index.mjs

const NAPI_OK = 0;
const NAPI_INVALID_ARG = 1;
const NAPI_STRING_EXPECTED = 3;
const NAPI_NUMBER_EXPECTED = 6;
const NAPI_BOOLEAN_EXPECTED = 7;
const NAPI_GENERIC_FAILURE = 9;
const NAPI_PENDING_EXCEPTION = 10;
const NAPI_CANCELED = 11;
const NAPI_HANDLE_SCOPE_MISMATCH = 13;
const NAPI_BIGINT_EXPECTED = 17;
const NAPI_NO_EXTERNAL_BUFFERS_ALLOWED = 22;

// https://nodejs.org/api/n-api.html#napi_property_attributes
const NAPI_WRITABLE = 1 << 0;
const NAPI_ENUMERABLE = 1 << 1;
const NAPI_CONFIGURABLE = 1 << 2;
const NAPI_STATIC = 1 << 10;

// https://nodejs.org/api/n-api.html#napi_typedarray_type
const typedArrays = [
  Int8Array,
  Uint8Array,
  Uint8ClampedArray,
  Int16Array,
  Uint16Array,
  Int32Array,
  Uint32Array,
  Float32Array,
  Float64Array,
  BigInt64Array,
  BigUint64Array
];

const environments = [];

export class Environment {
  scopes = [];
  referenceId = 1;
  references = new Map();
  deferred = [null];
  wrappedObjects = new WeakMap();
  externalObjects = new WeakMap();
  buffers = new Map();
  instanceData = 0;
  pendingException = null;

  constructor(instance) {
    this.id = environments.length;
    environments.push(this);

    this.instance = instance;
    this.table = instance.exports.__indirect_function_table;
    this.exports = {};

    this.pushScope();
    let values = this.scopes[this.scopes.length - 1];
    let exports = values.length;
    values.push(this.exports);

    try {
      if (this.instance.exports.napi_register_module_v1) {
        this.instance.exports.napi_register_module_v1(this.id, exports);
      }

      if (this.instance.exports.napi_register_wasm_v1) {
        this.instance.exports.napi_register_wasm_v1(this.id, exports);
      }
    } finally {
      this.popScope();
      if (this.pendingException) {
        let e = this.pendingException;
        this.pendingException = null;
        throw e;
      }
    }
  }

  destroy() {
    environments[this.id] = undefined;
  }

  getString(ptr, len = strlen(this.memory, ptr)) {
    return decoder.decode(this.memory.subarray(ptr, Math.max(0, ptr + len)));
  }

  pushScope() {
    let id = this.scopes.length;
    this.scopes.push(id ? [...this.scopes[id - 1]] : [undefined, null, globalThis, true, false]);
    return id;
  }

  popScope() {
    this.scopes.pop();

    // Update any buffers with values which might have been modified in WASM copy.
    for (let [buffer, slice] of this.buffers) {
      // Ignore if buffer or slice has been detached.
      if (buffer.byteLength && slice.byteLength) {
        buffer.set(slice);
      }
    }

    this.buffers.clear();
  }

  get(idx) {
    return this.scopes[this.scopes.length - 1][idx];
  }

  set(idx, value) {
    this.scopes[this.scopes.length - 1][idx] = value;
  }

  pushValue(value, scope = this.scopes.length - 1) {
    let values = this.scopes[scope];
    let id = values.length;
    values.push(value);
    return id;
  }

  createValue(value, result, scope) {
    if (typeof value === 'boolean') {
      this.setPointer(result, value ? 3 : 4);
      return NAPI_OK;
    } else if (typeof value === 'undefined') {
      this.setPointer(result, 0);
      return NAPI_OK;
    } else if (value === null) {
      this.setPointer(result, 1);
      return NAPI_OK;
    } else if (value === globalThis) {
      this.setPointer(result, 2);
      return NAPI_OK;
    }

    let id = this.pushValue(value, scope);
    this.setPointer(result, id);
    return NAPI_OK;
  }

  setPointer(ptr, value) {
    this.u32[ptr >> 2] = value;
    return NAPI_OK;
  }

  _u32 = new Uint32Array();
  get u32() {
    if (this._u32.byteLength === 0) {
      this._u32 = new Uint32Array(this.instance.exports.memory.buffer);
    }

    return this._u32;
  }

  _i32 = new Int32Array();
  get i32() {
    if (this._i32.byteLength === 0) {
      this._i32 = new Int32Array(this.instance.exports.memory.buffer);
    }

    return this._i32;
  }

  _u16 = new Uint16Array();
  get u16() {
    if (this._u16.byteLength === 0) {
      this._u16 = new Uint16Array(this.instance.exports.memory.buffer);
    }

    return this._u16;
  }

  _u64 = new BigUint64Array();
  get u64() {
    if (this._u64.byteLength === 0) {
      this._u64 = new BigUint64Array(this.instance.exports.memory.buffer);
    }

    return this._u64;
  }

  _i64 = new BigInt64Array();
  get i64() {
    if (this._i64.byteLength === 0) {
      this._i64 = new BigInt64Array(this.instance.exports.memory.buffer);
    }

    return this._i64;
  }

  _f64 = new Float64Array();
  get f64() {
    if (this._f64.byteLength === 0) {
      this._f64 = new Float64Array(this.instance.exports.memory.buffer);
    }

    return this._f64;
  }

  _buf = new Uint8Array();
  get memory() {
    if (this._buf.byteLength === 0) {
      this._buf = new Uint8Array(this.instance.exports.memory.buffer);
    }

    return this._buf;
  }

  getBufferInfo(buf, ptr) {
    if (this.buffers.has(buf)) {
      let b = this.buffers.get(buf);
      this.setPointer(ptr, b.byteOffset);
      return b.byteLength;
    }

    if (buf instanceof ArrayBuffer) {
      let b = this.copyBuffer(new Uint8Array(buf));
      this.setPointer(ptr, b.byteOffset);
      return b.byteLength;
    }

