<?php
// book_slots.php — Calcola gli slot disponibili per shop+staff+service+data (AJAX, JSON)
// Chiamato da book.php quando l'utente sceglie staff e data.
// Risposta: { ok:true, slots:["09:00","09:30",...] }  oppure  { ok:false, error:"..." }

if (session_status() === PHP_SESSION_NONE) {
    session_start();
}
header('Content-Type: application/json');

require_once(__DIR__ . '/userarea/class/db-functions.php');
$pdo = DBHandlerSelect::getInstance()->getConnection();

// --- Input ---
$shop_id    = (int)($_GET['shop'] ?? 0);
$service_id = (int)($_GET['service'] ?? 0);
$staff_id   = (int)($_GET['staff'] ?? 0);
$date       = trim($_GET['date'] ?? ''); // formato Y-m-d

if ($shop_id <= 0 || $service_id <= 0 || $staff_id <= 0 || $date === '') {
    echo json_encode(['ok' => false, 'error' => 'missing_params']);
    exit;
}

// Valida la data
$d = DateTime::createFromFormat('Y-m-d', $date);
if (!$d || $d->format('Y-m-d') !== $date) {
    echo json_encode(['ok' => false, 'error' => 'invalid_date']);
    exit;
}

try {
    // --- 1. Servizio: durata (indispensabile per capire se lo slot "ci sta") ---
    $svc = $pdo->prepare("SELECT duration_minutes FROM services WHERE id = ? AND shop_id = ? AND is_active = 1");
    $svc->execute([$service_id, $shop_id]);
    $service = $svc->fetch(PDO::FETCH_ASSOC);
    if (!$service) {
        echo json_encode(['ok' => false, 'error' => 'service_not_found']);
        exit;
    }
    $duration = (int)$service['duration_minutes'];
    if ($duration <= 0) $duration = 30; // fallback prudente

    // --- 2. Impostazioni salone (con fallback ai default se manca la riga) ---
    $st = $pdo->prepare("SELECT appointment_slot_interval, min_booking_notice_hours,
                                max_booking_days_ahead, allowed_start_minutes
                         FROM shop_settings WHERE shop_id = ?");
    $st->execute([$shop_id]);
    $set = $st->fetch(PDO::FETCH_ASSOC) ?: [];

    $slotInterval   = (int)($set['appointment_slot_interval'] ?? 30);
    if ($slotInterval <= 0) $slotInterval = 30;
    $minNoticeHours = (int)($set['min_booking_notice_hours'] ?? 2);
    $maxDaysAhead   = (int)($set['max_booking_days_ahead'] ?? 90);

    // Minuti d'inizio consentiti (es. "00,30"). Se vuoto → nessun filtro extra.
    $allowedMinutes = [];
    if (!empty($set['allowed_start_minutes'])) {
        foreach (explode(',', $set['allowed_start_minutes']) as $m) {
            $m = trim($m);
            if ($m !== '' && is_numeric($m)) $allowedMinutes[] = (int)$m;
        }
    }

    // --- 3. Finestra temporale: la data richiesta è dentro i limiti? ---
    $today    = new DateTime('today');
    $reqDay   = new DateTime($date . ' 00:00:00');
    $maxDay   = (clone $today)->modify("+{$maxDaysAhead} days");

    if ($reqDay < $today) {
        echo json_encode(['ok' => true, 'slots' => []]); // data passata → nessuno slot
        exit;
    }
    if ($reqDay > $maxDay) {
        echo json_encode(['ok' => true, 'slots' => []]); // troppo in là nel tempo
        exit;
    }

    // --- 4. Il salone è chiuso quel giorno? (chiusure straordinarie/ricorrenti) ---
    // is_recurring=1 → confronto solo mese-giorno (ricorre ogni anno).
    $off = $pdo->prepare("
        SELECT is_recurring, `date` FROM shop_day_off
        WHERE shop_id = ?
          AND ( `date` = ?  OR ( is_recurring = 1 AND DATE_FORMAT(`date`, '%m-%d') = ? ) )
        LIMIT 1
    ");
    $off->execute([$shop_id, $date, $d->format('m-d')]);
    if ($off->fetch()) {
        echo json_encode(['ok' => true, 'slots' => [], 'closed' => true]);
        exit;
    }

