action-impl.js

import {
  ActionTrust,
  DEFAULT_ACTION,
  RAW_OBJECT_ARGS_KEY,
  actionTrustToString,
} from '#core/constants/action-constants';
import {Keys} from '#core/constants/key-codes';
import {isAmp4Email} from '#core/document/format';
import {isEnabled} from '#core/dom';
import {isFiniteNumber} from '#core/types';
import {isArray, toArray} from '#core/types/array';
import {debounce, throttle} from '#core/types/function';
import {dict, getValueForExpr, hasOwn, map} from '#core/types/object';
import {getWin} from '#core/window';

import {Services} from '#service';

import {getDetail} from '#utils/event-helper';
import {dev, devAssert, user, userAssert} from '#utils/log';

import {reportError} from '../error-reporting';
import {getMode} from '../mode';
import {registerServiceBuilderForDoc} from '../service-helpers';

/** @const {string} */
const TAG_ = 'Action';

/** @const {string} */
const ACTION_MAP_ = '__AMP_ACTION_MAP__' + Math.random();

/** @const {string} */
const ACTION_QUEUE_ = '__AMP_ACTION_QUEUE__';

/** @const {string} */
const ACTION_HANDLER_ = '__AMP_ACTION_HANDLER__';

/** @const {number} */
const DEFAULT_DEBOUNCE_WAIT = 300; // ms

/** @const {number} */
const DEFAULT_THROTTLE_INTERVAL = 100; // ms

/** @const {!Object<string,!Array<string>>} */
const NON_AMP_ELEMENTS_ACTIONS_ = {
  'form': ['submit', 'clear'],
};

const DEFAULT_EMAIL_ALLOWLIST = [
  {tagOrTarget: 'AMP', method: 'setState'},
  {tagOrTarget: '*', method: 'focus'},
  {tagOrTarget: '*', method: 'hide'},
  {tagOrTarget: '*', method: 'show'},
  {tagOrTarget: '*', method: 'toggleClass'},
  {tagOrTarget: '*', method: 'toggleChecked'},
  {tagOrTarget: '*', method: 'toggleVisibility'},
];

/**
 * Interactable widgets which should trigger tap events when the user clicks
 * or activates via the keyboard. Not all are here, e.g. progressbar, tabpanel,
 * since they are text inputs, readonly, or composite widgets that shouldn't
 * need to trigger tap events from spacebar or enter on their own.
 * See https://www.w3.org/TR/wai-aria-1.1/#widget_roles
 * @const {!Object<boolean>}
 */
export const TAPPABLE_ARIA_ROLES = {
  'button': true,
  'checkbox': true,
  'link': true,
  'listbox': true,
  'menuitem': true,
  'menuitemcheckbox': true,
  'menuitemradio': true,
  'option': true,
  'radio': true,
  'scrollbar': true,
  'slider': true,
  'spinbutton': true,
  'switch': true,
  'tab': true,
  'treeitem': true,
};

/**
 * An expression arg value, e.g. `foo.bar` in `e:t.m(arg=foo.bar)`.
 * @typedef {{expression: string}}
 */
let ActionInfoArgExpressionDef;

/**
 * An arg value.
 * @typedef {(boolean|number|string|ActionInfoArgExpressionDef)}
 */
let ActionInfoArgValueDef;

/**
 * Map of arg names to their values, e.g. {arg: 123} in `e:t.m(arg=123)`.
 * @typedef {Object<string, ActionInfoArgValueDef>}
 */
let ActionInfoArgsDef;

/**
 * @typedef {{
 *   event: string,
 *   target: string,
 *   method: string,
 *   args: ?ActionInfoArgsDef,
 *   str: string
 * }}
 */
export let ActionInfoDef;

/**
 * Function called when an action is invoked.
 *
 * Optionally, takes this action's position within all actions triggered by
 * the same event, as well as said action array, as params.
 *
 * If the action is chainable, returns a Promise which resolves when the
 * action is complete. Otherwise, returns null.
 *
 * @typedef {function(!ActionInvocation, number=, !Array<!ActionInfoDef>=):?Promise}
 */
let ActionHandlerDef;

/**
 * @typedef {Event|DeferredEvent}
 */
export let ActionEventDef;

