arora_web/

lib.rs

//! Run an Arora device in the browser.
//!
//! The centerpiece is [`BrowserRuntime`], the reusable primitive that wires a
//! full [`arora::Runtime`] over an injected HAL, bridge, and data store and
//! exposes the JS-facing surface every browser device needs — a synchronous
//! `step()` plus Value↔JSON accessors on the store. [`AroraRuntime`] is the
//! bundled demo device built on it (in-process fakes + `SimpleDataStore`); each
//! downstream device ships its own thin `#[wasm_bindgen]` wrapper the same way.
//!
//! It also carries a lower-level surface: [`Engine`] and [`BehaviorTreeRunner`]
//! load guest modules (header JSON + executable bytes) and run behavior trees
//! directly on the engine, hosting modules via the browser's native
//! `WebAssembly` runtime — see `arora_engine::executor::browser`.
//!
//! This crate only carries non-trivial content when built for `wasm32-*`
//! targets. On the host it is an empty shim (deps are gated to `wasm32`) so it
//! can sit in the workspace and be verified by `cargo package` on publish
//! without pulling wasm-only deps into a host link.

#![cfg(target_arch = "wasm32")]

use std::cell::RefCell;
use std::collections::HashMap;
use std::pin::Pin;
use std::rc::Rc;

use arora_engine::{
    call::{CallBridge, Callable, CallableId},
    engine::EngineBuilder,
    executor::browser::{BrowserExecutor, SharedLoaderRc},
    load::load_module_from_parts,
};
use arora_types::module::low::Header;
use arora_types::{
    call::Call,
    value::{Enumeration, StructureField, StructureWithoutId, Value},
};
use uuid::Uuid;
use wasm_bindgen::prelude::*;

/// Route Rust panics to the browser console. Called from every entry point
/// (`BrowserRuntime::start`, `Engine::new`, `BehaviorTreeRunner::new`) rather
/// than from a `#[wasm_bindgen(start)]`: a reusable library must not claim the
/// module `start`, or every downstream cdylib that also defines one collides on
/// the `_start` symbol at link time. `set_once` makes repeat calls free.
fn install_panic_hook() {
    console_error_panic_hook::set_once();
}

// =============================================================================
// Browser runtime primitive
//
// `BrowserRuntime` is the reusable core for running any Arora device in the
// browser. It wires an `arora::Runtime` over an injected HAL, bridge, and data
// store (all trait objects, so the caller picks the backends), spawns the async
// io pump on the browser event loop, and exposes the JS-facing surface every
// browser device needs: a synchronous `step()` plus Value↔JSON accessors on the
// injected store.
//
// It is a plain Rust type, not a `#[wasm_bindgen]` export — the wasm-bindgen
// boundary cannot carry `Arc<dyn Trait>`. Each device ships a thin
// `#[wasm_bindgen]` cdylib that constructs its concrete HAL/bridge/store and
// behaviors, then forwards to a `BrowserRuntime` held inside. `AroraRuntime`
// below is one such wrapper (the in-process fakes); Vizij ships another.
// =============================================================================

use arora::runtime::{Runtime, StepOutcome};
use arora_behavior::Behavior;
use arora_bridge::{Bridge, FakeBridge};
use arora_hal::{FakeHal, Hal};
use arora_simple_data_store::SimpleDataStore;
use arora_types::data::{DataStore, Key, StateChange, Subscription};
use std::sync::Arc;

/// The reusable core of a browser-hosted Arora device.
///
/// Assemble it with [`BrowserRuntime::start`] over your chosen HAL, bridge, and
/// [`DataStore`]; queue one or more behaviors; then drive it a tick at a time
/// with [`step`](Self::step) (e.g. from `requestAnimationFrame` or a Web Worker
/// loop). Read and write the injected store across the JS boundary with the
/// Value↔JSON accessors — values cross as JSON in the Arora [`Value`] vocabulary,
/// e.g. `{"f32": 0.75}`.
pub struct BrowserRuntime {
    runtime: Runtime,
    store: Arc<dyn DataStore>,
    changes: Subscription,
}

impl BrowserRuntime {
    /// Boot an [`arora::Arora`] (engine + native behavior-tree nodes), inject the
    /// given `hal`, `bridge`, and `store` via [`Runtime::with_io_in`], and spawn
    /// the async io pump on the browser event loop. Queue behaviors next, then
    /// drive with [`step`](Self::step).
    pub async fn start(
        hal: Arc<dyn Hal>,
        bridge: Arc<dyn Bridge>,
        store: Arc<dyn DataStore>,
    ) -> Result<BrowserRuntime, JsValue> {
        install_panic_hook();
        let arora = arora::Arora::start()
            .await
            .map_err(|e| JsValue::from_str(&format!("arora start failed: {e:?}")))?;
        let changes = store.subscribe();
        let (runtime, io) = Runtime::with_io_in(arora, hal, bridge, store.clone());
        wasm_bindgen_futures::spawn_local(io);
        Ok(BrowserRuntime {
            runtime,
            store,
            changes,
        })
    }

