upgrade

too tired to write a detailed commit message or split into self-explanatory commits

src/commonMain/kotlin/com/infendro/otp/HOTP.kt

@@ -1,55 +1,32 @@
 package com.infendro.otp
 
-import com.infendro.bytearray.toInt
-import com.infendro.bytearray.toUByteArray
+import com.infendro.bytes.bytearray.toInt
+import com.infendro.bytes.long.toByteArray
 import com.infendro.hash.HashFunction
 import com.infendro.hash.sha1.SHA1
 import com.infendro.mac.HMAC
-import kotlin.math.pow
+import com.infendro.otp.util.pow
+import kotlin.experimental.and
 
 class HOTP(
-    function: HashFunction = SHA1,
-    private val length: Int = 6,
+    val function: HashFunction = SHA1,
+    val length: Int = 6,
 ) {
     private val hmac = HMAC(function)
 
-    fun verify(
-        secret: UByteArray,
-        counter: Long,
-        otp: String,
-    ): Boolean {
+    fun verify(secret: ByteArray, counter: Long, otp: String): Boolean {
         return generate(secret, counter) == otp
     }
 
-    fun generate(
-        secret: UByteArray,
-        counter: Long,
-    ): String {
+    fun generate(secret: ByteArray, counter: Long): String {
         require(counter >= 0)
-
-        val hash = generateHash(secret, counter.toUByteArray())
-        return otp(hash)
+        return otp(secret, counter)
     }
 
-    private fun generateHash(
-        secret: UByteArray,
-        value: UByteArray,
-    ): UByteArray {
-        return hmac.hash(secret, value)
-    }
-
-    private fun otp(
-        hash: UByteArray,
-    ): String {
-        val offset = (hash.last() and 0xFU).toInt()
-
-        var truncatedHash = hash
-            .drop(offset).take(4)
-            .toUByteArray()
-            .toInt() and 0x7FFFFFFF
-        truncatedHash %= 10.0.pow(length).toInt()
-
-        return truncatedHash.toString()
-            .padStart(length, '0')
+    private fun otp(secret: ByteArray, counter: Long): String {
+        val hash = hmac.hash(secret, counter.toByteArray())
+        val offset = (hash.last() and 0xF).toInt()
+        val otp = (hash.toInt(offset) and 0x7FFFFFFF) % 10.pow(length)
+        return "$otp".padStart(length, '0')
     }
 }