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

define('CACHE_DIR', __DIR__ . '/data/');
define('CACHE_FILE', CACHE_DIR . 'questions.json');
define('API_LOCK_FILE', CACHE_DIR . 'api.lock');
define('API_INTERVAL', 5);

static $cacheData = null;

$result = ['code' => 0, 'msg' => '', 'data' => null];

$action = $_REQUEST['action'] ?? 'question';
$id = isset($_REQUEST['id']) ? intval($_REQUEST['id']) : null;

switch($action){
    case 'question':
        $result['data'] = getQuestion($id ?? getCurrentId());
        break;
    case 'next':
        $result['data'] = getNextQuestionAuto();
        break;
    case 'fetch':
        $result['data'] = fetchNewQuestion();
        break;
    case 'answer':
        $result['data'] = checkAnswer($id, $_REQUEST['answer'] ?? '');
        break;
    case 'hint':
        $result['data'] = getHint($id);
        break;
    case 'list':
        $result['data'] = getQuestionList();
        break;
    case 'refresh':
        $result['data'] = refreshCache();
        break;
    case 'stats':
        $result['data'] = getStats();
        break;
    default:
        $result['code'] = 400;
        $result['msg'] = '未知操作';
}

echo json_encode($result, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);

function getStats(){
    global $cacheData;
    $cache = loadCache();
    return [
        'total_questions' => count($cache),
        'cache_file_size' => file_exists(CACHE_FILE) ? round(filesize(CACHE_FILE) / 1024, 2) . ' KB' : 0,
        'last_updated' => file_exists(CACHE_FILE) ? date('Y-m-d H:i:s', filemtime(CACHE_FILE)) : 'N/A',
        'memory_usage' => round(memory_get_peak_usage(true) / 1024, 2) . ' KB'
    ];
}

function getQuestion($id){
    $cache = loadCache();
    if(empty($cache)){
        return ['error' => '没有题目数据'];
    }
    if($id < 0 || $id >= count($cache)){
        return ['error' => '题目不存在', 'total' => count($cache)];
    }
    $item = $cache[$id];
    return [
        'id' => $id,
        'total' => count($cache),
        'question' => $item['question_content'],
        'author' => $item['type']['person'] ?? '',
        'type' => $item['type']['type'] ?? '',
        'grade' => $item['type']['grade'] ?? '',
        'dynasty' => $item['type']['dynasty'] ?? '',
        'options' => formatOptions($item['option_answers'] ?? [])
    ];
}

function getNextQuestionAuto(){
    $cache = loadCache();
    if(empty($cache)){
        return ['error' => '没有题目数据'];
    }
    $total = count($cache);
    $currentId = getCurrentId();
    $nextId = $currentId + 1;
    if($nextId >= $total){
        $nextId = 0;
    }
    setCurrentId($nextId);
    $result = getQuestion($nextId);
    $result['prev_id'] = $currentId;
    return $result;
}

function getCurrentId(){
    return isset($_SESSION['current_question_id']) ? intval($_SESSION['current_question_id']) : 0;
}

function setCurrentId($id){
    $_SESSION['current_question_id'] = $id;
}

function fetchNewQuestion(){
    $apiData = fetchFromBaiduApi();
    
    if($apiData === null){
        $cache = loadCache();
        if(!empty($cache)){
            $randomId = array_rand($cache);
            $result = formatQuestionItem($randomId, $cache[$randomId], count($cache));
            $result['from_cache'] = true;
            $result['api_status'] = 'failed';
            return $result;
        }
        return ['error' => 'API请求失败且无本地缓存'];
    }
    
    $cache = loadCache();
    $newCount = mergeToCache($apiData, $cache);
    
    $randomItem = $apiData[array_rand($apiData)];
    $result = formatQuestionItem(null, $randomItem, count($cache));
    $result['from_cache'] = false;
    $result['new_questions'] = $newCount;
    $result['api_status'] = 'success';
    
    return $result;
}

function formatQuestionItem($id, $item, $total, $fromCache = false, $newCount = 0){
    return [
        'id' => $id,
        'total' => $total,
        'question' => $item['question_content'],
        'author' => $item['type']['person'] ?? '',
        'type' => $item['type']['type'] ?? '',
        'grade' => $item['type']['grade'] ?? '',
        'dynasty' => $item['type']['dynasty'] ?? '',
        'options' => formatOptions($item['option_answers'] ?? []),
        'from_cache' => $fromCache,
        'new_questions' => $newCount
    ];
}

function checkAnswer($id, $answer){
    $cache = loadCache();
    if(empty($cache)){
        return ['error' => '没有题目数据'];
    }
    if($id < 0 || $id >= count($cache)){
        return ['error' => '题目不存在'];
    }
    $item = $cache[$id];
    $correctAnswer = findAnswer($item['option_answers'] ?? []);
    $isCorrect = ($answer === $correctAnswer);
    
