ui/src/controller/globals.ts

// Copyright (C) 2018 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import {assertExists} from '../base/logging';
import {Remote} from '../base/remote';
import {Action} from '../common/actions';
import {createEmptyState, State} from '../common/state';
import {ControllerAny} from './controller';
import {Engine, EnginePortAndId} from './engine';
import {rootReducer} from './reducer';
import {WasmEngineProxy} from './wasm_engine_proxy';

/**
 * Global accessors for state/dispatch in the controller.
 */
class Globals {
  private _state?: State;
  private _rootController?: ControllerAny;
  private _frontend?: Remote;
  private _runningControllers = false;
  private _queuedActions = new Array<Action>();

  initialize(rootController: ControllerAny, frontendProxy: Remote) {
    this._state = createEmptyState();
    this._rootController = rootController;
    this._frontend = frontendProxy;
  }

  dispatch(action: Action): void {
    this.dispatchMultiple([action]);
  }

  dispatchMultiple(actions: Action[]): void {
    this._queuedActions = this._queuedActions.concat(actions);

    // If we are in the middle of running the controllers, queue the actions
    // and run them at the end of the run, so the state is atomically updated
    // only at the end and all controllers see the same state.
    if (this._runningControllers) return;

    this.runControllers();
  }

  private runControllers() {
    if (this._runningControllers) throw new Error('Re-entrant call detected');

    // Run controllers locally until all state machines reach quiescence.
    let runAgain = false;
    let summary = this._queuedActions.map(action => action.type).join(', ');
    summary = `Controllers loop (${summary})`;
    console.time(summary);
    for (let iter = 0; runAgain || this._queuedActions.length > 0; iter++) {
      if (iter > 100) throw new Error('Controllers are stuck in a livelock');
      const actions = this._queuedActions;
      this._queuedActions = new Array<Action>();
      for (const action of actions) {
        console.debug('Applying action', action);
        this._state = rootReducer(this.state, action);
      }
      this._runningControllers = true;
      try {
        runAgain = assertExists(this._rootController).invoke();
      } finally {
        this._runningControllers = false;
      }
    }
    assertExists(this._frontend).send<void>('updateState', [this.state]);
    console.timeEnd(summary);
  }

  async createEngine(): Promise<Engine> {
    const portAndId = await assertExists(this._frontend)
                          .send<EnginePortAndId>('createEngine', []);
    return WasmEngineProxy.create(portAndId);
  }

  async destroyEngine(id: string): Promise<void> {
    await assertExists(this._frontend).send<void>('destroyEngine', [id]);
  }

  // TODO: this needs to be cleaned up.
  publish(what: 'OverviewData'|'TrackData'|'Threads'|'QueryResult', data: {}) {
    assertExists(this._frontend).send<void>(`publish${what}`, [data]);
  }

  get state(): State {
    return assertExists(this._state);
  }

  set state(state: State) {
    this._state = state;
  }

  resetForTesting() {
    this._state = undefined;
    this._rootController = undefined;
  }
}

export const globals = new Globals();