    /// The injected store, for direct access beyond the JSON accessors.
    pub fn store(&self) -> &Arc<dyn DataStore> {
        &self.store
    }

    /// Queue a [`Behavior`] to run on the next step.
    pub fn queue_behavior(&mut self, behavior: Box<dyn Behavior>) {
        self.runtime.queue_behavior(behavior);
    }

    /// Queue a behavior tree (Groot XML) to run on the next step.
    pub fn queue_groot_xml(&mut self, xml: &str) -> Result<(), JsValue> {
        self.runtime
            .queue_groot_xml(xml)
            .map_err(|e| JsValue::from_str(&format!("queue failed: {e}")))
    }

    /// Advance the runtime one tick. Returns `true` while live, `false` once the
    /// device has been unregistered (stop stepping then).
    pub fn step(&mut self) -> Result<bool, JsValue> {
        match self.runtime.step() {
            Ok(StepOutcome::Live) => Ok(true),
            Ok(StepOutcome::Unregistered) => Ok(false),
            Err(e) => Err(JsValue::from_str(&format!("step failed: {e}"))),
        }
    }

    /// Write one key into the store. `value_json` is an Arora [`Value`] as JSON,
    /// e.g. `{"f32": 0.75}`.
    pub fn set_value(&self, path: &str, value_json: &str) -> Result<(), JsValue> {
        let value: Value = serde_json::from_str(value_json)
            .map_err(|e| JsValue::from_str(&format!("invalid value json for {path}: {e}")))?;
        self.store
            .write(StateChange::set(path, value))
            .map_err(|e| JsValue::from_str(&format!("write {path} failed: {e}")))
    }

    /// Write several keys at once, as one store change. `values_json` is a JSON
    /// object mapping each key path to an Arora [`Value`], e.g.
    /// `{"sensor/x": {"f32": 0.75}}`.
    pub fn write_values(&self, values_json: &str) -> Result<(), JsValue> {
        let map: serde_json::Map<String, serde_json::Value> = serde_json::from_str(values_json)
            .map_err(|e| JsValue::from_str(&format!("invalid values json: {e}")))?;
        let mut change = StateChange::new();
        for (path, raw) in map {
            let value: Value = serde_json::from_value(raw)
                .map_err(|e| JsValue::from_str(&format!("invalid value for {path}: {e}")))?;
            change.set.insert(Key::new(path), Some(value));
        }
        self.store
            .write(change)
            .map_err(|e| JsValue::from_str(&format!("write failed: {e}")))
    }

    /// Read keys from the store. `paths` is a JS `string[]`; the result is a JS
    /// object mapping each path to its Arora [`Value`] (or `null` if absent).
    pub fn read_values(&self, paths: JsValue) -> Result<JsValue, JsValue> {
        let paths: Vec<String> = serde_wasm_bindgen::from_value(paths)
            .map_err(|e| JsValue::from_str(&format!("paths must be a string[]: {e}")))?;
        let keys: Vec<Key> = paths.iter().map(Key::new).collect();
        let values = self.store.read(&keys);
        let mut out = serde_json::Map::with_capacity(paths.len());
        for (path, value) in paths.into_iter().zip(values) {
            out.insert(path, value_to_json(value)?);
        }
        serde_wasm_bindgen::to_value(&serde_json::Value::Object(out))
            .map_err(|e| JsValue::from_str(&format!("serialize failed: {e}")))
    }

    /// A snapshot of every key currently in the store, as a JS object mapping
    /// path → Arora [`Value`].
    pub fn snapshot(&self) -> Result<JsValue, JsValue> {
        let state = self.store.snapshot();
        let mut out = serde_json::Map::with_capacity(state.storage.len());
        for (key, value) in state.storage {
            out.insert(key.path, value_to_json(value)?);
        }
        serde_wasm_bindgen::to_value(&serde_json::Value::Object(out))
            .map_err(|e| JsValue::from_str(&format!("serialize failed: {e}")))
    }

    /// Drain the keys that changed in the store since the last call, as a JS
    /// object mapping path → new Arora [`Value`] (or `null` for a cleared key).
    /// Poll-based counterpart to a push subscription: [`DataStore::subscribe`]
    /// delivers over a std channel JavaScript cannot await, so changes accumulate
    /// and are handed over on demand — call it right after [`step`](Self::step).
    pub fn drain_changes(&self) -> Result<JsValue, JsValue> {
        let mut out = serde_json::Map::new();
        while let Some(change) = self.changes.try_recv() {
            for (key, value) in change.set {
                out.insert(key.path, value_to_json(value)?);
            }
            for key in change.unset {
                out.insert(key.path, serde_json::Value::Null);
            }
        }
        serde_wasm_bindgen::to_value(&serde_json::Value::Object(out))
            .map_err(|e| JsValue::from_str(&format!("serialize failed: {e}")))
    }
}