/**
 * The structure that contains all details of the action method invocation.
 * @struct @const @package For type.
 */
export class ActionInvocation {
  /**
   * For example:
   *
   *   <div id="div" on="tap:myForm.submit(foo=bar)">
   *     <button id="btn">Submit</button>
   *   </div>
   *
   * `node` is #myForm.
   * `method` is "submit".
   * `args` is {'foo': 'bar'}.
   * `source` is #btn.
   * `caller` is #div.
   * `event` is a "click" Event object.
   * `actionEventType` is "tap".
   * `trust` depends on whether this action was a result of a user gesture.
   * `tagOrTarget` is "amp-form".
   * `sequenceId` is a pseudo-UUID.
   *
   * @param {!Node} node Element whose action is being invoked.
   * @param {string} method Name of the action being invoked.
   * @param {?JsonObject} args Named action arguments.
   * @param {?Element} source Element that generated the `event`.
   * @param {?Element} caller Element containing the on="..." action handler.
   * @param {?ActionEventDef} event The event object that triggered this action.
   * @param {!ActionTrust} trust The trust level of this invocation's trigger.
   * @param {?string} actionEventType The AMP event name that triggered this.
   * @param {?string} tagOrTarget The global target name or the element tagName.
   * @param {number} sequenceId An identifier for this action's sequence (all
   *   actions triggered by one event e.g. "tap:form1.submit, form2.submit").
   */
  constructor(
    node,
    method,
    args,
    source,
    caller,
    event,
    trust,
    actionEventType = '?',
    tagOrTarget = null,
    sequenceId = Math.random()
  ) {
    /** @type {!Node} */
    this.node = node;
    /** @const {string} */
    this.method = method;
    /** @const {?JsonObject} */
    this.args = args;
    /** @const {?Element} */
    this.source = source;
    /** @const {?Element} */
    this.caller = caller;
    /** @const {?ActionEventDef} */
    this.event = event;
    /** @const {!ActionTrust} */
    this.trust = trust;
    /** @const {?string} */
    this.actionEventType = actionEventType;
    /** @const {string} */
    this.tagOrTarget = tagOrTarget || node.tagName;
    /** @const {number} */
    this.sequenceId = sequenceId;
  }

  /**
   * Returns true if the trigger event has a trust equal to or greater than
   * `minimumTrust`. Otherwise, logs a user error and returns false.
   * @param {ActionTrust} minimumTrust
   * @return {boolean}
   */
  satisfiesTrust(minimumTrust) {
    // Sanity check.
    if (!isFiniteNumber(this.trust)) {
      dev().error(TAG_, `Invalid trust for '${this.method}': ${this.trust}`);
      return false;
    }
    if (this.trust < minimumTrust) {
      const t = actionTrustToString(this.trust);
      user().error(
        TAG_,
        `"${this.actionEventType}" event with "${t}" trust is not allowed to ` +
          `invoke "${this.tagOrTarget.toLowerCase()}.${this.method}".`
      );
      return false;
    }
    return true;
  }
}

/**
 * TODO(dvoytenko): consider splitting this class into two:
 * 1. A class that has a method "trigger(element, eventType, data)" and
 *    simply can search target in DOM and trigger methods on it.
 * 2. A class that configures event recognizers and rules and then
 *    simply calls action.trigger.
 */
export class ActionService {
  /**
   * @param {!./ampdoc-impl.AmpDoc} ampdoc
   * @param {(!Document|!ShadowRoot)=} opt_root
   */
  constructor(ampdoc, opt_root) {
    /** @const {!./ampdoc-impl.AmpDoc} */
    this.ampdoc = ampdoc;

    /** @const {!Document|!ShadowRoot} */
    this.root_ = opt_root || ampdoc.getRootNode();

    /** @const {boolean} */
    this.isEmail_ =
      this.ampdoc.isSingleDoc() &&
      isAmp4Email(/** @type {!Document} */ (this.root_));

    /**
     * Optional allowlist of actions, e.g.:
     *
     *     [{tagOrTarget: 'AMP', method: 'navigateTo'},
     *      {tagOrTarget: 'AMP-FORM', method: 'submit'},
     *      {tagOrTarget: '*', method: 'show'}]
     *
     * If not null, any actions that are not in the allowlist will be ignored
     * and throw a user error at invocation time. Note that `tagOrTarget` is
     * always the canonical uppercased form (same as
     * `Element.prototype.tagName`). If `tagOrTarget` is the wildcard '*', then
     * the allowlisted method is allowed on any tag or target.
     *
     * For AMP4Email format documents, allowed actions are autogenerated.
     * @private {?Array<{tagOrTarget: string, method: string}>}
     */
    this.allowlist_ = this.isEmail_ ? DEFAULT_EMAIL_ALLOWLIST : null;

    /** @const @private {!Object<string, ActionHandlerDef>} */
    this.globalTargets_ = map();

    /**
     * @const @private {!Object<string, {handler: ActionHandlerDef, minTrust: ActionTrust}>}
     */
    this.globalMethodHandlers_ = map();

    // Add core events.
    this.addEvent('tap');
    this.addEvent('submit');
    this.addEvent('change');
    this.addEvent('input-debounced');
    this.addEvent('input-throttled');
    this.addEvent('valid');
    this.addEvent('invalid');
  }

