<?php
header('Content-Type: application/json; charset=utf-8');
date_default_timezone_set('Asia/Ho_Chi_Minh');

$chatFile = __DIR__ . '/chat.txt';

if (!file_exists($chatFile)) {
    file_put_contents($chatFile, '');
}

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $raw = file_get_contents('php://input');
    $body = json_decode($raw, true);

    $action = $_POST['action'] ?? ($body['action'] ?? 'send');

    if ($action === 'clear') {
        $seed = json_encode([
            'sender' => 'Hệ thống',
            'message' => 'Lịch sử phòng chat đã được làm mới.',
            'time' => date('H:i:s')
        ], JSON_UNESCAPED_UNICODE) . PHP_EOL;
        file_put_contents($chatFile, $seed, LOCK_EX);
    } else {
        $sender = trim($_POST['sender'] ?? ($body['sender'] ?? 'Khách'));
        $message = trim($_POST['message'] ?? ($body['message'] ?? ''));

        if ($sender === '') {
            $sender = 'Khách';
        }

        if ($message !== '') {
            $entry = [
                'sender' => mb_substr($sender, 0, 50, 'UTF-8'),
                'message' => mb_substr($message, 0, 500, 'UTF-8'),
                'time' => date('H:i:s')
            ];
            $line = json_encode($entry, JSON_UNESCAPED_UNICODE) . PHP_EOL;
            file_put_contents($chatFile, $line, FILE_APPEND | LOCK_EX);
        }
    }
}

$lines = file($chatFile, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$messages = [];

if (is_array($lines)) {
    foreach ($lines as $line) {
        $decoded = json_decode($line, true);
        if (is_array($decoded) && isset($decoded['message'])) {
            $messages[] = $decoded;
        }
    }
}

echo json_encode([
    'status' => 'success',
    'count' => count($messages),
    'messages' => $messages
], JSON_UNESCAPED_UNICODE);