/// Serialize an optional Arora value to JSON (`null` when absent).
fn value_to_json(value: Option<Value>) -> Result<serde_json::Value, JsValue> {
    match value {
        Some(v) => serde_json::to_value(v)
            .map_err(|e| JsValue::from_str(&format!("serialize value failed: {e}"))),
        None => Ok(serde_json::Value::Null),
    }
}

// =============================================================================
// Opinionated Arora runtime (demo)
//
// A `#[wasm_bindgen]` device built on `BrowserRuntime` with the in-process fake
// HAL and bridge over a plain `SimpleDataStore`. The basic behavior-tree control
// nodes are wired natively into the engine, so no node module needs to be
// fetched or loaded. Drive it by calling `step()`.
// =============================================================================

/// JS-callable handle to a running opinionated Arora runtime.
#[wasm_bindgen]
pub struct AroraRuntime {
    inner: BrowserRuntime,
}

#[wasm_bindgen]
impl AroraRuntime {
    /// Start the runtime with an in-process fake HAL and bridge over a plain
    /// `SimpleDataStore`. Spawns the async io pump on the browser event loop;
    /// drive the runtime by calling `step()`.
    pub async fn start() -> Result<AroraRuntime, JsValue> {
        let inner = BrowserRuntime::start(
            Arc::new(FakeHal::new()),
            Arc::new(FakeBridge::new()),
            Arc::new(SimpleDataStore::new()),
        )
        .await?;
        Ok(AroraRuntime { inner })
    }

    /// Advance the runtime one step. Returns `true` while live, `false` once the
    /// device has been unregistered (stop calling then).
    pub fn step(&mut self) -> Result<bool, JsValue> {
        self.inner.step()
    }

    /// Queue a behavior tree (Groot XML) to run on the next step.
    #[wasm_bindgen(js_name = queueGrootXml)]
    pub fn queue_groot_xml(&mut self, xml: &str) -> Result<(), JsValue> {
        self.inner.queue_groot_xml(xml)
    }

    /// Write one key into the store (Arora [`Value`] as JSON, e.g. `{"f32": 1}`).
    #[wasm_bindgen(js_name = setValue)]
    pub fn set_value(&self, path: &str, value_json: &str) -> Result<(), JsValue> {
        self.inner.set_value(path, value_json)
    }

    /// Read keys from the store; `paths` is a `string[]`, result maps path→Value.
    #[wasm_bindgen(js_name = readValues)]
    pub fn read_values(&self, paths: JsValue) -> Result<JsValue, JsValue> {
        self.inner.read_values(paths)
    }

    /// A snapshot of every key in the store as a path→Value object.
    pub fn snapshot(&self) -> Result<JsValue, JsValue> {
        self.inner.snapshot()
    }
}

/// JS-callable handle to a configured Arora engine.
#[wasm_bindgen]
pub struct Engine {
    inner: std::pin::Pin<Box<arora_engine::engine::Engine>>,
    loader: SharedLoaderRc,
    function_module: HashMap<Uuid, Uuid>,
    module_headers: HashMap<Uuid, String>,
}

#[wasm_bindgen]
impl Engine {
    #[wasm_bindgen(constructor)]
    pub fn new() -> Engine {
        install_panic_hook();
        let executor = BrowserExecutor::new();
        let loader = executor.shared();
        let inner = EngineBuilder::new().add_executor(executor).build();
        Engine {
            inner,
            loader,
            function_module: HashMap::new(),
            module_headers: HashMap::new(),
        }
    }

    /// Load a module given its header (as JSON) and executable bytes.
    /// Returns the module's UUID as a string.
    ///
    /// Compiles and instantiates synchronously: Chrome rejects both above
    /// 8 MB on the main thread — use `prepareModule` + `loadPreparedModule`
    /// for large executables.
    #[wasm_bindgen(js_name = loadModule)]
    pub fn load_module(&mut self, header_json: &str, executable: &[u8]) -> Result<String, JsValue> {
        self.load_module_inner(header_json, executable.to_vec().into_boxed_slice())
    }

    /// Asynchronously compile and instantiate a module's executable
    /// (via `WebAssembly.instantiate`, no main-thread size limit).
    /// Follow up with `loadPreparedModule` to complete the load.
    #[wasm_bindgen(js_name = prepareModule)]
    pub fn prepare_module(&self, header_json: &str, executable: Vec<u8>) -> js_sys::Promise {
        prepare_module_impl(self.loader.clone(), header_json, executable)
    }

