<?php

namespace App\Services;

use App\Contracts\DatabaseListerInterface;
use Illuminate\Support\Facades\DB;
use InvalidArgumentException;
use Throwable;

class PgsqlDatabaseService implements DatabaseListerInterface
{
    private const PROTECTED = ['postgres', 'template0', 'template1'];

    private const QUERY = <<<'SQL'
SELECT
    d.datname AS db_name,
    '—' AS created,
    0 AS active_days,
    CASE WHEN d.datallowconn THEN 'ONLINE' ELSE 'RESTRICTED' END AS state,
    COALESCE(to_char(s.stats_reset, 'YYYY-MM-DD HH24:MI:SS'), '—') AS last_index_activity,
    '—' AS last_backup
FROM pg_database d
LEFT JOIN pg_stat_database s ON s.datname = d.datname
WHERE d.datistemplate = false
SQL;

    private string $connection = 'pgsql';

    public function using(string $connection): self
    {
        $clone = clone $this;
        $clone->connection = $connection;

        return $clone;
    }

    public function listDatabases(string $sort, string $dir, string $search = ''): array
    {
        try {
            $rows = collect(DB::connection($this->connection)->select(self::QUERY))
                ->map(fn ($row) => (array) $row);

            if ($search !== '') {
                $needle = mb_strtolower($search);
                $rows = $rows->filter(fn (array $row) => str_contains(mb_strtolower($row['db_name'] ?? ''), $needle)
                    || str_contains(mb_strtolower($row['state'] ?? ''), $needle));
            }

            $rows = $rows->sortBy(fn (array $row) => $row[$sort] ?? '', SORT_REGULAR, $dir === 'desc');

            return [
                'rows' => $rows->values()->all(),
                'meta' => [
                    'total' => $rows->count(),
                    'server' => config('database.connections.' . $this->connection . '.host'),
                    'driver' => 'pgsql',
                    'sql_started' => null,
                    'uptime_days' => null,
                ],
                'error' => null,
            ];
        } catch (Throwable) {
            return [
                'rows' => [],
                'meta' => [
                    'total' => 0,
                    'server' => config('database.connections.' . $this->connection . '.host'),
                    'driver' => 'pgsql',
                    'sql_started' => null,
                    'uptime_days' => null,
                ],
                'error' => 'Unable to load PostgreSQL databases. Check connectivity and credentials.',
            ];
        }
    }

    public function makeOffline(string $databaseName): void
    {
        $databaseName = $this->validateName($databaseName);

        if ($this->isProtected($databaseName)) {
            throw new InvalidArgumentException('System databases cannot be restricted.');
        }

        $quoted = '"' . str_replace('"', '""', $databaseName) . '"';

        DB::connection($this->connection)->statement("ALTER DATABASE {$quoted} CONNECTION LIMIT 0");
        DB::connection($this->connection)->statement(
            "SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname = ? AND pid <> pg_backend_pid()",
            [$databaseName]
        );
    }

    public function isProtected(string $databaseName): bool
    {
        return in_array(mb_strtolower($databaseName), self::PROTECTED, true);
    }

    public function supportsOffline(): bool
    {
        return true;
    }

    private function validateName(string $databaseName): string
    {
        $databaseName = trim($databaseName);

        if (! preg_match('/^[a-zA-Z0-9_]+$/', $databaseName)) {
            throw new InvalidArgumentException('Invalid database name.');
        }

        return $databaseName;
    }
}