ui/src/public/plugin.ts

// Copyright (C) 2024 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 {Trace} from './trace';
import {App} from './app';
import {RouteArgs} from './route_schema';

/**
 * This interface defines the shape of the plugins's class constructor (i.e. the
 * the constructor and all static members of the plugin's class.
 *
 * This class constructor is registered with the core.
 *
 * On trace load, the core will create a new class instance by calling new on
 * this constructor and then call its onTraceLoad() function.
 * @template T The type of the plugin instance.
 */
export interface PerfettoPluginStatic<T extends PerfettoPlugin> {
  /**
   * A unique identifier for the plugin.
   *
   * This ID is used to identify the plugin within the Perfetto UI. It is
   * recommended to use a reverse domain name style (e.g.,
   * `dev.perfetto.MyPlugin`).
   */
  readonly id: string;

  /**
   * An optional human-readable description of the plugin.
   *
   * This description may be displayed in the UI to provide more information
   * about the plugin's functionality.
   */
  readonly description?: string;

  /**
   * An optional list of other plugins that this plugin depends on.
   *
   * The Perfetto UI ensures that all dependencies are loaded before activating
   * this plugin.
   */
  readonly dependencies?: ReadonlyArray<PerfettoPluginStatic<PerfettoPlugin>>;

  /**
   * Called when the plugin is activated, before a trace has been loaded.
   *
   * This method is suitable for registering commands, sidebar items, or pages
   * that are not dependent on a loaded trace.
   *
   * @param app The {@link App} instance, providing access to app-wide
   *   functionality.
   * @param args The initial route arguments when the app was loaded.
   */
  onActivate?(app: App, args: RouteArgs): void;

  /**
   * Returns a list of metric visualisations provided by this plugin.
   *
   * Metric visualisations are used to display data from trace metrics in a
   * graphical format.
   *
   * @returns An array of {@link MetricVisualisation} objects.
   */
  metricVisualisations?(): MetricVisualisation[];

  /**
   * The constructor for the plugin's trace-scoped instance.
   *
   * This constructor is called when a trace is loaded, creating a new instance
   * of the plugin that is scoped to the loaded trace.
   *
   * @param trace The {@link Trace} instance, providing access to trace-scoped
   *   functionality.
   */
  new (trace: Trace): T;
}

/**
 * This interface defines the shape of a plugin's trace-scoped instance, which
 * is created from the class constructor above at trace load time.
 */
export interface PerfettoPlugin {
  /**
   * Called when a trace is loaded.
   *
   * This method is suitable for performing trace-specific initialization, such
   * as querying trace data or registering trace-scoped UI elements.
   *
   * @param ctx The {@link Trace} instance, providing access to trace-scoped
   *   functionality.
   * @param args Optional arguments passed to the plugin during trace loading.
   */
  onTraceLoad?(ctx: Trace, args?: {[key: string]: unknown}): Promise<void>;
}

/**
 * Represents a metric visualisation provided by a plugin.
 *
 * Metric visualisations are used to display data from trace metrics in a
 * graphical format, typically using Vega or Vega-Lite specifications.
 */
export interface MetricVisualisation {
  /**
   * The name of the metric (e.g., 'android_camera').
   *
   * This name corresponds to a metric generated by the trace processor.
   */
  metric: string;

  /**
   * A Vega or Vega-Lite visualisation specification.
   *
   * The data from the metric, extracted by the `path` property, will be
   * exposed as a datasource named "metric" within the Vega(-Lite) spec.
   */
  spec: string;

  /**
   * A path index into the metric data.
   *
   * This path specifies how to extract the relevant data from the metric's
   * protobuf output. For example, if the metric returns:
   * ```protobuf
   * {
   *   foo {
   *     bar {
   *       baz: { name: "a" }
   *       baz: { name: "b" }
   *       baz: { name: "c" }
   *     }
   *   }
   * }
   * ```
   * This becomes the following JSON:
   * ```json
   * { "foo": { "bar": { "baz": [
   *  {"name": "a"},
   *  {"name": "b"},
   *  {"name": "c"},
   * ]}}}
   * ```
   * And given `path = ["foo", "bar", "baz"]`, the extracted data
   * `[ {"name": "a"}, {"name": "b"}, {"name": "c"} ]` is passed to the
   * Vega(-Lite) visualisation.
   */
  path: string[];
}

/**
 * Manages registered plugins and their instances.
 *
 * Use this to get instances of other plugins (for inter-plugin
 * communication) or access metric visualizations. Note that plugin instances
 * are only available after a trace has been loaded.
 */
export interface PluginManager {
  /**
   * Retrieves an instance of a registered plugin.
   *
   * This method can only be called after a trace has been loaded, as plugin
   * instances are trace-scoped.
   *
   * @param plugin The static plugin class (constructor) of the plugin to
   *   retrieve.
   * @returns The trace-scoped instance of the requested plugin.
   * @template T The type of the plugin instance.
   */
  getPlugin<T extends PerfettoPlugin>(plugin: PerfettoPluginStatic<T>): T;

  /**
   * Returns a list of all metric visualisations provided by all registered
   * plugins.
   *
   * @returns An array of {@link MetricVisualisation} objects.
   */
  metricVisualisations(): MetricVisualisation[];
}