    // If this is a view into WASM memory, no copies needed.
    if (buf.buffer === this.instance.exports.memory.buffer) {
      this.setPointer(ptr, buf.byteOffset);
      return buf.byteLength;
    }

    let b = this.copyBuffer(new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength));
    this.setPointer(ptr, b.byteOffset);
    return b.byteLength;
  }

  copyBuffer(data) {
    let ptr = this.instance.exports.napi_wasm_malloc(data.byteLength);
    let mem = this.memory;
    mem.set(data, ptr);
    let buf = mem.subarray(ptr, ptr + data.byteLength);
    let finalize = (_env, data) => {
      if (this.instance.exports.napi_wasm_free) {
        this.instance.exports.napi_wasm_free(data);
      }
    };

    finalizationRegistry.register(buf, new FinalizeRecord(this.id, finalize, 0, ptr));
    this.buffers.set(data, buf);
    return buf;
  }

  createFunction(cb, data) {
    let env = this;
    let fn = env.table.get(cb);
    let func = function (...args) {
      let scope = env.pushScope();

      try {
        let values = env.scopes[scope];
        let info = values.length;
        values.push({
          thisArg: this,
          args,
          data,
          newTarget: new.target
        });

        let res = fn(env.id, info);
        return env.get(res);
      } finally {
        env.popScope();
        if (env.pendingException) {
          let e = env.pendingException;
          env.pendingException = null;
          throw e;
        }
      }
    };

    return func;
  }

  readPropertyDescriptor(ptr) {
    // https://nodejs.org/api/n-api.html#napi_property_descriptor
    let buf = this.u32;
    let utf8name = buf[ptr++];
    let nameValue = buf[ptr++];
    let method = buf[ptr++];
    let getter = buf[ptr++];
    let setter = buf[ptr++];
    let val = buf[ptr++];
    let attrs = buf[ptr++];
    let data = buf[ptr++];

    let name = utf8name ? this.getString(utf8name) : this.get(nameValue);
    let writable = Boolean(attrs & NAPI_WRITABLE);
    let enumerable = Boolean(attrs & NAPI_ENUMERABLE);
    let configurable = Boolean(attrs & NAPI_CONFIGURABLE);
    let isStatic = Boolean(attrs & NAPI_STATIC);
    let get = getter ? this.createFunction(getter, data) : undefined;
    let set = setter ? this.createFunction(setter, data) : undefined;
    let value = method ? this.createFunction(method, data) : val ? this.get(val) : undefined;

    let descriptor = {
      name,
      static: isStatic,
      configurable,
      enumerable
    };
    if (get || set) {
      descriptor.get = get;
      descriptor.set = set;
    } else if (value) {
      descriptor.writable = writable;
      descriptor.value = value;
    }

    return descriptor;
  }
}

const decoder = new TextDecoder("utf-8", { ignoreBOM: true, fatal: true });
const latin1Decoder = new TextDecoder('latin1');
const utf16Decoder = new TextDecoder('utf-16');
const encoder = new TextEncoder();

class FinalizeRecord {
  constructor(env, finalize, hint, data) {
    this.env = env;
    this.finalize = finalize;
    this.hint = hint;
    this.data = data;
  }
}

const finalizationRegistry = new FinalizationRegistry(buffer => {
  if (buffer.finalize) {
    buffer.finalize(buffer.env, buffer.data, buffer.hint);
  }
});

class ExternalValue {}

const threadsafeFunctions = [];

class ThreadSafeFunction {
  constructor(env, fn, nativeFn, context) {
    this.env = env;
    this.fn = fn;
    this.nativeFn = nativeFn;
    this.context = context;
    this.id = threadsafeFunctions.length;
    threadsafeFunctions.push(this);
  }
}

const asyncWork = [null];

class AsyncWork {
  constructor(env, execute, complete, data) {
    this.env = env;
    this.execute = execute;
    this.complete = complete;
    this.data = data;
    this.id = asyncWork.length;
    asyncWork.push(this);
  }
}

