rea/src/browser/CdpTargetSession.ts

import {
  CDP_DISCOVERY_RESPONSE_TIMEOUT_MS,
  DEFAULT_CDP_COMMAND_TIMEOUT_MS,
} from "../domain/browserDeadline.js";
import type { BrowserObservationEndpoint } from "../domain/browserObservation.js";
import { AnalysisError } from "../domain/analysisErrorBase.js";
import { analysisErrorWithCleanupFailure } from "../domain/analysisErrorCleanup.js";
import { BrowserObservationError } from "../domain/browserObservationError.js";
import type { BrowserObservationOperation } from "../domain/browserObservationErrors.js";
import { CdpConnection } from "./CdpConnection.js";
import {
  CdpTargetSessionOwner,
  bindCdpTransportCleanup,
} from "./CdpTargetSessionOwner.js";
import {
  cdpTargetWebSocket,
  discoverCdpBrowserSocket,
  discoverCdpEndpoint,
  withCdpDiscoveryDeadline,
  type CdpEndpointDiscovery,
  type CdpEndpointTarget,
} from "./CdpEndpoint.js";

/** One CDP connection scoped either by a flat browser session or page socket. */
export interface CdpTargetSession {
  readonly connection: CdpConnection;
  readonly sessionId: string | undefined;
}

/** Discovery for one caller-selected endpoint and the browser socket that read it. */
export interface CdpOpenedEndpoint {
  readonly discovery: CdpEndpointDiscovery;
  /**
   * Browser socket kept for the target session, because a browser may ask
   * the user to approve each socket. HTTP discovery opens no socket.
   */
  readonly connection: CdpConnection | undefined;
}

/**
 * Discover one passive browser endpoint through its selected transport. A
 * browser socket's handshake and discovery share one discovery deadline.
 */
export const openCdpEndpoint = async (
  endpoint: BrowserObservationEndpoint,
  operation: BrowserObservationOperation,
  signal?: AbortSignal,
  timeoutMs?: number,
  owner?: CdpTargetSessionOwner,
  commandTimeoutMs?: number,
): Promise<CdpOpenedEndpoint> => {
  if (endpoint.transport === "http_discovery")
    return {
      discovery: await discoverCdpEndpoint(endpoint.url, operation, signal),
      connection: undefined,
    };
  const discoveryTimeoutMs = timeoutMs ?? CDP_DISCOVERY_RESPONSE_TIMEOUT_MS;
  // The browser-socket handshake and discovery commands stay on the discovery
  // deadline. The selected command deadline starts only after discovery returns.
  const discoveryLimits = {
    commandTimeoutMs: discoveryTimeoutMs,
    // Stay past the discovery abort so a stalled open is labeled as discovery,
    // not as a command_timeout_ms handshake.
    handshakeTimeoutMs: discoveryTimeoutMs + 1_000,
  };
  return await withCdpDiscoveryDeadline(
    operation,
    signal,
    async (deadlineSignal) => {
      const connection =
        owner === undefined
          ? await CdpConnection.connect(
              endpoint.url,
              operation,
              deadlineSignal,
              discoveryLimits,
            )
          : await owner.connect(
              endpoint.url,
              operation,
              { signal: deadlineSignal },
              "browser-endpoint",
              discoveryLimits,
            );
      try {
        const discovery = await discoverCdpBrowserSocket(
          connection,
          endpoint.url,
          operation,
          deadlineSignal,
        );
        connection.selectCommandTimeout(
          commandTimeoutMs ?? DEFAULT_CDP_COMMAND_TIMEOUT_MS,
        );
        return {
          discovery,
          connection,
        };
      } catch (cause: unknown) {
        if (owner === undefined) {
          await connection.close();
          throw cause;
        }
        try {
          await owner.finish(connection);
        } catch (cleanupCause: unknown) {
          throw combineOpenFailure(cause, cleanupCause, operation);
        }
        throw cause;
      }
    },
    discoveryTimeoutMs,
  );
};