    /// Load a module whose executable was staged by `prepareModule`.
    /// Returns the module's UUID as a string.
    #[wasm_bindgen(js_name = loadPreparedModule)]
    pub fn load_prepared_module(&mut self, header_json: &str) -> Result<String, JsValue> {
        self.load_module_inner(header_json, Box::new([]))
    }

    fn load_module_inner(
        &mut self,
        header_json: &str,
        executable: Box<[u8]>,
    ) -> Result<String, JsValue> {
        let header: Header = serde_json::from_str(header_json)
            .map_err(|e| JsValue::from_str(&format!("invalid header json: {e}")))?;
        let header_json_str = header_json.to_string();
        let loaded = load_module_from_parts(&mut *self.inner, header, executable)
            .map_err(|e| JsValue::from_str(&format!("load_module failed: {e}")))?;
        for fn_id in &loaded.function_ids {
            self.function_module.insert(*fn_id, loaded.id);
        }
        self.module_headers.insert(loaded.id, header_json_str);
        Ok(loaded.id.to_string())
    }

    /// Returns a JSON array of all loaded module headers.
    #[wasm_bindgen(js_name = listModules)]
    pub fn list_modules(&self) -> String {
        let headers: Vec<serde_json::Value> = self
            .module_headers
            .values()
            .filter_map(|s| serde_json::from_str(s).ok())
            .collect();
        serde_json::to_string(&headers).unwrap_or_else(|_| "[]".to_string())
    }

    /// Call a function. `call_json` is a JSON document matching
    /// `arora_engine::call::Call`. Returns the result as a JSON string.
    #[wasm_bindgen]
    pub fn call(&mut self, call_json: &str) -> Result<String, JsValue> {
        let call: Call = serde_json::from_str(call_json)
            .map_err(|e| JsValue::from_str(&format!("invalid call json: {e}")))?;
        let module_id = if let Some(m) = call.module_id {
            m
        } else {
            *self
                .function_module
                .get(&call.id)
                .ok_or_else(|| JsValue::from_str("no module known for function"))?
        };
        let result = self
            .inner
            .arora_call(&module_id, call)
            .map_err(|e| JsValue::from_str(&format!("call failed: {e}")))?;
        serde_json::to_string(&result)
            .map_err(|e| JsValue::from_str(&format!("serialize failed: {e}")))
    }
}

impl Default for Engine {
    fn default() -> Self {
        Self::new()
    }
}

/// Shared implementation of `prepareModule`: parses the header for the
/// module id, then stages an asynchronously-instantiated module in the
/// loader. Returns a `Promise<void>`.
fn prepare_module_impl(
    loader: SharedLoaderRc,
    header_json: &str,
    executable: Vec<u8>,
) -> js_sys::Promise {
    let header: Result<Header, _> = serde_json::from_str(header_json);
    wasm_bindgen_futures::future_to_promise(async move {
        let header = header.map_err(|e| JsValue::from_str(&format!("invalid header json: {e}")))?;
        loader.prepare(header.id, executable).await?;
        Ok(JsValue::UNDEFINED)
    })
}

// =============================================================================
// Behavior-tree runner
//
// A self-contained BT runtime built directly on arora's engine primitives —
// no dependency on the arora-behavior-tree crate.
// =============================================================================

// UUID constants from arora-behavior-tree-types generated code.
// TickId struct id: 6f49e650-84ca-4899-a9bd-1f3bf17fab51
const TICK_ID_STRUCT_BYTES: [u8; 16] = [
    0x6f, 0x49, 0xe6, 0x50, 0x84, 0xca, 0x48, 0x99, 0xa9, 0xbd, 0x1f, 0x3b, 0xf1, 0x7f, 0xab, 0x51,
];
// TickId::callable_id field: 237992d2-17d1-459f-bca1-7185fa6a69d7
const TICK_ID_CALLABLE_FIELD_BYTES: [u8; 16] = [
    0x23, 0x79, 0x92, 0xd2, 0x17, 0xd1, 0x45, 0x9f, 0xbc, 0xa1, 0x71, 0x85, 0xfa, 0x6a, 0x69, 0xd7,
];
// Status::Success variant: 766e9e9a-446d-4e46-83e6-14b7ca101169
const STATUS_SUCCESS_BYTES: [u8; 16] = [
    0x76, 0x6e, 0x9e, 0x9a, 0x44, 0x6d, 0x4e, 0x46, 0x83, 0xe6, 0x14, 0xb7, 0xca, 0x10, 0x11, 0x69,
];
// Status::Failure variant: 2468f46c-bb60-425c-9a4d-9ad326ccc7e2
const STATUS_FAILURE_BYTES: [u8; 16] = [
    0x24, 0x68, 0xf4, 0x6c, 0xbb, 0x60, 0x42, 0x5c, 0x9a, 0x4d, 0x9a, 0xd3, 0x26, 0xcc, 0xc7, 0xe2,
];
// Status enum type: 325a5767-e344-4532-860e-0749bcf2e428
const STATUS_ENUM_BYTES: [u8; 16] = [
    0x32, 0x5a, 0x57, 0x67, 0xe3, 0x44, 0x45, 0x32, 0x86, 0x0e, 0x07, 0x49, 0xbc, 0xf2, 0xe4, 0x28,
];
// _ret special out-parameter: 5f726574-0000-4000-8000-000000000000 ("_ret" in ASCII)
const RET_PARAM_BYTES: [u8; 16] = [
    0x5f, 0x72, 0x65, 0x74, 0x00, 0x00, 0x40, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];