export const napi = {
  napi_open_handle_scope(env_id, result) {
    let env = environments[env_id];
    let id = env.pushScope();
    return env.setPointer(result, id);
  },
  napi_close_handle_scope(env_id, scope) {
    let env = environments[env_id];
    if (scope !== env.scopes.length - 1) {
      return NAPI_HANDLE_SCOPE_MISMATCH;
    }
    env.popScope();
    return NAPI_OK;
  },
  napi_open_escapable_handle_scope(env_id, result) {
    let env = environments[env_id];
    let id = env.pushScope();
    return env.setPointer(result, id);
  },
  napi_close_escapable_handle_scope(env_id, scope) {
    let env = environments[env_id];
    if (scope !== env.scopes.length - 1) {
      return NAPI_HANDLE_SCOPE_MISMATCH;
    }
    env.popScope();
    return NAPI_OK;
  },
  napi_escape_handle(env_id, scope_id, escapee, result) {
    let env = environments[env_id];
    let value = env.get(escapee);
    // Create a value in the outer scope.
    return env.createValue(value, result, scope_id - 1);
  },
  napi_create_object(env_id, result) {
    let env = environments[env_id];
    return env.createValue({}, result);
  },
  napi_set_property(env_id, object, key, value) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.get(key);
    let val = env.get(value);
    obj[name] = val;
    return NAPI_OK;
  },
  napi_get_property(env_id, object, key, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.get(key);
    return env.createValue(obj[name], result);
  },
  napi_delete_property(env_id, object, key, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.get(key);
    let res = false;
    try {
      res = delete obj[name];
    } catch (err) {}
    if (result) {
      env.memory[result] = res ? 1 : 0;
    }
    return NAPI_OK;
  },
  napi_has_property(env_id, object, key, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.get(key);
    // return env.setPointer(result, name in obj ? 1 : 0);
    env.memory[result] = name in obj ? 1 : 0;
    return NAPI_OK;
  },
  napi_has_own_property(env_id, object, key, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.get(key);
    env.memory[result] = obj.hasOwnProperty(name) ? 1 : 0;
    return NAPI_OK;
  },
  napi_set_named_property(env_id, object, utf8Name, value) {
    let env = environments[env_id];
    let obj = env.get(object);
    let val = env.get(value);
    let name = env.getString(utf8Name);
    obj[name] = val;
    return NAPI_OK;
  },
  napi_get_named_property(env_id, object, utf8Name, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.getString(utf8Name);
    return env.createValue(obj[name], result);
  },
  napi_has_named_property(env_id, object, utf8Name, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let name = env.getString(utf8Name);
    env.memory[result] = name in obj ? 1 : 0;
    return NAPI_OK;
  },
  napi_get_property_names(env_id, object, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let properties = Object.keys(obj);
    return env.createValue(properties, result);
  },
  napi_get_all_property_names(env_id, object, key_mode, key_filter, key_conversion, result) {
    throw new Error('not implemented');
  },
  napi_define_properties(env_id, object, property_count, properties) {
    let env = environments[env_id];
    let obj = env.get(object);
    let ptr = properties >> 2;
    for (let i = 0; i < property_count; i++) {
      let descriptor = env.readPropertyDescriptor(ptr);
      Object.defineProperty(obj, descriptor.name, descriptor);
      ptr += 8;
    }
    return NAPI_OK;
  },
  napi_object_freeze(env_id, object) {
    let env = environments[env_id];
    let obj = env.get(object);
    Object.freeze(obj);
    return NAPI_OK;
  },
  napi_object_seal(env_id, object) {
    let env = environments[env_id];
    let obj = env.get(object);
    Object.seal(obj);
    return NAPI_OK;
  },
  napi_get_prototype(env_id, object, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    return env.createValue(Object.getPrototypeOf(obj), result);
  },
  napi_define_class(env_id, utf8name, length, constructor, data, property_count, properties, result) {
    let env = environments[env_id];
    let func = env.createFunction(constructor, data);

    Object.defineProperty(func, 'name', {
      value: env.getString(utf8name, length),
      configurable: true
    });

    let ptr = properties >> 2;
    for (let i = 0; i < property_count; i++) {
      let descriptor = env.readPropertyDescriptor(ptr);
      if (descriptor.static) {
        Object.defineProperty(func, descriptor.name, descriptor);
      } else {
        Object.defineProperty(func.prototype, descriptor.name, descriptor);
      }
      ptr += 8;
    }

