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* @module Watchers/DOMWatcher
*/
import * as MC from "@lisn/globals/minification-constants";
import * as MH from "@lisn/globals/minification-helpers";
import {
MutationCategory,
CommaSeparatedStr,
AtLeastOne,
} from "@lisn/globals/types";
import { DOM_CATEGORIES_SPACE } from "@lisn/utils/dom";
import {
getIgnoreMove,
clearIgnoreMove,
ignoreMove,
} from "@lisn/utils/dom-alter";
import { waitForElement } from "@lisn/utils/dom-events";
import { logError } from "@lisn/utils/log";
import { omitKeys } from "@lisn/utils/misc";
import { objToStrKey } from "@lisn/utils/text";
import { validateStrList } from "@lisn/utils/validation";
import {
CallbackHandler,
Callback,
wrapCallback,
} from "@lisn/modules/callback";
import { newXMap } from "@lisn/modules/x-map";
import debug from "@lisn/debug/debug";
/**
* {@link DOMWatcher} listens for changes do the DOM tree. It's built on top of
* {@link https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver | MutationObserver}.
*
* It manages registered callbacks globally and reuses MutationObservers for
* more efficient performance.
*
* Each instance of DOMWatcher manages up to two MutationObservers: one
* for `childList` changes and one for attribute changes, and it disconnects
* them when there are no active callbacks for the relevant type.
*
* `characterData` and changes to base
* {@link https://developer.mozilla.org/en-US/docs/Web/API/Node | Node}s
* (non-{@link https://developer.mozilla.org/en-US/docs/Web/API/Element | Element})
* are not supported.
*/
export class DOMWatcher {
/**
* Call the given handler whenever there's a matching mutation within this
* DOMWatcher's {@link DOMWatcherConfig.root | root}.
*
* If {@link OnMutationOptions.skipInitial | options.skipInitial} is `false`
* (default), _and_ {@link OnMutationOptions.selector | options.selector} is
* given, _and_ {@link OnMutationOptions.categories | options.categories}
* includes "added", the handler is also called (almost) immediately with all
* existing elements matching the selector under this DOMWatcher's
* {@link DOMWatcherConfig.root | root}.
*
* **IMPORTANT:** The same handler can _not_ be added multiple times, even if
* the options differ. If the handler has already been added, it is removed
* and re-added with the current options.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the options are not valid.
*/
readonly onMutation: (
handler: OnMutationHandler,
options?: OnMutationOptions,
) => Promise<void>;
/**
* Removes a previously added handler.
*/
readonly offMutation: (handler: OnMutationHandler) => void;
/**
* Ignore an upcoming moving/adding/removing of an element.
*
* The operation must complete within the next cycle, by the time
* MutationObserver calls us.
*
* Use this to prevent this instance of DOMWatcher from calling any callbacks
* that listen for relevant changes as a result of this operation, to prevent
* loops for example.
*
* **IMPORTANT:**
*
* Ignoring moving of an element from a parent _inside_ this DOMWatcher's
* root to another parent that's _outside_ the root, will work as expected,
* even though the "adding to the new parent" mutation will not be observed.
* This is because the element's current parent at the time of the mutation
* callback can be examined.
*
* However if you want to ignore moving of an element _from a parent outside
* this DOMWatcher's root_ you need to specify from: null since the "removal
* from the old parent" mutation would not be observed and there's no way to
* examine it's previous parent at the time the "adding to the new parent"
* mutation is observed.
*
* For this reason, setting `options.from` to be an element that's not under
* the root is internally treated the same as `options.from: null`.
*/
readonly ignoreMove: (target: Element, options: MoveOptions) => void;
/**
* Creates a new instance of DOMWatcher with the given
* {@link DOMWatcherConfig}. It does not save it for future reuse.
*/
static create(config?: DOMWatcherConfig) {
return new DOMWatcher(getConfig(config), CONSTRUCTOR_KEY);
}
/**
* Returns an existing instance of DOMWatcher with the given
* {@link DOMWatcherConfig}, or creates a new one.
