// location: lib/async_hooks.js


// 1. 真正的储存位置
const storageList = [];
const storageHook = createHook({
  init(asyncId, type, triggerAsyncId, resource) {
    const currentResource = executionAsyncResource();
    // Value of currentResource is always a non null object
    for (let i = 0; i < storageList.length; ++i) {
      storageList[i]._propagate(resource, currentResource);
    }
  }
});

function createHook(fns) {
  return new AsyncHook(fns);
}

// 2. ALS Class 的实现
class AsyncLocalStorage {
  constructor() {
    this.kResourceStore = Symbol('kResourceStore');
    this.enabled = false;
  }

  _enable() {
    if (!this.enabled) {
      this.enabled = true;
      ArrayPrototypePush(storageList, this);
      storageHook.enable();
    }
  }

  run(store, callback, ...args) {
    // Avoid creation of an AsyncResource if store is already active
    if (ObjectIs(store, this.getStore())) {
      return ReflectApply(callback, null, args);
    }

    this._enable();

    // 新老 resource 交接班
    const resource = executionAsyncResource(); // 新的resource
    const oldStore = resource[this.kResourceStore];  // 老的resource

    resource[this.kResourceStore] = store; // 新的resource，traceId存放的地方

    try {
      return ReflectApply(callback, null, args); 
    } finally {
      resource[this.kResourceStore] = oldStore; // 等callback执行结束，将老的oldStore归还
    }
  }


  getStore() {
    if (this.enabled) {
      const resource = executionAsyncResource();
      return resource[this.kResourceStore];
    }
  }
}

import { AsyncLocalStorage } from 'node:async_hooks';

const asyncLocalStorage = new AsyncLocalStorage();

let traceId = 0;
asyncLocalStorage.run(traceId++, () => {
  console.log(asyncLocalStorage.getStore())
  setImmediate(() => {
    console.log(asyncLocalStorage.getStore())
  })
});

asyncLocalStorage.run('test', () => {})

// location: lib/async_hooks.js

class AsyncHook {
  constructor({
    init,
    before,
    after,
    destroy,
    promiseResolve
  }) {
    this[init_symbol] = init;
    this[before_symbol] = before;
    this[after_symbol] = after;
    this[destroy_symbol] = destroy;
    this[promise_resolve_symbol] = promiseResolve;
  }

  enable() {
    // The set of callbacks for a hook should be the same regardless of whether
    // enable()/disable() are run during their execution. The following
    // references are reassigned to the tmp arrays if a hook is currently being
    // processed.
    const {
      0: hooks_array,
      1: hook_fields
    } = getHookArrays();

    // Each hook is only allowed to be added once.
    if (ArrayPrototypeIncludes(hooks_array, this))
      return this;

    const prev_kTotals = hook_fields[kTotals];

    // createHook() has already enforced that the callbacks are all functions,
    // so here simply increment the count of whether each callbacks exists or
    // not.
    hook_fields[kTotals] = hook_fields[kInit] += +!!this[init_symbol];
    hook_fields[kTotals] += hook_fields[kBefore] += +!!this[before_symbol];
    hook_fields[kTotals] += hook_fields[kAfter] += +!!this[after_symbol];
    hook_fields[kTotals] += hook_fields[kDestroy] += +!!this[destroy_symbol];
    hook_fields[kTotals] +=
      hook_fields[kPromiseResolve] += +!!this[promise_resolve_symbol];
    ArrayPrototypePush(hooks_array, this);

    if (prev_kTotals === 0 && hook_fields[kTotals] > 0) {
      enableHooks();
    }

    updatePromiseHookMode();

    return this;
  }

}

// location: lib/internal/async_hooks.js

const async_wrap = internalBinding('async_wrap');
const { setCallbackTrampoline } = async_wrap;

function enableHooks() {
  async_hook_fields[kCheck] += 1;

  setCallbackTrampoline(callbackTrampoline);
}

// d.ts file
declare function InternalBinding(binding: 'blob'): {
  createBlob(sources: Array<Uint8Array | InternalBlobBinding.BlobHandle>, length: number): InternalBlobBinding.BlobHandle;
  FixedSizeBlobCopyJob: typeof InternalBlobBinding.FixedSizeBlobCopyJob;
  getDataObject(id: string): [handle: InternalBlobBinding.BlobHandle | undefined, length: number, type: string] | undefined;
  storeDataObject(id: string, handle: InternalBlobBinding.BlobHandle, size: number, type: string): void;
  revokeDataObject(id: string): void;
};

// location: lib/internal/bootstrap/loader.js

// This file creates the internal module & binding loaders used by built-in
// modules. In contrast, user land modules are loaded using
// lib/internal/modules/cjs/loader.js (CommonJS Modules) or
// lib/internal/modules/esm/* (ES Modules).

// C++ binding loaders:
// - internalBinding(): the private internal C++ binding loader, inaccessible
//   from user land unless through `require('internal/test/binding')`.
//   These C++ bindings are created using NODE_MODULE_CONTEXT_AWARE_INTERNAL()
//   and have their nm_flags set to NM_F_INTERNAL.

