McpPage.ts

/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import type {
  Dialog,
  ElementHandle,
  Page,
  Viewport,
} from './third_party/index.js';
import {takeSnapshot} from './tools/snapshot.js';
import type {ContextPage} from './tools/ToolDefinition.js';
import type {
  EmulationSettings,
  GeolocationOptions,
  TextSnapshot,
  TextSnapshotNode,
} from './types.js';

/**
 * Per-page state wrapper. Consolidates dialog, snapshot, emulation,
 * and metadata that were previously scattered across Maps in McpContext.
 *
 * Internal class consumed only by McpContext. Fields are public for direct
 * read/write access. The dialog field is private because it requires an
 * event listener lifecycle managed by the constructor/dispose pair.
 */
export class McpPage implements ContextPage {
  readonly pptrPage: Page;
  readonly id: number;

  // Snapshot
  textSnapshot: TextSnapshot | null = null;
  uniqueBackendNodeIdToMcpId = new Map<string, string>();

  // Emulation
  emulationSettings: EmulationSettings = {};

  // Metadata
  isolatedContextName?: string;
  devToolsPage?: Page;

  // Dialog
  #dialog?: Dialog;
  #dialogHandler: (dialog: Dialog) => void;

  constructor(page: Page, id: number) {
    this.pptrPage = page;
    this.id = id;
    this.#dialogHandler = (dialog: Dialog): void => {
      this.#dialog = dialog;
    };
    page.on('dialog', this.#dialogHandler);
  }

  get dialog(): Dialog | undefined {
    return this.#dialog;
  }

  clearDialog(): void {
    this.#dialog = undefined;
  }

  get networkConditions(): string | null {
    return this.emulationSettings.networkConditions ?? null;
  }

  get cpuThrottlingRate(): number {
    return this.emulationSettings.cpuThrottlingRate ?? 1;
  }

  get geolocation(): GeolocationOptions | null {
    return this.emulationSettings.geolocation ?? null;
  }

  get viewport(): Viewport | null {
    return this.emulationSettings.viewport ?? null;
  }

  get userAgent(): string | null {
    return this.emulationSettings.userAgent ?? null;
  }

  get colorScheme(): 'dark' | 'light' | null {
    return this.emulationSettings.colorScheme ?? null;
  }

  dispose(): void {
    this.pptrPage.off('dialog', this.#dialogHandler);
  }

  async getElementByUid(uid: string): Promise<ElementHandle<Element>> {
    if (!this.textSnapshot) {
      throw new Error(
        `No snapshot found for page ${this.id ?? '?'}. Use ${takeSnapshot.name} to capture one.`,
      );
    }
    const node = this.textSnapshot.idToNode.get(uid);
    if (!node) {
      throw new Error(`Element uid "${uid}" not found on page ${this.id}.`);
    }
    return this.#resolveElementHandle(node, uid);
  }

  async #resolveElementHandle(
    node: TextSnapshotNode,
    uid: string,
  ): Promise<ElementHandle<Element>> {
    const message = `Element with uid ${uid} no longer exists on the page.`;
    try {
      const handle = await node.elementHandle();
      if (!handle) {
        throw new Error(message);
      }
      return handle;
    } catch (error) {
      throw new Error(message, {
        cause: error,
      });
    }
  }

  getAXNodeByUid(uid: string) {
    return this.textSnapshot?.idToNode.get(uid);
  }
}