*
* **NOTE:** It saves it for future reuse, so don't use this for temporary
* short-lived watchers.
*/
static reuse(config?: DOMWatcherConfig) {
const myConfig = getConfig(config);
const configStrKey = objToStrKey(omitKeys(myConfig, { _root: null }));
const root = myConfig._root === MH.getBody() ? null : myConfig._root;
let instance = instances.get(root)?.get(configStrKey);
if (!instance) {
instance = new DOMWatcher(myConfig, CONSTRUCTOR_KEY);
instances.sGet(root).set(configStrKey, instance);
}
return instance;
}
private constructor(
config: DOMWatcherConfigInternal,
key: typeof CONSTRUCTOR_KEY,
) {
if (key !== CONSTRUCTOR_KEY) {
throw MH.illegalConstructorError("DOMWatcher.create");
}
const logger = debug
? new debug.Logger({ name: "DOMWatcher", logAtCreation: config })
: null;
const buffer = newXMap<Element, MutationOperationInternal>((t) => ({
_target: t,
_categoryBitmask: 0,
_attributes: MH.newSet(),
_addedTo: null,
_removedFrom: null,
}));
const allCallbacks = MH.newMap<
OnMutationHandler,
{
_callback: OnMutationCallback;
_options: OnMutationOptionsInternal;
}
>();
// ----------
let timer: ReturnType<typeof setTimeout> | null = null;
const mutationHandler = (records: MutationRecord[]) => {
debug: logger?.debug9(`Got ${records.length} new records`, records);
for (const record of records) {
const target = MH.targetOf(record);
const recType = record.type;
/* istanbul ignore next */
if (!MH.isElement(target)) {
continue;
}
if (recType === MC.S_CHILD_LIST) {
for (const child of record.addedNodes) {
if (MH.isElement(child)) {
const operation = buffer.sGet(child);
operation._addedTo = target;
operation._categoryBitmask |= ADDED_BIT;
}
}
for (const child of record.removedNodes) {
if (MH.isElement(child)) {
const operation = buffer.sGet(child);
operation._removedFrom = target;
operation._categoryBitmask |= REMOVED_BIT;
}
}
//
} else if (recType === MC.S_ATTRIBUTES && record.attributeName) {
const operation = buffer.sGet(target);
operation._attributes.add(record.attributeName);
operation._categoryBitmask |= ATTRIBUTE_BIT;
}
}
// Schedule flushing of the buffer asynchronously so that we can combine
// the records from the two MutationObservers.
if (!timer && MH.sizeOf(buffer)) {
timer = MH.setTimer(() => {
debug: logger?.debug9(`Processing ${buffer.size} operations`);
for (const operation of buffer.values()) {
if (shouldSkipOperation(operation)) {
debug: logger?.debug10("Skipping operation", operation);
} else {
processOperation(operation);
}
}
buffer.clear();
timer = null;
}, 0);
}
};
const observers: Record<MutationType, MyObserver> = {
[MC.S_CHILD_LIST]: {
_observer: MH.newMutationObserver(mutationHandler),
_isActive: false,
},
[MC.S_ATTRIBUTES]: {
_observer: MH.newMutationObserver(mutationHandler),
_isActive: false,
},
};
// ----------
const createCallback = (
handler: OnMutationHandler,
options: OnMutationOptionsInternal,
): OnMutationCallback => {
MH.remove(allCallbacks.get(handler)?._callback);
debug: logger?.debug5("Adding/updating handler", options);
const callback = wrapCallback(handler);
callback.onRemove(() => deleteHandler(handler));
allCallbacks.set(handler, { _callback: callback, _options: options });
return callback;
};
// ----------
const setupOnMutation = async (
handler: OnMutationHandler,
userOptions: OnMutationOptions | undefined,
) => {
const options = getOptions(userOptions ?? {});
const callback = createCallback(handler, options);
let root = config._root ?? MH.getBody();
Iif (!root) {
root = await waitForElement(MH.getBody);
} else {
// So that the call is always async
await null;
}
if (callback.isRemoved()) {
return;
}
if (options._categoryBitmask & (ADDED_BIT | REMOVED_BIT)) {
activateObserver(root, MC.S_CHILD_LIST);
}
if (options._categoryBitmask & ATTRIBUTE_BIT) {
activateObserver(root, MC.S_ATTRIBUTES);
}
if (
userOptions?.skipInitial ||
!options._selector ||
!(options._categoryBitmask & ADDED_BIT)
) {
return;
}
// As some of the matching elements that currently exist in the root may
// have just been added and therefore in the MutationObserver's queue, to
// avoid calling the handler with those entries twice, we empty its queue
// now and process it (which would also invoke the newly added callback).
