Less memory intensive Hex Checker

app/src/main/java/com/vitorpamplona/amethyst/service/HexValidator.kt

@@ -0,0 +1,23 @@
+package com.vitorpamplona.amethyst.service
+
+object HexValidator {
+
+    private fun isHex2(c: Char): Boolean {
+        return when (c) {
+            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'A', 'B', 'C', 'D', 'E', 'F', ' ' -> true
+            else -> false
+        }
+    }
+
+    fun isHex(hex: String?): Boolean {
+        if (hex == null) return false
+        var isHex = true
+        for (c in hex.toCharArray()) {
+            if (!isHex2(c)) {
+                isHex = false
+                break
+            }
+        }
+        return isHex
+    }
+}

app/src/main/java/com/vitorpamplona/amethyst/service/model/PrivateDmEvent.kt

@@ -4,6 +4,7 @@ import android.util.Log
 import androidx.compose.runtime.Immutable
 import com.vitorpamplona.amethyst.model.HexKey
 import com.vitorpamplona.amethyst.model.toHexKey
+import com.vitorpamplona.amethyst.service.HexValidator
 import fr.acinq.secp256k1.Hex
 import nostr.postr.Utils
 import nostr.postr.toHex
@@ -23,11 +24,18 @@ class PrivateDmEvent(
      * nip-04 EncryptedDmEvent but may omit the recipient, too. This value can be queried and used
      * for initial messages.
      */
-    private fun recipientPubKey() = tags.firstOrNull { it.size > 1 && it[0] == "p" }
+    private fun recipientPubKey() = tags.firstOrNull { it.size > 1 && it[0] == "p" }?.get(1)
 
-    fun recipientPubKeyBytes() = recipientPubKey()?.runCatching { Hex.decode(this[1]) }?.getOrNull()
+    fun recipientPubKeyBytes() = recipientPubKey()?.runCatching { Hex.decode(this) }?.getOrNull()
 
-    fun verifiedRecipientPubKey() = recipientPubKey()?.runCatching { Hex.decode(this[1]).toHexKey() }?.getOrNull() // makes sure its a valid one
+    fun verifiedRecipientPubKey(): HexKey? {
+        val recipient = recipientPubKey()
+        return if (HexValidator.isHex(recipient)) {
+            recipient
+        } else {
+            null
+        }
+    }
 
     fun talkingWith(oneSideHex: String): HexKey {
         return if (pubKey == oneSideHex) verifiedRecipientPubKey() ?: pubKey else pubKey