  /**
   * @param {string} name
   * TODO(dvoytenko): switch to a system where the event recognizers are
   * registered with Action instead, e.g. "doubletap", "tap to zoom".
   */
  addEvent(name) {
    if (name == 'tap') {
      // TODO(dvoytenko): if needed, also configure touch-based tap, e.g. for
      // fast-click.
      this.root_.addEventListener('click', (event) => {
        if (!event.defaultPrevented) {
          const element = dev().assertElement(event.target);
          this.trigger(element, name, event, ActionTrust.HIGH);
        }
      });
      this.root_.addEventListener('keydown', (event) => {
        const {key, target} = event;
        const element = dev().assertElement(target);
        if (key == Keys.ENTER || key == Keys.SPACE) {
          const role = element.getAttribute('role');
          const isTapEventRole =
            role && hasOwn(TAPPABLE_ARIA_ROLES, role.toLowerCase());
          if (!event.defaultPrevented && isTapEventRole) {
            const hasAction = this.trigger(
              element,
              name,
              event,
              ActionTrust.HIGH
            );
            // Only if the element has an action do we prevent the default.
            // In the absence of an action, e.g. on="[event].method", we do not
            // want to stop default behavior.
            if (hasAction) {
              event.preventDefault();
            }
          }
        }
      });
    } else if (name == 'submit') {
      this.root_.addEventListener(name, (event) => {
        const element = dev().assertElement(event.target);
        // For get requests, the delegating to the viewer needs to happen
        // before this.
        this.trigger(element, name, event, ActionTrust.HIGH);
      });
    } else if (name == 'change') {
      this.root_.addEventListener(name, (event) => {
        const element = dev().assertElement(event.target);
        this.addTargetPropertiesAsDetail_(event);
        this.trigger(element, name, event, ActionTrust.HIGH);
      });
    } else if (name == 'input-debounced') {
      const debouncedInput = debounce(
        this.ampdoc.win,
        (event) => {
          const target = dev().assertElement(event.target);
          this.trigger(
            target,
            name,
            /** @type {!ActionEventDef} */ (event),
            ActionTrust.HIGH
          );
        },
        DEFAULT_DEBOUNCE_WAIT
      );

      this.root_.addEventListener('input', (event) => {
        // Create a DeferredEvent to avoid races where the browser cleans up
        // the event object before the async debounced function is called.
        const deferredEvent = new DeferredEvent(event);
        this.addTargetPropertiesAsDetail_(deferredEvent);
        debouncedInput(deferredEvent);
      });
    } else if (name == 'input-throttled') {
      const throttledInput = throttle(
        this.ampdoc.win,
        (event) => {
          const target = dev().assertElement(event.target);
          this.trigger(
            target,
            name,
            /** @type {!ActionEventDef} */ (event),
            ActionTrust.HIGH
          );
        },
        DEFAULT_THROTTLE_INTERVAL
      );

      this.root_.addEventListener('input', (event) => {
        const deferredEvent = new DeferredEvent(event);
        this.addTargetPropertiesAsDetail_(deferredEvent);
        throttledInput(deferredEvent);
      });
    } else if (name == 'valid' || name == 'invalid') {
      this.root_.addEventListener(name, (event) => {
        const element = dev().assertElement(event.target);
        this.trigger(element, name, event, ActionTrust.HIGH);
      });
    }
  }

  /**
   * Registers the action target that will receive all designated actions.
   * @param {string} name
   * @param {ActionHandlerDef} handler
   */
  addGlobalTarget(name, handler) {
    this.globalTargets_[name] = handler;
  }

  /**
   * Registers the action handler for a common method.
   * @param {string} name
   * @param {ActionHandlerDef} handler
   * @param {ActionTrust} minTrust
   */
  addGlobalMethodHandler(name, handler, minTrust = ActionTrust.DEFAULT) {
    this.globalMethodHandlers_[name] = {handler, minTrust};
  }

  /**
   * Triggers the specified event on the target element.
   * @param {!Element} target
   * @param {string} eventType
   * @param {?ActionEventDef} event
   * @param {!ActionTrust} trust
   * @param {?JsonObject=} opt_args
   * @return {boolean} true if the target has an action.
   */
  trigger(target, eventType, event, trust, opt_args) {
    return this.action_(target, eventType, event, trust, opt_args);
  }

  /**
   * Triggers execution of the method on a target/method.
   * @param {!Element} target
   * @param {string} method
   * @param {?JsonObject} args
   * @param {?Element} source
   * @param {?Element} caller
   * @param {?ActionEventDef} event
   * @param {ActionTrust} trust
   */
  execute(target, method, args, source, caller, event, trust) {
    const invocation = new ActionInvocation(
      target,
      method,
      args,
      source,
      caller,
      event,
      trust
    );
    this.invoke_(invocation);
  }

  /**
   * Installs action handler for the specified element. The action handler is
   * responsible for checking invocation trust.
   *
   * For AMP elements, use base-element.registerAction() instead.
   *
   * @param {!Element} target
   * @param {ActionHandlerDef} handler
   */
  installActionHandler(target, handler) {
    // TODO(dvoytenko, #7063): switch back to `target.id` with form proxy.
    const targetId = target.getAttribute('id') || '';

    devAssert(
      isAmpTagName(targetId) ||
        target.tagName.toLowerCase() in NON_AMP_ELEMENTS_ACTIONS_,
      'AMP or special element expected: %s',
      target.tagName + '#' + targetId
    );

    if (target[ACTION_HANDLER_]) {
      dev().error(TAG_, `Action handler already installed for ${target}`);
      return;
    }
    target[ACTION_HANDLER_] = handler;

    /** @const {Array<!ActionInvocation>} */
    const queuedInvocations = target[ACTION_QUEUE_];
    if (isArray(queuedInvocations)) {
      // Invoke and clear all queued invocations now handler is installed.
      Services.timerFor(getWin(target)).delay(() => {
        // TODO(dvoytenko, #1260): dedupe actions.
        queuedInvocations.forEach((invocation) => {
          try {
            handler(invocation);
          } catch (e) {
            dev().error(TAG_, 'Action execution failed:', invocation, e);
          }
        });
        target[ACTION_QUEUE_].length = 0;
      }, 1);
    }
  }