    return env.createValue(func, result);
  },
  napi_create_reference(env_id, value, refcount, result) {
    let env = environments[env_id];
    let id = env.referenceId++;
    env.references.set(id, {
      value: env.get(value),
      refcount
    });
    return env.setPointer(result, id);
  },
  napi_delete_reference(env_id, ref) {
    let env = environments[env_id];
    env.references.delete(ref);
    return NAPI_OK;
  },
  napi_get_reference_value(env_id, ref, result) {
    let env = environments[env_id];
    let reference = env.references.get(ref);
    return env.createValue(reference.value, result);
  },
  napi_reference_ref(env_id, ref, result) {
    let env = environments[env_id];
    let reference = env.references.get(ref);
    reference.refcount++;
    return env.setPointer(result, reference.refcount);
  },
  napi_reference_unref(env_id, ref, result) {
    let env = environments[env_id];
    let reference = env.references.get(ref);
    if (reference.refcount === 0) {
      return NAPI_GENERIC_FAILURE;
    }
    reference.refcount--;
    return env.setPointer(result, reference.refcount);
  },
  napi_add_env_cleanup_hook() {
    return NAPI_OK;
  },
  napi_remove_env_cleanup_hook() {
    return NAPI_OK;
  },
  napi_add_async_cleanup_hook() {
    return NAPI_OK;
  },
  napi_remove_async_cleanup_hook() {
    return NAPI_OK;
  },
  napi_set_instance_data(env_id, data, finalize_cb, finalize_hint) {
    let env = environments[env_id];
    env.instanceData = data;
    return NAPI_OK;
  },
  napi_get_instance_data(env_id, data) {
    let env = environments[env_id];
    return env.setPointer(data, env.instanceData);
  },
  napi_get_boolean(env_id, value, result) {
    let env = environments[env_id];
    return env.setPointer(result, value ? 3 : 4);
  },
  napi_get_value_bool(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "boolean") {
      return NAPI_BOOLEAN_EXPECTED;
    }
    env.memory[result] = val ? 1 : 0;
    return NAPI_OK;
  },
  napi_create_int32(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(value, result);
  },
  napi_get_value_int32(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "number") {
      return NAPI_NUMBER_EXPECTED;
    }
    env.i32[result >> 2] = val;
    return NAPI_OK;
  },
  napi_create_uint32(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(value, result);
  },
  napi_get_value_uint32(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "number") {
      return NAPI_NUMBER_EXPECTED;
    }
    return env.setPointer(result, val);
  },
  napi_create_int64(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(Number(value), result);
  },
  napi_get_value_int64(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "number") {
      return NAPI_NUMBER_EXPECTED;
    }
    env.i64[result >> 3] = val;
    return NAPI_OK;
  },
  napi_create_double(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(value, result);
  },
  napi_get_value_double(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "number") {
      return NAPI_NUMBER_EXPECTED;
    }
    env.f64[result >> 3] = val;
    return NAPI_OK;
  },
  napi_create_bigint_int64(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(BigInt.asIntN(64, value), result);
  },
  napi_get_value_bigint_int64(env_id, value, result, lossless) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "bigint") {
      return NAPI_BIGINT_EXPECTED;
    }
    env.i64[result >> 3] = val;
    if (lossless) {
      env.memory[lossless] = BigInt.asIntN(64, val) === val ? 1 : 0;
    }
    return NAPI_OK;
  },
  napi_create_bigint_uint64(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(BigInt.asUintN(64, value), result);
  },
  napi_get_value_bigint_uint64(env_id, value, result, lossless) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "bigint") {
      return NAPI_BIGINT_EXPECTED;
    }
    env.u64[result >> 3] = val;
    if (lossless) {
      env.memory[lossless] = BigInt.asUintN(64, val) === val ? 1 : 0;
    }
    return NAPI_OK;
  },
  napi_create_bigint_words(env_id, sign_bit, word_count, words, result) {
    let env = environments[env_id];
    let buf = env.u64;
    let ptr = words >> 3;
    let res = 0n;
    let shift = 0n;

    for (let i = 0; i < word_count; i++) {
      let word = buf[ptr++];
      res += word << shift;
      shift += 64n;
    }

    res *= BigInt((-1) ** sign_bit);
    return env.createValue(res, result);
  },
  napi_get_value_bigint_words(env_id, value, sign_bit, word_count, words) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "bigint") {
      return NAPI_BIGINT_EXPECTED;
    }

    let count = env.u32[word_count >> 2];

    if (sign_bit) {
      env.i32[sign_bit] = val < 0n ? 1 : 0;
    }

    let i = 0;
    if (words) {
      let mask = (1n << 64n) - 1n;
      let buf = env.u64;
      let ptr = words >> 3;
      if (val < 0n) {
        val = -val;
      }

      for (; i < count && val !== 0n; i++) {
        buf[ptr++] = val & mask;
        val >>= 64n;
      }
    }

    while (val > 0n) {
      i++;
      val >>= 64n;
    }

    return env.setPointer(word_count, i);
  },
  napi_get_null(env_id, result) {
    let env = environments[env_id];
    return env.setPointer(result, 1);
  },
  napi_create_array(env_id, result) {
    let env = environments[env_id];
    return env.createValue([], result);
  },
  napi_create_array_with_length(env_id, length, result) {
    let env = environments[env_id];
    return env.createValue(new Array(length), result);
  },
  napi_set_element(env_id, object, index, value) {
    let env = environments[env_id];
    let obj = env.get(object);
    let val = env.get(value);
    obj[index] = val;
    return NAPI_OK;
  },
  napi_get_element(env_id, object, index, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let val = obj[index];
    return env.createValue(val, result);
  },
  napi_has_element(env_id, object, index, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    env.memory[result] = obj.hasOwnProperty(index) ? 1 : 0;
    return NAPI_OK;
  },
  napi_delete_element(env_id, object, index, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let res = false;
    try {
      res = delete obj[index];
    } catch (err) {}
    if (result) {
      env.memory[result] = res ? 1 : 0;
    }
    return NAPI_OK;
  },
  napi_get_array_length(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    return env.setPointer(result, val.length);
  },
  napi_get_undefined(env_id, result) {
    let env = environments[env_id];
    return env.setPointer(result, 0);
  },
  napi_create_function(env_id, utf8name, length, cb, data, result) {
    let env = environments[env_id];
    let func = env.createFunction(cb, data);

