add PublicJwtService

src/main/kotlin/ltd/hlaeja/jwt/service/PublicJwtService.kt

@@ -0,0 +1,28 @@
+package ltd.hlaeja.jwt.service
+
+import io.jsonwebtoken.Claims
+import io.jsonwebtoken.Jws
+import io.jsonwebtoken.JwtParser
+import io.jsonwebtoken.Jwts
+import ltd.hlaeja.jwt.util.PublicKeyProvider
+import org.springframework.beans.factory.annotation.Value
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty
+import org.springframework.stereotype.Service
+
+@Service
+@ConditionalOnProperty(prefix = "jwt", name = ["public-key"])
+class PublicJwtService(
+    @Value("\${jwt.public-key}")
+    jwtPublicKey: String,
+) {
+
+    private val parser: JwtParser = Jwts.parser()
+        .verifyWith(PublicKeyProvider.load(jwtPublicKey))
+        .build()
+
+    fun <T> verify(
+        token: String,
+        block: (claims: Jws<Claims>) -> T,
+    ): T = parser.parseSignedClaims(token)
+        .let(block)
+}