  /**
   * Checks if the given element has registered a particular action type.
   * @param {!Element} element
   * @param {string} actionEventType
   * @param {!Element=} opt_stopAt
   * @return {boolean}
   */
  hasAction(element, actionEventType, opt_stopAt) {
    return !!this.findAction_(element, actionEventType, opt_stopAt);
  }

  /**
   * Checks if the given element's registered action resolves to at least one
   * existing element by id or a global target (e.g. "AMP").
   * @param {!Element} element
   * @param {string} actionEventType
   * @param {!Element=} opt_stopAt
   * @return {boolean}
   */
  hasResolvableAction(element, actionEventType, opt_stopAt) {
    const action = this.findAction_(element, actionEventType, opt_stopAt);
    if (!action) {
      return false;
    }
    return action.actionInfos.some((action) => {
      const {target} = action;
      return !!this.getActionNode_(target);
    });
  }

  /**
   * Checks if the given element's registered action resolves to at least one
   * existing element by id or a global target (e.g. "AMP").
   * @param {!Element} element
   * @param {string} actionEventType
   * @param {!Element} targetElement
   * @param {!Element=} opt_stopAt
   * @return {boolean}
   */
  hasResolvableActionForTarget(
    element,
    actionEventType,
    targetElement,
    opt_stopAt
  ) {
    const action = this.findAction_(element, actionEventType, opt_stopAt);
    if (!action) {
      return false;
    }
    return action.actionInfos.some((actionInfo) => {
      const {target} = actionInfo;
      return this.getActionNode_(target) == targetElement;
    });
  }

  /**
   * For global targets e.g. "AMP", returns the document root. Otherwise,
   * `target` is an element id and the corresponding element is returned.
   * @param {string} target
   * @return {?Document|?Element|?ShadowRoot}
   * @private
   */
  getActionNode_(target) {
    return this.globalTargets_[target]
      ? this.root_
      : this.root_.getElementById(target);
  }

  /**
   * Sets the action allowlist. Can be used to clear it.
   * @param {!Array<{tagOrTarget: string, method: string}>} allowlist
   */
  setAllowlist(allowlist) {
    devAssert(
      allowlist.every((v) => v.tagOrTarget && v.method),
      'Action allowlist entries should be of shape { tagOrTarget: string, method: string }'
    );
    this.allowlist_ = allowlist;
  }

  /**
   * Adds an action to the allowlist.
   * @param {string} tagOrTarget The tag or target to allowlist, e.g.
   *     'AMP-LIST', '*'.
   * @param {string|Array<string>} methods The method(s) to allowlist, e.g. 'show', 'hide'.
   * @param {Array<string>=} opt_forFormat
   */
  addToAllowlist(tagOrTarget, methods, opt_forFormat) {
    // TODO(wg-performance): When it becomes possible to getFormat(),
    // we can store `format_` instead of `isEmail_` and check
    // (opt_forFormat && !opt_forFormat.includes(this.format_))
    if (opt_forFormat && opt_forFormat.includes('email') !== this.isEmail_) {
      return;
    }
    if (!this.allowlist_) {
      this.allowlist_ = [];
    }
    if (!isArray(methods)) {
      methods = [methods];
    }
    methods.forEach((method) => {
      if (
        this.allowlist_.some(
          (v) => v.tagOrTarget == tagOrTarget && v.method == method
        )
      ) {
        return;
      }
      this.allowlist_.push({tagOrTarget, method});
    });
  }

  /**
   * @param {!Element} source
   * @param {string} actionEventType
   * @param {?ActionEventDef} event
   * @param {!ActionTrust} trust
   * @param {?JsonObject=} opt_args
   * @return {boolean} True if the element has an action.
   * @private
   */
  action_(source, actionEventType, event, trust, opt_args) {
    const action = this.findAction_(source, actionEventType);
    if (!action) {
      return false;
    }
    // Use a pseudo-UUID to uniquely identify this sequence of actions.
    // A sequence is all actions triggered by a single event.
    const sequenceId = Math.random();
    // Invoke actions serially, where each action waits for its predecessor
    // to complete. `currentPromise` is the i'th promise in the chain.
    /** @type {?Promise} */
    let currentPromise = null;
    action.actionInfos.forEach((actionInfo) => {
      const {args, method, str, target} = actionInfo;
      const dereferencedArgs = dereferenceArgsVariables(args, event, opt_args);
      const invokeAction = () => {
        const node = this.getActionNode_(target);
        if (!node) {
          this.error_(`Target "${target}" not found for action [${str}].`);
          return;
        }
        const invocation = new ActionInvocation(
          node,
          method,
          dereferencedArgs,
          source,
          action.node,
          event,
          trust,
          actionEventType,
          node.tagName || target,
          sequenceId
        );
        return this.invoke_(invocation);
      };
      // Wait for the previous action, if any.
      currentPromise = currentPromise
        ? currentPromise.then(invokeAction)
        : invokeAction();
    });

    return action.actionInfos.length >= 1;
  }

  /**
   * @param {string} message
   * @param {?Element=} opt_element
   * @private
   */
  error_(message, opt_element) {
    if (opt_element) {
      // reportError() supports displaying the element in dev console.
      const e = user().createError(`[${TAG_}] ${message}`);
      reportError(e, opt_element);
      throw e;
    } else {
      user().error(TAG_, message);
    }
  }

