feat(chats): right-click context menu on encrypted files — download + forward

Right-click on encrypted file attachments in DMs now shows a context menu:
- "Save to disk" — decrypts and saves via native file dialog
- "Forward" — placeholder callback for forwarding to another conversation

Also caches decrypted bytes (not just image bitmap) so save doesn't
re-download. Non-image files also get decrypted on load for save support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/chats/ChatFileAttachment.kt

@@ -20,6 +20,8 @@
  */
 package com.vitorpamplona.amethyst.desktop.ui.chats
 
+import androidx.compose.foundation.gestures.detectTapGestures
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
@@ -31,11 +33,15 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Download
+import androidx.compose.material.icons.filled.Forward
 import androidx.compose.material.icons.filled.InsertDriveFile
 import androidx.compose.material.icons.filled.Lock
 import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
 import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
@@ -44,23 +50,31 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.ImageBitmap
 import androidx.compose.ui.graphics.toComposeImageBitmap
+import androidx.compose.ui.input.pointer.isSecondaryPressed
+import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.desktop.service.media.EncryptedMediaService
 import com.vitorpamplona.quartz.nip17Dm.files.ChatMessageEncryptedFileHeaderEvent
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
+import java.awt.FileDialog
+import java.awt.Frame
+import java.io.File
 import org.jetbrains.skia.Image as SkiaImage
 
 @Composable
 fun ChatFileAttachment(
     event: ChatMessageEncryptedFileHeaderEvent,
+    onForward: ((ChatMessageEncryptedFileHeaderEvent) -> Unit)? = null,
     modifier: Modifier = Modifier,
 ) {
     val url = event.url()
@@ -68,20 +82,26 @@ fun ChatFileAttachment(
     val keyBytes = event.key()
     val nonce = event.nonce()
     val isImage = mimeType?.startsWith("image/") == true
+    val scope = rememberCoroutineScope()
 
     var decryptedImage by remember { mutableStateOf<ImageBitmap?>(null) }
+    var decryptedBytes by remember { mutableStateOf<ByteArray?>(null) }
     var isLoading by remember { mutableStateOf(false) }
     var error by remember { mutableStateOf<String?>(null) }
+    var showContextMenu by remember { mutableStateOf(false) }
 
     // Auto-decrypt images
     LaunchedEffect(url) {
-        if (isImage && keyBytes != null && nonce != null) {
+        if (keyBytes != null && nonce != null && url != null) {
             isLoading = true
             try {
                 val bytes = EncryptedMediaService.downloadAndDecrypt(url, keyBytes, nonce)
-                withContext(Dispatchers.Default) {
-                    val skImage = SkiaImage.makeFromEncoded(bytes)
-                    decryptedImage = skImage.toComposeImageBitmap()
+                decryptedBytes = bytes
+                if (isImage) {
+                    withContext(Dispatchers.Default) {
+                        val skImage = SkiaImage.makeFromEncoded(bytes)
+                        decryptedImage = skImage.toComposeImageBitmap()
+                    }
                 }
             } catch (e: Exception) {
                 error = e.message
@@ -91,85 +111,184 @@ fun ChatFileAttachment(
         }
     }
 
