# Pacer

A native Android pacing/metronome app that plays 880 Hz beeps at a user-set BPM to maintain
walking pace. Runs in the background for 2+ hour walks without draining battery. Plays
alongside other audio apps (podcasts, music) without requesting audio focus.

Ported from the web version at https://jeena.net/pacer/

## Building on Arch Linux

### 1. Install Java 17

```bash
sudo pacman -S jdk17-openjdk
```

Set `JAVA_HOME` (add to `~/.bashrc` or `~/.zshrc`):

```bash
export JAVA_HOME=/usr/lib/jvm/java-17-openjdk
export PATH="$JAVA_HOME/bin:$PATH"
```

Verify: `java -version` should show `openjdk version "17.x.x"`.

### 2. Install Android SDK via AUR

```bash
# Remove old package if previously installed (it leaves files behind — clean them up too)
sudo pacman -Rns android-sdk
sudo rm -rf /opt/android-sdk/platform-tools /opt/android-sdk/tools

# Install modern SDK tools
paru -S android-sdk-cmdline-tools-latest android-sdk-platform-tools android-sdk-build-tools android-platform
```

The packages install to `/opt/android-sdk`. Add to `~/.bashrc` or `~/.zshrc`:

```bash
export ANDROID_HOME=/opt/android-sdk
export PATH="$ANDROID_HOME/cmdline-tools/latest/bin:$ANDROID_HOME/platform-tools:$PATH"
```

Reload: `source ~/.bashrc`

### 3. Accept SDK Licenses

```bash
sudo /opt/android-sdk/cmdline-tools/latest/bin/sdkmanager --licenses
```

### 4. Bootstrap the Gradle Wrapper

The first time only, install system Gradle to generate the wrapper binary:

```bash
sudo pacman -S gradle
cd /path/to/Pacer
gradle wrapper --gradle-version 8.7 --distribution-type bin
sudo pacman -Rs gradle  # optional: remove system gradle afterwards
```

### 5. Build

```bash
./gradlew assembleDebug
```

The debug APK will be at: `app/build/outputs/apk/debug/app-debug.apk`

### 6. Install on a Device

Enable USB debugging (Settings > Developer Options > USB Debugging), connect via USB, then:

```bash
./gradlew installDebug
# or
adb install app/build/outputs/apk/debug/app-debug.apk
```

## Troubleshooting

**`ANDROID_HOME not set`** — Reload your shell profile or open a new terminal.

**`License for package ... not accepted`** — Run `sudo /opt/android-sdk/cmdline-tools/latest/bin/sdkmanager --licenses`.

**`Unsupported class file major version`** — Wrong Java version. Confirm `java -version` shows
17 and `JAVA_HOME` points to `/usr/lib/jvm/java-17-openjdk`.

**`Permission denied` on `/opt/android-sdk`** — Run sdkmanager with `sudo`.

**`Failed to install build-tools;34.0.0 ... SDK directory is not writable`** — AGP tried to
auto-download build-tools instead of using the installed version. Ensure `buildToolsVersion = "36.1.0"`
is set in `app/build.gradle.kts`.

## Development

See `AGENTS.md` for the developer/agent workflow guide.
See `BACKLOG.md` for all user stories and acceptance criteria.

```bash
./gradlew test    # unit tests
./gradlew lint    # lint checks
```