<?php
require_once __DIR__ . '/config.php';

if (session_status() === PHP_SESSION_NONE && !headers_sent()) {
    @session_start();
}

function clm_cfg($key = null)
{
    $config = clm_config();
    return $key === null ? $config : ($config[$key] ?? null);
}

function clm_safe_identifier($value): string
{
    return preg_replace('/[^a-zA-Z0-9_]/', '', (string)$value);
}

function clm_tables(): array
{
    $prefix = clm_safe_identifier(clm_cfg('table_prefix') ?: 'clm_');

    return [
        'apps' => $prefix . 'apps',
        'licenses' => $prefix . 'licenses',
        'activations' => $prefix . 'activations',
    ];
}

function clm_table(string $name): string
{
    $tables = clm_tables();
    return $tables[$name] ?? clm_safe_identifier((clm_cfg('table_prefix') ?: 'clm_') . $name);
}

function clm_html($value): string
{
    return htmlspecialchars((string)$value, ENT_QUOTES, 'UTF-8');
}

function clm_base_url(): string
{
    if (PHP_SAPI === 'cli') {
        return '';
    }

    $scheme = (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off') ? 'https' : 'http';
    $host = $_SERVER['HTTP_HOST'] ?? 'localhost';
    $dir = rtrim(str_replace('\\', '/', dirname($_SERVER['SCRIPT_NAME'] ?? '/central_license_manager/index.php')), '/');

    if ($dir === '.' || $dir == '/') {
        $dir = '';
    }

    return $scheme . '://' . $host . $dir;
}

function clm_using_parent_db(): bool
{
    $config = clm_cfg();

    return $config['db_host'] === ''
        && $config['db_name'] === ''
        && $config['db_user'] === ''
        && file_exists(__DIR__ . '/../db/config.php');
}

function clm_db(): PDO
{
    static $pdo = null;

    if ($pdo instanceof PDO) {
        return $pdo;
    }

    $config = clm_cfg();

    if (clm_using_parent_db()) {
        require_once __DIR__ . '/../db/config.php';
        $pdo = db();
        return $pdo;
    }

    if ($config['db_host'] === '' || $config['db_name'] === '' || $config['db_user'] === '') {
        throw new RuntimeException('Central License Manager DB is not configured. Set CLM_DB_HOST, CLM_DB_NAME, CLM_DB_USER and CLM_DB_PASS in config.php or the environment before moving this folder to another server.');
    }

    $dsn = 'mysql:host=' . $config['db_host'] . ';dbname=' . $config['db_name'] . ';charset=' . ($config['db_charset'] ?: 'utf8mb4');
    $pdo = new PDO($dsn, $config['db_user'], $config['db_pass'], [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    ]);

    return $pdo;
}

function clm_column_exists(string $table, string $column): bool
{
    $table = clm_safe_identifier($table);
    $column = clm_safe_identifier($column);
    $stmt = clm_db()->prepare("SHOW COLUMNS FROM `{$table}` LIKE ?");
    $stmt->execute([$column]);
    return (bool)$stmt->fetch();
}

function clm_ensure_schema(): void
{
    static $ready = false;

    if ($ready) {
        return;
    }

    $ready = true;
    $pdo = clm_db();
    $tables = clm_tables();
    $apps = $tables['apps'];
    $licenses = $tables['licenses'];
    $activations = $tables['activations'];

    $pdo->exec("CREATE TABLE IF NOT EXISTS `{$apps}` (
        `id` INT AUTO_INCREMENT PRIMARY KEY,
        `slug` VARCHAR(120) NOT NULL UNIQUE,
        `name` VARCHAR(190) NOT NULL,
        `status` ENUM('active', 'inactive') NOT NULL DEFAULT 'active',
        `notes` TEXT DEFAULT NULL,
        `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        `updated_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4");

    $pdo->exec("CREATE TABLE IF NOT EXISTS `{$licenses}` (
        `id` INT AUTO_INCREMENT PRIMARY KEY,
        `app_id` INT NOT NULL,
        `license_key` VARCHAR(255) NOT NULL UNIQUE,
        `max_activations` INT NOT NULL DEFAULT 1,
        `max_counters` INT NOT NULL DEFAULT 1,
        `status` ENUM('active', 'suspended', 'expired') NOT NULL DEFAULT 'active',
        `owner` VARCHAR(255) DEFAULT NULL,
        `address` TEXT DEFAULT NULL,
        `customer_name` VARCHAR(255) DEFAULT NULL,
        `customer_email` VARCHAR(255) DEFAULT NULL,
        `notes` TEXT DEFAULT NULL,
        `expires_at` DATETIME DEFAULT NULL,
        `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        `updated_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
        INDEX `idx_clm_app_id` (`app_id`),
        FOREIGN KEY (`app_id`) REFERENCES `{$apps}`(`id`) ON DELETE CASCADE
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4");

