<?php
declare(strict_types=1);
require_once __DIR__ . '/common.php';

// Interner Chat ist für alle Mitarbeiter da, nicht nur Admins.
api_require_method('GET', 'POST');
$staff = api_require_staff();
$pdo = get_db();

if ($_SERVER['REQUEST_METHOD'] === 'GET') {
    $withId = (int) ($_GET['with'] ?? 0);

    if ($withId) {
        $withStmt = $pdo->prepare('SELECT id, name FROM staff WHERE id = ?');
        $withStmt->execute([$withId]);
        $withStaff = $withStmt->fetch();
        if (!$withStaff) {
            api_error(404, 'STAFF_NOT_FOUND', 'Der Mitarbeiter wurde nicht gefunden.');
        }

        $pdo->prepare('UPDATE staff_chat_messages SET is_read = 1 WHERE from_staff_id = ? AND to_staff_id = ?')
            ->execute([$withId, $staff['id']]);

        $cStmt = $pdo->prepare(
            'SELECT m.*, sf.name AS from_name
             FROM staff_chat_messages m
             JOIN staff sf ON sf.id = m.from_staff_id
             WHERE (m.from_staff_id = ? AND m.to_staff_id = ?)
                OR (m.from_staff_id = ? AND m.to_staff_id = ?)
             ORDER BY m.created_at ASC LIMIT 300'
        );
        $cStmt->execute([$staff['id'], $withId, $withId, $staff['id']]);
        $conversation = $cStmt->fetchAll();

        api_json([
            'with' => ['id' => (int) $withStaff['id'], 'name' => $withStaff['name']],
            'messages' => array_map(fn(array $m) => [
                'id' => (int) $m['id'],
                'fromStaffId' => (int) $m['from_staff_id'],
                'fromName' => $m['from_name'],
                'message' => $m['message'],
                'createdAt' => $m['created_at'],
            ], $conversation),
        ]);
    }

    $allStaff = $pdo->prepare('SELECT id, name FROM staff WHERE is_active = 1 AND id != ? ORDER BY name');
    $allStaff->execute([$staff['id']]);
    $contacts = $allStaff->fetchAll();

    $unreadStmt = $pdo->prepare(
        'SELECT from_staff_id, COUNT(*) AS cnt FROM staff_chat_messages WHERE to_staff_id = ? AND is_read = 0 GROUP BY from_staff_id'
    );
    $unreadStmt->execute([$staff['id']]);
    $unreadByStaff = [];
    foreach ($unreadStmt->fetchAll() as $row) {
        $unreadByStaff[(int) $row['from_staff_id']] = (int) $row['cnt'];
    }

    $lastStmt = $pdo->prepare(
        "SELECT CASE WHEN from_staff_id = ? THEN to_staff_id ELSE from_staff_id END AS other_id,
                MAX(created_at) AS last_at
         FROM staff_chat_messages
         WHERE from_staff_id = ? OR to_staff_id = ?
         GROUP BY other_id"
    );
    $lastStmt->execute([$staff['id'], $staff['id'], $staff['id']]);
    $lastByStaff = [];
    foreach ($lastStmt->fetchAll() as $row) {
        $lastByStaff[(int) $row['other_id']] = $row['last_at'];
    }

    api_json([
        'contacts' => array_map(fn(array $s) => [
            'id' => (int) $s['id'],
            'name' => $s['name'],
            'unreadCount' => $unreadByStaff[(int) $s['id']] ?? 0,
            'lastMessageAt' => $lastByStaff[(int) $s['id']] ?? null,
        ], $contacts),
    ]);
}

$body = api_request_body();
$action = $body['action'] ?? '';

if ($action === 'send') {
    $toId = (int) ($body['toId'] ?? 0);
    $message = trim((string) ($body['message'] ?? ''));

    if ($toId === 0) api_error(422, 'RECIPIENT_REQUIRED', 'Bitte einen Empfänger angeben.');
    if ($message === '') api_error(422, 'MESSAGE_REQUIRED', 'Bitte eine Nachricht eingeben.');
    if (strlen($message) > 5000) api_error(422, 'MESSAGE_TOO_LONG', 'Die Nachricht ist zu lang.');

    $toCheck = $pdo->prepare('SELECT COUNT(*) FROM staff WHERE id = ? AND is_active = 1');
    $toCheck->execute([$toId]);
    if (!(bool) $toCheck->fetchColumn()) {
        api_error(422, 'RECIPIENT_NOT_FOUND', 'Der Empfänger wurde nicht gefunden.');
    }

    $pdo->prepare('INSERT INTO staff_chat_messages (from_staff_id, to_staff_id, message, created_at) VALUES (?,?,?,?)')
        ->execute([$staff['id'], $toId, $message, db_now()]);
    api_json(['id' => (int) $pdo->lastInsertId()]);
}

api_error(422, 'INVALID_ACTION', 'Unbekannte Aktion.');