    // --- 5. Orari di apertura per quel giorno della settimana ---
    // day_of_week: usiamo 1=lunedì ... 7=domenica (ISO). Adegua se il salone usa 0=domenica.
    $dow = (int)$d->format('N'); // 1..7
    $hrs = $pdo->prepare("SELECT is_open, open_time, close_time, open_time_2, close_time_2
                          FROM shop_hours WHERE shop_id = ? AND day_of_week = ?");
    $hrs->execute([$shop_id, $dow]);
    $hours = $hrs->fetch(PDO::FETCH_ASSOC);

    if (!$hours || (int)$hours['is_open'] !== 1) {
        echo json_encode(['ok' => true, 'slots' => [], 'closed' => true]);
        exit;
    }

    // Raccogliamo le fasce di apertura (mattina + eventuale pomeriggio)
    $ranges = [];
    if (!empty($hours['open_time']) && !empty($hours['close_time'])) {
        $ranges[] = [$hours['open_time'], $hours['close_time']];
    }
    if (!empty($hours['open_time_2']) && !empty($hours['close_time_2'])) {
        $ranges[] = [$hours['open_time_2'], $hours['close_time_2']];
    }
    if (empty($ranges)) {
        echo json_encode(['ok' => true, 'slots' => [], 'closed' => true]);
        exit;
    }

    // --- 6. Appuntamenti già presi per quello staff in quel giorno ---
    // Solo pending/confirmed/completed occupano; cancelled/no_show liberano.
    $ap = $pdo->prepare("
        SELECT start_at, end_at FROM appointments
        WHERE staff_id = ?
          AND DATE(start_at) = ?
          AND status IN ('pending','confirmed','completed')
    ");
    $ap->execute([$staff_id, $date]);
    $busy = [];
    foreach ($ap->fetchAll(PDO::FETCH_ASSOC) as $row) {
        $busy[] = [strtotime($row['start_at']), strtotime($row['end_at'])];
    }

    // --- 7. Soglia minima: non prima di adesso + preavviso minimo ---
    $earliest = (new DateTime())->modify("+{$minNoticeHours} hours");

    // --- 8. Generazione slot ---
    $slots = [];
    foreach ($ranges as [$openStr, $closeStr]) {
        $open  = new DateTime($date . ' ' . $openStr);
        $close = new DateTime($date . ' ' . $closeStr);

        $cursor = clone $open;
        while (true) {
            // Fine servizio se iniziasse a $cursor
            $end = (clone $cursor)->modify("+{$duration} minutes");

            // Lo slot deve stare INTERO dentro la fascia
            if ($end > $close) break;

            $startTs = $cursor->getTimestamp();
            $endTs   = $end->getTimestamp();

            $valid = true;

            // Filtro minuti d'inizio consentiti (es. solo :00 e :30)
            if (!empty($allowedMinutes) && !in_array((int)$cursor->format('i'), $allowedMinutes, true)) {
                $valid = false;
            }

            // Non nel passato / rispetta preavviso minimo
            if ($valid && $cursor < $earliest) {
                $valid = false;
            }

            // Non deve sovrapporsi a un appuntamento esistente
            if ($valid) {
                foreach ($busy as [$bStart, $bEnd]) {
                    if ($startTs < $bEnd && $endTs > $bStart) { // overlap classico
                        $valid = false;
                        break;
                    }
                }
            }

            if ($valid) {
                $slots[] = $cursor->format('H:i');
            }

            $cursor->modify("+{$slotInterval} minutes");
        }
    }

    // Ordina e deduplica (se le fasce si toccano)
    $slots = array_values(array_unique($slots));
    sort($slots);

    echo json_encode(['ok' => true, 'slots' => $slots]);
} catch (Throwable $e) {
    error_log('book_slots: ' . $e->getMessage());
    echo json_encode(['ok' => false, 'error' => 'server_error']);
    exit;
}