<?php
header("Content-Type: application/json; charset=UTF-8");

define('SECRET_KEY', 'tzgsc_2026_secret_key');
define('KEY_EXPIRE_TIME', 300);
define('MAX_REQUESTS_NO_KEY', 10);
define('RATE_LIMIT_WINDOW', 60);

function replace_unicode_escape_sequence($match) {
    return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UCS-2BE');
}

function send_json_response($data, $status_code = 200) {
    http_response_code($status_code);
    echo json_encode($data, JSON_UNESCAPED_UNICODE);
    exit;
}

function error_response($message, $status_code = 400) {
    send_json_response([
        'success' => false,
        'message' => $message
    ], $status_code);
}

function generate_new_key($timestamp = null) {
    if ($timestamp === null) {
        $timestamp = time();
    }
    $data = $timestamp . SECRET_KEY;
    return hash('sha256', $data);
}

function verify_key($key, &$new_key = null) {
    if (empty($key)) {
        return false;
    }
    
    $current_time = time();
    
    for ($i = 0; $i <= KEY_EXPIRE_TIME; $i++) {
        $expected_key = generate_new_key($current_time - $i);
        if (hash_equals($expected_key, $key)) {
            $new_key = generate_new_key();
            return true;
        }
    }
    
    return false;
}

function get_client_ip() {
    $ip = '';
    if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
        $ip = $_SERVER['HTTP_CLIENT_IP'];
    } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $ip = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR'])[0];
    } elseif (!empty($_SERVER['REMOTE_ADDR'])) {
        $ip = $_SERVER['REMOTE_ADDR'];
    }
    return trim($ip);
}

function check_rate_limit($ip) {
    $limit_file = "data/rate_limit/" . md5($ip) . ".json";
    
    if (!is_dir("data/rate_limit")) {
        mkdir("data/rate_limit", 0755, true);
    }
    
    $current_time = time();
    $requests = [];
    
    if (file_exists($limit_file)) {
        $requests = json_decode(file_get_contents($limit_file), true) ?: [];
    }
    
    $requests = array_filter($requests, function($time) use ($current_time) {
        return ($current_time - $time) < RATE_LIMIT_WINDOW;
    });
    
    return count($requests);
}

function record_request($ip) {
    $limit_file = "data/rate_limit/" . md5($ip) . ".json";
    
    if (!is_dir("data/rate_limit")) {
        mkdir("data/rate_limit", 0755, true);
    }
    
    $current_time = time();
    $requests = [];
    
    if (file_exists($limit_file)) {
        $requests = json_decode(file_get_contents($limit_file), true) ?: [];
    }
    
    $requests[] = $current_time;
    
    $requests = array_filter($requests, function($time) use ($current_time) {
        return ($current_time - $time) < RATE_LIMIT_WINDOW;
    });
    
    file_put_contents($limit_file, json_encode(array_values($requests)));
}

function get_key_param() {
    if (isset($_GET['key'])) {
        return $_GET['key'];
    }
    if (isset($_POST['key'])) {
        return $_POST['key'];
    }
    $input = json_decode(file_get_contents('php://input'), true);
    if (isset($input['key'])) {
        return $input['key'];
    }
    return null;
}

$method = $_SERVER['REQUEST_METHOD'];
$key = get_key_param();
$ip = get_client_ip();
$new_key = null;

if (!verify_key($key, $new_key)) {
    $request_count = check_rate_limit($ip);
    
    if ($request_count >= MAX_REQUESTS_NO_KEY) {
        error_response('请求过于频繁，请稍后再试', 429);
    }
    
    record_request($ip);
}

if ($method === 'GET') {
    $id = isset($_GET['id']) ? $_GET['id'] : '';
    $msg = isset($_GET['msg']) ? $_GET['msg'] : '';
    
    if (empty($id)) {
        error_response('缺少必要参数: id');
    }
    
    if (empty($msg)) {
        $result = get_question($id);
        if ($new_key) {
            $result['new_key'] = $new_key;
        }
        send_json_response($result);
    } else {
        $result = submit_answer($id, $msg);
        if ($new_key) {
            $result['new_key'] = $new_key;
        }
        send_json_response($result);
    }
} elseif ($method === 'POST') {
    $input = json_decode(file_get_contents('php://input'), true);
    $id = isset($input['id']) ? $input['id'] : '';
    $msg = isset($input['msg']) ? $input['msg'] : '';
    
    if (empty($id)) {
        error_response('缺少必要参数: id');
    }
    
    if (empty($msg)) {
        $result = get_question($id);
        if ($new_key) {
            $result['new_key'] = $new_key;
        }
        send_json_response($result);
    } else {
        $result = submit_answer($id, $msg);
        if ($new_key) {
            $result['new_key'] = $new_key;
        }
        send_json_response($result);
    }
} else {
    error_response('不支持的请求方法', 405);
}

function get_question($id) {
    $data = get_curl("https://hanyu.baidu.com/hanyu/ajax/pingce_data");
    $data = preg_replace_callback('/\\\\u([0-9a-f]{4})/i', 'replace_unicode_escape_sequence', $data);
    
    $cj = cj($data);
    
