<?php
require_once(__DIR__ . '/../hr_auth_check.php');

header('Content-Type: application/json');

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['success' => false, 'message' => 'Metodo non consentito.']);
    exit;
}

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

$id            = (int)($_POST['id'] ?? 0);
$employeeId    = (int)($_POST['employee_id'] ?? 0);
$topicId       = (int)($_POST['training_topic_id'] ?? 0);
$completedDate = trim($_POST['completed_date'] ?? '');
$deliveredBy   = trim($_POST['delivered_by'] ?? '');
$description   = trim($_POST['description'] ?? '');
$trainingType  = trim($_POST['training_type'] ?? 'initial');
$freqRaw       = $_POST['update_frequency_months'] ?? '';
$remRaw        = $_POST['reminder_days'] ?? '';

if ($employeeId <= 0) {
    echo json_encode(['success' => false, 'message' => 'ID dipendente non valido.']);
    exit;
}
if ($topicId <= 0) {
    echo json_encode(['success' => false, 'message' => 'Selezionare un corso.']);
    exit;
}
if ($completedDate === '') {
    echo json_encode(['success' => false, 'message' => 'La data di completamento è obbligatoria.']);
    exit;
}
if (!in_array($trainingType, ['initial', 'refresher'], true)) {
    $trainingType = 'initial';
}

$topicStmt = $pdo->prepare("SELECT default_frequency_months, default_reminder_days FROM training_topics WHERE id = :id");
$topicStmt->execute(['id' => $topicId]);
$topic = $topicStmt->fetch(PDO::FETCH_ASSOC);
if (!$topic) {
    echo json_encode(['success' => false, 'message' => 'Corso non trovato.']);
    exit;
}

$freq = ($freqRaw === '' || $freqRaw === null) ? null : max(0, (int)$freqRaw);
$rem  = ($remRaw  === '' || $remRaw  === null) ? null : max(0, (int)$remRaw);

/* Effective frequency for next_due_date: explicit override or topic default */
$effFreq = $freq !== null ? $freq : ($topic['default_frequency_months'] !== null ? (int)$topic['default_frequency_months'] : null);

$nextDue = null;
if ($effFreq !== null && $effFreq > 0) {
    $d = DateTime::createFromFormat('Y-m-d', $completedDate);
    if ($d) {
        $d->modify('+' . (int)$effFreq . ' months');
        $nextDue = $d->format('Y-m-d');
    }
}

$deliveredBy = $deliveredBy !== '' ? $deliveredBy : null;
$description = $description !== '' ? $description : null;

try {
    $pdo->beginTransaction();

    if ($id > 0) {
        $old = $pdo->prepare("SELECT * FROM employee_trainings WHERE id = :id");
        $old->execute(['id' => $id]);
        $oldRow = $old->fetch(PDO::FETCH_ASSOC);
        if (!$oldRow) {
            $pdo->rollBack();
            echo json_encode(['success' => false, 'message' => 'Formazione non trovata.']);
            exit;
        }

        $upd = $pdo->prepare("
            UPDATE employee_trainings
            SET training_topic_id       = :topic_id,
                completed_date          = :completed_date,
                delivered_by            = :delivered_by,
                description             = :description,
                training_type           = :training_type,
                update_frequency_months = :freq,
                reminder_days           = :rem,
                next_due_date           = :next_due,
                updated_at              = NOW()
            WHERE id = :id
        ");
        $upd->execute([
            'topic_id'       => $topicId,
            'completed_date' => $completedDate,
            'delivered_by'   => $deliveredBy,
            'description'    => $description,
            'training_type'  => $trainingType,
            'freq'           => $freq,
            'rem'            => $rem,
            'next_due'       => $nextDue,
            'id'             => $id,
        ]);

        $fields = [
            'training_topic_id'       => $topicId,
            'completed_date'          => $completedDate,
            'delivered_by'            => $deliveredBy,
            'description'             => $description,
            'training_type'           => $trainingType,
            'update_frequency_months' => $freq,
            'reminder_days'           => $rem,
            'next_due_date'           => $nextDue,
        ];
        $logStmt = $pdo->prepare("
            INSERT INTO employee_training_log
                (employee_id, training_id, action, field, old_value, new_value, changed_by, changed_at)
            VALUES
                (:eid, :tid, 'updated', :field, :old_v, :new_v, :cb, NOW())
        ");
        foreach ($fields as $f => $newV) {
            $oldV = $oldRow[$f] ?? null;
            if ((string)$oldV !== (string)$newV) {
                $logStmt->execute([
                    'eid'    => $employeeId,
                    'tid'    => $id,
                    'field'  => $f,
                    'old_v'  => $oldV,
                    'new_v'  => $newV,
                    'cb'     => $currentUserId,
                ]);
            }
        }

        $pdo->commit();
        echo json_encode(['success' => true, 'id' => $id]);
        exit;
    }

    $ins = $pdo->prepare("
        INSERT INTO employee_trainings
            (employee_id, training_topic_id, completed_date,
             delivered_by, description,
             training_type, update_frequency_months, reminder_days, next_due_date,
             created_by, created_at, updated_at)
        VALUES
            (:eid, :tid, :completed_date,
             :delivered_by, :description,
             :training_type, :freq, :rem, :next_due,
             :cb, NOW(), NOW())
    ");
    $ins->execute([
        'eid'            => $employeeId,
        'tid'            => $topicId,
        'completed_date' => $completedDate,
        'delivered_by'   => $deliveredBy,
        'description'    => $description,
        'training_type'  => $trainingType,
        'freq'           => $freq,
        'rem'            => $rem,
        'next_due'       => $nextDue,
        'cb'             => $currentUserId,
    ]);
    $newId = (int)$pdo->lastInsertId();

    $pdo->prepare("
        INSERT INTO employee_training_log
            (employee_id, training_id, action, field, old_value, new_value, changed_by, changed_at)
        VALUES
            (:eid, :tid, 'created', NULL, NULL, NULL, :cb, NOW())
    ")->execute(['eid' => $employeeId, 'tid' => $newId, 'cb' => $currentUserId]);

    $pdo->commit();
    echo json_encode(['success' => true, 'id' => $newId]);
} catch (Exception $e) {
    if ($pdo->inTransaction()) $pdo->rollBack();
    echo json_encode(['success' => false, 'message' => $e->getMessage()]);
}