    $pdo->exec("CREATE TABLE IF NOT EXISTS `{$activations}` (
        `id` INT AUTO_INCREMENT PRIMARY KEY,
        `license_id` INT NOT NULL,
        `fingerprint` VARCHAR(255) NOT NULL,
        `domain` VARCHAR(255) DEFAULT NULL,
        `product` VARCHAR(255) DEFAULT NULL,
        `product_version` VARCHAR(120) DEFAULT NULL,
        `app_slug` VARCHAR(120) DEFAULT NULL,
        `status` ENUM('active', 'deactivated') NOT NULL DEFAULT 'active',
        `activation_token` VARCHAR(255) DEFAULT NULL,
        `activated_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        `last_seen_at` DATETIME DEFAULT NULL,
        `deactivated_at` DATETIME DEFAULT NULL,
        UNIQUE KEY `uniq_clm_license_machine` (`license_id`, `fingerprint`),
        INDEX `idx_clm_activation_status` (`status`),
        INDEX `idx_clm_activation_domain` (`domain`),
        FOREIGN KEY (`license_id`) REFERENCES `{$licenses}`(`id`) ON DELETE CASCADE
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4");

    $licenseAlterMap = [
        'customer_name' => "ALTER TABLE `{$licenses}` ADD COLUMN `customer_name` VARCHAR(255) DEFAULT NULL AFTER `address`",
        'customer_email' => "ALTER TABLE `{$licenses}` ADD COLUMN `customer_email` VARCHAR(255) DEFAULT NULL AFTER `customer_name`",
        'notes' => "ALTER TABLE `{$licenses}` ADD COLUMN `notes` TEXT DEFAULT NULL AFTER `customer_email`",
        'expires_at' => "ALTER TABLE `{$licenses}` ADD COLUMN `expires_at` DATETIME DEFAULT NULL AFTER `notes`",
        'max_counters' => "ALTER TABLE `{$licenses}` ADD COLUMN `max_counters` INT NOT NULL DEFAULT 1 AFTER `max_activations`",
    ];

    foreach ($licenseAlterMap as $column => $sql) {
        if (!clm_column_exists($licenses, $column)) {
            $pdo->exec($sql);
        }
    }

    $activationAlterMap = [
        'product_version' => "ALTER TABLE `{$activations}` ADD COLUMN `product_version` VARCHAR(120) DEFAULT NULL AFTER `product`",
        'app_slug' => "ALTER TABLE `{$activations}` ADD COLUMN `app_slug` VARCHAR(120) DEFAULT NULL AFTER `product_version`",
        'status' => "ALTER TABLE `{$activations}` ADD COLUMN `status` ENUM('active', 'deactivated') NOT NULL DEFAULT 'active' AFTER `app_slug`",
        'activation_token' => "ALTER TABLE `{$activations}` ADD COLUMN `activation_token` VARCHAR(255) DEFAULT NULL AFTER `status`",
        'last_seen_at' => "ALTER TABLE `{$activations}` ADD COLUMN `last_seen_at` DATETIME DEFAULT NULL AFTER `activated_at`",
        'deactivated_at' => "ALTER TABLE `{$activations}` ADD COLUMN `deactivated_at` DATETIME DEFAULT NULL AFTER `last_seen_at`",
    ];

    foreach ($activationAlterMap as $column => $sql) {
        if (!clm_column_exists($activations, $column)) {
            $pdo->exec($sql);
        }
    }

    clm_resolve_app((string)clm_cfg('default_app_slug'), (string)clm_cfg('default_app_name'), true);
}

function clm_slugify($value): string
{
    $value = strtolower(trim((string)$value));
    $value = preg_replace('/[^a-z0-9]+/', '-', $value);
    $value = trim((string)$value, '-');

    if ($value === '') {
        $value = strtolower((string)(clm_cfg('default_app_slug') ?: 'legacy'));
    }

    return $value;
}

function clm_secret_valid($secret): bool
{
    return hash_equals((string)clm_cfg('api_secret'), (string)$secret);
}

function clm_resolve_app(string $slug = '', string $name = '', bool $createIfMissing = false): ?array
{
    clm_ensure_schema();

    $tables = clm_tables();
    $apps = $tables['apps'];
    $slug = clm_slugify($slug !== '' ? $slug : ($name !== '' ? $name : (string)clm_cfg('default_app_slug')));
    $name = trim($name) !== '' ? trim($name) : ucwords(str_replace('-', ' ', $slug));

