//! Android's JNI hand-off.
//!
//! cpal's AAudio backend (and anything else built on the `ndk` crates) asks
//! the `ndk-context` crate for the JavaVM and an Android Context. Somebody has
//! to put them there; tao 0.37 does, but the tao this Tauri resolves (0.35)
//! keeps its own copy and never publishes it, so the audio thread panicked on
//! its first breath with "android context was not initialized".
//!
//! `JNI_OnLoad` runs the moment `System.loadLibrary("app_lib")` loads us,
//! before any activity exists. The Application object is reachable then
//! through `ActivityThread.currentApplication()`, which is what every
//! "give me a Context from native code" library relies on. Nothing else in
//! the tree defines `JNI_OnLoad` (checked: wry 0.55, tao 0.35), so the export
//! is ours to make.

use jni::objects::JObject;
use jni::sys::{jint, JavaVM as RawJavaVm, JNI_VERSION_1_6};
use jni::JavaVM;

#[no_mangle]
pub extern "system" fn JNI_OnLoad(vm: *mut RawJavaVm, _reserved: *mut std::ffi::c_void) -> jint {
    let Ok(jvm) = (unsafe { JavaVM::from_raw(vm) }) else {
        return JNI_VERSION_1_6;
    };
    // The loading thread is a Java thread, already attached.
    let Ok(mut env) = jvm.get_env() else {
        return JNI_VERSION_1_6;
    };
    let app: Option<JObject> = env
        .call_static_method(
            "android/app/ActivityThread",
            "currentApplication",
            "()Landroid/app/Application;",
            &[],
        )
        .and_then(|v| v.l())
        .ok()
        .filter(|o| !o.is_null());
    match app.and_then(|a| env.new_global_ref(&a).ok()) {
        Some(global) => {
            unsafe {
                ndk_context::initialize_android_context(
                    vm.cast(),
                    global.as_obj().as_raw().cast(),
                );
            }
            // The context lives as long as the process; the global ref must too.
            std::mem::forget(global);
            log::info!("android: JNI context published for the audio backend");
        }
        None => {
            eprintln!("android: could not reach ActivityThread.currentApplication(); audio output will be unavailable");
        }
    }
    JNI_VERSION_1_6
}