fn value_to_status(v: &Value) -> &'static str {
    if let Value::Enumeration(e) = v {
        if *e.variant_id.as_bytes() == STATUS_SUCCESS_BYTES {
            return "success";
        }
        if *e.variant_id.as_bytes() == STATUS_FAILURE_BYTES {
            return "failure";
        }
    }
    "running"
}

/// A node argument expression: either a literal value or a reference to a
/// named variable (identified by UUID).
#[derive(serde::Deserialize, Clone, Debug)]
#[serde(rename_all = "snake_case")]
enum BtExpression {
    VariableId(Uuid),
    Value(Value),
}

/// A single BT node – mirrors the arora-behavior-tree YAML schema.
#[derive(serde::Deserialize, Debug)]
struct BtNode {
    id: Uuid,
    function: Uuid,
    #[serde(default)]
    children: Option<Vec<Uuid>>,
    /// Parameter arguments: maps parameter UUID to a literal value or variable.
    /// Use the special key `5f726574-0000-4000-8000-000000000000` (_ret) to
    /// capture the return value into a variable; the node then always succeeds.
    #[serde(default)]
    arguments: HashMap<Uuid, BtExpression>,
}

/// Metadata extracted from a module header for one exported function.
struct FnMeta {
    module_id: Uuid,
    /// Parameter ID of the `children: TickId[]` argument, present only for
    /// control nodes (seq, fallback, parallel …).
    children_param_id: Option<Uuid>,
}

/// An arora Callable that wraps one BT node.
struct NodeCallable {
    node_id: Uuid,
    fn_id: Uuid,
    module_id: Uuid,
    children_param_id: Option<Uuid>,
    children_callable_ids: Vec<u64>,
    arguments: HashMap<Uuid, BtExpression>,
    variables: Rc<RefCell<HashMap<Uuid, Value>>>,
    trace: Rc<RefCell<Vec<(Uuid, &'static str)>>>,
}

impl Callable for NodeCallable {
    fn call(&self, caller: &mut dyn CallBridge) -> Result<Value, arora_engine::call::CallError> {
        let tick_id_type = Uuid::from_bytes(TICK_ID_STRUCT_BYTES);
        let callable_field = Uuid::from_bytes(TICK_ID_CALLABLE_FIELD_BYTES);
        let ret_param_id = Uuid::from_bytes(RET_PARAM_BYTES);

        let mut args = Vec::new();

        if let Some(children_param_id) = self.children_param_id {
            let elements: Vec<StructureWithoutId> = self
                .children_callable_ids
                .iter()
                .map(|&id| StructureWithoutId {
                    fields: vec![StructureField {
                        id: callable_field,
                        value: Box::new(Value::U64(id)),
                    }],
                })
                .collect();
            args.push(StructureField {
                id: children_param_id,
                value: Box::new(Value::ArrayStructure {
                    id: tick_id_type,
                    elements,
                }),
            });
        }

        for (&param_id, expr) in &self.arguments {
            if param_id == ret_param_id {
                continue;
            }
            let value = match expr {
                BtExpression::Value(v) => v.clone(),
                BtExpression::VariableId(var_id) => self
                    .variables
                    .borrow()
                    .get(var_id)
                    .cloned()
                    .unwrap_or(Value::Unit),
            };
            args.push(StructureField {
                id: param_id,
                value: Box::new(value),
            });
        }

        // Build a map of param_id -> variable_id for mutable arguments so we can
        // write mutated values back to the variable store after the call.
        let mutable_param_vars: HashMap<Uuid, Uuid> = self
            .arguments
            .iter()
            .filter_map(|(&param_id, expr)| {
                if param_id == ret_param_id {
                    return None;
                }
                if let BtExpression::VariableId(var_id) = expr {
                    Some((param_id, *var_id))
                } else {
                    None
                }
            })
            .collect();

        let result = caller.arora_call(
            &self.module_id,
            Call {
                module_id: None,
                id: self.fn_id,
                args,
            },
        )?;