-    Card(
-        modifier = modifier.fillMaxWidth(),
-        colors =
-            CardDefaults.cardColors(
-                containerColor = MaterialTheme.colorScheme.surfaceContainerHigh,
-            ),
-    ) {
-        Column(modifier = Modifier.padding(8.dp)) {
-            // Encryption indicator
-            Row(verticalAlignment = Alignment.CenterVertically) {
-                Icon(
-                    Icons.Default.Lock,
-                    contentDescription = "Encrypted",
-                    modifier = Modifier.size(14.dp),
-                    tint = MaterialTheme.colorScheme.primary,
-                )
-                Spacer(Modifier.width(4.dp))
-                Text(
-                    "Encrypted file",
-                    style = MaterialTheme.typography.labelSmall,
-                    color = MaterialTheme.colorScheme.primary,
-                )
-            }
-
-            Spacer(Modifier.height(4.dp))
-
-            when {
-                isLoading -> {
-                    CircularProgressIndicator(
-                        modifier = Modifier.size(24.dp).align(Alignment.CenterHorizontally),
-                    )
-                }
-
-                decryptedImage != null -> {
-                    androidx.compose.foundation.Image(
-                        bitmap = decryptedImage!!,
-                        contentDescription = "Encrypted image",
-                        modifier =
-                            Modifier
-                                .fillMaxWidth()
-                                .heightIn(max = 300.dp)
-                                .clip(RoundedCornerShape(8.dp)),
-                        contentScale = ContentScale.FillWidth,
-                    )
-                }
-
-                error != null -> {
-                    Text(
-                        "Failed to decrypt: $error",
-                        style = MaterialTheme.typography.bodySmall,
-                        color = MaterialTheme.colorScheme.error,
-                    )
-                }
-
-                else -> {
-                    // Non-image file
-                    Row(verticalAlignment = Alignment.CenterVertically) {
-                        Icon(
-                            Icons.Default.InsertDriveFile,
-                            contentDescription = "File",
-                            modifier = Modifier.size(32.dp),
+    Box {
+        Card(
+            modifier =
+                modifier
+                    .fillMaxWidth()
+                    .pointerInput(Unit) {
+                        detectTapGestures(
+                            onPress = {
+                                // Right-click detection handled via awaiting press
+                                // Context menu is shown on secondary button via the other modifier
+                            },
                         )
-                        Spacer(Modifier.width(8.dp))
-                        Column {
-                            Text(
-                                mimeType ?: "Unknown file",
-                                style = MaterialTheme.typography.bodySmall,
+                    }.pointerInput(Unit) {
+                        awaitPointerEventScope {
+                            while (true) {
+                                val event = awaitPointerEvent()
+                                if (event.buttons.isSecondaryPressed &&
+                                    event.changes.any { it.pressed && !it.previousPressed }
+                                ) {
+                                    showContextMenu = true
+                                }
+                            }
+                        }
+                    },
+            colors =
+                CardDefaults.cardColors(
+                    containerColor = MaterialTheme.colorScheme.surfaceContainerHigh,
+                ),
+        ) {
+            Column(modifier = Modifier.padding(8.dp)) {
+                // Encryption indicator
+                Row(verticalAlignment = Alignment.CenterVertically) {
+                    Icon(
+                        Icons.Default.Lock,
+                        contentDescription = "Encrypted",
+                        modifier = Modifier.size(14.dp),
+                        tint = MaterialTheme.colorScheme.primary,
+                    )
+                    Spacer(Modifier.width(4.dp))
+                    Text(
+                        "Encrypted file",
+                        style = MaterialTheme.typography.labelSmall,
+                        color = MaterialTheme.colorScheme.primary,
+                    )
+                }
+
+                Spacer(Modifier.height(4.dp))
+
+                when {
+                    isLoading -> {
+                        CircularProgressIndicator(
+                            modifier = Modifier.size(24.dp).align(Alignment.CenterHorizontally),
+                        )
+                    }
+
+                    decryptedImage != null -> {
+                        androidx.compose.foundation.Image(
+                            bitmap = decryptedImage!!,
+                            contentDescription = "Encrypted image",
+                            modifier =
+                                Modifier
+                                    .fillMaxWidth()
+                                    .heightIn(max = 300.dp)
+                                    .clip(RoundedCornerShape(8.dp)),
+                            contentScale = ContentScale.FillWidth,
+                        )
+                    }
+
+                    error != null -> {
+                        Text(
+                            "Failed to decrypt: $error",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.error,
+                        )
+                    }
+
+                    else -> {
+                        // Non-image file
+                        Row(verticalAlignment = Alignment.CenterVertically) {
+                            Icon(
+                                Icons.Default.InsertDriveFile,
+                                contentDescription = "File",
+                                modifier = Modifier.size(32.dp),
                             )
-                            event.size()?.let { size ->
+                            Spacer(Modifier.width(8.dp))
+                            Column {
                                 Text(
-                                    "${size / 1024}KB",
-                                    style = MaterialTheme.typography.labelSmall,
-                                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                                    mimeType ?: "Unknown file",
+                                    style = MaterialTheme.typography.bodySmall,
                                 )
+                                event.size()?.let { size ->
+                                    Text(
+                                        "${size / 1024}KB",
+                                        style = MaterialTheme.typography.labelSmall,
+                                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                                    )
+                                }
                             }
                         }
                     }
                 }
             }
         }
+
+        // Right-click context menu
+        DropdownMenu(
+            expanded = showContextMenu,
+            onDismissRequest = { showContextMenu = false },
+        ) {
+            DropdownMenuItem(
+                text = { Text("Save to disk") },
+                leadingIcon = {
+                    Icon(Icons.Default.Download, contentDescription = null, modifier = Modifier.size(18.dp))
+                },
+                enabled = decryptedBytes != null,
+                onClick = {
+                    showContextMenu = false
+                    scope.launch {
+                        saveDecryptedFile(decryptedBytes!!, mimeType, event.hash())
+                    }
+                },
+            )
+            if (onForward != null) {
+                DropdownMenuItem(
+                    text = { Text("Forward") },
+                    leadingIcon = {
+                        Icon(Icons.Default.Forward, contentDescription = null, modifier = Modifier.size(18.dp))
+                    },
+                    onClick = {
+                        showContextMenu = false
+                        onForward(event)
+                    },
+                )
+            }
+        }
     }
 }
+
+/**
+ * Save decrypted bytes to disk via a native save dialog.
+ */
+private suspend fun saveDecryptedFile(
+    bytes: ByteArray,
+    mimeType: String?,
+    hash: String?,
+) {
+    val extension = mimeTypeToExtension(mimeType)
+    val suggestedName = "${hash?.take(12) ?: "file"}.$extension"
+
+    val file =
+        withContext(Dispatchers.Main) {
+            val dialog =
+                FileDialog(null as Frame?, "Save Decrypted File", FileDialog.SAVE).apply {
+                    this.file = suggestedName
+                }
+            dialog.isVisible = true
+            val dir = dialog.directory ?: return@withContext null
+            File(dir, dialog.file ?: return@withContext null)
+        } ?: return
+
+    withContext(Dispatchers.IO) {
+        file.writeBytes(bytes)
+    }
+}
+
+private fun mimeTypeToExtension(mimeType: String?): String =
+    when (mimeType) {
+        "image/jpeg" -> "jpg"
+        "image/png" -> "png"
+        "image/gif" -> "gif"
+        "image/webp" -> "webp"
+        "image/svg+xml" -> "svg"
+        "video/mp4" -> "mp4"
+        "video/webm" -> "webm"
+        "video/quicktime" -> "mov"
+        "audio/mpeg" -> "mp3"
+        "audio/ogg" -> "ogg"
+        "audio/wav" -> "wav"
+        "audio/flac" -> "flac"
+        else -> "bin"
+    }