<?php

function calculateNextSendTime(string $recurringDays, string $recurringTime): ?string
{
    $daysMap = [
        'sunday' => 0,
        'monday' => 1,
        'tuesday' => 2,
        'wednesday' => 3,
        'thursday' => 4,
        'friday' => 5,
        'saturday' => 6
    ];

    $days = array_map('trim', explode(',', strtolower($recurringDays)));
    $days = array_filter($days, fn($d) => isset($daysMap[$d]));
    $days = array_map(fn($d) => $daysMap[$d], $days);

    if (empty($days)) {
        return null;
    }

    $timeParts = explode(':', $recurringTime);
    $hour = (int) ($timeParts[0] ?? 0);
    $minute = (int) ($timeParts[1] ?? 0);

    $now = new DateTime('now', new DateTimeZone('America/Mexico_City'));
    $currentDay = (int) $now->format('w');
    $currentHour = (int) $now->format('H');
    $currentMinute = (int) $now->format('i');

    sort($days);

    foreach ($days as $day) {
        if ($day > $currentDay || ($day === $currentDay && ($hour > $currentHour || ($hour === $currentHour && $minute > $currentMinute)))) {
            $next = clone $now;
            $next->setTime($hour, $minute);
            $next->modify('+' . ($day - $currentDay) . ' days');
            return $next->format('Y-m-d H:i:s');
        }
    }

    $daysAhead = (7 - $currentDay) + $days[0];
    $next = clone $now;
    $next->setTime($hour, $minute);
    $next->modify('+' . $daysAhead . ' days');
    
    return $next->format('Y-m-d H:i:s');
}

function getRecurringDaysOptions(): array
{
    return [
        ['value' => 'monday', 'label' => 'Lunes'],
        ['value' => 'tuesday', 'label' => 'Martes'],
        ['value' => 'wednesday', 'label' => 'Miércoles'],
        ['value' => 'thursday', 'label' => 'Jueves'],
        ['value' => 'friday', 'label' => 'Viernes'],
        ['value' => 'saturday', 'label' => 'Sábado'],
        ['value' => 'sunday', 'label' => 'Domingo']
    ];
}

function formatRecurringDays(string $days): string
{
    $daysMap = [
        'monday' => 'Lun',
        'tuesday' => 'Mar',
        'wednesday' => 'Mié',
        'thursday' => 'Jue',
        'friday' => 'Vie',
        'saturday' => 'Sáb',
        'sunday' => 'Dom'
    ];

    $daysArray = array_map('trim', explode(',', strtolower($days)));
    
    $result = [];
    foreach ($daysArray as $day) {
        $result[] = $daysMap[$day] ?? $day;
    }
    
    return implode(', ', $result);
}

function isValidRecurringDays(string $days): bool
{
    $validDays = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'];
    $daysArray = array_map('trim', explode(',', strtolower($days)));
    
    foreach ($daysArray as $day) {
        if (!in_array($day, $validDays)) {
            return false;
        }
    }
    
    return !empty($daysArray);
}