    $stmt = clm_db()->prepare("SELECT * FROM `{$apps}` WHERE slug = ? LIMIT 1");
    $stmt->execute([$slug]);
    $app = $stmt->fetch();

    if ($app) {
        return $app;
    }

    if (!$createIfMissing) {
        return null;
    }

    $stmt = clm_db()->prepare("INSERT INTO `{$apps}` (slug, name, status) VALUES (?, ?, 'active')");
    $stmt->execute([$slug, $name]);

    $stmt = clm_db()->prepare("SELECT * FROM `{$apps}` WHERE slug = ? LIMIT 1");
    $stmt->execute([$slug]);
    return $stmt->fetch() ?: null;
}

function clm_app_by_id(int $id): ?array
{
    clm_ensure_schema();

    $apps = clm_table('apps');
    $stmt = clm_db()->prepare("SELECT * FROM `{$apps}` WHERE id = ? LIMIT 1");
    $stmt->execute([$id]);
    $row = $stmt->fetch();

    return $row ?: null;
}

function clm_update_app_record(array $app, array $data): array
{
    clm_ensure_schema();

    $apps = clm_table('apps');
    $fields = [];
    $params = [];

    if (array_key_exists('name', $data) || array_key_exists('slug', $data)) {
        $name = trim((string)($data['name'] ?? (string)$app['name']));
        $slugInput = trim((string)($data['slug'] ?? (string)$app['slug']));

        if ($name === '' && $slugInput === '') {
            throw new RuntimeException('App name or slug is required.');
        }

        $slug = clm_slugify($slugInput !== '' ? $slugInput : $name);
        $name = $name !== '' ? $name : ucwords(str_replace('-', ' ', $slug));

        $check = clm_db()->prepare("SELECT id FROM `{$apps}` WHERE slug = ? AND id <> ? LIMIT 1");
        $check->execute([$slug, (int)$app['id']]);
        if ($check->fetch()) {
            throw new RuntimeException('Another app already uses this slug.');
        }

        $fields[] = '`name` = ?';
        $params[] = $name;
        $fields[] = '`slug` = ?';
        $params[] = $slug;
    }

    if (isset($data['status'])) {
        $status = strtolower(trim((string)$data['status']));
        if (in_array($status, ['active', 'inactive'], true)) {
            $fields[] = '`status` = ?';
            $params[] = $status;
        }
    }

    if (empty($fields)) {
        return clm_app_by_id((int)$app['id']) ?: $app;
    }

    $params[] = (int)$app['id'];
    $stmt = clm_db()->prepare("UPDATE `{$apps}` SET " . implode(', ', $fields) . " WHERE id = ?");
    $stmt->execute($params);

    return clm_app_by_id((int)$app['id']) ?: $app;
}

function clm_license_with_app_by_key(string $licenseKey): ?array
{
    clm_ensure_schema();

    $tables = clm_tables();
    $licenses = $tables['licenses'];
    $apps = $tables['apps'];

    $stmt = clm_db()->prepare("SELECT l.*, a.slug AS app_slug, a.name AS app_name
        FROM `{$licenses}` l
        INNER JOIN `{$apps}` a ON a.id = l.app_id
        WHERE l.license_key = ?
        LIMIT 1");
    $stmt->execute([strtoupper(trim($licenseKey))]);
    $row = $stmt->fetch();

    return $row ?: null;
}

function clm_license_with_app_by_id(int $id): ?array
{
    clm_ensure_schema();

    $tables = clm_tables();
    $licenses = $tables['licenses'];
    $apps = $tables['apps'];

    $stmt = clm_db()->prepare("SELECT l.*, a.slug AS app_slug, a.name AS app_name
        FROM `{$licenses}` l
        INNER JOIN `{$apps}` a ON a.id = l.app_id
        WHERE l.id = ?
        LIMIT 1");
    $stmt->execute([$id]);
    $row = $stmt->fetch();

    return $row ?: null;
}

function clm_generate_license_key(string $prefix = 'FLAT'): string
{
    $prefix = preg_replace('/[^A-Z0-9]/', '', strtoupper(trim($prefix))) ?: 'FLAT';

    do {
        $key = $prefix
            . '-' . strtoupper(bin2hex(random_bytes(2)))
            . '-' . strtoupper(bin2hex(random_bytes(2)))
            . '-' . strtoupper(bin2hex(random_bytes(2)));
    } while (clm_license_with_app_by_key($key));

    return $key;
}

function clm_make_token(string $licenseKey, string $fingerprint): string
{
    return hash_hmac('sha256', strtoupper(trim($licenseKey)) . $fingerprint, (string)clm_cfg('api_secret'));
}

function clm_active_activation_count(int $licenseId): int
{
    clm_ensure_schema();

