diff --git a/packages/xo-collection/.editorconfig b/packages/xo-collection/.editorconfig
new file mode 100644
index 000000000..b6db0112a
--- /dev/null
+++ b/packages/xo-collection/.editorconfig
@@ -0,0 +1,65 @@
+# http://EditorConfig.org
+#
+# Julien Fontanet's configuration
+# https://gist.github.com/julien-f/8096213
+
+# Top-most EditorConfig file.
+root = true
+
+# Common config.
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespaces = true
+
+# CoffeeScript
+#
+# https://github.com/polarmobile/coffeescript-style-guide/blob/master/README.md
+[*.{,lit}coffee]
+indent_size = 2
+indent_style = space
+
+# Markdown
+[*.{md,mdwn,mdown,markdown}]
+indent_size = 4
+indent_style = space
+
+# Package.json
+#
+# This indentation style is the one used by npm.
+[/package.json]
+indent_size = 2
+indent_style = space
+
+# Jade
+[*.jade]
+indent_size = 2
+indent_style = space
+
+# JavaScript
+#
+# Two spaces seems to be the standard most common style, at least in
+# Node.js (http://nodeguide.com/style.html#tabs-vs-spaces).
+[*.{js,jsx,ts,tsx}]
+indent_size = 2
+indent_style = space
+
+# Less
+[*.less]
+indent_size = 2
+indent_style = space
+
+# Sass
+#
+# Style used for http://libsass.com
+[*.s[ac]ss]
+indent_size = 2
+indent_style = space
+
+# YAML
+#
+# Only spaces are allowed.
+[*.yaml]
+indent_size = 2
+indent_style = space
diff --git a/packages/xo-collection/.gitignore b/packages/xo-collection/.gitignore
new file mode 100644
index 000000000..827e4e420
--- /dev/null
+++ b/packages/xo-collection/.gitignore
@@ -0,0 +1,7 @@
+/dist/
+/node_modules/
+
+npm-debug.log
+npm-debug.log.*
+pnpm-debug.log
+pnpm-debug.log.*
diff --git a/packages/xo-collection/.mocha.js b/packages/xo-collection/.mocha.js
new file mode 100644
index 000000000..b888fb4d5
--- /dev/null
+++ b/packages/xo-collection/.mocha.js
@@ -0,0 +1,3 @@
+try { require('clarify') } catch (_) {}
+try { require('trace') } catch (_) {}
+try { require('source-map-support/register') } catch (_) {}
diff --git a/packages/xo-collection/.mocha.opts b/packages/xo-collection/.mocha.opts
new file mode 100644
index 000000000..6cfd94898
--- /dev/null
+++ b/packages/xo-collection/.mocha.opts
@@ -0,0 +1 @@
+--require ./.mocha.js
diff --git a/packages/xo-collection/.npmignore b/packages/xo-collection/.npmignore
new file mode 100644
index 000000000..c31ee82cb
--- /dev/null
+++ b/packages/xo-collection/.npmignore
@@ -0,0 +1,10 @@
+/examples/
+example.js
+example.js.map
+*.example.js
+*.example.js.map
+
+/test/
+/tests/
+*.spec.js
+*.spec.js.map
diff --git a/packages/xo-collection/.travis.yml b/packages/xo-collection/.travis.yml
new file mode 100644
index 000000000..1a582c426
--- /dev/null
+++ b/packages/xo-collection/.travis.yml
@@ -0,0 +1,9 @@
+language: node_js
+node_js:
+ - stable
+ - 6
+ - 4
+
+# Use containers.
+# http://docs.travis-ci.com/user/workers/container-based-infrastructure/
+sudo: false
diff --git a/packages/xo-collection/LICENSE b/packages/xo-collection/LICENSE
new file mode 100644
index 000000000..cebe0354b
--- /dev/null
+++ b/packages/xo-collection/LICENSE
@@ -0,0 +1,662 @@
+GNU AFFERO GENERAL PUBLIC LICENSE
+ Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc.
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+ Preamble
+
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+software and other kinds of works, specifically designed to ensure
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+
+ The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works. By contrast,
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+share and change all versions of a program--to make sure it remains free
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+
+ When we speak of free software, we are referring to freedom, not
+price. Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
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+
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+ Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+ 12. No Surrender of Others' Freedom.
+
+ If conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License. If you cannot convey a
+covered work so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you may
+not convey it at all. For example, if you agree to terms that obligate you
+to collect a royalty for further conveying from those to whom you convey
+the Program, the only way you could satisfy both those terms and this
+License would be to refrain entirely from conveying the Program.
+
+ 13. Remote Network Interaction; Use with the GNU General Public License.
