add external signer

shared/src/commonMain/kotlin/su/reya/coop/ExternalSigner.kt

@@ -0,0 +1,56 @@
+package su.reya.coop
+
+import rust.nostr.sdk.AsyncNostrSigner
+import rust.nostr.sdk.Event
+import rust.nostr.sdk.PublicKey
+import rust.nostr.sdk.UnsignedEvent
+
+interface ExternalSignerLauncher {
+    suspend fun launch(
+        content: String,
+        type: String,
+        pubkey: String? = null,
+        id: String? = null
+    ): String?
+}
+
+object ExternalSignerLauncherProvider {
+    var launcher: ExternalSignerLauncher? = null
+}
+
+/**
+ * A cross-platform implementation of AsyncNostrSigner that delegates
+ * to a platform-specific launcher (NIP-55 on Android).
+ */
+class ExternalSigner(private val launcher: ExternalSignerLauncher) : AsyncNostrSigner {
+    override suspend fun getPublicKeyAsync(): PublicKey? {
+        val result = launcher.launch("", "get_public_key")
+        return result?.let { PublicKey.parse(it) }
+    }
+
+    override suspend fun signEventAsync(unsignedEvent: UnsignedEvent): Event? {
+        val result =
+            launcher.launch(unsignedEvent.asJson(), "sign_event", id = unsignedEvent.id()?.toHex())
+        return result?.let { Event.fromJson(it) }
+    }
+
+    override suspend fun nip04EncryptAsync(publicKey: PublicKey, content: String): String {
+        return launcher.launch(content, "nip04_encrypt", publicKey.toHex())
+            ?: throw Exception("Encryption failed")
+    }
+
+    override suspend fun nip04DecryptAsync(publicKey: PublicKey, encryptedContent: String): String {
+        return launcher.launch(encryptedContent, "nip04_decrypt", publicKey.toHex())
+            ?: throw Exception("Decryption failed")
+    }
+
+    override suspend fun nip44EncryptAsync(publicKey: PublicKey, content: String): String {
+        return launcher.launch(content, "nip44_encrypt", publicKey.toHex())
+            ?: throw Exception("Encryption failed")
+    }
+
+    override suspend fun nip44DecryptAsync(publicKey: PublicKey, payload: String): String {
+        return launcher.launch(payload, "nip44_decrypt", publicKey.toHex())
+            ?: throw Exception("Decryption failed")
+    }
+}

shared/src/commonMain/kotlin/su/reya/coop/NostrViewModel.kt

@@ -372,6 +372,7 @@ class NostrViewModel(
     private suspend fun createSigner(secret: String): AsyncNostrSigner {
         return when {
             secret.startsWith("nsec1") -> Keys.parse(secret)
+
             secret.startsWith("bunker://") -> {
                 val appKeys = getOrInitAppKeys()
                 val bunker = NostrConnectUri.parse(secret)
@@ -379,6 +380,12 @@ class NostrViewModel(
                 NostrConnect(uri = bunker, appKeys, timeout, null)
             }
 
+            secret == "external" -> {
+                val launcher = ExternalSignerLauncherProvider.launcher
+                    ?: throw IllegalStateException("External signer not supported on this platform")
+                ExternalSigner(launcher)
+            }
+
             else -> throw IllegalArgumentException("Invalid secret format")
         }
     }