// This file is compiled as if it's wrapped in a function with arguments
// passed by node::RunBootstrapping()
/* global process, getLinkedBinding, getInternalBinding, primordials */


// Set up internalBinding() in the closure.
/**
 * @type {InternalBinding}
 */
let internalBinding;
{
  const bindingObj = ObjectCreate(null);
  // eslint-disable-next-line no-global-assign
  internalBinding = function internalBinding(module) {
    let mod = bindingObj[module];
    if (typeof mod !== 'object') {
      mod = bindingObj[module] = getInternalBinding(module);
      ArrayPrototypePush(moduleLoadList, `Internal Binding ${module}`);
    }
    return mod;
  };
}

// location: src/async_wrap.cc

// 该文件结尾处
// 在node_binding.h里面定义了宏macro
// #define NODE_MODULE_CONTEXT_AWARE_INTERNAL(modname, regfunc)
NODE_MODULE_CONTEXT_AWARE_INTERNAL(async_wrap, node::AsyncWrap::Initialize);  
NODE_MODULE_EXTERNAL_REFERENCE(async_wrap, node::AsyncWrap::RegisterExternalReferences);

// location: lib/internal/async_hooks.js

// Properties in active_hooks are used to keep track of the set of hooks being
// executed in case another hook is enabled/disabled. The new set of hooks is
// then restored once the active set of hooks is finished executing.
const active_hooks = {
  // Array of all AsyncHooks that will be iterated whenever an async event
  // fires. Using var instead of (preferably const) in order to assign
  // active_hooks.tmp_array if a hook is enabled/disabled during hook
  // execution.
  array: [],
  // Use a counter to track nested calls of async hook callbacks and make sure
  // the active_hooks.array isn't altered mid execution.
  call_depth: 0,
  // Use to temporarily store and updated active_hooks.array if the user
  // enables or disables a hook while hooks are being processed. If a hook is
  // enabled() or disabled() during hook execution then the current set of
  // active hooks is duplicated and set equal to active_hooks.tmp_array. Any
  // subsequent changes are on the duplicated array. When all hooks have
  // completed executing active_hooks.tmp_array is assigned to
  // active_hooks.array.
  tmp_array: null,
  // Keep track of the field counts held in active_hooks.tmp_array. Because the
  // async_hook_fields can't be reassigned, store each uint32 in an array that
  // is written back to async_hook_fields when active_hooks.array is restored.
  tmp_fields: null
};


module.exports = {
  executionAsyncId,
  triggerAsyncId,
  // Private API
  getHookArrays,
  symbols: {
    async_id_symbol, trigger_async_id_symbol,
    init_symbol, before_symbol, after_symbol, destroy_symbol,
    promise_resolve_symbol, owner_symbol
  },
  // ..
  executionAsyncResource,
  // Internal Embedder API
  // ...
  nativeHooks: {  
    init: emitInitNative, //  <====== 看这里
    before: emitBeforeNative,
    after: emitAfterNative,
    destroy: emitDestroyNative,
    promise_resolve: emitPromiseResolveNative
  },
};

// location: lib/internal/async_hooks.js

// Emit From Native //

// Used by C++ to call all init() callbacks. Because some state can be setup
// from C++ there's no need to perform all the same operations as in
// emitInitScript.
function emitInitNative(asyncId, type, triggerAsyncId, resource) {
  active_hooks.call_depth += 1;
  resource = lookupPublicResource(resource);
  // Use a single try/catch for all hooks to avoid setting up one per iteration.
  try {
    // Using var here instead of let because "for (var ...)" is faster than let.
    // Refs: https://github.com/nodejs/node/pull/30380#issuecomment-552948364
    // eslint-disable-next-line no-var
    for (var i = 0; i < active_hooks.array.length; i++) {
      if (typeof active_hooks.array[i][init_symbol] === 'function') {
        active_hooks.array[i][init_symbol](
          asyncId, type, triggerAsyncId,
          resource
        );
      }
    }
  } catch (e) {
    fatalError(e);
  } finally {
    active_hooks.call_depth -= 1;
  }

  // Hooks can only be restored if there have been no recursive hook calls.
  // Also the active hooks do not need to be restored if enable()/disable()
  // weren't called during hook execution, in which case active_hooks.tmp_array
  // will be null.
  if (active_hooks.call_depth === 0 && active_hooks.tmp_array !== null) {
    restoreActiveHooks();
  }
}

// location: lib/internal/bootstrap.js

const { nativeHooks } = require('internal/async_hooks');
internalBinding('async_wrap').setupHooks(nativeHooks);

// location: src/async_wrap.cc

void AsyncWrap::Initialize(Local<Object> target,
                           Local<Value> unused,
                           Local<Context> context,
                           void* priv) {
  Environment* env = Environment::GetCurrent(context);
  Isolate* isolate = env->isolate();
  HandleScope scope(isolate);

  env->SetMethod(target, "setupHooks", SetupHooks);
  env->SetMethod(target, "setCallbackTrampoline", SetCallbackTrampoline);
  env->SetMethod(target, "pushAsyncContext", PushAsyncContext);
  env->SetMethod(target, "popAsyncContext", PopAsyncContext);
  env->SetMethod(target, "executionAsyncResource", ExecutionAsyncResource);
  env->SetMethod(target, "clearAsyncIdStack", ClearAsyncIdStack);
  env->SetMethod(target, "queueDestroyAsyncId", QueueDestroyAsyncId);
  env->SetMethod(target, "setPromiseHooks", SetPromiseHooks);
  env->SetMethod(target, "registerDestroyHook", RegisterDestroyHook);

