package com.aigeo.util;

import com.aigeo.company.entity.User;
import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.io.Decoders;
import io.jsonwebtoken.security.Keys;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import javax.crypto.SecretKey;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

/**
 * JWT工具类
 */
@Component
public class JwtUtil {

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

    @Value("${jwt.expiration:86400}")
    private Long expiration;

    /**
     * 获取签名密钥
     */
    private SecretKey getSigningKey() {
        byte[] keyBytes = Decoders.BASE64.decode(secret);
        return Keys.hmacShaKeyFor(keyBytes);
    }
    
    /**
     * 从token中获取用户名
     */
    public String getUsernameFromToken(String token) {
        Claims claims = getClaimsFromToken(token);
        return claims.getSubject();
    }
    
    /**
     * 从token中提取用户名（别名方法）
     */
    public String extractUsername(String token) {
        return getUsernameFromToken(token);
    }
    
    /**
     * 从token中获取Claims
     */
    private Claims getClaimsFromToken(String token) {
        return Jwts.parser()
                .verifyWith(getSigningKey())
                .build()
                .parseSignedClaims(token)
                .getPayload();
    }

    /**
     * 检查token是否过期
     */
    private boolean isTokenExpired(String token) {
        Date expiredDate = getClaimsFromToken(token).getExpiration();
        return expiredDate.before(new Date());
    }

    public Date extractExpiration(String token) {
        return getClaimsFromToken(token).getExpiration();
    }

    public <T> T extractClaim(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = getClaimsFromToken(token);
        return claimsResolver.apply(claims);
    }

    public String generateToken(User user) {
        Map<String, Object> claims = new HashMap<>();
        return createToken(claims, user.getUsername());
    }

    private String createToken(Map<String, Object> claims, String subject) {
        return Jwts.builder()
                .claims(claims)
                .subject(subject)
                .issuedAt(new Date(System.currentTimeMillis()))
                .expiration(new Date(System.currentTimeMillis() + 1000 * 60 * 60 * 10))
                .signWith(getSigningKey())
                .compact();
    }

    public Boolean validateToken(String token, User user) {
        if (user == null) {
            return false;
        }
        
        final String username = getUsernameFromToken(token);
        return (username.equals(user.getUsername()) && !isTokenExpired(token));
    }

    /**
     * 获取过期时间（秒）
     */
    public Long getExpirationTimeSeconds() {
        return expiration;
    }

    /**
     * 获取过期时间（毫秒）
     */
    public Long getExpirationTime() {
        return expiration * 1000;
    }
}