    $activations = clm_table('activations');
    $stmt = clm_db()->prepare("SELECT COUNT(*) FROM `{$activations}` WHERE license_id = ? AND status = 'active'");
    $stmt->execute([$licenseId]);

    return (int)$stmt->fetchColumn();
}

function clm_license_is_expired(array $license): bool
{
    if (empty($license['expires_at'])) {
        return false;
    }

    $expiresAt = strtotime((string)$license['expires_at']);
    return $expiresAt !== false && $expiresAt < time();
}

function clm_upsert_activation(array $license, string $fingerprint, string $domain = '', string $product = '', string $productVersion = ''): array
{
    clm_ensure_schema();

    $activations = clm_table('activations');
    $pdo = clm_db();
    $token = clm_make_token((string)$license['license_key'], $fingerprint);
    $product = trim($product) !== '' ? trim($product) : (string)$license['app_name'];

    $stmt = $pdo->prepare("SELECT * FROM `{$activations}` WHERE license_id = ? AND fingerprint = ? LIMIT 1");
    $stmt->execute([(int)$license['id'], $fingerprint]);
    $existing = $stmt->fetch();
    $currentActive = clm_active_activation_count((int)$license['id']);

    if ($existing) {
        if (($existing['status'] ?? 'active') !== 'active' && $currentActive >= (int)$license['max_activations']) {
            return [
                'success' => false,
                'error' => 'Maximum activation limit reached.'
            ];
        }

        $stmt = $pdo->prepare("UPDATE `{$activations}`
            SET domain = ?,
                product = ?,
                product_version = ?,
                app_slug = ?,
                status = 'active',
                activation_token = ?,
                last_seen_at = NOW(),
                deactivated_at = NULL
            WHERE id = ?");
        $stmt->execute([
            $domain !== '' ? $domain : null,
            $product,
            $productVersion !== '' ? $productVersion : null,
            (string)$license['app_slug'],
            $token,
            (int)$existing['id'],
        ]);
    } else {
        if ($currentActive >= (int)$license['max_activations']) {
            return [
                'success' => false,
                'error' => 'Maximum activation limit reached.'
            ];
        }

        $stmt = $pdo->prepare("INSERT INTO `{$activations}`
            (license_id, fingerprint, domain, product, product_version, app_slug, status, activation_token, last_seen_at)
            VALUES (?, ?, ?, ?, ?, ?, 'active', ?, NOW())");
        $stmt->execute([
            (int)$license['id'],
            $fingerprint,
            $domain !== '' ? $domain : null,
            $product,
            $productVersion !== '' ? $productVersion : null,
            (string)$license['app_slug'],
            $token,
        ]);
    }

    return [
        'success' => true,
        'activation_token' => $token,
    ];
}

function clm_request_data(): array
{
    $data = [];
    $raw = file_get_contents('php://input');

    if (is_string($raw) && trim($raw) !== '') {
        $decoded = json_decode($raw, true);
        if (is_array($decoded)) {
            $data = $decoded;
        }
    }

    if (!empty($_POST)) {
        $data = array_merge($data, $_POST);
    }

    if (!empty($_GET)) {
        $data = array_merge($data, $_GET);
    }

    return $data;
}

function clm_json(array $data, int $status = 200): void
{
    if (!headers_sent()) {
        http_response_code($status);
        header('Content-Type: application/json; charset=UTF-8');
    }

    echo json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
    exit;
}

function clm_issue_license_record(array $data): array
{
    clm_ensure_schema();

    $tables = clm_tables();
    $licenses = $tables['licenses'];
    $app = clm_resolve_app((string)($data['app_slug'] ?? ''), (string)($data['app_name'] ?? ''), true);

    if (!$app) {
        throw new RuntimeException('Unable to resolve app.');
    }

    $licenseKey = strtoupper(trim((string)($data['license_key'] ?? '')));
    if ($licenseKey === '') {
        $licenseKey = clm_generate_license_key((string)($data['prefix'] ?? 'FLAT'));
    }

    $maxActivations = max(1, (int)($data['max_activations'] ?? 1));
    $maxCounters = max(1, (int)($data['max_counters'] ?? 1));
    $owner = trim((string)($data['owner'] ?? ''));
    $address = trim((string)($data['address'] ?? ''));
    $customerName = trim((string)($data['customer_name'] ?? $owner));
    $customerEmail = trim((string)($data['customer_email'] ?? ''));
    $notes = trim((string)($data['notes'] ?? ''));
    $expiresAt = trim((string)($data['expires_at'] ?? ''));

