[O] Convert more stuff to kotlin

src/main/java/icu/samnyan/aqua/sega/aimedb/AimeDbDecoder.kt

@@ -0,0 +1,69 @@
+package icu.samnyan.aqua.sega.aimedb
+
+import icu.samnyan.aqua.sega.aimedb.exception.InvalidRequestException
+import icu.samnyan.aqua.sega.aimedb.util.Encryption
+import io.netty.buffer.ByteBuf
+import io.netty.channel.ChannelHandlerContext
+import io.netty.handler.codec.ByteToMessageDecoder
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import org.springframework.beans.factory.config.BeanDefinition
+import org.springframework.context.annotation.Scope
+import org.springframework.stereotype.Component
+
+/**
+ * @author samnyan (privateamusement@protonmail.com)
+ */
+@Component
+@Scope(BeanDefinition.SCOPE_PROTOTYPE)
+class AimeDbDecoder : ByteToMessageDecoder() {
+    var length = 0
+    val logger: Logger = LoggerFactory.getLogger(AimeDbDecoder::class.java)
+
+    /**
+     * Decrypt the incoming request including frame management
+     * @param ctx ChannelHandlerContext
+     * @param input ByteBuf in
+     * @param out List<Object>
+    </Object> */
+    @Throws(Exception::class)
+    override fun decode(ctx: ChannelHandlerContext, input: ByteBuf, out: MutableList<Any>) {
+        if (input.readableBytes() < 16) return
+        if (length == 0) {
+            length = getLength(input)
+            logger.info("Aime Server Request Length: $length")
+        }
+
+        if (input.readableBytes() < length) return
+
+        // Create a byte array to store the encrypted data
+        val result = Encryption.decrypt(input.readBytes(length))
+
+        val resultMap: MutableMap<String, Any> = HashMap()
+        resultMap["type"] = result.getShortLE(0x04).toInt()
+        resultMap["data"] = result
+
+        logger.debug("Aime Server Request Type: " + resultMap["type"])
+
+        out.add(resultMap)
+    }
+
+    /**
+     * Get the length from request
+     *
+     * @param input the request
+     * @return int the length of this request
+     */
+    private fun getLength(input: ByteBuf): Int {
+        val currentPos = input.readerIndex()
+        val result = Encryption.decrypt(input)
+
+        // Check the header
+        if (result.getByte(0).toInt() != 0x3e) {
+            throw InvalidRequestException()
+        }
+
+        // Read the length from offset 6
+        return result.getShortLE(currentPos + 6).toInt()
+    }
+}