<?php

class TenantResolver
{
    /**
     * Returns the current subdomain from HTTP_HOST (e.g., school1 for school1.example.com).
     */
    public static function currentSubdomain(): ?string
    {
        $host = $_SERVER['HTTP_HOST'] ?? '';
        if (!$host) return null;
        // Strip port
        $host = preg_replace('/:\\d+$/', '', $host);
        $parts = explode('.', $host);
        if (count($parts) < 3) {
            // No subdomain (like localhost or example.com)
            return null;
        }
        // Return first label (handles multi-level like school1.dev.example.com -> school1)
        return strtolower($parts[0]);
    }

    /**
     * Map subdomain to a school display name using data/tenants.json if present.
     * tenants.json structure: { "subdomain-key": "School Display Name" }
     */
    public static function schoolFromSubdomain(Storage $storage): ?string
    {
        $sub = self::currentSubdomain();
        if (!$sub) return null;
        try {
            $tenants = $storage->get('tenants', []);
            if (!empty($tenants[$sub]) && is_string($tenants[$sub])) {
                return $tenants[$sub];
            }
        } catch (\Throwable $e) {
            // ignore
        }
        // Fallback heuristic: humanize the subdomain (school-one -> School One)
        $guess = trim($sub);
        if ($guess === '') return null;
        $guess = str_replace(['-', '_'], ' ', $guess);
        return ucwords($guess);
    }

    /**
     * Determine a school candidate for the current request:
     * - Prefer explicit $provided (POST/GET)
     * - Then subdomain mapping
     */
    public static function resolveSchool(Storage $storage, ?string $provided = null): ?string
    {
        $provided = is_string($provided) ? trim($provided) : '';
        if ($provided !== '') return $provided;
        return self::schoolFromSubdomain($storage);
    }
}