Add FFI JNI JSON RPC bridge (#2326)

* Add FFI JNI JSON RPC bridge
* Add FFI instance list API

easytier-contrib/easytier-android-jni/src/json_rpc_api.rs

@@ -0,0 +1,91 @@
+use std::{
+    ffi::{CStr, c_char},
+    ptr,
+};
+
+use easytier_ffi::{call_json_rpc, free_string};
+use jni::JNIEnv;
+use jni::objects::{JClass, JString};
+use jni::sys::jstring;
+
+use crate::{
+    error::{get_last_error, throw_exception},
+    strings::{jstring_to_cstring, optional_jstring_to_cstring},
+};
+
+pub(crate) fn call_json_rpc_jni(
+    mut env: JNIEnv,
+    _class: JClass,
+    service_name: JString,
+    method_name: JString,
+    domain_name: JString,
+    payload_json: JString,
+) -> jstring {
+    let service_name_cstr = match jstring_to_cstring(&mut env, &service_name) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid service name: {}", e));
+            return ptr::null_mut();
+        }
+    };
+    let method_name_cstr = match jstring_to_cstring(&mut env, &method_name) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid method name: {}", e));
+            return ptr::null_mut();
+        }
+    };
+    let domain_name_cstr = match optional_jstring_to_cstring(&mut env, &domain_name) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid domain name: {}", e));
+            return ptr::null_mut();
+        }
+    };
+    let payload_json_cstr = match jstring_to_cstring(&mut env, &payload_json) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid payload JSON: {}", e));
+            return ptr::null_mut();
+        }
+    };
+
+    let domain_name_ptr = domain_name_cstr
+        .as_ref()
+        .map_or(ptr::null(), |cstr| cstr.as_ptr());
+    let mut response_ptr: *const c_char = ptr::null();
+    let result = unsafe {
+        call_json_rpc(
+            service_name_cstr.as_ptr(),
+            method_name_cstr.as_ptr(),
+            domain_name_ptr,
+            payload_json_cstr.as_ptr(),
+            &mut response_ptr,
+        )
+    };
+
+    if result != 0 {
+        if let Some(error) = get_last_error() {
+            throw_exception(&mut env, &error);
+        }
+        return ptr::null_mut();
+    }
+
+    if response_ptr.is_null() {
+        throw_exception(&mut env, "JSON RPC returned a null response");
+        return ptr::null_mut();
+    }
+
+    let response = unsafe { CStr::from_ptr(response_ptr) }
+        .to_string_lossy()
+        .into_owned();
+    free_string(response_ptr);
+
+    match env.new_string(&response) {
+        Ok(jstr) => jstr.into_raw(),
+        Err(_) => {
+            throw_exception(&mut env, "Failed to create JSON RPC response string");
+            ptr::null_mut()
+        }
+    }
+}