        // Write back mutated parameter values to bound variables.
        for mutated in &result.mutated {
            if let Some(&var_id) = mutable_param_vars.get(&mutated.id) {
                self.variables
                    .borrow_mut()
                    .insert(var_id, *mutated.value.clone());
            }
        }

        let has_ret = self.arguments.contains_key(&ret_param_id);
        if has_ret {
            if let Some(BtExpression::VariableId(var_id)) = self.arguments.get(&ret_param_id) {
                self.variables
                    .borrow_mut()
                    .insert(*var_id, result.ret.clone());
            }
        }

        let s = if has_ret {
            "success"
        } else {
            value_to_status(&result.ret)
        };
        self.trace.borrow_mut().push((self.node_id, s));

        if has_ret {
            Ok(Value::Enumeration(Enumeration {
                id: Uuid::from_bytes(STATUS_ENUM_BYTES),
                variant_id: Uuid::from_bytes(STATUS_SUCCESS_BYTES),
                value: Box::new(Value::Unit),
            }))
        } else {
            Ok(result.ret)
        }
    }
}

/// Recursively registers callables for `node_id` and all descendants.
/// Returns the callable id of the registered root callable.
fn register_node(
    engine: &mut dyn CallBridge,
    node_id: Uuid,
    node_index: &HashMap<Uuid, BtNode>,
    fn_meta: &HashMap<Uuid, FnMeta>,
    trace: &Rc<RefCell<Vec<(Uuid, &'static str)>>>,
    variables: &Rc<RefCell<HashMap<Uuid, Value>>>,
) -> Result<u64, String> {
    let node = node_index
        .get(&node_id)
        .ok_or_else(|| format!("node {node_id} not found in tree"))?;
    let meta = fn_meta
        .get(&node.function)
        .ok_or_else(|| format!("function {} not registered in fn_meta", node.function))?;

    let children_callable_ids = match &node.children {
        None => vec![],
        Some(ids) => ids
            .iter()
            .map(|&child_id| register_node(engine, child_id, node_index, fn_meta, trace, variables))
            .collect::<Result<Vec<_>, _>>()?,
    };

    let callable: Rc<dyn Callable> = Rc::new(NodeCallable {
        node_id,
        fn_id: node.function,
        module_id: meta.module_id,
        children_param_id: meta.children_param_id,
        children_callable_ids,
        arguments: node.arguments.clone(),
        variables: variables.clone(),
        trace: trace.clone(),
    });
    let id = engine.arora_register_callable(callable);
    Ok(id.id)
}

/// JS-callable handle for loading modules and executing behavior trees.
///
/// Usage:
/// 1. `new BehaviorTreeRunner()`
/// 2. `runner.loadModule(headerJson, wasmBytes)` – can be called for multiple modules
/// 3. `runner.run(nodesJson)` – returns `{status, trace}`
/// 4. Or `runner.setVariable(varId, valueJson)` + `runner.tick(nodesJson)` for
///    stateful tick-by-tick execution with variable bindings.
#[wasm_bindgen]
pub struct BehaviorTreeRunner {
    inner: Pin<Box<arora_engine::engine::Engine>>,
    loader: SharedLoaderRc,
    fn_meta: HashMap<Uuid, FnMeta>,
    variables: Rc<RefCell<HashMap<Uuid, Value>>>,
    module_headers: HashMap<Uuid, String>,
}

#[wasm_bindgen]
impl BehaviorTreeRunner {
    #[wasm_bindgen(constructor)]
    pub fn new() -> BehaviorTreeRunner {
        install_panic_hook();
        let executor = BrowserExecutor::new();
        let loader = executor.shared();
        let inner = EngineBuilder::new().add_executor(executor).build();
        BehaviorTreeRunner {
            inner,
            loader,
            fn_meta: HashMap::new(),
            variables: Rc::new(RefCell::new(HashMap::new())),
            module_headers: HashMap::new(),
        }
    }

    /// Load a WASM module. `header_json` must be the module's YAML header
    /// converted to JSON (the JS side can use js-yaml for that).
    /// Returns the module UUID string.
    ///
    /// Compiles and instantiates synchronously: Chrome rejects both above
    /// 8 MB on the main thread — use `prepareModule` + `loadPreparedModule`
    /// for large executables.
    #[wasm_bindgen(js_name = loadModule)]
    pub fn load_module(&mut self, header_json: &str, executable: &[u8]) -> Result<String, JsValue> {
        self.load_module_inner(header_json, executable.to_vec().into_boxed_slice())
    }

