package com.qf.myafterprojecy.utils;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Component;

import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

/**
 * JWT工具类，用于生成和验证token
 */
@Component
public class JwtUtils {

    @Value("${jwt.secret:default_secret_key_for_development}")
    private String secret;

    @Value("${jwt.expiration:86400000}")
    private long expiration;

    @Value("${jwt.token-prefix:Bearer}")
    private String tokenPrefix;

    /**
     * 从token中获取用户名
     */
    public String getUsernameFromToken(String token) {
        return getClaimFromToken(token, Claims::getSubject);
    }

    /**
     * 从token中获取过期时间
     */
    public Date getExpirationDateFromToken(String token) {
        return getClaimFromToken(token, Claims::getExpiration);
    }

    /**
     * 从token中获取指定的claim
     */
    public <T> T getClaimFromToken(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = getAllClaimsFromToken(token);
        return claimsResolver.apply(claims);
    }

    /**
     * 获取token中的所有claims
     */
    private Claims getAllClaimsFromToken(String token) {
        return Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();
    }

    /**
     * 检查token是否过期
     */
    private Boolean isTokenExpired(String token) {
        final Date expiration = getExpirationDateFromToken(token);
        return expiration.before(new Date());
    }

    /**
     * 生成token
     */
    public String generateToken(UserDetails userDetails) {
        Map<String, Object> claims = new HashMap<>();
        claims.put("authorities", userDetails.getAuthorities());
        return doGenerateToken(claims, userDetails.getUsername());
    }

    /**
     * 生成token的核心方法
     */
    private String doGenerateToken(Map<String, Object> claims, String subject) {
        return Jwts.builder()
                .setClaims(claims)
                .setSubject(subject)
                .setIssuedAt(new Date(System.currentTimeMillis()))
                .setExpiration(new Date(System.currentTimeMillis() + expiration))
                .signWith(SignatureAlgorithm.HS512, secret)
                .compact();
    }

    /**
     * 验证token
     */
    public Boolean validateToken(String token, UserDetails userDetails) {
        final String username = getUsernameFromToken(token);
        return (username.equals(userDetails.getUsername()) && !isTokenExpired(token));
    }

    /**
     * 获取token前缀
     */
    public String getTokenPrefix() {
        return tokenPrefix;
    }
}