  /**
   * @param {!ActionInvocation} invocation
   * @return {?Promise}
   * @private
   */
  invoke_(invocation) {
    const {method, tagOrTarget} = invocation;

    // Check that this action is allowlisted (if a allowlist is set).
    if (this.allowlist_) {
      if (!isActionAllowlisted(invocation, this.allowlist_)) {
        this.error_(
          `"${tagOrTarget}.${method}" is not allowlisted ${JSON.stringify(
            this.allowlist_
          )}.`
        );
        return null;
      }
    }

    // Handle global targets e.g. "AMP".
    const globalTarget = this.globalTargets_[tagOrTarget];
    if (globalTarget) {
      return globalTarget(invocation);
    }

    // Subsequent handlers assume that invocation target is an Element.
    const node = dev().assertElement(invocation.node);

    // Handle global actions e.g. "<any-element-id>.toggle".
    const globalMethod = this.globalMethodHandlers_[method];
    if (globalMethod && invocation.satisfiesTrust(globalMethod.minTrust)) {
      return globalMethod.handler(invocation);
    }

    // Handle element-specific actions.
    const lowerTagName = node.tagName.toLowerCase();
    if (isAmpTagName(lowerTagName)) {
      if (node.enqueAction) {
        node.enqueAction(invocation);
      } else {
        this.error_(`Unrecognized AMP element "${lowerTagName}".`, node);
      }
      return null;
    }

    // Special non-AMP elements with AMP ID or known supported actions.
    const nonAmpActions = NON_AMP_ELEMENTS_ACTIONS_[lowerTagName];
    // TODO(dvoytenko, #7063): switch back to `target.id` with form proxy.
    const targetId = node.getAttribute('id') || '';
    if (
      isAmpTagName(targetId) ||
      (nonAmpActions && nonAmpActions.indexOf(method) > -1)
    ) {
      const handler = node[ACTION_HANDLER_];
      if (handler) {
        handler(invocation);
      } else {
        node[ACTION_QUEUE_] = node[ACTION_QUEUE_] || [];
        node[ACTION_QUEUE_].push(invocation);
      }
      return null;
    }

    // Unsupported method.
    this.error_(
      `Target (${tagOrTarget}) doesn't support "${method}" action.`,
      invocation.caller
    );

    return null;
  }

  /**
   * @param {!Element} target
   * @param {string} actionEventType
   * @param {!Element=} opt_stopAt
   * @return {?{node: !Element, actionInfos: !Array<!ActionInfoDef>}}
   */
  findAction_(target, actionEventType, opt_stopAt) {
    // Go from target up the DOM tree and find the applicable action.
    let n = target;
    while (n) {
      if (opt_stopAt && n == opt_stopAt) {
        return null;
      }
      const actionInfos = this.matchActionInfos_(n, actionEventType);
      if (actionInfos && isEnabled(n)) {
        return {node: n, actionInfos: devAssert(actionInfos)};
      }
      n = n.parentElement;
    }
    return null;
  }

  /**
   * @param {!Element} node
   * @param {string} actionEventType
   * @return {?Array<!ActionInfoDef>}
   */
  matchActionInfos_(node, actionEventType) {
    const actionMap = this.getActionMap_(node, actionEventType);
    if (!actionMap) {
      return null;
    }
    return actionMap[actionEventType] || null;
  }

  /**
   * @param {!Element} node
   * @param {string} actionEventType
   * @return {?Object<string, !Array<!ActionInfoDef>>}
   */
  getActionMap_(node, actionEventType) {
    let actionMap = node[ACTION_MAP_];
    if (actionMap === undefined) {
      actionMap = null;
      if (node.hasAttribute('on')) {
        const action = node.getAttribute('on');
        actionMap = parseActionMap(action, node);
        node[ACTION_MAP_] = actionMap;
      } else if (node.hasAttribute('execute')) {
        const action = node.getAttribute('execute');
        actionMap = parseActionMap(`${actionEventType}:${action}`, node);
        node[ACTION_MAP_] = actionMap;
      }
    }
    return actionMap;
  }

  /**
   * Resets a node's actions with those defined in the given actions string.
   * @param {!Element} node
   * @param {string} actionsStr
   */
  setActions(node, actionsStr) {
    node.setAttribute('on', actionsStr);

    // Clear cache.
    delete node[ACTION_MAP_];
  }

  /**
   * Given a browser 'change' or 'input' event, add `detail` property to it
   * containing allowlisted properties of the target element. Noop if `detail`
   * is readonly.
   * @param {!ActionEventDef} event
   * @private
   */
  addTargetPropertiesAsDetail_(event) {
    const detail = /** @type {!JsonObject} */ (map());
    const {target} = event;

    if (target.value !== undefined) {
      detail['value'] = target.value;
    }

    // Check tagName instead since `valueAsNumber` isn't supported on IE.
    if (target.tagName == 'INPUT') {
      // Probably supported natively but convert anyways for consistency.
      detail['valueAsNumber'] = Number(target.value);
    }

    if (target.checked !== undefined) {
      detail['checked'] = target.checked;
    }

    if (target.min !== undefined || target.max !== undefined) {
      detail['min'] = target.min;
      detail['max'] = target.max;
    }

    if (target.files) {
      detail['files'] = toArray(target.files).map((file) => ({
        'name': file.name,
        'size': file.size,
        'type': file.type,
      }));
    }

    if (Object.keys(detail).length > 0) {
      try {
        event.detail = detail;
      } catch {} // event.detail is readonly
    }
  }
}