    Object.defineProperty(func, 'name', {
      value: env.getString(utf8name, length),
      configurable: true
    });

    return env.createValue(func, result);
  },
  napi_call_function(env_id, recv, func, argc, argv, result) {
    let env = environments[env_id];
    let thisArg = env.get(recv);
    let fn = env.get(func);
    let args = new Array(argc);
    let mem = env.u32;
    for (let i = 0; i < argc; i++) {
      args[i] = env.get(mem[argv >> 2]);
      argv += 4;
    }

    try {
      let res = fn.apply(thisArg, args);
      return env.createValue(res, result);
    } catch (err) {
      env.pendingException = err;
      return NAPI_PENDING_EXCEPTION;
    }
  },
  napi_new_instance(env_id, cons, argc, argv, result) {
    let env = environments[env_id];
    let Class = env.get(cons);
    let args = new Array(argc);
    let mem = env.u32;
    for (let i = 0; i < argc; i++) {
      args[i] = env.get(mem[argv >> 2]);
      argv += 4;
    }

    try {
      let value = new Class(...args);
      return env.createValue(value, result);
    } catch (err) {
      env.pendingException = err;
      return NAPI_PENDING_EXCEPTION;
    }
  },
  napi_get_cb_info(env_id, cbinfo, argc, argv, thisArg, data) {
    let env = environments[env_id];
    let info = env.get(cbinfo);
    env.setPointer(argc, info.args.length);
    for (let i = 0; i < info.args.length; i++) {
      env.createValue(info.args[i], argv);
      argv += 4;
    }
    env.createValue(info.thisArg, thisArg);
    env.setPointer(data, info.data);
    return NAPI_OK;
  },
  napi_get_new_target(env_id, cbinfo, result) {
    let env = environments[env_id];
    let info = env.get(cbinfo);
    return env.createValue(info.newTarget, result);
  },
  napi_create_threadsafe_function(
    env_id,
    func,
    async_resource,
    async_resource_name,
    max_queue_size,
    initial_thread_count,
    thread_finalize_data,
    thread_finalize_cb,
    context,
    call_js_cb,
    result
  ) {
    let env = environments[env_id];
    let fn = func ? env.get(func) : undefined;
    let cb = call_js_cb ? env.table.get(call_js_cb) : undefined;
    let f = new ThreadSafeFunction(env, fn, cb, context);

    if (thread_finalize_cb) {
      let cb = env.table.get(thread_finalize_cb);
      finalizationRegistry.register(f, new FinalizeRecord(env_id, cb, 0, f.id));
    }

    env.setPointer(result, f.id);
    return NAPI_OK;
  },
  napi_ref_threadsafe_function() {
    return NAPI_OK;
  },
  napi_unref_threadsafe_function() {
    return NAPI_OK;
  },
  napi_acquire_threadsafe_function() {
    return NAPI_OK;
  },
  napi_release_threadsafe_function(func, mode) {
    threadsafeFunctions[func] = undefined;
    return NAPI_OK;
  },
  napi_call_threadsafe_function(func, data, is_blocking) {
    let f = threadsafeFunctions[func];
    f.env.pushScope();
    try {
      if (f.nativeFn) {
        let id = f.fn ? f.env.pushValue(f.fn) : 0;
        f.nativeFn(f.env.id, id, f.context, data);
      } else if (f.fn) {
        f.fn();
      }
    } finally {
      f.env.popScope();
    }
  },
  napi_get_threadsafe_function_context(func, result) {
    let f = threadsafeFunctions[func];
    f.env.setPointer(result, f.context);
    return NAPI_OK;
  },
  napi_create_async_work(env_id, async_resource, async_resource_name, execute, complete, data, result) {
    let env = environments[env_id];
    let executeFn = execute ? env.table.get(execute) : undefined;
    let completeFn = complete ? env.table.get(complete) : undefined;
    let w = new AsyncWork(env, executeFn, completeFn, data);
    env.setPointer(result, w.id);
    return NAPI_OK;
  },
  napi_delete_async_work(env, work) {
    asyncWork[work] = undefined;
    return NAPI_OK;
  },
  napi_queue_async_work(env, work) {
    queueMicrotask(() => {
      let w = asyncWork[work];
      if (w) {
        w.execute(env, w.data);
        w.complete(env, NAPI_OK, w.data);
      }
    });
    return NAPI_OK;
  },
  napi_cancel_async_work() {
    let w = asyncWork[work];
    w.complete(env, NAPI_CANCELED, w.data);
    asyncWork[work] = undefined;
    return NAPI_OK;
  },
  napi_throw(env_id, error) {
    let env = environments[env_id];
    env.pendingException = env.get(error);
    return NAPI_OK;
  },
  napi_throw_error(env_id, code, msg) {
    let env = environments[env_id];
    let err = new Error(env.getString(msg));
    err.code = code;
    env.pendingException = err;
    return NAPI_OK;
  },
  napi_throw_type_error(env_id, code, msg) {
    let env = environments[env_id];
    let err = new TypeError(env.getString(msg));
    err.code = code;
    env.pendingException = err;
    return NAPI_OK;
  },
  napi_throw_range_error(env_id, code, msg) {
    let env = environments[env_id];
    let err = new RangeError(env.getString(msg));
    err.code = code;
    env.pendingException = err;
    return NAPI_OK;
  },
  napi_create_error(env_id, code, msg, result) {
    let env = environments[env_id];
    let err = new Error(env.get(msg));
    err.code = env.get(code);
    return env.createValue(err, result);
  },
  napi_create_type_error(env_id, code, msg, result) {
    let env = environments[env_id];
    let err = new TypeError(env.get(msg));
    err.code = env.get(code);
    return env.createValue(err, result);
  },
  napi_create_range_error(env_id, code, msg, result) {
    let env = environments[env_id];
    let err = new RangeError(env.get(msg));
    err.code = env.get(code);
    return env.createValue(err, result);
  },
  napi_get_and_clear_last_exception(env_id, result) {
    let env = environments[env_id];
    let e = env.pendingException;
    env.pendingException = null;
    return env.createValue(e, result);
  },
  napi_is_exception_pending(env_id, result) {
    let env = environments[env_id];
    env.memory[result] = env.pendingException ? 1 : 0;
    return NAPI_OK;
  },
  napi_fatal_exception(env_id, err) {
    throw new Error('not implemented');
  },
  napi_fatal_error(location, location_len, message, message_len) {
    throw new Error('not implemented');
  },
  napi_get_global(env_id, result) {
    let env = environments[env_id];
    return env.setPointer(result, 2);
  },
  napi_create_buffer(env_id, length, data, result) {
    let env = environments[env_id];
    let ptr = env.instance.exports.napi_wasm_malloc(length);
    if (data) {
      env.setPointer(data, ptr);
    }

