<?php

namespace App\Services\Prediction\Signals;

use Illuminate\Support\Facades\DB;

/**
 * SQL dialect helpers for the small set of MySQL/SQLite differences the
 * signal classes care about. Centralises the isSqlite ternaries that were
 * duplicated across DayOfWeekSignal and StickinessSignal.
 */
final class DbDialect
{
    private static function isSqlite(): bool
    {
        return DB::connection()->getDriverName() === 'sqlite';
    }

    /**
     * Day-of-week expression returning 1=Sun..7=Sat (MySQL DAYOFWEEK convention).
     * Targets a column on the queried table.
     */
    public static function dayOfWeekExpr(string $column): string
    {
        return self::isSqlite()
            ? "(CAST(strftime('%w', {$column}) AS INTEGER) + 1)"
            : "DAYOFWEEK({$column})";
    }

    /**
     * Whole-day difference between MAX and MIN of a datetime column, suitable
     * for use in an aggregate selectRaw.
     */
    public static function maxMinDayDiffExpr(string $column): string
    {
        return self::isSqlite()
            ? "CAST((julianday(MAX({$column})) - julianday(MIN({$column}))) AS INTEGER)"
            : "DATEDIFF(MAX({$column}), MIN({$column}))";
    }
}