package sn.ladoum.bergerie.security;

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.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Service;

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

@Service
public class JwtService {

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

    @Value("${app.jwt.expiration-ms}")
    private long expirationMs;

    public String generateToken(UserDetails userDetails) {
        Map<String, Object> claims = new HashMap<>();
        userDetails.getAuthorities().stream().findFirst()
                .ifPresent(a -> claims.put("role", a.getAuthority()));
        return buildToken(claims, userDetails.getUsername());
    }

    public String extractUsername(String token) {
        return extractClaim(token, Claims::getSubject);
    }

    public boolean isTokenValid(String token, UserDetails userDetails) {
        String username = extractUsername(token);
        return username.equals(userDetails.getUsername()) && !isExpired(token);
    }

    private boolean isExpired(String token) {
        return extractClaim(token, Claims::getExpiration).before(new Date());
    }

    private <T> T extractClaim(String token, Function<Claims, T> resolver) {
        Claims claims = Jwts.parser()
                .verifyWith(getSigningKey())
                .build()
                .parseSignedClaims(token)
                .getPayload();
        return resolver.apply(claims);
    }

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

    private SecretKey getSigningKey() {
        byte[] keyBytes = Decoders.BASE64.decode(java.util.Base64.getEncoder()
                .encodeToString(secret.getBytes()));
        return Keys.hmacShaKeyFor(keyBytes);
    }
}