    // Return a view into WASM memory.
    let buf = typeof globalThis.Buffer !== 'undefined'
      ? globalThis.Buffer.from(env.memory.buffer, ptr, length)
      : env.memory.subarray(ptr, ptr + length);

    let finalize = (_env, data) => {
      if (env.instance.exports.napi_wasm_free) {
        env.instance.exports.napi_wasm_free(data);
      }
    };

    finalizationRegistry.register(buf, new FinalizeRecord(env_id, finalize, 0, ptr));
    return env.createValue(buf, result);
  },
  napi_create_buffer_copy(env_id, length, data, result_data, result) {
    let env = environments[env_id];
    let ptr = env.instance.exports.napi_wasm_malloc(length);
    env.memory.set(env.memory.subarray(data, data + length), ptr);
    if (result_data) {
      env.setPointer(result_data, ptr);
    }

    // Return a view into WASM memory.
    let res = typeof globalThis.Buffer !== 'undefined'
      ? globalThis.Buffer.from(env.memory.buffer, ptr, length)
      : env.memory.subarray(ptr, ptr + length);

    let finalize = (_env, data) => {
      if (env.instance.exports.napi_wasm_free) {
        env.instance.exports.napi_wasm_free(data);
      }
    };

    finalizationRegistry.register(buf, new FinalizeRecord(env_id, finalize, 0, ptr));
    return env.createValue(res, result);
  },
  napi_create_external_buffer(env_id, length, data, finalize_cb, finalize_hint, result) {
    let env = environments[env_id];
    let buf = typeof globalThis.Buffer !== 'undefined'
      ? globalThis.Buffer.from(env.memory.buffer, data, length)
      : env.memory.subarray(data, data + length);
    if (finalize_cb) {
      let cb = env.table.get(finalize_cb);
      finalizationRegistry.register(buf, new FinalizeRecord(env_id, cb, finalize_hint, data));
    }

