package com.ruoyi.auth.service;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Locale;
import java.util.concurrent.TimeUnit;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.ruoyi.common.core.constant.CacheConstants;
import com.ruoyi.common.core.exception.ServiceException;
import com.ruoyi.common.core.utils.StringUtils;
import com.ruoyi.common.core.utils.ip.IpUtils;
import com.ruoyi.common.redis.service.RedisService;

/**
 * 登录频率限制服务
 */
@Component
public class LoginRateLimitService
{
    private static final String UNKNOWN = "unknown";
    private static final String SESSION_HEADER = "X-Login-Session";

    @Autowired
    private RedisService redisService;

    /**
     * 按 IP、账号、登录会话三个维度限制登录尝试频率。
     */
    public void checkLoginRate(String username, HttpServletRequest request)
    {
        String normalizedUsername = StringUtils.defaultString(username).trim().toLowerCase(Locale.ROOT);
        String ip = StringUtils.defaultIfEmpty(IpUtils.getIpAddr(request), UNKNOWN);
        String sessionId = resolveSessionId(request);

        checkDimension("ip", ip);
        checkDimension("account", normalizedUsername);
        checkDimension("session", sessionId);
    }

    private void checkDimension(String dimension, String identity)
    {
        String key = CacheConstants.LOGIN_RATE_LIMIT_KEY + dimension + ":" + digest(identity);
        long count = redisService.incrementCacheValue(key, CacheConstants.LOGIN_RATE_LIMIT_WINDOW, TimeUnit.SECONDS);
        if (count > CacheConstants.LOGIN_RATE_LIMIT_MAX_COUNT)
        {
            long remainingSeconds = redisService.getExpire(key);
            long retryAfter = remainingSeconds > 0 ? remainingSeconds : CacheConstants.LOGIN_RATE_LIMIT_WINDOW;
            throw new ServiceException(String.format("登录尝试过于频繁，请%s秒后重试", retryAfter));
        }
    }

    private String resolveSessionId(HttpServletRequest request)
    {
        String sessionId = request.getHeader(SESSION_HEADER);
        if (StringUtils.isNotEmpty(sessionId))
        {
            return sessionId;
        }
        String userAgent = StringUtils.defaultString(request.getHeader("User-Agent"));
        return IpUtils.getIpAddr(request) + "|" + userAgent;
    }

    private String digest(String value)
    {
        try
        {
            byte[] bytes = MessageDigest.getInstance("SHA-256").digest(value.getBytes(StandardCharsets.UTF_8));
            StringBuilder result = new StringBuilder(bytes.length * 2);
            for (byte current : bytes)
            {
                result.append(String.format("%02x", current));
            }
            return result.toString();
        }
        catch (NoSuchAlgorithmException e)
        {
            throw new IllegalStateException("SHA-256 algorithm is unavailable", e);
        }
    }
}