<?php
/**
 * Calendar events for the training calendar (training_calendar.php).
 * Returns FullCalendar event objects for the *current* training record per
 * (employee, topic) that has a next_due_date, colored by computed status.
 * HR-only.
 */
require_once(__DIR__ . '/../hr_auth_check.php');
header('Content-Type: application/json');

try {
    // $pdo and $currentUserId provided by hr_auth_check.php

    $start = $_GET['start'] ?? null;
    $end   = $_GET['end'] ?? null;
    $fStatus = isset($_GET['status']) ? trim($_GET['status']) : '';
    $fDept   = isset($_GET['department_id']) && $_GET['department_id'] !== '' ? (int)$_GET['department_id'] : 0;
    $fTopic  = isset($_GET['topic_id'])      && $_GET['topic_id']      !== '' ? (int)$_GET['topic_id']      : 0;
    $fEmp    = isset($_GET['employee_id'])   && $_GET['employee_id']   !== '' ? (int)$_GET['employee_id']   : 0;

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

    // Deadlines only (one-time trainings have no next_due_date)
    $where[] = "et.next_due_date IS NOT NULL";

    // Only the most recent record per (employee, topic)
    $where[] = "NOT EXISTS (
        SELECT 1 FROM employee_trainings et2
        WHERE et2.employee_id = et.employee_id
          AND et2.training_topic_id = et.training_topic_id
          AND (et2.completed_date > et.completed_date
               OR (et2.completed_date = et.completed_date AND et2.id > et.id))
    )";

    if ($start && $end) {
        $where[] = "et.next_due_date >= :start AND et.next_due_date <= :end";
        $params['start'] = $start;
        $params['end']   = $end;
    }
    if ($fDept > 0)  { $where[] = "e.department_id = :did";      $params['did'] = $fDept; }
    if ($fTopic > 0) { $where[] = "et.training_topic_id = :tid"; $params['tid'] = $fTopic; }
    if ($fEmp > 0)   { $where[] = "et.employee_id = :eid";       $params['eid'] = $fEmp; }

    $whereSql = 'WHERE ' . implode(' AND ', $where);

    $stmt = $pdo->prepare("
        SELECT et.id, et.employee_id, et.next_due_date, et.reminder_days,
               tt.name AS topic_name, tt.default_reminder_days AS topic_default_rem,
               e.first_name, e.last_name
        FROM employee_trainings et
        JOIN training_topics tt ON tt.id = et.training_topic_id
        JOIN employees e        ON e.id = et.employee_id
        $whereSql
    ");
    $stmt->execute($params);
    $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

    $today  = new DateTime('today');
    $events = [];

    foreach ($rows as $r) {
        $rem = $r['reminder_days'] !== null
            ? (int)$r['reminder_days']
            : ($r['topic_default_rem'] !== null ? (int)$r['topic_default_rem'] : 30);

        $due = DateTime::createFromFormat('Y-m-d', $r['next_due_date']);
        if (!$due) continue;
        $daysLeft = (int)$today->diff($due)->format('%r%a');

        if ($daysLeft < 0)        { $code = 'expired';   $color = '#dc3545'; }
        elseif ($daysLeft <= $rem){ $code = 'due_soon';  $color = '#e8930c'; }
        else                      { $code = 'compliant'; $color = '#198754'; }

        if ($fStatus !== '' && $fStatus !== $code) continue;

        $name = trim($r['first_name'] . ' ' . $r['last_name']);
        $events[] = [
            'id'              => (int)$r['id'],
            'title'           => $name . ' — ' . $r['topic_name'],
            'start'           => $r['next_due_date'],
            'allDay'          => true,
            'backgroundColor' => $color,
            'borderColor'     => $color,
            'url'             => 'employee-profile.php?id=' . (int)$r['employee_id'] . '#tab-training',
        ];
    }

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