// Then we skip any elements returned in querySelectorAll that were in
// the queue.
const childQueue = observers[MC.S_CHILD_LIST]._observer.takeRecords();
mutationHandler(childQueue);
for (const element of [
...MH.querySelectorAll(root, options._selector),
...(root.matches(options._selector) ? [root] : []),
]) {
const initOperation: MutationOperationInternal = {
_target: element,
_categoryBitmask: ADDED_BIT,
_attributes: MH.newSet(),
_addedTo: MH.parentOf(element),
_removedFrom: null,
};
const bufferedOperation = buffer.get(element);
const diffOperation = getDiffOperation(
initOperation,
bufferedOperation,
);
if (diffOperation) {
if (shouldSkipOperation(diffOperation)) {
debug: logger?.debug10("Skipping operation", diffOperation);
} else {
debug: logger?.debug5("Calling initially with", diffOperation);
await invokeCallback(callback, diffOperation);
}
}
}
};
// ----------
const deleteHandler = (handler: OnMutationHandler) => {
MH.deleteKey(allCallbacks, handler);
let activeCategories = 0;
for (const entry of allCallbacks.values()) {
activeCategories |= entry._options._categoryBitmask;
}
if (!(activeCategories & (ADDED_BIT | REMOVED_BIT))) {
deactivateObserver(MC.S_CHILD_LIST);
}
if (!(activeCategories & ATTRIBUTE_BIT)) {
deactivateObserver(MC.S_ATTRIBUTES);
}
};
// ----------
const processOperation = (operation: MutationOperationInternal) => {
debug: logger?.debug10("Processing operation", operation);
for (const entry of allCallbacks.values()) {
const categoryBitmask = entry._options._categoryBitmask;
const target = entry._options._target;
const selector = entry._options._selector;
if (!(operation._categoryBitmask & categoryBitmask)) {
debug: logger?.debug10(`Category does not match: ${categoryBitmask}`);
continue;
}
const currentTargets = [];
if (target) {
if (!operation._target.contains(target)) {
debug: logger?.debug10("Target does not match", target);
continue;
}
currentTargets.push(target);
}
if (selector) {
const matches = [...MH.querySelectorAll(operation._target, selector)];
if (operation._target.matches(selector)) {
matches.push(operation._target);
}
if (!MH.lengthOf(matches)) {
debug: logger?.debug10(`Selector does not match: ${selector}`);
continue;
}
currentTargets.push(...matches);
}
invokeCallback(entry._callback, operation, currentTargets);
}
};
// ----------
const activateObserver = (root: Element, mutationType: MutationType) => {
if (!observers[mutationType]._isActive) {
debug: logger?.debug3(
`Activating mutation observer for '${mutationType}'`,
);
observers[mutationType]._observer.observe(root, {
[mutationType]: true,
subtree: config._subtree,
});
observers[mutationType]._isActive = true;
}
};
// ----------
const deactivateObserver = (mutationType: MutationType) => {
if (observers[mutationType]._isActive) {
debug: logger?.debug3(
`Disconnecting mutation observer for '${mutationType}'`,
);
observers[mutationType]._observer.disconnect();
observers[mutationType]._isActive = false;
}
};
// ----------
const shouldSkipOperation = (
operation: MutationOperationInternal,
): boolean => {
const target = operation._target;
const requestToSkip = getIgnoreMove(target);
if (!requestToSkip) {
return false;
}
const removedFrom = operation._removedFrom;
const addedTo = MH.parentOf(target);
const requestFrom = requestToSkip.from;
const requestTo = requestToSkip.to;
const root = config._root ?? MH.getBody();
// If "from" is currently outside our root, we may not have seen a
// removal operation.