/**
 * @param {string} lowercaseTagName
 * @return {boolean}
 * @private
 */
function isAmpTagName(lowercaseTagName) {
  return lowercaseTagName.substring(0, 4) === 'amp-';
}

/**
 * Returns `true` if the given action invocation is allowlisted in the given
 * allowlist. Default actions' alias, 'activate', are automatically
 * allowlisted if their corresponding registered alias is allowlisted.
 * @param {!ActionInvocation} invocation
 * @param {!Array<{tagOrTarget: string, method: string}>} allowlist
 * @return {boolean}
 * @private
 */
function isActionAllowlisted(invocation, allowlist) {
  let {method} = invocation;
  const {node, tagOrTarget} = invocation;
  // Use alias if default action is invoked.
  if (
    method === DEFAULT_ACTION &&
    typeof node.getDefaultActionAlias == 'function'
  ) {
    method = node.getDefaultActionAlias();
  }
  const lcMethod = method.toLowerCase();
  const lcTagOrTarget = tagOrTarget.toLowerCase();
  return allowlist.some((w) => {
    if (
      w.tagOrTarget.toLowerCase() === lcTagOrTarget ||
      w.tagOrTarget === '*'
    ) {
      if (w.method.toLowerCase() === lcMethod) {
        return true;
      }
    }
    return false;
  });
}

/**
 * A clone of an event object with its function properties replaced.
 * This is useful e.g. for event objects that need to be passed to an async
 * context, but the browser might have cleaned up the original event object.
 * This clone replaces functions with error throws since they won't behave
 * normally after the original object has been destroyed.
 * @private visible for testing
 */
export class DeferredEvent {
  /**
   * @param {!Event} event
   */
  constructor(event) {
    /** @type {?Object} */
    this.detail = null;

    cloneWithoutFunctions(event, this);
  }
}

/**
 * Clones an object and replaces its function properties with throws.
 * @param {!T} original
 * @param {!T=} opt_dest
 * @return {!T}
 * @template T
 * @private
 */
function cloneWithoutFunctions(original, opt_dest) {
  const clone = opt_dest || map();
  for (const prop in original) {
    const value = original[prop];
    if (typeof value === 'function') {
      clone[prop] = notImplemented;
    } else {
      clone[prop] = original[prop];
    }
  }
  return clone;
}

/** @private */
function notImplemented() {
  devAssert(null, 'Deferred events cannot access native event functions.');
}

/**
 * @param {string} action
 * @param {!Element} context
 * @return {?Object<string, !Array<!ActionInfoDef>>}
 * @private Visible for testing only.
 */
export function parseActionMap(action, context) {
  const assertAction = assertActionForParser.bind(null, action, context);
  const assertToken = assertTokenForParser.bind(null, action, context);

  let actionMap = null;

  const toks = new ParserTokenizer(action);
  let tok;
  let peek;
  do {
    tok = toks.next();
    if (
      tok.type == TokenType.EOF ||
      (tok.type == TokenType.SEPARATOR && tok.value == ';')
    ) {
      // Expected, ignore.
    } else if (tok.type == TokenType.LITERAL || tok.type == TokenType.ID) {
      // Format: event:target.method

      // Event: "event:"
      const event = tok.value;

      // Target: ":target." separator
      assertToken(toks.next(), [TokenType.SEPARATOR], ':');

      const actions = [];

      // Handlers for event.
      do {
        const target = assertToken(toks.next(), [
          TokenType.LITERAL,
          TokenType.ID,
        ]).value;

        // Method: ".method". Method is optional.
        let method = DEFAULT_ACTION;
        let args = null;

        peek = toks.peek();
        if (peek.type == TokenType.SEPARATOR && peek.value == '.') {
          toks.next(); // Skip '.'
          method =
            assertToken(toks.next(), [TokenType.LITERAL, TokenType.ID]).value ||
            method;

          // Optionally, there may be arguments: "(key = value, key = value)".
          peek = toks.peek();
          if (peek.type == TokenType.SEPARATOR && peek.value == '(') {
            toks.next(); // Skip '('
            args = tokenizeMethodArguments(toks, assertToken, assertAction);
          }
        }

        actions.push({
          event,
          target,
          method,
          args:
            args && getMode().test && Object.freeze
              ? Object.freeze(args)
              : args,
          str: action,
        });

        peek = toks.peek();
      } while (
        peek.type == TokenType.SEPARATOR &&
        peek.value == ',' &&
        toks.next()
      ); // skip "," when found

      if (!actionMap) {
        actionMap = map();
      }

      actionMap[event] = actions;
    } else {
      // Unexpected token.
      assertAction(false, `; unexpected token [${tok.value || ''}]`);
    }
  } while (tok.type != TokenType.EOF);