    /// Asynchronously compile and instantiate a module's executable
    /// (via `WebAssembly.instantiate`, no main-thread size limit).
    /// Follow up with `loadPreparedModule` to complete the load.
    #[wasm_bindgen(js_name = prepareModule)]
    pub fn prepare_module(&self, header_json: &str, executable: Vec<u8>) -> js_sys::Promise {
        prepare_module_impl(self.loader.clone(), header_json, executable)
    }

    /// Load a module whose executable was staged by `prepareModule`.
    /// Returns the module UUID string.
    #[wasm_bindgen(js_name = loadPreparedModule)]
    pub fn load_prepared_module(&mut self, header_json: &str) -> Result<String, JsValue> {
        self.load_module_inner(header_json, Box::new([]))
    }

    fn load_module_inner(
        &mut self,
        header_json: &str,
        executable: Box<[u8]>,
    ) -> Result<String, JsValue> {
        let header: Header = serde_json::from_str(header_json)
            .map_err(|e| JsValue::from_str(&format!("invalid header: {e}")))?;
        let module_id = header.id;
        let header_json_str = header_json.to_string();

        for export in &header.exports {
            let arora_types::module::low::ExportSymbol::Function(f) = export;
            let children_param_id = f.parameters.first().and_then(|p| {
                if let arora_types::module::low::TypeRef::Array { id } = &p.ty {
                    if id == &Uuid::from_bytes(TICK_ID_STRUCT_BYTES) {
                        Some(p.id)
                    } else {
                        None
                    }
                } else {
                    None
                }
            });

            self.fn_meta.insert(
                f.id,
                FnMeta {
                    module_id,
                    children_param_id,
                },
            );
        }

        let result = load_module_from_parts(&mut *self.inner, header, executable)
            .map_err(|e| JsValue::from_str(&format!("load failed: {e}")))?;
        self.module_headers.insert(result.id, header_json_str);
        Ok(result.id.to_string())
    }

    /// Returns a JSON array of all loaded module headers.
    #[wasm_bindgen(js_name = listModules)]
    pub fn list_modules(&self) -> String {
        let headers: Vec<serde_json::Value> = self
            .module_headers
            .values()
            .filter_map(|s| serde_json::from_str(s).ok())
            .collect();
        serde_json::to_string(&headers).unwrap_or_else(|_| "[]".to_string())
    }

    /// Initialize or update a variable. `var_id` is a UUID string; `value_json`
    /// is the serialized `Value` (e.g. `{"f32": 0.0}`).
    #[wasm_bindgen(js_name = setVariable)]
    pub fn set_variable(&mut self, var_id: &str, value_json: &str) -> Result<(), JsValue> {
        let var_id: Uuid = var_id
            .parse()
            .map_err(|_| JsValue::from_str("bad var_id: not a valid UUID"))?;
        let value: Value = serde_json::from_str(value_json)
            .map_err(|e| JsValue::from_str(&format!("bad value JSON: {e}")))?;
        self.variables.borrow_mut().insert(var_id, value);
        Ok(())
    }

    /// Run one tick of the behavior tree. Variables persist across calls.
    ///
    /// `nodes_json` is a JSON array where each element is:
    ///   `{ id, function, children?, arguments?, return_binding? }`
    ///
    /// Returns: `{ "status": "...", "trace": [...], "variables": { varId: value } }`
    pub fn tick(&mut self, nodes_json: &str) -> Result<String, JsValue> {
        let nodes: Vec<BtNode> = serde_json::from_str(nodes_json)
            .map_err(|e| JsValue::from_str(&format!("bad nodes JSON: {e}")))?;
        if nodes.is_empty() {
            return Err(JsValue::from_str("tree has no nodes"));
        }

        let root_id = nodes[0].id;
        let node_index: HashMap<Uuid, BtNode> = nodes.into_iter().map(|n| (n.id, n)).collect();
        let trace: Rc<RefCell<Vec<(Uuid, &'static str)>>> = Rc::new(RefCell::new(Vec::new()));

        let fn_meta = &self.fn_meta;
        let root_callable_id = register_node(
            &mut *self.inner,
            root_id,
            &node_index,
            fn_meta,
            &trace,
            &self.variables,
        )
        .map_err(|e| JsValue::from_str(&format!("setup error: {e}")))?;

        let callable_id = CallableId {
            id: root_callable_id,
        };
        let result = Callable::call(&callable_id, &mut *self.inner)
            .map_err(|e| JsValue::from_str(&format!("tick error: {e}")))?;
        let status = value_to_status(&result);

        let trace_json: Vec<serde_json::Value> = trace
            .borrow()
            .iter()
            .map(|(id, s)| serde_json::json!({ "nodeId": id.to_string(), "status": s }))
            .collect();

        let vars_json: serde_json::Map<String, serde_json::Value> = self
            .variables
            .borrow()
            .iter()
            .filter_map(|(id, v)| serde_json::to_value(v).ok().map(|jv| (id.to_string(), jv)))
            .collect();