    return env.createValue(buf, result);
  },
  napi_get_buffer_info(env_id, value, data, length) {
    let env = environments[env_id];
    let buf = env.get(value);
    let len = env.getBufferInfo(buf, data);
    return env.setPointer(length, len);
  },
  napi_create_arraybuffer(env_id, length, data, result) {
    let env = environments[env_id];
    let buf = new ArrayBuffer(length);
    if (data) {
      // This copies the ArrayBuffer into the WASM memory.
      env.getBufferInfo(buf, data);
    }
    return env.createValue(buf, result);
  },
  napi_create_external_arraybuffer(env_id, data, length, finalize_cb, finalize_hint, result) {
    // There is no way to actually create an external ArrayBuffer without copying.
    // You can only create typed arrays as subarrays, not ArrayBuffer.
    return NAPI_NO_EXTERNAL_BUFFERS_ALLOWED;
  },
  napi_get_arraybuffer_info(env_id, value, data, length) {
    let env = environments[env_id];
    let len = env.getBufferInfo(env.get(value), data);
    return env.setPointer(length, len);
  },
  napi_detach_arraybuffer(env_id, arraybuffer) {
    let env = environments[env_id];
    let buffer = env.get(arraybuffer);
    if (typeof structuredClone === 'function') {
      structuredClone(buffer, {transfer: [buffer]});
    }
    return NAPI_OK;
  },
  napi_is_detached_arraybuffer(env_id, arraybuffer, result) {
    let env = environments[env_id];
    let buffer = env.get(arraybuffer);
    env.memory[result] = buffer.byteLength === 0 ? 1 : 0; // ??
    return NAPI_OK;
  },
  napi_create_typedarray(env_id, type, length, arraybuffer, offset, result) {
    let env = environments[env_id];
    let Class = typedArrays[type];
    let buffer = env.get(arraybuffer);
    let buf = new Class(buffer, offset, length);
    return env.createValue(buf, result);
  },
  napi_create_dataview(env_id, byte_length, arraybuffer, byte_offset, result) {
    let env = environments[env_id];
    let buffer = env.get(arraybuffer);
    let view = new DataView(buffer, byte_offset, byte_length);
    return env.createValue(view, result);
  },
  napi_get_typedarray_info(env_id, typedarray, type, length, data, arraybuffer, byte_offset) {
    let env = environments[env_id];
    let val = env.get(typedarray);
    env.setPointer(type, typedArrays.findIndex(constructor => val instanceof constructor));
    env.setPointer(length, val.length);
    env.getBufferInfo(val, data);
    env.createValue(val.buffer, arraybuffer);
    return env.setPointer(byte_offset, val.byteOffset);
  },
  napi_get_dataview_info(env_id, dataview, byte_length, data, arraybuffer, byte_offset) {
    let env = environments[env_id];
    let val = env.get(dataview);
    env.setPointer(byte_length, val.byteLength);
    env.getBufferInfo(val, data);
    env.createValue(val.buffer, arraybuffer);
    return env.setPointer(byte_offset, val.byteOffset);
  },
  napi_create_string_utf8(env_id, str, length, result) {
    let env = environments[env_id];
    let s = decoder.decode(env.memory.subarray(str, str + length));
    return env.createValue(s, result);
  },
  napi_get_value_string_utf8(env_id, value, buf, bufsize, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "string") {
      return NAPI_STRING_EXPECTED;
    }
    if (buf == 0) {
      return env.setPointer(result, utf8Length(val));
    }
    let res = encoder.encodeInto(val, env.memory.subarray(buf, buf + bufsize - 1));
    env.memory[buf + res.written] = 0; // null terminate
    return env.setPointer(result, res.written);
  },
  napi_create_string_latin1(env_id, str, length, result) {
    let env = environments[env_id];
    let s = latin1Decoder.decode(env.memory.subarray(str, str + length));
    return env.createValue(s, result);
  },
  napi_get_value_string_latin1(env_id, value, buf, bufsize, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "string") {
      return NAPI_STRING_EXPECTED;
    }
    if (buf == 0) {
      return env.setPointer(result, val.length);
    }
    let mem = env.memory;
    let len = Math.min(val.length, bufsize - 1);
    for (let i = 0; i < len; i++) {
      let code = val.charCodeAt(i);
      mem[buf++] = code;
    }
    mem[buf] = 0; // null terminate
    return env.setPointer(result, len);
  },
  napi_create_string_utf16(env_id, str, length, result) {
    let env = environments[env_id];
    let s = utf16Decoder.decode(env.memory.subarray(str, str + length * 2));
    return env.createValue(s, result);
  },
  napi_get_value_string_utf16(env_id, value, buf, bufsize, result) {
    let env = environments[env_id];
    let val = env.get(value);
    if (typeof val !== "string") {
      return NAPI_STRING_EXPECTED;
    }
    if (buf == 0) {
      return env.setPointer(result, val.length);
    }
    let mem = env.u16;
    let ptr = buf >> 1;
    let len = Math.min(val.length, bufsize - 1);
    for (let i = 0; i < len; i++) {
      let code = val.charCodeAt(i);
      mem[ptr++] = code;
    }
    mem[ptr] = 0; // null terminate
    return env.setPointer(result, len);
  },
  napi_create_date(env_id, time, result) {
    let env = environments[env_id];
    return env.createValue(new Date(time), result);
  },
  napi_get_date_value(env_id, value, result) {
    let env = environments[env_id];
    let date = env.get(value);
    env.f64[result >> 3] = date.valueOf();
  },
  napi_create_symbol(env_id, description, result) {
    let env = environments[env_id];
    let desc = env.get(description);
    return env.createValue(Symbol(desc), result);
  },
  napi_coerce_to_bool(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(Boolean(env.get(value)), result);
  },
  napi_coerce_to_number(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(Number(env.get(value)), result);
  },
  napi_coerce_to_object(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(Object(env.get(value)), result);
  },
  napi_coerce_to_string(env_id, value, result) {
    let env = environments[env_id];
    return env.createValue(String(env.get(value)), result);
  },
  napi_typeof(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    return env.setPointer(result, (() => {
      switch (typeof val) {
        case 'undefined':
          return 0;
        case 'boolean':
          return 2;
        case 'number':
          return 3;
        case 'string':
          return 4;
        case 'symbol':
          return 5;
        case 'object':
          if (val === null) {
            return 1;
          } else if (val instanceof ExternalValue) {
            return 8;
          }
          return 6;
        case 'function':
          return 7;
        case 'bigint':
          return 9;
      }
    })());
  },
  napi_instanceof(env_id, object, constructor, result) {
    let env = environments[env_id];
    let obj = env.get(object);
    let cons = env.get(constructor);
    env.memory[result] = obj instanceof cons ? 1 : 0;
    return NAPI_OK;
  },
  napi_is_array(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    env.memory[result] = Array.isArray(val) ? 1 : 0;
    return NAPI_OK;
  },
  napi_is_buffer(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    env.memory[result] = (typeof globalThis.Buffer !== 'undefined' ? globalThis.Buffer.isBuffer(val) : val instanceof Uint8Array) ? 1 : 0;
    return NAPI_OK;
  },
  napi_is_date(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    env.memory[result] = val instanceof Date ? 1 : 0;
    return NAPI_OK;
  },
  napi_is_error(env_id, value, result) {
    let env = environments[env_id];
    let err = env.get(value);
    env.memory[result] = err instanceof Error ? 1 : 0;
    return NAPI_OK;
  },
  napi_is_typedarray(env_id, value, result) {
    let env = environments[env_id];
    let buf = env.get(value);
    env.memory[result] = ArrayBuffer.isView(buf) && !(buf instanceof DataView) ? 1 : 0;
    return NAPI_OK;
  },
  napi_is_dataview(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    env.memory[result] = val instanceof DataView ? 1 : 0;
    return NAPI_OK;
  },
  napi_strict_equals(env_id, lhs, rhs, result) {
    let env = environments[env_id];
    env.memory[result] = env.get(lhs) === env.get(rhs) ? 1 : 0;
    return NAPI_OK;
  },
  napi_wrap(env_id, js_object, native_object, finalize_cb, finalize_hint, result) {
    let env = environments[env_id];
    let obj = env.get(js_object);
    env.wrappedObjects.set(obj, native_object);
    if (finalize_cb) {
      let cb = env.table.get(finalize_cb);
      finalizationRegistry.register(obj, new FinalizeRecord(env_id, cb, finalize_hint, native_object));
    }

