// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import {GraphView} from './GraphView.js';

// A class that maps each context to its corresponding graph.
// It controls which graph to render when the context is switched or updated.
export class GraphManager {
  private readonly graphMapByContextId = new Map<string, GraphView>();

  createContext(contextId: string): void {
    const graph = new GraphView(contextId);
    this.graphMapByContextId.set(contextId, graph);
  }

  destroyContext(contextId: string): void {
    if (!this.graphMapByContextId.has(contextId)) {
      return;
    }

    const graph = this.graphMapByContextId.get(contextId);
    if (!graph) {
      return;
    }

    this.graphMapByContextId.delete(contextId);
  }

  hasContext(contextId: string): boolean {
    return this.graphMapByContextId.has(contextId);
  }

  clearGraphs(): void {
    this.graphMapByContextId.clear();
  }

  /**
   * Get graph by contextId.
   * If the user starts listening for WebAudio events after the page has been running a context for awhile,
   * the graph might be undefined.
   */
  getGraph(contextId: string): GraphView|null {
    return this.graphMapByContextId.get(contextId) || null;
  }
}