# AIKeyboard — HeliBoard + Gemma 4 On-Device AI Correction

HeliBoard fork that adds on-device spell and grammar correction powered by
**Gemma 4 E2B-it** running locally via Google's **LiteRT-LM** SDK.

After you finish typing a sentence (`.`, `!`, `?`), the model checks it and —
if it finds an error — shows `…` immediately, then the corrected sentence in
the suggestion strip. Tap it to replace the original text, or long-press to
dismiss. Everything runs on-device, no network, no cloud API.

---

## How it works

```text
User types "guten rag."
          ↓
InputLogic detects sentence-ending punctuation
(skipped in password / URL / e-mail fields)
          ↓
AiTriggerHook (500 ms debounce) extracts last sentence
          ↓
"…" placeholder appears in suggestion strip immediately
          ↓
AiCorrectionEngine.correctSentence()
  → LiteRT-LM Engine (GPU first, CPU fallback)
  → Gemma 4 E2B-it .litertlm model
          ↓
AiSuggestionManager.postSuggestion("Guten Tag.", "guten rag.")
          ↓
Suggestion strip shows "Guten Tag." in italic/accent color
          ↓
Tap  → original text replaced with correction
Long-press → suggestion dismissed
```

### Components

| File | Role |
| ---- | ---- |
| `app/…/ai/AiCorrectionEngine.kt` | LiteRT-LM wrapper; GPU→CPU fallback; warm-up on start |
| `app/…/ai/AiTriggerHook.kt` | Sentence detection, debounce, loading placeholder |
| `app/…/ai/AiSuggestionManager.kt` | Posts corrections and loading state to suggestion strip |
| `patches/0001-InputLogic-ai-hook.patch` | Hook in `InputLogic.java` after `commitCodePoint` |
| `patches/0002-LatinIME-ai-lifecycle.patch` | AI object lifecycle, pick intercept, memory trim |
| `patches/0003-SuggestionStrip-ai-style.patch` | Italic + accent color for AI suggestions |

---

## Requirements

- Android device with **ARM64** (arm64-v8a), Android 11+ (API 31)
- Android Studio **Ladybug** or newer / Gradle 8+
- NDK **28.0.13004108**
- **Gemma 4 E2B-it** model in `.litertlm` format (~2.6 GB)  
  Download: <https://huggingface.co/litert-community/gemma-4-E2B-it-litert-lm>

---

## Setup

### 1. Clone and prepare HeliBoard sources

```bash
git clone http://172.17.2.68:3001/nova/AIKeyboard.git
cd AIKeyboard
bash setup_heliboard.sh
```

`setup_heliboard.sh` clones HeliBoard from GitHub and applies the three AI
integration patches automatically.

### 2. Push the model to the device

```bash
adb push gemma-4-E2B-it.litertlm /data/local/tmp/gemma-4-E2B-it.litertlm
adb shell chmod 644 /data/local/tmp/gemma-4-E2B-it.litertlm
```

### 3. Build and install

```bash
./gradlew installDebug
```

Enable **AIKeyboard** as your input method in Android Settings → System →
Languages & input → On-screen keyboard.

---

## Features

### AI correction flow

- Triggers after `.` `!` `?` `…` at the end of a sentence
- 500 ms debounce prevents firing on rapid punctuation (e.g. `...`)
- `…` placeholder appears immediately so the user knows the AI is working
- Correction shown in **italic** with accent color; normal suggestions are unaffected
- Tap to accept, long-press to dismiss

### Field-type safety

AI correction is automatically skipped in:

- Password fields
- URL / URI fields
- E-mail address fields
- Web password / phonetic input fields

### Model warm-up

The Gemma 4 engine is loaded in the background as soon as the keyboard
service starts (`onCreate`), so the first correction after a sentence
appears without the initial loading delay.

### Memory management

Under critical memory pressure (`TRIM_MEMORY_RUNNING_CRITICAL`), the engine
is released automatically. It reloads on the next sentence.

### Backend selection

`AiCorrectionEngine` tries **GPU** (WebGPU/Vulkan via LiteRT-LM) first.
If GPU initialization fails, it falls back to **CPU** immediately. A runtime
GPU inference error triggers a permanent CPU switch for the session.

Tested on:

- Google Pixel 7 (Tensor G2) — CPU backend (OpenCL not available)
- Devices with Mali-G710 — GPU via WebGPU/Vulkan

---

## Patch details

The three patches modify HeliBoard source files in `heliboard/`:

**0001 — InputLogic hook**  
After every committed code point, checks `AiTriggerHook.isSentenceEnder()`.
Only fires for general text input (not password/URL/email fields). Reads up
to 500 chars before the cursor and calls `onSentenceEndDetected()`.

**0002 — LatinIME lifecycle**  
Instantiates `AiCorrectionEngine`, `AiSuggestionManager`, and `AiTriggerHook`
in `onCreate()` and triggers warm-up. Cleans up in `onDestroy()` and
`onTrimMemory()`. Overrides `showAiSuggestion()` with a `mAiSuggestionVisible`
guard that prevents `setNeutralSuggestionStrip()` from clearing an active AI
suggestion. Intercepts `pickSuggestionManually()` to handle loading placeholders
(ignore tap) and accepted corrections (delete original → commit corrected text).
Implements `dismissAiSuggestion()` for long-press dismiss.

**0003 — SuggestionStrip styling**  
Detects `KIND_AI_FLAG` (`0x10000`) for accepted corrections (italic + accent
color) and `KIND_AI_LOADING_FLAG` (`0x20000`) for the loading placeholder
(normal color, no italic, not tappable).

---

## Model placement

The model must be at `/data/local/tmp/gemma-4-E2B-it.litertlm` on the device.
This path is configured in `AiCorrectionEngine.MODEL_PATH`.

The model file is **not** tracked in this repository (2.6 GB, `.litertlm` is
in `.gitignore`).

---

## License

The AI integration layer (`app/src/main/java/helium314/keyboard/latin/ai/`)
is original work added to this project.

HeliBoard itself is licensed under **GPL-3.0-only**. See
`heliboard/LICENSE` after running `setup_heliboard.sh`.