<?php
require_once(__DIR__ . '/auth_check.php');
header('Content-Type: application/json');
require_once(__DIR__ . '/../../class/db-functions.php');

try {
    $db = DBHandlerSelect::getInstance();
    $pdo = $db->getConnection();

    $start = $_GET['start'] ?? null;
    $end = $_GET['end'] ?? null;
    $filterStatus = $_GET['status'] ?? '';
    $filterDept = $_GET['department'] ?? '';
    $filterEmployee = $_GET['employee'] ?? '';

    $sql = "SELECT DISTINCT d.id, d.topic, d.due_date, d.status, d.notification_days, d.departments,
                   s.name AS subject_name, s.color AS subject_color
            FROM scad_deadlines d
            LEFT JOIN scad_subjects s ON s.id = d.subject_id
            LEFT JOIN scad_deadline_employee de ON de.deadline_id = d.id
            LEFT JOIN employees e ON e.id = de.employee_id";

    $where = [];
    $params = [];

    if ($start && $end) {
        $where[] = "d.due_date >= ? AND d.due_date <= ?";
        $params[] = $start;
        $params[] = $end;
    }

    if ($filterStatus === 'non-completata') {
        $where[] = "d.status != 'completed'";
    } elseif ($filterStatus === 'completata') {
        $where[] = "d.status = 'completed'";
    } elseif ($filterStatus === 'scaduta') {
        $where[] = "d.status = 'active' AND d.due_date < CURDATE()";
    } elseif ($filterStatus === 'in-scadenza') {
        $where[] = "d.status = 'active' AND d.due_date >= CURDATE() AND d.due_date <= DATE_ADD(CURDATE(), INTERVAL d.notification_days DAY)";
    } elseif ($filterStatus === 'attiva') {
        $where[] = "d.status = 'active' AND d.due_date > DATE_ADD(CURDATE(), INTERVAL d.notification_days DAY)";
    }

    if ($filterDept) {
        $where[] = "(e.department = ? OR FIND_IN_SET(?, d.departments))";
        $params[] = $filterDept;
        $params[] = $filterDept;
    }

    if ($filterEmployee) {
        $where[] = "CONCAT(e.first_name, ' ', e.last_name) = ?";
        $params[] = $filterEmployee;
    }

    if (!empty($where)) {
        $sql .= " WHERE " . implode(' AND ', $where);
    }

    $stmt = $pdo->prepare($sql);
    $stmt->execute($params);
    $deadlines = $stmt->fetchAll(PDO::FETCH_ASSOC);

    $today = date('Y-m-d');
    $events = [];

    foreach ($deadlines as $d) {
        $isCompleted = $d['status'] === 'completed';
        $isOverdue = !$isCompleted && $d['due_date'] < $today;
        $approachDate = date('Y-m-d', strtotime($today . ' + ' . (int)$d['notification_days'] . ' days'));
        $isApproaching = !$isCompleted && !$isOverdue && $d['due_date'] <= $approachDate;

        if ($isCompleted)       { $color = '#198754'; }
        elseif ($isOverdue)     { $color = '#dc3545'; }
        elseif ($isApproaching) { $color = '#e8930c'; }
        else                    { $color = '#5a8fd8'; }

        $title = $d['topic'];
        if (!empty($d['subject_name'])) $title = $d['subject_name'] . ': ' . $title;

        $events[] = [
            'id'              => $d['id'],
            'title'           => $title,
            'start'           => $d['due_date'],
            'backgroundColor' => $color,
            'borderColor'     => !empty($d['subject_color']) ? $d['subject_color'] : $color,
            'url'             => 'scadenzario/detail.php?id=' . $d['id'],
        ];
    }

    echo json_encode($events);

} catch (Exception $e) {
    echo json_encode([]);
}