punktfunk/crates/punktfunk-android/src/lib.rs

//! punktfunk Android client — the JNI bridge ("nativecore") over `punktfunk-core`.
//!
//! Architecture: the **Rust-heavy** client model (like `punktfunk-client-linux`, *not* the
//! thin-native-over-C-ABI Apple model). This `cdylib` links `punktfunk-core` directly and drives
//! the whole `punktfunk/1` protocol through [`punktfunk_core::client::NativeClient`]; Kotlin owns
//! only the Android-framework surface (Compose UI, `SurfaceView` lifecycle, input capture,
//! `NsdManager` discovery, Keystore). The JNI seam below is the one place the two languages meet.
//!
//! Why Rust-heavy: Kotlin cannot `import` the cbindgen C header the way Swift can, so a native
//! bridge is unavoidable. Writing it in Rust lets the Android client reuse the Linux client's
//! orchestration verbatim — audio jitter ring, the VK keymap inverse, latency/skew math, the
//! input capture state machine, trust/pairing logic — instead of re-porting it into Kotlin.
//!
//! JNI symbols map to `io.unom.punktfunk.kit.NativeBridge` in the `:kit` Gradle module
//! (`clients/android`). The current surface is the scaffold's native-link proof
//! (`abiVersion`/`coreVersion`) plus the session handle lifecycle in [`session`]; the per-plane
//! pumps (video → AMediaCodec, audio → Oboe), input, audio, pairing and mode renegotiation are
//! the next milestone (see the TODOs in [`session`]).

use jni::objects::JObject;
use jni::sys::jint;
use jni::JNIEnv;

mod session;

/// Initialize `android_logger` once when the JVM loads the library. Logs land in logcat under the
/// `punktfunk` tag. Android-only — there is no JVM (and no logcat) on the host build.
#[cfg(target_os = "android")]
#[no_mangle]
pub extern "system" fn JNI_OnLoad(
    _vm: *mut jni::sys::JavaVM,
    _reserved: *mut std::ffi::c_void,
) -> jint {
    android_logger::init_once(
        android_logger::Config::default()
            .with_max_level(log::LevelFilter::Info)
            .with_tag("punktfunk"),
    );
    log::info!(
        "punktfunk_android loaded (core ABI v{})",
        punktfunk_core::ABI_VERSION
    );
    jni::sys::JNI_VERSION_1_6
}

/// `NativeBridge.abiVersion(): Int` — the core's C-ABI version. A non-error return is the
/// scaffold's proof that `System.loadLibrary` found the `.so`, the JNI symbol resolved, and the
/// linked `punktfunk-core` is the one we expect.
#[no_mangle]
pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_abiVersion(
    _env: JNIEnv,
    _this: JObject,
) -> jint {
    punktfunk_core::ABI_VERSION as jint
}

/// `NativeBridge.coreVersion(): String` — the crate version, proving JNI string marshaling works.
#[no_mangle]
pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_coreVersion<'local>(
    env: JNIEnv<'local>,
    _this: JObject<'local>,
) -> jni::sys::jstring {
    match env.new_string(env!("CARGO_PKG_VERSION")) {
        Ok(s) => s.into_raw(),
        Err(_) => JObject::null().into_raw(),
    }
}