        Ok(serde_json::json!({
          "status": status,
          "trace": trace_json,
          "variables": vars_json,
        })
        .to_string())
    }

    /// Run a behavior tree to completion (ticks until not Running).
    ///
    /// `nodes_json` is a JSON array where each element is:
    ///   `{ id: "<uuid>", function: "<uuid>", children?: ["<uuid>", ...] }`
    /// The first element is the root node.
    ///
    /// Returns a JSON string:
    ///   `{ "status": "success"|"failure"|"running",
    ///      "trace": [{"nodeId": "<uuid>", "status": "..."}] }`
    pub fn run(&mut self, nodes_json: &str) -> Result<String, JsValue> {
        let nodes: Vec<BtNode> = serde_json::from_str(nodes_json)
            .map_err(|e| JsValue::from_str(&format!("bad nodes JSON: {e}")))?;
        if nodes.is_empty() {
            return Err(JsValue::from_str("tree has no nodes"));
        }

        let root_id = nodes[0].id;
        let node_index: HashMap<Uuid, BtNode> = nodes.into_iter().map(|n| (n.id, n)).collect();
        let trace: Rc<RefCell<Vec<(Uuid, &'static str)>>> = Rc::new(RefCell::new(Vec::new()));

        let fn_meta = &self.fn_meta;
        let root_callable_id = register_node(
            &mut *self.inner,
            root_id,
            &node_index,
            fn_meta,
            &trace,
            &self.variables,
        )
        .map_err(|e| JsValue::from_str(&format!("setup error: {e}")))?;

        let callable_id = CallableId {
            id: root_callable_id,
        };

        let mut last_status = "running";
        for _ in 0..10_000 {
            let result = Callable::call(&callable_id, &mut *self.inner)
                .map_err(|e| JsValue::from_str(&format!("tick error: {e}")))?;
            last_status = value_to_status(&result);
            if last_status != "running" {
                break;
            }
        }

        let trace_json: Vec<serde_json::Value> = trace
            .borrow()
            .iter()
            .map(|(id, s)| serde_json::json!({ "nodeId": id.to_string(), "status": s }))
            .collect();

        let out = serde_json::json!({
          "status": last_status,
          "trace": trace_json,
        });
        Ok(out.to_string())
    }
}

impl Default for BehaviorTreeRunner {
    fn default() -> Self {
        Self::new()
    }
}

// =============================================================================
// Type registry
//
// A minimal wasm-compatible registry for resolving type UUIDs to names.
// Loads from the records.json files emitted by arora-module-rust::generate_records.
// =============================================================================

/// JS-callable type registry that resolves type UUIDs to human-readable names.
#[wasm_bindgen]
pub struct Registry {
    entries: HashMap<Uuid, (String, Option<Uuid>)>,
}

#[derive(serde::Deserialize)]
struct RecordEntry {
    id: Uuid,
    name: String,
    parent: Option<Uuid>,
}

#[wasm_bindgen]
impl Registry {
    #[wasm_bindgen(constructor)]
    pub fn new() -> Registry {
        Registry {
            entries: HashMap::new(),
        }
    }

    /// Load type records from a JSON array: `[{id, name, parent?}, ...]`.
    #[wasm_bindgen(js_name = loadRecordsJson)]
    pub fn load_records_json(&mut self, json: &str) -> Result<(), JsValue> {
        let records: Vec<RecordEntry> = serde_json::from_str(json)
            .map_err(|e| JsValue::from_str(&format!("invalid records JSON: {e}")))?;
        for r in records {
            self.entries.insert(r.id, (r.name, r.parent));
        }
        Ok(())
    }

    /// Resolve a UUID string to a dot-separated name path (e.g. `"behavior_tree.Status"`).
    /// Returns `None` if the UUID is not known.
    #[wasm_bindgen(js_name = resolveId)]
    pub fn resolve_id(&self, id: &str) -> Option<String> {
        let uuid: Uuid = id.parse().ok()?;
        self.compute_path(&uuid)
    }

    fn compute_path(&self, id: &Uuid) -> Option<String> {
        let (name, parent) = self.entries.get(id)?;
        match parent {
            None => Some(name.clone()),
            Some(parent_id) if !self.entries.contains_key(parent_id) => Some(name.clone()),
            Some(parent_id) => Some(format!("{}.{}", self.compute_path(parent_id)?, name)),
        }
    }
}

impl Default for Registry {
    fn default() -> Self {
        Self::new()
    }
}