package util;

import java.io.*;
import java.net.*;
import java.util.zip.GZIPInputStream;
import exception.*;

public class HttpUtil {
    private static final int TIMEOUT = 10000;
    private static final String USER_AGENT = 
        "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36";
    
    public static String get(String urlStr, String encoding) throws SpiderException {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        
        try {
            URL url = new URL(urlStr);
            connection = (HttpURLConnection) url.openConnection();
            
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(TIMEOUT);
            connection.setReadTimeout(TIMEOUT);
            connection.setRequestProperty("User-Agent", USER_AGENT);
            connection.setRequestProperty("Accept-Encoding", "gzip, deflate");
            
            int responseCode = connection.getResponseCode();
            if (responseCode != HttpURLConnection.HTTP_OK) {
                throw new NetworkException("HTTP响应错误: " + responseCode, 
                    NetworkException.ErrorType.RESPONSE_ERROR);
            }
            
            String contentEncoding = connection.getContentEncoding();
            InputStream inputStream = connection.getInputStream();
            
            if (contentEncoding != null && contentEncoding.toLowerCase().contains("gzip")) {
                inputStream = new GZIPInputStream(inputStream);
            }
            
            reader = new BufferedReader(new InputStreamReader(inputStream, encoding));
            StringBuilder result = new StringBuilder();
            String line;
            
            while ((line = reader.readLine()) != null) {
                result.append(line).append("\n");
            }
            
            return result.toString();
            
        } catch (MalformedURLException e) {
            throw new NetworkException("URL格式错误: " + urlStr, 
                NetworkException.ErrorType.HOST_NOT_FOUND, e);
        } catch (SocketTimeoutException e) {
            throw new NetworkException("连接超时: " + urlStr, 
                NetworkException.ErrorType.CONNECTION_TIMEOUT, e);
        } catch (IOException e) {
            throw new NetworkException("网络IO错误: " + e.getMessage(), 
                NetworkException.ErrorType.CONNECTION_REFUSED, e);
        } finally {
            if (reader != null) {
                try { reader.close(); } catch (IOException e) {}
            }
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
    
    public static String extractTag(String html, String startTag, String endTag) 
            throws ParseException {
        int startIndex = html.indexOf(startTag);
        if (startIndex == -1) {
            throw new ParseException("未找到开始标签: " + startTag, 
                ParseException.ErrorType.TAG_NOT_FOUND);
        }
        
        int endIndex = html.indexOf(endTag, startIndex + startTag.length());
        if (endIndex == -1) {
            throw new ParseException("未找到结束标签: " + endTag, 
                ParseException.ErrorType.TAG_NOT_FOUND);
        }
        
        return html.substring(startIndex + startTag.length(), endIndex).trim();
    }
    
    public static String extractTagSafe(String html, String startTag, String endTag) {
        try {
            return extractTag(html, startTag, endTag);
        } catch (ParseException e) {
            return "未找到";
        }
    }
}