  return actionMap;
}

/**
 * Tokenizes and returns method arguments, e.g. target.method(arguments).
 * @param {!ParserTokenizer} toks
 * @param {!Function} assertToken
 * @param {!Function} assertAction
 * @return {?ActionInfoArgsDef}
 * @private
 */
function tokenizeMethodArguments(toks, assertToken, assertAction) {
  let peek = toks.peek();
  let tok;
  let args = null;
  // Object literal. Format: {...}
  if (peek.type == TokenType.OBJECT) {
    // Don't parse object literals. Tokenize as a single expression
    // fragment and delegate to specific action handler.
    args = map();
    const {value} = toks.next();
    args[RAW_OBJECT_ARGS_KEY] = value;
    assertToken(toks.next(), [TokenType.SEPARATOR], ')');
  } else {
    // Key-value pairs. Format: key = value, ....
    do {
      tok = toks.next();
      const {type, value} = tok;
      if (type == TokenType.SEPARATOR && (value == ',' || value == ')')) {
        // Expected: ignore.
      } else if (type == TokenType.LITERAL || type == TokenType.ID) {
        // Key: "key = "
        assertToken(toks.next(), [TokenType.SEPARATOR], '=');
        // Value is either a literal or an expression: "foo.bar.baz"
        tok = assertToken(toks.next(/* convertValue */ true), [
          TokenType.LITERAL,
          TokenType.ID,
        ]);
        const argValueTokens = [tok];
        // Expressions have one or more dereferences: ".identifier"
        if (tok.type == TokenType.ID) {
          for (
            peek = toks.peek();
            peek.type == TokenType.SEPARATOR && peek.value == '.';
            peek = toks.peek()
          ) {
            toks.next(); // Skip '.'.
            tok = assertToken(toks.next(false), [TokenType.ID]);
            argValueTokens.push(tok);
          }
        }
        const argValue = argValueForTokens(argValueTokens);
        if (!args) {
          args = map();
        }
        args[value] = argValue;
        peek = toks.peek();
        assertAction(
          peek.type == TokenType.SEPARATOR &&
            (peek.value == ',' || peek.value == ')'),
          'Expected either [,] or [)]'
        );
      } else {
        // Unexpected token.
        assertAction(false, `; unexpected token [${tok.value || ''}]`);
      }
    } while (!(tok.type == TokenType.SEPARATOR && tok.value == ')'));
  }
  return args;
}

/**
 * @param {Array<!TokenDef>} tokens
 * @return {?ActionInfoArgValueDef}
 * @private
 */
function argValueForTokens(tokens) {
  if (tokens.length == 0) {
    return null;
  } else if (tokens.length == 1) {
    return /** @type {(boolean|number|string)} */ (tokens[0].value);
  } else {
    const values = tokens.map((token) => token.value);
    const expression = values.join('.');
    return /** @type {ActionInfoArgExpressionDef} */ ({expression});
  }
}

/**
 * Dereferences expression args in `args` using values in data.
 * @param {?ActionInfoArgsDef} args
 * @param {?ActionEventDef} event
 * @param {?JsonObject=} opt_args
 * @return {?JsonObject}
 * @private
 */
export function dereferenceArgsVariables(args, event, opt_args) {
  if (!args) {
    return args;
  }
  const data = opt_args || dict({});
  if (event) {
    const detail = getDetail(/** @type {!Event} */ (event));
    if (detail) {
      data['event'] = detail;
    }
  }
  const applied = map();
  Object.keys(args).forEach((key) => {
    let value = args[key];
    // Only JSON expression strings that contain dereferences (e.g. `foo.bar`)
    // are processed as ActionInfoArgExpressionDef. We also support
    // dereferencing strings like `foo` iff there is a corresponding key in
    // `data`. Otherwise, `foo` is treated as a string "foo".
    if (typeof value == 'object' && value.expression) {
      const expr = /** @type {ActionInfoArgExpressionDef} */ (value).expression;
      const exprValue = getValueForExpr(data, expr);
      // If expr can't be found in data, use null instead of undefined.
      value = exprValue === undefined ? null : exprValue;
    }
    if (data[value]) {
      applied[key] = data[value];
    } else {
      applied[key] = value;
    }
  });
  return applied;
}

/**
 * @param {string} s
 * @param {!Element} context
 * @param {?T} condition
 * @param {string=} opt_message
 * @return {T}
 * @template T
 * @private
 */
function assertActionForParser(s, context, condition, opt_message) {
  return userAssert(
    condition,
    'Invalid action definition in %s: [%s] %s',
    context,
    s,
    opt_message || ''
  );
}

/**
 * @param {string} s
 * @param {!Element} context
 * @param {!TokenDef} tok
 * @param {Array<TokenType>} types
 * @param {*=} opt_value
 * @return {!TokenDef}
 * @private
 */
function assertTokenForParser(s, context, tok, types, opt_value) {
  if (opt_value !== undefined) {
    assertActionForParser(
      s,
      context,
      types.includes(tok.type) && tok.value == opt_value,
      `; expected [${opt_value}]`
    );
  } else {
    assertActionForParser(s, context, types.includes(tok.type));
  }
  return tok;
}

/**
 * @enum {number}
 */
const TokenType = {
  INVALID: 0,
  EOF: 1,
  SEPARATOR: 2,
  LITERAL: 3,
  ID: 4,
  OBJECT: 5,
};

/**
 * @typedef {{type: TokenType, value: *}}
 */
let TokenDef;

