feat: precompute all AI tone results in parallel

Instead of computing on-tap, all 9 tones are precomputed in parallel
after a 1-second debounce when the user stops typing. Tone chips only
appear once results are ready. Tapping a chip instantly shows the
precomputed result. Text changes cancel and restart the computation.

https://claude.ai/code/session_01RbCYGrbbapRMike8WQy41F

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/creators/aihelp/AiWritingHelpPanel.kt

@@ -26,24 +26,20 @@ import androidx.compose.animation.shrinkVertically
 import androidx.compose.foundation.background
 import androidx.compose.foundation.horizontalScroll
 import androidx.compose.foundation.layout.Arrangement
-import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.foundation.verticalScroll
-import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.FilterChip
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
-import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.unit.dp
@@ -55,8 +51,8 @@ import com.vitorpamplona.amethyst.ui.stringRes
 @Composable
 fun AiWritingHelpPanel(
     isVisible: Boolean,
-    isProcessing: Boolean,
-    result: WritingResult?,
+    readyResults: Map<WritingTone, WritingResult>,
+    selectedResult: WritingResult?,
     onToneSelected: (WritingTone) -> Unit,
     onApply: () -> Unit,
     onDismiss: () -> Unit,
@@ -72,19 +68,7 @@ fun AiWritingHelpPanel(
                     .fillMaxWidth()
                     .padding(horizontal = 8.dp),
         ) {
-            if (isProcessing) {
-                Box(
-                    modifier =
-                        Modifier
-                            .fillMaxWidth()
-                            .padding(vertical = 12.dp),
-                    contentAlignment = Alignment.Center,
-                ) {
-                    CircularProgressIndicator(modifier = Modifier.size(24.dp))
-                }
-            }
-
-            result?.let {
+            selectedResult?.let {
                 AiResultCard(
                     result = it,
                     onApply = onApply,
@@ -92,7 +76,11 @@ fun AiWritingHelpPanel(
                 )
             }
 
-            ToneChipRow(onToneSelected = onToneSelected)
+            ToneChipRow(
+                readyTones = readyResults.keys,
+                selectedTone = selectedResult?.tone,
+                onToneSelected = onToneSelected,
+            )
         }
     }
 }
@@ -141,7 +129,11 @@ private fun AiResultCard(
 }
 
 @Composable
-private fun ToneChipRow(onToneSelected: (WritingTone) -> Unit) {
+private fun ToneChipRow(
+    readyTones: Set<WritingTone>,
+    selectedTone: WritingTone?,
+    onToneSelected: (WritingTone) -> Unit,
+) {
     val scrollState = rememberScrollState()
     Row(
         modifier =
@@ -152,11 +144,13 @@ private fun ToneChipRow(onToneSelected: (WritingTone) -> Unit) {
         horizontalArrangement = Arrangement.spacedBy(6.dp),
     ) {
         WritingTone.entries.forEach { tone ->
-            FilterChip(
-                selected = false,
-                onClick = { onToneSelected(tone) },
-                label = { Text(toneDisplayName(tone)) },
-            )
+            if (tone in readyTones) {
+                FilterChip(
+                    selected = tone == selectedTone,
+                    onClick = { onToneSelected(tone) },
+                    label = { Text(toneDisplayName(tone)) },
+                )
+            }
         }
     }
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/home/ShortNotePostScreen.kt

@@ -563,9 +563,9 @@ private fun NewPostScreenBody(
 
         AiWritingHelpPanel(
             isVisible = postViewModel.showAiPanel,
-            isProcessing = postViewModel.isAiProcessing,
-            result = postViewModel.aiResult,
-            onToneSelected = postViewModel::requestAiTransform,
+            readyResults = postViewModel.aiResults,
+            selectedResult = postViewModel.aiSelectedResult,
+            onToneSelected = postViewModel::selectAiResult,
             onApply = postViewModel::applyAiResult,
             onDismiss = postViewModel::dismissAiResult,
         )

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/home/ShortNotePostViewModel.kt