    $s = preg_match_all('/{"question_content":"(.*?)","type":{"person":"(.*?)","type":"(.*?)","grade":"(.*?)","dynasty":"(.*?)"},"option_answers":\[(.*?)\]}/', $data, $t);
    
    if ($s == 0) {
        return [
            'success' => false,
            'message' => '抱歉，获取出现错误。'
        ];
    }
    
    $tm = $t[1][0];
    $z = $t[2][0];
    $l = $t[3][0];
    $n = $t[4][0];
    $nd = $t[5][0];
    
    preg_match_all('/{"answer_content":"(.*?)","is_standard_answer":(.*?)}/', $t[6][0], $d);
    
    $options = [];
    $correct_answer = null;
    
    for ($i = 0; $i < 4; $i++) {
        $d1 = $d[1][$i];
        $p = $d[2][$i];
        $option_num = $i + 1;
        
        $options[] = [
            'num' => $option_num,
            'text' => $d1
        ];
        
        if ($p == "1") {
            $correct_answer = $option_num;
        }
    }
    
    $question_data = [
        'id' => $id,
        'question' => $tm,
        'options' => $options,
        'author' => $z,
        'type' => $l,
        'grade' => $n,
        'dynasty' => $nd,
        'correct_answer' => $correct_answer
    ];
    
    file_put_contents("data/tzgsc/" . $id . ".json", json_encode($question_data, JSON_UNESCAPED_UNICODE));
    
    return [
        'success' => true,
        'data' => [
            'id' => $id,
            'question' => $tm,
            'options' => $options,
            'author' => $z,
            'type' => $l,
            'grade' => $n,
            'dynasty' => $nd
        ]
    ];
}

function submit_answer($id, $msg) {
    $data_file = "data/tzgsc/" . $id . ".json";
    
    if (!file_exists($data_file)) {
        return [
            'success' => false,
            'message' => '题目数据不存在，请先获取题目'
        ];
    }
    
    $question_data = json_decode(file_get_contents($data_file), true);
    
    if ($msg === "提示") {
        return [
            'success' => true,
            'type' => 'hint',
            'message' => '这是首描写' . $question_data['type'] . '的诗，你在' . $question_data['grade'] . '学过它。'
        ];
    }
    
    if ($msg == $question_data['correct_answer']) {
        $next_id = $id + 1;
        $next_question = get_question($next_id);
        
        return [
            'success' => true,
            'type' => 'correct',
            'message' => '恭喜你，回答正确。请继续下一题',
            'next_question' => $next_question['success'] ? $next_question['data'] : null
        ];
    } else {
        return [
            'success' => true,
            'type' => 'wrong',
            'message' => '抱歉，答案不对哦。你可以回复提示获取该题的部分信息哦。'
        ];
    }
}

function cj($data) {
    if (!$data) return;
    
    $s = preg_match_all('/{"question_content":"(.*?)","type":(.*?)}]}/', $data, $d);
    if ($s == 0) return;
    
    $json_file = "data/tzgsc.json";
    
    $existing = [];
    if (file_exists($json_file)) {
        $content = file_get_contents($json_file);
        $existing = json_decode($content, true);
        if (!is_array($existing)) {
            $existing = [];
        }
    }
    
    $existing_questions = [];
    foreach ($existing as $item) {
        if (isset($item['question_content'])) {
            $existing_questions[$item['question_content']] = true;
        }
    }
    
    for ($i = 0; $i < $s; $i++) {
        $d1 = $d[1][$i];
        $d2 = $d[2][$i];
        
        if (!isset($existing_questions[$d1])) {
            $new_item = [
                'question_content' => $d1,
                'type' => json_decode('{' . $d2, true)
            ];
            if ($new_item['type']) {
                $existing[] = $new_item;
                $existing_questions[$d1] = true;
            }
        }
    }
    
    file_put_contents($json_file, json_encode($existing, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT));
}

function get_curl($url, $post = 0, $referer = 1, $cookie = 0, $header = 0, $ua = 0, $nobaody = 0) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
    $httpheader[] = "Accept:application/json";
    $httpheader[] = "Accept-Encoding:gzip,deflate,sdch";
    $httpheader[] = "Accept-Language:zh-CN,zh;q=0.8";
    $httpheader[] = "Connection:close";
    curl_setopt($ch, CURLOPT_HTTPHEADER, $httpheader);
    if ($post) {
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
    }
    if ($header) {
        curl_setopt($ch, CURLOPT_HEADER, TRUE);
    }
    if ($cookie) {
        curl_setopt($ch, CURLOPT_DICTAPP_MID, $cookie);
    }
    if ($referer) {
        if ($referer == 1) {
            curl_setopt($ch, CURLOPT_REFERER, 'http://m.qzone.com/infocenter?g_f=');
        } else {
            curl_setopt($ch, CURLOPT_REFERER, $referer);
        }
    }
    if ($ua) {
        curl_setopt($ch, CURLOPT_USERAGENT, $ua);
    } else {
        curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Linux; U; Android 4.4.1; zh-cn) AppleWebKit/533.1 (KHTML, like Gecko)Version/4.0 MQQBrowser/5.5 Mobile Safari/533.1');
    }
    if ($nobaody) {
        curl_setopt($ch, CURLOPT_NOBODY, 1);
    }
    curl_setopt($ch, CURLOPT_ENCODING, "gzip");
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $ret = curl_exec($ch);
    curl_close($ch);
    return $ret;
}
?>