/** Open one authorized target through its supported browser or page transport. */
export const openCdpTargetSession = async (
  discovery: CdpEndpointDiscovery,
  target: CdpEndpointTarget,
  operation: BrowserObservationOperation,
  signal?: AbortSignal,
  limits?: {
    readonly maxPayloadBytes?: number;
    readonly commandTimeoutMs?: number;
  },
  owner?: CdpTargetSessionOwner,
): Promise<CdpTargetSession> => {
  const webSocket = cdpTargetWebSocket(discovery, target, operation);
  const connection =
    owner === undefined
      ? await CdpConnection.connect(webSocket.url, operation, signal, limits)
      : await owner.connect(
          webSocket.url,
          operation,
          signal === undefined ? {} : { signal },
          target.id,
          limits,
        );
  if (webSocket.scope === "page") return { connection, sessionId: undefined };
  try {
    return await attachCdpTargetSession(
      connection,
      target,
      operation,
      signal,
      owner,
    );
  } catch (cause: unknown) {
    if (owner === undefined) throw cause;
    try {
      await owner.finish(connection);
    } catch (cleanupCause: unknown) {
      throw combineOpenFailure(cause, cleanupCause, operation);
    }
    throw cause;
  }
};

/** Attach one target through an open browser socket, which the session then owns. */
export const attachCdpTargetSession = async (
  connection: CdpConnection,
  target: CdpEndpointTarget,
  operation: BrowserObservationOperation,
  signal?: AbortSignal,
  owner?: CdpTargetSessionOwner,
): Promise<CdpTargetSession> => {
  try {
    const attached = await connection.send(
      "Target.attachToTarget",
      { targetId: target.id, flatten: true },
      undefined,
      signal,
    );
    return { connection, sessionId: attachedSessionId(attached, operation) };
  } catch (cause: unknown) {
    if (owner === undefined) {
      await connection.close();
      throw cause;
    }
    throw cause;
  }
};

const combineOpenFailure = (
  primary: unknown,
  cleanup: unknown,
  operation: BrowserObservationOperation,
): unknown =>
  primary instanceof AnalysisError && cleanup instanceof AnalysisError
    ? bindCdpTransportCleanup(
        cleanup,
        analysisErrorWithCleanupFailure(primary, cleanup, operation),
      )
    : new AggregateError(
        [primary, cleanup],
        `CDP operation ${operation} failed and its transport cleanup is incomplete.`,
        { cause: primary },
      );

/** Disable enabled domains, detach browser sessions, and close REA's socket. */
export const closeCdpTargetSession = async (
  targetSession: CdpTargetSession,
  enabledDomains: readonly string[],
  signal?: AbortSignal,
  owner?: CdpTargetSessionOwner,
): Promise<void> => {
  if (owner !== undefined) {
    await owner.finish(targetSession.connection, () =>
      cleanupCdpTargetCommands(targetSession, enabledDomains, signal),
    );
    return;
  }
  await cleanupCdpTargetCommands(targetSession, enabledDomains, signal);
  await targetSession.connection.close();
};

const cleanupCdpTargetCommands = async (
  targetSession: CdpTargetSession,
  enabledDomains: readonly string[],
  signal?: AbortSignal,
): Promise<void> => {
  const { connection, sessionId } = targetSession;
  const cleanup = new AbortController();
  const domainSignal =
    signal === undefined
      ? cleanup.signal
      : AbortSignal.any([cleanup.signal, signal]);
  const timeout = setTimeout(() => cleanup.abort(), 1_000);
  timeout.unref();
  try {
    if (signal?.aborted !== true) {
      for (const domain of enabledDomains) {
        if (domainSignal.aborted) break;
        try {
          await connection.send(
            `${domain}.disable`,
            {},
            sessionId,
            domainSignal,
          );
        } catch {
          // Best-effort domain cleanup; transport close is the definitive boundary.
        }
      }
    }
    // Cancellation skips optional domain shutdown but still releases the
    // attached session using its independent, bounded cleanup signal.
    if (!cleanup.signal.aborted && sessionId !== undefined)
      try {
        await connection.send(
          "Target.detachFromTarget",
          { sessionId },
          undefined,
          cleanup.signal,
        );
      } catch {
        // Best-effort detach; transport close is the definitive boundary.
      }
  } finally {
    clearTimeout(timeout);
    cleanup.abort();
  }
};

const attachedSessionId = (
  value: unknown,
  operation: BrowserObservationOperation,
): string => {
  if (
    typeof value !== "object" ||
    value === null ||
    !("sessionId" in value) ||
    typeof value.sessionId !== "string" ||
    value.sessionId.length === 0
  )
    throw new BrowserObservationError(operation, "protocol_error");
  return value.sessionId;
};