if (
(removedFrom === requestFrom || !root.contains(requestFrom)) &&
addedTo === requestTo
) {
clearIgnoreMove(target);
return true;
}
return false;
};
// ----------
this.ignoreMove = ignoreMove;
// ----------
this.onMutation = setupOnMutation;
// ----------
this.offMutation = (handler) => {
debug: logger?.debug5("Removing handler");
MH.remove(allCallbacks.get(handler)?._callback);
};
}
}
/**
* @interface
*/
export type DOMWatcherConfig = {
/**
* The root element to observe for changes.
*
* It cannot be overridden on a per-callback basis.
*
* @defaultValue document.body
*/
root?: Element | null;
/**
* Whether to observe root's subtree for changes or just direct descendants.
*
* It cannot be overridden on a per-callback basis.
*
* @defaultValue true
*/
subtree?: boolean;
};
/**
* @interface
*/
export type OnMutationOptions = {
/**
* If this is given, then the handler would only be called for operations
* where the target is _either_ the given element or an ancestor of it, i.e.
* it {@link https://developer.mozilla.org/en-US/docs/Web/API/Node/contains | Node:contains} it.
*
* @defaultValue undefined
*/
target?: Element;
/**
* If this is given, then the handler would only be called for operations
* where the target matches the given selector _or contains an element
* matching the given selector_.
*
* @defaultValue undefined
*/
selector?: string;
/**
* Specifies a list of {@link MutationCategory}s to target for.
*
* If not given, then the handler is called for any of the supported
* mutations.
*
* It can be a comma-separated list of category names or an array of such
* names.
*
* @defaultValue undefined
*/
categories?: CommaSeparatedStr<MutationCategory> | MutationCategory[];
/**
* Do not call the handler until there's a future matching mutation.
*
* By default, if `selector` is given, and `categories` includes `added`, we
* call the handler (almost) immediately with all elements matching selector
* relative to this DOMWatcher's root.
*
* The initial operation will contain just the element and
* `addedTo: <current parent>`.
*
* @defaultValue false
*/
skipInitial?: boolean;
};
export type MoveOptions = AtLeastOne<{
/**
* If to is missing or null, it's a removal operation.
*/
to: Element | null;
/**
* If from is missing or null, it's an insertion operation.
*/
from: Element | null;
}>;
export type MutationOperation = {
/**
* The target that was changed.
*/
target: Element;
/**
* The target that the callback was interested in.
*
* If `selector` is given as part of {@link OnMutationOptions}, then
* `currentTarget` will point to the target that matched the selector
* starting at the operation's `target` as the root. If the operation's
* `target` contains more than one element matching selector, the callback
* will be called once for _each_ matching child.
*
* If `target` is given as part of {@link OnMutationOptions}, then
* `currentTarget` will be that element.
*/
currentTarget: Element;
/**
* The list of attributes that were changed in this round.
*/
attributes: Set<string>;
/**
* The element that the target was added to, i.e. it's new parent. It is null
* if the target was not moved to a new element _during this round_. It does
* not mean that this is its current parent.
*/
addedTo: Element | null;
/**
* The element that the target was removed from, i.e. it's old parent. It is
* null if the target was not removed from a previous element _during this
* round_. It does not mean it did not previously have a parent, but that its
* removal was not observed.