    $stmt = clm_db()->prepare("INSERT INTO `{$licenses}`
        (app_id, license_key, max_activations, max_counters, status, owner, address, customer_name, customer_email, notes, expires_at)
        VALUES (?, ?, ?, ?, 'active', ?, ?, ?, ?, ?, ?)");
    $stmt->execute([
        (int)$app['id'],
        $licenseKey,
        $maxActivations,
        $maxCounters,
        $owner !== '' ? $owner : null,
        $address !== '' ? $address : null,
        $customerName !== '' ? $customerName : null,
        $customerEmail !== '' ? $customerEmail : null,
        $notes !== '' ? $notes : null,
        $expiresAt !== '' ? $expiresAt : null,
    ]);

    $license = clm_license_with_app_by_key($licenseKey);

    if (!$license) {
        throw new RuntimeException('License was created but could not be reloaded.');
    }

    return $license;
}

function clm_update_license_record(array $license, array $data): array
{
    clm_ensure_schema();

    $licenses = clm_table('licenses');
    $fields = [];
    $params = [];

    if (isset($data['status'])) {
        $status = strtolower(trim((string)$data['status']));
        if (in_array($status, ['active', 'suspended', 'expired'], true)) {
            $fields[] = '`status` = ?';
            $params[] = $status;
        }
    }

    if (isset($data['max_activations']) && (int)$data['max_activations'] > 0) {
        $fields[] = '`max_activations` = ?';
        $params[] = max(1, (int)$data['max_activations']);
    }

    if (isset($data['max_counters']) && (int)$data['max_counters'] > 0) {
        $fields[] = '`max_counters` = ?';
        $params[] = max(1, (int)$data['max_counters']);
    }

    if (array_key_exists('owner', $data)) {
        $fields[] = '`owner` = ?';
        $owner = trim((string)$data['owner']);
        $params[] = $owner !== '' ? $owner : null;
    }

    if (array_key_exists('address', $data)) {
        $fields[] = '`address` = ?';
        $address = trim((string)$data['address']);
        $params[] = $address !== '' ? $address : null;
    }

    if (array_key_exists('customer_name', $data)) {
        $fields[] = '`customer_name` = ?';
        $customerName = trim((string)$data['customer_name']);
        $params[] = $customerName !== '' ? $customerName : null;
    }

    if (array_key_exists('customer_email', $data)) {
        $fields[] = '`customer_email` = ?';
        $customerEmail = trim((string)$data['customer_email']);
        $params[] = $customerEmail !== '' ? $customerEmail : null;
    }

    if (array_key_exists('notes', $data)) {
        $fields[] = '`notes` = ?';
        $notes = trim((string)$data['notes']);
        $params[] = $notes !== '' ? $notes : null;
    }

    if (array_key_exists('expires_at', $data)) {
        $fields[] = '`expires_at` = ?';
        $expiresAt = trim((string)$data['expires_at']);
        $params[] = $expiresAt !== '' ? $expiresAt : null;
    }

    if (isset($data['app_slug']) || isset($data['app_name'])) {
        $app = clm_resolve_app((string)($data['app_slug'] ?? ''), (string)($data['app_name'] ?? ''), true);
        if ($app) {
            $fields[] = '`app_id` = ?';
            $params[] = (int)$app['id'];
        }
    }

    if (empty($fields)) {
        return clm_license_with_app_by_id((int)$license['id']) ?: $license;
    }

    $params[] = (int)$license['id'];
    $sql = "UPDATE `{$licenses}` SET " . implode(', ', $fields) . " WHERE id = ?";
    $stmt = clm_db()->prepare($sql);
    $stmt->execute($params);

    return clm_license_with_app_by_id((int)$license['id']) ?: $license;
}

function clm_set_flash(string $type, string $message): void
{
    $_SESSION['clm_flash'] = [
        'type' => $type,
        'message' => $message,
    ];
}

function clm_get_flash(): ?array
{
    if (empty($_SESSION['clm_flash'])) {
        return null;
    }

    $flash = $_SESSION['clm_flash'];
    unset($_SESSION['clm_flash']);

    return is_array($flash) ? $flash : null;
}

function clm_redirect(string $location): void
{
    header('Location: ' . $location);
    exit;
}

function clm_manager_mode_label(): string
{
    return clm_using_parent_db() ? 'Using current app database' : 'Using standalone CLM database settings';
}