    if (result) {
      return napi.napi_create_reference(env_id, js_object, 1, result);
    }

    return NAPI_OK;
  },
  napi_unwrap(env_id, js_object, result) {
    let env = environments[env_id];
    let obj = env.get(js_object);
    let native_object = env.wrappedObjects.get(obj);
    env.setPointer(result, native_object);
    return NAPI_OK;
  },
  napi_remove_wrap(env_id, js_object, result) {
    let env = environments[env_id];
    let obj = env.get(js_object);
    let native_object = env.wrappedObjects.get(obj);
    finalizationRegistry.unregister(obj);
    env.wrappedObjects.delete(obj);
    return env.setPointer(result, native_object);
  },
  napi_type_tag_object(env_id, js_object, type_tag) {
    throw new Error('not implemented');
  },
  napi_check_object_type_tag(env_id, js_object, type_tag) {
    throw new Error('not implemented');
  },
  napi_add_finalizer(env_id, js_object, native_object, finalize_cb, finalize_hint, result) {
    let env = environments[env_id];
    let obj = env.get(js_object);
    let cb = env.table.get(finalize_cb);
    finalizationRegistry.register(obj, new FinalizeRecord(env_id, cb, finalize_hint, native_object));
    if (result) {
      return napi.napi_create_reference(env_id, js_object, 1, result);
    }

    return NAPI_OK;
  },
  napi_create_promise(env_id, deferred, promise) {
    let env = environments[env_id];
    let p = new Promise((resolve, reject) => {
      let id = env.deferred.length;
      env.deferred.push({resolve, reject});
      env.setPointer(deferred, id);
    });
    return env.createValue(p, promise);
  },
  napi_resolve_deferred(env_id, deferred, resolution) {
    let env = environments[env_id];
    let { resolve } = env.deferred[deferred];
    let value = env.get(resolution);
    resolve(value);
    env.deferred[deferred] = undefined;
    return NAPI_OK;
  },
  napi_reject_deferred(env_id, deferred, rejection) {
    let env = environments[env_id];
    let { reject } = env.deferred[deferred];
    let value = env.get(rejection);
    reject(value);
    env.deferred[deferred] = undefined;
    return NAPI_OK;
  },
  napi_is_promise(env_id, value, result) {
    let env = environments[env_id];
    let val = env.get(value);
    env.memory[result] = val instanceof Promise ? 1 : 0;
    return NAPI_OK;
  },
  napi_run_script(env_id, script, result) {
    let env = environments[env_id];
    let source = env.get(script);
    let res = (0, eval)(source);
    return env.createValue(res, result);
  },
  napi_create_external(env_id, data, finalize_cb, finalize_hint, result) {
    let env = environments[env_id];
    let external = new ExternalValue;
    env.externalObjects.set(external, data);
    if (finalize_cb) {
      let cb = env.table.get(finalize_cb);
      finalizationRegistry.register(external, new FinalizeRecord(env_id, cb, finalize_hint, data));
    }
    return env.createValue(external, result);
  },
  napi_get_value_external(env_id, value, result) {
    let env = environments[env_id];
    let external = env.get(value);
    let val = env.externalObjects.get(external);
    if (!val) {
      return NAPI_INVALID_ARG;
    }
    return env.setPointer(result, val);
  },
  napi_adjust_external_memory() {
    return NAPI_OK;
  }
};

function strlen(buf, ptr) {
  let len = 0;
  while (buf[ptr] !== 0) {
    len++;
    ptr++;
  }

  return len;
}

function utf8Length(string) {
  let len = 0;
  for (let i = 0; i < string.length; i++) {
    let c = string.charCodeAt(i);

    if (c >= 0xd800 && c <= 0xdbff && i < string.length - 1) {
      let c2 = string.charCodeAt(++i);
      if ((c2 & 0xfc00) === 0xdc00) {
        c = ((c & 0x3ff) << 10) + (c2 & 0x3ff) + 0x10000;
      } else {
        // unmatched surrogate.
        i--;
      }
    }

    if ((c & 0xffffff80) === 0) {
      len++;
    } else if ((c & 0xfffff800) === 0) {
      len += 2;
    } else if ((c & 0xffff0000) === 0) {
      len += 3;
    } else if ((c & 0xffe00000) === 0) {
      len += 4;
    }
  }
  return len;
}