/** @private @const {string} */
const WHITESPACE_SET = ' \t\n\r\f\v\u00A0\u2028\u2029';

/** @private @const {string} */
const SEPARATOR_SET = ';:.()=,|!';

/** @private @const {string} */
const STRING_SET = '"\'';

/** @private @const {string} */
const OBJECT_SET = '{}';

/** @private @const {string} */
const SPECIAL_SET = WHITESPACE_SET + SEPARATOR_SET + STRING_SET + OBJECT_SET;

/** @private */
class ParserTokenizer {
  /**
   * @param {string} str
   */
  constructor(str) {
    /** @private @const {string} */
    this.str_ = str;

    /** @private {number} */
    this.index_ = -1;
  }

  /**
   * Returns the next token and advances the position.
   * @param {boolean=} opt_convertValues
   * @return {!TokenDef}
   */
  next(opt_convertValues) {
    const tok = this.next_(opt_convertValues || false);
    this.index_ = tok.index;
    return tok;
  }

  /**
   * Returns the next token but keeps the current position.
   * @param {boolean=} opt_convertValues
   * @return {!TokenDef}
   */
  peek(opt_convertValues) {
    return this.next_(opt_convertValues || false);
  }

  /**
   * @param {boolean} convertValues
   * @return {!{type: TokenType, value: *, index: number}}
   */
  next_(convertValues) {
    let newIndex = this.index_ + 1;
    if (newIndex >= this.str_.length) {
      return {type: TokenType.EOF, index: this.index_};
    }

    let c = this.str_.charAt(newIndex);

    // Whitespace: standard set.
    if (WHITESPACE_SET.indexOf(c) != -1) {
      newIndex++;
      for (; newIndex < this.str_.length; newIndex++) {
        if (WHITESPACE_SET.indexOf(this.str_.charAt(newIndex)) == -1) {
          break;
        }
      }
      if (newIndex >= this.str_.length) {
        return {type: TokenType.EOF, index: newIndex};
      }
      c = this.str_.charAt(newIndex);
    }

    // A numeric. Notice that it steals the `.` from separators.
    if (
      convertValues &&
      (isNum(c) ||
        (c == '.' &&
          newIndex + 1 < this.str_.length &&
          isNum(this.str_[newIndex + 1])))
    ) {
      let hasFraction = c == '.';
      let end = newIndex + 1;
      for (; end < this.str_.length; end++) {
        const c2 = this.str_.charAt(end);
        if (c2 == '.') {
          hasFraction = true;
          continue;
        }
        if (!isNum(c2)) {
          break;
        }
      }
      const s = this.str_.substring(newIndex, end);
      const value = hasFraction ? parseFloat(s) : parseInt(s, 10);
      newIndex = end - 1;
      return {type: TokenType.LITERAL, value, index: newIndex};
    }

    // Different separators.
    if (SEPARATOR_SET.indexOf(c) != -1) {
      return {type: TokenType.SEPARATOR, value: c, index: newIndex};
    }

    // String literal.
    if (STRING_SET.indexOf(c) != -1) {
      let end = -1;
      for (let i = newIndex + 1; i < this.str_.length; i++) {
        if (this.str_.charAt(i) == c) {
          end = i;
          break;
        }
      }
      if (end == -1) {
        return {type: TokenType.INVALID, index: newIndex};
      }
      const value = this.str_.substring(newIndex + 1, end);
      newIndex = end;
      return {type: TokenType.LITERAL, value, index: newIndex};
    }

    // Object literal.
    if (c == '{') {
      let numberOfBraces = 1;
      let end = -1;
      for (let i = newIndex + 1; i < this.str_.length; i++) {
        const char = this.str_[i];
        if (char == '{') {
          numberOfBraces++;
        } else if (char == '}') {
          numberOfBraces--;
        }
        if (numberOfBraces <= 0) {
          end = i;
          break;
        }
      }
      if (end == -1) {
        return {type: TokenType.INVALID, index: newIndex};
      }
      const value = this.str_.substring(newIndex, end + 1);
      newIndex = end;
      return {type: TokenType.OBJECT, value, index: newIndex};
    }

    // Advance until next special character.
    let end = newIndex + 1;
    for (; end < this.str_.length; end++) {
      if (SPECIAL_SET.indexOf(this.str_.charAt(end)) != -1) {
        break;
      }
    }
    const s = this.str_.substring(newIndex, end);
    newIndex = end - 1;

    // Boolean literal.
    if (convertValues && (s == 'true' || s == 'false')) {
      const value = s == 'true';
      return {type: TokenType.LITERAL, value, index: newIndex};
    }

    // Identifier.
    if (!isNum(s.charAt(0))) {
      return {type: TokenType.ID, value: s, index: newIndex};
    }

    // Key.
    return {type: TokenType.LITERAL, value: s, index: newIndex};
  }
}

/**
 * Tests whether a chacter is a number.
 * @param {string} c
 * @return {boolean}
 */
function isNum(c) {
  return c >= '0' && c <= '9';
}

/**
 * @param {!./ampdoc-impl.AmpDoc} ampdoc
 */
export function installActionServiceForDoc(ampdoc) {
  registerServiceBuilderForDoc(
    ampdoc,
    'action',
    ActionService,
    /* opt_instantiate */ true
  );
}