  PropertyAttribute ReadOnlyDontDelete =
      static_cast<PropertyAttribute>(ReadOnly | DontDelete);
  // ...
}

// location: src/async_wrap.cc

static void SetupHooks(const FunctionCallbackInfo<Value>& args) {
  Environment* env = Environment::GetCurrent(args);

  CHECK(args[0]->IsObject());

  // All of init, before, after, destroy, and promise_resolve are supplied by
  // async_hooks internally, so this should only ever be called once. At which
  // time all the functions should be set. Detect this by checking if
  // init !IsEmpty().
  CHECK(env->async_hooks_init_function().IsEmpty());

  Local<Object> fn_obj = args[0].As<Object>();

#define SET_HOOK_FN(name)                                                      \
  do {                                                                         \
    Local<Value> v =                                                           \
        fn_obj->Get(env->context(),                                            \
                    FIXED_ONE_BYTE_STRING(env->isolate(), #name))              \
            .ToLocalChecked();                                                 \
    CHECK(v->IsFunction());                                                    \
    env->set_async_hooks_##name##_function(v.As<Function>());                  \
  } while (0)

  SET_HOOK_FN(init);
  SET_HOOK_FN(before);
  SET_HOOK_FN(after);
  SET_HOOK_FN(destroy);
  SET_HOOK_FN(promise_resolve);
#undef SET_HOOK_FN
}

// location: src/async_wrap.cc

void AsyncWrap::EmitAsyncInit(Environment* env,
                              Local<Object> object,
                              Local<String> type,
                              double async_id,
                              double trigger_async_id) {
  CHECK(!object.IsEmpty());
  CHECK(!type.IsEmpty());
  AsyncHooks* async_hooks = env->async_hooks();

  // Nothing to execute, so can continue normally.
  if (async_hooks->fields()[AsyncHooks::kInit] == 0) {
    return;
  }

  HandleScope scope(env->isolate());
  Local<Function> init_fn = env->async_hooks_init_function();

  Local<Value> argv[] = {
    Number::New(env->isolate(), async_id),
    type,
    Number::New(env->isolate(), trigger_async_id),
    object,
  };

  TryCatchScope try_catch(env, TryCatchScope::CatchMode::kFatal);
  USE(init_fn->Call(env->context(), object, arraysize(argv), argv));
}

// location: v8.h

/**
 * A JavaScript function object (ECMA-262, 15.3).
 */
class V8_EXPORT Function : public Object {}

// location: lib/internal/bootstrap/loader.js

// This file creates the internal module & binding loaders used by built-in
// modules. In contrast, user land modules are loaded using
// lib/internal/modules/cjs/loader.js (CommonJS Modules) or
// lib/internal/modules/esm/* (ES Modules).
//
// This file is compiled and run by node.cc before bootstrap/node.js
// was called, therefore the loaders are bootstrapped before we start to
// actually bootstrap Node.js. It creates the following objects:
//
// C++ binding loaders:
// - process.binding(): the legacy C++ binding loader, accessible from user land
//   because it is an object attached to the global process object.
//   These C++ bindings are created using NODE_BUILTIN_MODULE_CONTEXT_AWARE()
//   and have their nm_flags set to NM_F_BUILTIN. We do not make any guarantees
//   about the stability of these bindings, but still have to take care of
//   compatibility issues caused by them from time to time.
// - process._linkedBinding(): intended to be used by embedders to add
//   additional C++ bindings in their applications. These C++ bindings
//   can be created using NODE_MODULE_CONTEXT_AWARE_CPP() with the flag
//   NM_F_LINKED.
// - internalBinding(): the private internal C++ binding loader, inaccessible
//   from user land unless through `require('internal/test/binding')`.
//   These C++ bindings are created using NODE_MODULE_CONTEXT_AWARE_INTERNAL()
//   and have their nm_flags set to NM_F_INTERNAL.
//
// Internal JavaScript module loader:
// - NativeModule: a minimal module system used to load the JavaScript core
//   modules found in lib/**/*.js and deps/**/*.js. All core modules are
//   compiled into the node binary via node_javascript.cc generated by js2c.py,
//   so they can be loaded faster without the cost of I/O. This class makes the
//   lib/internal/*, deps/internal/* modules and internalBinding() available by
//   default to core modules, and lets the core modules require itself via
//   require('internal/bootstrap/loaders') even when this file is not written in
//   CommonJS style.
//
// Other objects:
// - process.moduleLoadList: an array recording the bindings and the modules
//   loaded in the process and the order in which they are loaded.

'use strict';

// This file is compiled as if it's wrapped in a function with arguments
// passed by node::RunBootstrapping()
/* global process, getLinkedBinding, getInternalBinding, primordials */