<?php
declare(strict_types=1);

final class Settings
{
    public const BASE_DIR = '/usr/local/hitme_plugins/global-autoresponders';
    public const CONFIG_DIR = self::BASE_DIR . '/config';
    public const DATA_DIR = self::BASE_DIR . '/data';
    public const STATE_DIR = self::BASE_DIR . '/state';
    public const LOG_DIR = self::BASE_DIR . '/logs';
    public const AUDIT_LOG = self::LOG_DIR . '/audit.log';
    public const EXTERNAL_SETTINGS = self::CONFIG_DIR . '/plugin-settings.conf';

    /** @var array<string,string> */
    private array $values;

    /**
     * @param array<string,string> $values
     */
    private function __construct(array $values)
    {
        $this->values = $values;
        $this->validate();
    }

    public static function load(string $path): self
    {
        $values = self::defaults();
        if (is_file($path)) {
            $lines = file($path, FILE_IGNORE_NEW_LINES);
            if ($lines !== false) {
                foreach ($lines as $line) {
                    $line = trim($line);
                    if ($line === '' || str_starts_with($line, '#') || !str_contains($line, '=')) {
                        continue;
                    }
                    [$key, $value] = explode('=', $line, 2);
                    $values[trim($key)] = trim($value);
                }
            }
        }
        return new self($values);
    }

    /**
     * @return array<string,string>
     */
    public static function defaults(): array
    {
        return [
            'DEFAULT_PLUGIN_LANGUAGE' => 'pl',
            'DEFAULT_ENABLE' => 'true',
            'GLOBAL_AUTORESPONDER_TIMEZONE' => 'Europe/Warsaw',
            'GLOBAL_AUTORESPONDER_BACKEND' => 'da',
            'GLOBAL_AUTORESPONDER_DYNAMIC_MAILBOX_SCOPE' => 'true',
            'GLOBAL_AUTORESPONDER_MAX_SUBJECT_BYTES' => '255',
            'GLOBAL_AUTORESPONDER_MAX_BODY_BYTES' => '20000',
        ];
    }

    public function getString(string $key, string $default = ''): string
    {
        return $this->values[$key] ?? $default;
    }

    public function getBool(string $key, bool $default = false): bool
    {
        $raw = strtolower($this->getString($key, $default ? 'true' : 'false'));
        return in_array($raw, ['1', 'true', 'yes', 'on'], true);
    }

    public function getInt(string $key, int $default): int
    {
        $raw = $this->getString($key, (string)$default);
        return preg_match('/^-?[0-9]+$/', $raw) ? (int)$raw : $default;
    }

    public function defaultLanguage(): string
    {
        $lang = strtolower($this->getString('DEFAULT_PLUGIN_LANGUAGE', 'pl'));
        return preg_match('/^[a-z]{2}$/', $lang) ? $lang : 'pl';
    }

    public function defaultEnable(): bool
    {
        return $this->getBool('DEFAULT_ENABLE', true);
    }

    public function timezone(): string
    {
        return $this->getString('GLOBAL_AUTORESPONDER_TIMEZONE', 'Europe/Warsaw');
    }

    public function backendMode(): string
    {
        return $this->getString('GLOBAL_AUTORESPONDER_BACKEND', 'da');
    }

    public function scheduleMode(): string
    {
        return $this->backendMode() === 'da' ? 'directadmin_period' : 'exact_hour';
    }

    public function dynamicMailboxScope(): bool
    {
        return $this->getBool('GLOBAL_AUTORESPONDER_DYNAMIC_MAILBOX_SCOPE', true);
    }

    public function maxSubjectBytes(): int
    {
        return $this->getInt('GLOBAL_AUTORESPONDER_MAX_SUBJECT_BYTES', 255);
    }

    public function maxBodyBytes(): int
    {
        return $this->getInt('GLOBAL_AUTORESPONDER_MAX_BODY_BYTES', 20000);
    }

    public function loadOrCreateSecret(string $path = self::CONFIG_DIR . '/secret.key'): string
    {
        if (is_file($path)) {
            $secret = trim((string)file_get_contents($path));
            if ($secret !== '') {
                return $secret;
            }
        }
        $dir = dirname($path);
        if (!is_dir($dir)) {
            mkdir($dir, 0700, true);
        }
        $secret = bin2hex(random_bytes(32));
        file_put_contents($path, $secret . "\n", LOCK_EX);
        @chmod($path, 0600);
        return $secret;
    }

    private function validate(): void
    {
        try {
            new DateTimeZone($this->timezone());
        } catch (Throwable) {
            throw new InvalidArgumentException('Invalid timezone: ' . $this->timezone());
        }
        if (!in_array($this->backendMode(), ['da', 'exim'], true)) {
            throw new InvalidArgumentException('Invalid backend mode: ' . $this->backendMode());
        }
        if ($this->maxSubjectBytes() < 1 || $this->maxBodyBytes() < 1) {
            throw new InvalidArgumentException('Invalid size limits');
        }
    }
}