*/
removedFrom: Element | null;
};
/**
* The handler is invoked with one argument:
*
* - a {@link MutationOperation} for a set of mutations related to a particular
* element
*
* The handler could be invoked multiple times in each "round" (cycle of event
* loop) if there are mutation operations for more than one element that match
* the supplied {@link OnMutationOptions}.
*/
export type OnMutationHandlerArgs = [MutationOperation];
export type OnMutationCallback = Callback<OnMutationHandlerArgs>;
export type OnMutationHandler =
| CallbackHandler<OnMutationHandlerArgs>
| OnMutationCallback;
// ----------------------------------------
type DOMWatcherConfigInternal = {
_root: Element | null;
_subtree: boolean;
};
type OnMutationOptionsInternal = {
_target: Element | null;
_selector: string;
_categoryBitmask: number;
};
type MyObserver = {
_observer: MutationObserver;
_isActive: boolean;
};
type MutationType = "childList" | "attributes";
type MutationOperationInternal = {
_target: Element;
_attributes: Set<string>;
_addedTo: Element | null;
_removedFrom: Element | null;
_categoryBitmask: number;
};
const CONSTRUCTOR_KEY: unique symbol = MC.SYMBOL() as typeof CONSTRUCTOR_KEY;
const instances = newXMap<Element | null, Map<string, DOMWatcher>>(() =>
MH.newMap(),
);
const getConfig = (
config: DOMWatcherConfig | undefined,
): DOMWatcherConfigInternal => {
return {
_root: config?.root ?? null,
_subtree: config?.subtree ?? true,
};
};
const CATEGORIES_BITS = DOM_CATEGORIES_SPACE.bit;
const ADDED_BIT = CATEGORIES_BITS[MC.S_ADDED];
const REMOVED_BIT = CATEGORIES_BITS[MC.S_REMOVED];
const ATTRIBUTE_BIT = CATEGORIES_BITS[MC.S_ATTRIBUTE];
// ----------------------------------------
const getOptions = (options: OnMutationOptions): OnMutationOptionsInternal => {
let categoryBitmask = 0;
const categories = validateStrList(
"categories",
options.categories,
DOM_CATEGORIES_SPACE.has,
);
if (categories) {
for (const cat of categories) {
categoryBitmask |= CATEGORIES_BITS[cat];
}
} else {
categoryBitmask = DOM_CATEGORIES_SPACE.bitmask; // default: all
}
const selector = options.selector ?? "";
Iif (!MH.isString(selector)) {
throw MH.usageError("'selector' must be a string");
}
return {
_categoryBitmask: categoryBitmask,
_target: options.target ?? null,
_selector: selector,
};
};
const getDiffOperation = (
operationA: MutationOperationInternal,
operationB: MutationOperationInternal | undefined,
): MutationOperationInternal | null => {
if (!operationB || operationA._target !== operationB._target) {
return operationA;
}
const attributes = MH.newSet<string>();
for (const attr of operationA._attributes) {
Iif (!operationB._attributes.has(attr)) {
attributes.add(attr);
}
}
const categoryBitmask =
operationA._categoryBitmask ^ operationB._categoryBitmask;
const addedTo =
operationA._addedTo === operationB._addedTo ? null : operationA._addedTo;
const removedFrom =
operationA._removedFrom === operationB._removedFrom
? null
: operationA._removedFrom;
if (!MH.sizeOf(attributes) && !categoryBitmask && !addedTo && !removedFrom) {
return null;
}
return {
_target: operationA._target,
_categoryBitmask: categoryBitmask,
_attributes: attributes,
_addedTo: addedTo,
_removedFrom: removedFrom,
};
};
const invokeCallback = (
callback: OnMutationCallback,
operation: MutationOperationInternal,
currentTargets: Element[] = [],
) => {
if (!MH.lengthOf(currentTargets)) {
currentTargets = [operation._target];
}
for (const currentTarget of currentTargets) {
callback
.invoke({
target: operation._target,
currentTarget,
attributes: operation._attributes,
addedTo: operation._addedTo,
removedFrom: operation._removedFrom,
})
.catch(logError);
}
};
|