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hookable.js
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hookable.js
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const Bluebird = require("bluebird");
const assert = require("assert");
class Hook {
constructor({ event_matcher, callback, is_blocking = true }) {
assert.equal(typeof callback, "function");
assert.equal(typeof is_blocking, "boolean");
this.event_matcher = event_matcher;
this.callback = callback;
this.is_blocking = is_blocking;
}
appliesTo(event_description) {
return event_description.isEquivalentTo(this.event_matcher);
}
}
class EventMatcher {
constructor({ when, subject_path = /.*/, action }) {
if (arguments[0] instanceof EventMatcher) {
return arguments[0];
}
assert.equal(typeof when, "string");
assert(subject_path instanceof RegExp);
assert(typeof action === "string" || Array.isArray(action));
this.when = when;
this.subject_path = subject_path;
this.action = action;
}
containsAction(action_name) {
if (typeof this.action === "string") {
return this.action === action_name;
}
if (Array.isArray(this.action)) {
return this.action.includes(action_name);
}
return false;
}
}
class CollectionEventMatcher extends EventMatcher {
constructor({ when, collection_name, action }) {
super({
when,
subject_path: new RegExp(`collections.${collection_name}`),
action,
});
assert.equal(typeof collection_name, "string");
this.collection_name = collection_name;
}
}
class ResourceEventMatcher extends EventMatcher {
constructor({ when, collection_name, action }) {
super({
when,
subject_path: new RegExp(`collections.${collection_name}\\..*`),
action,
});
assert.equal(typeof collection_name, "string");
this.collection_name = collection_name;
}
}
class EventDescription {
constructor({ when, subject_path = "", action, metadata = {} }) {
assert.equal(typeof when, "string");
assert.equal(typeof subject_path, "string");
assert.equal(typeof action, "string");
assert.equal(typeof metadata, "object");
this.when = when;
this.subject_path = subject_path;
this.action = action;
this.metadata = metadata;
}
isEquivalentTo(source_event) {
return (
this.matchWhen(source_event) &&
this.matchAction(source_event) &&
this.matchSubjectPath(source_event)
);
}
matchWhen(source_event) {
return this.when === source_event.when;
}
matchAction(source_event) {
if (typeof source_event.action === "string") {
return source_event.action === this.action;
}
if (Array.isArray(source_event.action)) {
return source_event.action.includes(this.action);
}
return false;
}
matchSubjectPath(source_event) {
return source_event.subject_path.test(this.subject_path);
}
}
class Hookable {
constructor() {
this.hooks = [];
}
addHook(event_description, callback, is_blocking) {
const event_matcher = new EventMatcher(event_description);
const hook = new Hook({ event_matcher, callback, is_blocking });
this.hooks.push(hook);
}
async emit(_event_description, data = {}) {
const emitted_event = new EventDescription(_event_description);
return await Bluebird.reduce(
this.hooks.filter(hook => hook.appliesTo(emitted_event)),
async (acc, hook) =>
(await hook.callback(emitted_event, acc)) || acc,
data
);
}
}
module.exports = {
Hookable,
ResourceEventMatcher,
CollectionEventMatcher,
EventMatcher,
};

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hookable.js (3 KB)

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