if ($value === null) {
                unset($headers[$name]);
                continue;
            }

            $headers[$name] = (string) $value;
        }

        header_remove('X-Powered-By');

        foreach ($headers as $name => $value) {
            header($name . ': ' . $value, true);
        }
    }

    private function buildContentSecurityPolicy(bool $isHttps): string
    {
        $directives = [
            "default-src 'self'",
            "base-uri 'self'",
            "form-action 'self'",
            "frame-ancestors 'self'",
            "object-src 'none'",
            "connect-src 'self'",
            "font-src 'self' data:",
            "img-src 'self' data:",
            "manifest-src 'self'",
            "script-src 'self'",
            "style-src 'self'",
        ];

        if ($isHttps) {
            $directives[] = 'upgrade-insecure-requests';
        }

        return implode('; ', $directives);
    }

    private function isHttpsRequest(): bool
    {
        $https = $_SERVER['HTTPS'] ?? null;

        if (is_string($https) && $https !== '' && strtolower($https) !== 'off') {
            return true;
        }

        $forwardedProto = $_SERVER['HTTP_X_FORWARDED_PROTO'] ?? '';

        if (is_string($forwardedProto) && strtolower($forwardedProto) === 'https') {
            return true;
        }

        return (string) ($_SERVER['SERVER_PORT'] ?? '') === '443';
    }
}