    return [
        'id' => $id,
        'correct' => $isCorrect,
        'your_answer' => $answer,
        'correct_answer' => $correctAnswer,
        'next_id' => $id + 1,
        'has_next' => $id + 1 < count($cache)
    ];
}

function getHint($id){
    $cache = loadCache();
    if(empty($cache)){
        return ['error' => '没有题目数据'];
    }
    if($id < 0 || $id >= count($cache)){
        return ['error' => '题目不存在'];
    }
    $item = $cache[$id];
    return [
        'id' => $id,
        'hint' => '这是首描写' . ($item['type']['type'] ?? '') . '的诗，你在' . ($item['type']['grade'] ?? '') . '学过它。',
        'author' => $item['type']['person'] ?? '',
        'dynasty' => $item['type']['dynasty'] ?? ''
    ];
}

function getQuestionList(){
    $cache = loadCache();
    if(empty($cache)){
        return ['total' => 0, 'list' => []];
    }
    $list = [];
    foreach($cache as $i => $item){
        $list[] = [
            'id' => $i,
            'question' => mb_substr($item['question_content'], 0, 30, 'UTF-8') . '...',
            'author' => $item['type']['person'] ?? '',
            'dynasty' => $item['type']['dynasty'] ?? ''
        ];
    }
    return ['total' => count($list), 'list' => $list];
}

function refreshCache(){
    $apiData = fetchFromBaiduApi();
    if($apiData === null){
        return ['refreshed' => false, 'error' => 'API请求失败'];
    }
    $cache = loadCache();
    $newCount = mergeToCache($apiData, $cache);
    return ['refreshed' => true, 'total' => count($cache), 'new_questions' => $newCount];
}

function loadCache(){
    global $cacheData;
    
    if($cacheData !== null){
        return $cacheData;
    }
    
    if(!file_exists(CACHE_FILE)){
        $cacheData = [];
        return [];
    }
    
    $content = file_get_contents(CACHE_FILE);
    if($content === false){
        $cacheData = [];
        return [];
    }
    
    $data = json_decode($content, true);
    if(!is_array($data) || !isset($data['questions'])){
        $cacheData = [];
        return [];
    }
    
    $cacheData = $data['questions'];
    return $cacheData;
}

function saveCache($questions){
    global $cacheData;
    
    if(!is_dir(CACHE_DIR)){
        mkdir(CACHE_DIR, 0755, true);
    }
    
    $data = [
        'updated' => date('Y-m-d H:i:s'),
        'count' => count($questions),
        'questions' => $questions
    ];
    
    $tempFile = CACHE_FILE . '.tmp';
    $result = file_put_contents($tempFile, json_encode($data, JSON_UNESCAPED_UNICODE), LOCK_EX);
    
    if($result !== false){
        rename($tempFile, CACHE_FILE);
    }
    
    $cacheData = $questions;
}

function fetchFromBaiduApi(){
    if(file_exists(API_LOCK_FILE)){
        $lockTime = intval(file_get_contents(API_LOCK_FILE));
        if(time() - $lockTime < API_INTERVAL){
            return null;
        }
    }
    
    file_put_contents(API_LOCK_FILE, time());
    
    $url = 'https://hanyu.baidu.com/hanyu/ajax/pingce_data';
    $ch = curl_init();
    curl_setopt_array($ch, [
        CURLOPT_URL => $url,
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_SSL_VERIFYPEER => false,
        CURLOPT_SSL_VERIFYHOST => false,
        CURLOPT_TIMEOUT => 5,
        CURLOPT_CONNECTTIMEOUT => 3,
        CURLOPT_USERAGENT => 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36',
        CURLOPT_HTTPHEADER => [
            'Accept: application/json',
            'Accept-Language: zh-CN,zh;q=0.9'
        ]
    ]);
    $response = curl_exec($ch);
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);
    
    if($httpCode !== 200 || empty($response)){
        return null;
    }
    
    $json = json_decode($response, true);
    if(!isset($json['data']) || !is_array($json['data'])){
        return null;
    }
    
    return $json['data'];
}

function mergeToCache($newData, &$existingCache){
    if(empty($newData)){
        return 0;
    }
    
    $existingKeys = [];
    foreach($existingCache as $item){
        $key = $item['question_content'] ?? '';
        $existingKeys[$key] = true;
    }
    
    $newCount = 0;
    foreach($newData as $item){
        $key = $item['question_content'] ?? '';
        if(!isset($existingKeys[$key])){
            $existingCache[] = $item;
            $existingKeys[$key] = true;
            $newCount++;
        }
    }
    
    if($newCount > 0){
        saveCache($existingCache);
    }
    
    return $newCount;
}

function formatOptions($options){
    $result = [];
    foreach($options as $i => $opt){
        $result[] = [
            'index' => $i + 1,
            'content' => $opt['answer_content'] ?? ''
        ];
    }
    return $result;
}

function findAnswer($options){
    foreach($options as $i => $opt){
        if(($opt['is_standard_answer'] ?? 0) === 1){
            return (string)($i + 1);
        }
    }
    return '';
}
?>