@@ -147,7 +147,12 @@ import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.RandomInstance
 import com.vitorpamplona.quartz.utils.TimeUtils
 import kotlinx.collections.immutable.ImmutableList
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.async
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.launch
@@ -302,17 +307,19 @@ open class ShortNotePostViewModel :
     // TODO: Remove useMockAi before shipping. Set to true to test UI without Gemini Nano.
     private val useMockAi = true
 
-    var aiResult by mutableStateOf<WritingResult?>(null)
+    var aiResults by mutableStateOf<Map<WritingTone, WritingResult>>(emptyMap())
+    var aiSelectedResult by mutableStateOf<WritingResult?>(null)
     var aiStatus by mutableStateOf<WritingAssistantStatus>(WritingAssistantStatus.Unavailable)
-    var isAiProcessing by mutableStateOf(false)
     private var writingAssistant: WritingAssistant? = null
+    private var aiComputeJob: Job? = null
+    private var lastComputedText: String = ""
 
     val showAiPanel: Boolean
         get() {
             val prefEnabled =
                 accountViewModel.settings.uiSettingsFlow.automaticallyProposeAiImprovements.value ==
                     BooleanType.ALWAYS
-            return prefEnabled && aiStatus is WritingAssistantStatus.Available
+            return prefEnabled && aiStatus is WritingAssistantStatus.Available && aiResults.isNotEmpty()
         }
 
     fun initWritingAssistant(context: android.content.Context) {
@@ -329,35 +336,61 @@ open class ShortNotePostViewModel :
         }
     }
 
-    fun requestAiTransform(tone: WritingTone) {
-        val text = message.text.toString()
-        if (text.isBlank() || isAiProcessing) return
+    fun precomputeAiResults() {
+        val assistant = writingAssistant ?: return
+        if (aiStatus !is WritingAssistantStatus.Available) return
+        val prefEnabled =
+            accountViewModel.settings.uiSettingsFlow.automaticallyProposeAiImprovements.value ==
+                BooleanType.ALWAYS
+        if (!prefEnabled) return
 
-        isAiProcessing = true
-        aiResult = null
-        viewModelScope.launch(Dispatchers.IO) {
-            try {
-                val result = writingAssistant?.transform(text, tone)
-                aiResult = result
-            } catch (e: Exception) {
-                if (e is kotlinx.coroutines.CancellationException) throw e
-                aiResult = null
-            } finally {
-                isAiProcessing = false
+        val text = message.text.toString().trim()
+        if (text.isBlank() || text == lastComputedText) return
+
+        aiComputeJob?.cancel()
+        aiResults = emptyMap()
+        aiSelectedResult = null
+
+        aiComputeJob =
+            viewModelScope.launch(Dispatchers.IO) {
+                delay(1000)
+                lastComputedText = text
+
+                coroutineScope {
+                    WritingTone.entries
+                        .map { tone ->
+                            async {
+                                try {
+                                    assistant.transform(text, tone)
+                                } catch (e: Exception) {
+                                    if (e is CancellationException) throw e
+                                    null
+                                }
+                            }
+                        }.forEach { deferred ->
+                            val result = deferred.await() ?: return@forEach
+                            aiResults = aiResults + (result.tone to result)
+                        }
+                }
             }
-        }
+    }
+
+    fun selectAiResult(tone: WritingTone) {
+        aiSelectedResult = aiResults[tone]
     }
 
     fun applyAiResult() {
-        aiResult?.let {
+        aiSelectedResult?.let {
             message.setTextAndPlaceCursorAtEnd(it.transformedText)
-            aiResult = null
+            aiSelectedResult = null
+            aiResults = emptyMap()
+            lastComputedText = ""
             draftTag.newVersion()
         }
     }
 
     fun dismissAiResult() {
-        aiResult = null
+        aiSelectedResult = null
     }
 
     fun lnAddress(): String? = account.userProfile().lnAddress()
@@ -1200,6 +1233,7 @@ open class ShortNotePostViewModel :
             emojiSuggestions?.processCurrentWord(lastWord)
         }
 
+        precomputeAiResults()
         draftTag.newVersion()
     }