<?php
/**
 * GET    /api/teacher/students?classId=42     — Liste mit A11y + Nachteilsausgleich
 * POST   /api/teacher/students                 — neue Schüler*in anlegen
 * PATCH  /api/teacher/students                 — Flag/Property aktualisieren
 * DELETE /api/teacher/students?studentId=X     — Soft-Delete (deleted_at = NOW())
 */
declare(strict_types=1);
require_once __DIR__ . '/../../bootstrap.php';

$method = v2_validate_method_in(['GET', 'POST', 'PATCH', 'DELETE']);
$auth = v2_auth_require('teacher');
$teacherId = (int) ($auth['sub'] ?? 0);

// Helper: Klassen-Zugehörigkeit prüfen
function class_owned(int $classId, int $teacherId): bool {
    return (bool) v2_db_one(
        'SELECT id FROM classes WHERE id = :c AND teacher_id = :t',
        [':c' => $classId, ':t' => $teacherId]
    );
}
function student_owned(int $studentId, int $teacherId): bool {
    return (bool) v2_db_one("
        SELECT s.id FROM students s
        JOIN classes c ON c.id = s.class_id
        WHERE s.id = :sid AND c.teacher_id = :tid
    ", [':sid' => $studentId, ':tid' => $teacherId]);
}

// ── GET ───────────────────────────────────────────────────────────
if ($method === 'GET') {
    $classId = (int) ($_GET['classId'] ?? 0);
    if (!$classId) v2_response_error(400, 'missing_classId', 'classId fehlt.');
    if (!class_owned($classId, $teacherId)) v2_response_error(403, 'forbidden', 'Klasse nicht deine.');

    $rows = v2_db_all("
        SELECT s.id, s.username, s.display_name, s.avatar_slug, s.first_name, s.last_name,
               s.easy_language, s.high_contrast, s.reduced_motion,
               s.screen_reader, s.nachteilsausgleich, s.last_login
        FROM students s
        WHERE s.class_id = :cid AND s.deleted_at IS NULL
        ORDER BY s.display_name, s.username
    ", [':cid' => $classId]);

    v2_response_ok(['students' => array_map(fn($r) => [
        'id' => (int) $r['id'],
        'username' => $r['username'],
        'displayName' => $r['display_name'] ?? $r['username'],
        'firstName' => $r['first_name'],
        'lastName' => $r['last_name'],
        'avatarSlug' => $r['avatar_slug'] ?? 'fuchs-explorer',
        'easyLanguage' => (bool) $r['easy_language'],
        'highContrast' => (bool) $r['high_contrast'],
        'reducedMotion' => (bool) $r['reduced_motion'],
        'screenReader' => (bool) $r['screen_reader'],
        'nachteilsausgleich' => (bool) $r['nachteilsausgleich'],
        'lastLogin' => $r['last_login'],
    ], $rows)]);
}

// ── POST: neue Schüler*in anlegen ────────────────────────────────
if ($method === 'POST') {
    $body = v2_request_body_json_required();
    v2_validate_required($body, ['classId', 'username', 'password']);

    $classId = (int) $body['classId'];
    if (!class_owned($classId, $teacherId)) v2_response_error(403, 'forbidden', 'Klasse nicht deine.');

    $username = trim((string) $body['username']);
    $password = (string) $body['password'];
    if (strlen($username) < 2) v2_response_error(400, 'username_too_short', 'Username muss mind. 2 Zeichen haben.');
    if (strlen($password) < 4) v2_response_error(400, 'password_too_short', 'Passwort muss mind. 4 Zeichen haben.');

    // Username-Uniqueness IN dieser Klasse
    $existing = v2_db_one(
        'SELECT id FROM students WHERE class_id = :c AND username = :u AND deleted_at IS NULL',
        [':c' => $classId, ':u' => $username]
    );
    if ($existing) v2_response_error(409, 'username_taken', "Username '$username' ist in dieser Klasse schon vergeben.");

    $displayName = trim((string) ($body['displayName'] ?? '')) ?: $username;
    $firstName   = trim((string) ($body['firstName'] ?? '')) ?: null;
    $lastName    = trim((string) ($body['lastName']  ?? '')) ?: null;
    $avatarSlug  = trim((string) ($body['avatarSlug'] ?? '')) ?: 'fuchs-explorer';
    $easyLang    = !empty($body['easyLanguage']) ? 1 : 0;
    $nachteil    = !empty($body['nachteilsausgleich']) ? 1 : 0;

    $hash = password_hash($password, PASSWORD_DEFAULT);

    v2_db_exec(
        'INSERT INTO students
           (class_id, username, password, display_name, first_name, last_name,
            avatar_slug, easy_language, nachteilsausgleich, is_anonymous)
         VALUES (:cid, :u, :p, :dn, :fn, :ln, :av, :ez, :na, 0)',
        [
            ':cid' => $classId, ':u' => $username, ':p' => $hash,
            ':dn' => $displayName, ':fn' => $firstName, ':ln' => $lastName,
            ':av' => $avatarSlug, ':ez' => $easyLang, ':na' => $nachteil,
        ]
    );

    v2_response_created([
        'id' => (int) v2_db_insert_id(),
        'username' => $username,
        'displayName' => $displayName,
    ]);
}

// ── PATCH: Flag/Property updaten ─────────────────────────────────
if ($method === 'PATCH') {
    $body = v2_request_body_json_required();
    v2_validate_required($body, ['studentId']);
    $studentId = (int) $body['studentId'];
    if (!student_owned($studentId, $teacherId)) v2_response_error(403, 'forbidden', 'Schüler*in nicht in deiner Klasse.');

    $updates = [];
    $params = [':id' => $studentId];
    foreach (['nachteilsausgleich', 'easyLanguage', 'highContrast', 'reducedMotion', 'screenReader'] as $k) {
        if (array_key_exists($k, $body)) {
            $col = strtolower(preg_replace('/([A-Z])/', '_$1', $k));
            $updates[] = "`$col` = :$col";
            $params[":$col"] = $body[$k] ? 1 : 0;
        }
    }
    // Optional auch Anzeigename/Avatar updatable
    foreach (['displayName' => 'display_name', 'avatarSlug' => 'avatar_slug',
              'firstName' => 'first_name', 'lastName' => 'last_name'] as $k => $col) {
        if (array_key_exists($k, $body)) {
            $updates[] = "`$col` = :$k";
            $params[":$k"] = $body[$k];
        }
    }
    if (empty($updates)) v2_response_error(400, 'no_changes', 'Keine Felder zum Aktualisieren.');

    v2_db_exec("UPDATE students SET " . implode(', ', $updates) . " WHERE id = :id", $params);
    v2_response_ok(['ok' => true]);
}

// ── DELETE: Soft-Delete ──────────────────────────────────────────
$studentId = (int) ($_GET['studentId'] ?? 0);
if (!$studentId) v2_response_error(400, 'missing_studentId', 'studentId fehlt.');
if (!student_owned($studentId, $teacherId)) v2_response_error(403, 'forbidden', 'Schüler*in nicht in deiner Klasse.');
v2_db_exec('UPDATE students SET deleted_at = NOW() WHERE id = :id', [':id' => $studentId]);
v2_response_ok(['ok' => true]);