+
+ Notwithstanding any other provision of this License, if you modify the
+Program, your modified version must prominently offer all users
+interacting with it remotely through a computer network (if your version
+supports such interaction) an opportunity to receive the Corresponding
+Source of your version by providing access to the Corresponding Source
+from a network server at no charge, through some standard or customary
+means of facilitating copying of software. This Corresponding Source
+shall include the Corresponding Source for any work covered by version 3
+of the GNU General Public License that is incorporated pursuant to the
+following paragraph.
+
+ Notwithstanding any other provision of this License, you have
+permission to link or combine any covered work with a work licensed
+under version 3 of the GNU General Public License into a single
+combined work, and to convey the resulting work. The terms of this
+License will continue to apply to the part which is the covered work,
+but the work with which it is combined will remain governed by version
+3 of the GNU General Public License.
+
+ 14. Revised Versions of this License.
+
+ The Free Software Foundation may publish revised and/or new versions of
+the GNU Affero General Public License from time to time. Such new versions
+will be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+ Each version is given a distinguishing version number. If the
+Program specifies that a certain numbered version of the GNU Affero General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
+Foundation. If the Program does not specify a version number of the
+GNU Affero General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+ If the Program specifies that a proxy can decide which future
+versions of the GNU Affero General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+ Later license versions may give you additional or different
+permissions. However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+ 15. Disclaimer of Warranty.
+
+ THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+ 16. Limitation of Liability.
+
+ IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+ 17. Interpretation of Sections 15 and 16.
+
+ If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+ END OF TERMS AND CONDITIONS
+
+ How to Apply These Terms to Your New Programs
+
+ If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+ To do so, attach the following notices to the program. It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+
+ Copyright (C)
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as published
+ by the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program. If not, see .
+
+Also add information on how to contact you by electronic and paper mail.
+
+ If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source. For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code. There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+ You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+.
+
diff --git a/packages/xo-collection/README.md b/packages/xo-collection/README.md
new file mode 100644
index 000000000..7456895d4
--- /dev/null
+++ b/packages/xo-collection/README.md
@@ -0,0 +1,265 @@
+# xo-collection [](https://travis-ci.org/marsaud/collection)
+
+> Generic in-memory collection with events
+
+## Install
+
+Installation of the [npm package](https://npmjs.org/package/xo-collection):
+
+```
+> npm install --save xo-collection
+```
+
+## Usage
+
+```javascript
+var Collection = require('xo-collection')
+```
+
+### Creation
+
+```javascript
+// Creates a new collection.
+var col = new Collection()
+```
+
+### Manipulation
+
+**Inserting a new item**
+
+```javascript
+col.add('foo', true)
+```
+
+- **Throws** `DuplicateItem` if the item is already in the collection.
+
+**Updating an existing item**
+
+```javascript
+col.update('foo', false)
+```
+
+- **Throws** `NoSuchItem` if the item is not in the collection.
+
+**Inserting or updating an item**
+
+```javascript
+col.set('bar', true)
+```
+
+**Notifying an external update**
+
+> If an item is an object, it can be updated directly without using
+> the `set`/`update` methods.
+>
+> To make sure the collection stays in sync and the correct events are
+> sent, the `touch` method can be used to notify the change.
+
+```javascript
+var baz = {}
+
+col.add('baz', baz)
+
+baz.prop = true
+col.touch('baz')
+```
+
+> Because this is a much used pattern, `touch` returns the item to
+> allow its direct modification.
+
+```javascript
+col.touch('baz').prop = false
+```
+
+- **Throws** `NoSuchItem` if the item is not in the collection.
+- **Throws** `IllegalTouch` if the item is not an object.
+
+**Removing an existing item**
+
+```javascript
+col.remove('bar')
+```
+
+- **Throws** `NoSuchItem` if the item is not in the collection.
+
+**Removing an item without error**
+
+This is the symmetric method of `set()`: it removes the item if it
+exists otherwise does nothing.
+
+```javascript
+col.unset('bar')
+```
+
+**Removing all items**
+
+```javascript
+col.clear()
+```
+
+### Query
+
+**Checking the existence of an item**
+
+```javascript
+var hasBar = col.has('bar')
+```
+
+**Getting an existing item**
+
+```javascript
+var foo = col.get('foo')
+
+// The second parameter can be used to specify a fallback in case the
+// item does not exist.
+var bar = col.get('bar', 6.28)
+```
+
+- **Throws** `NoSuchItem` if the item is not in the collection and no
+ fallback has been passed.
+
+**Getting a read-only view of the collection**
+
+> This property is useful for example to iterate over the collection
+> or to make advanced queries with the help of utility libraries such
+> as lodash.
+
+```javascript
+var _ = require('lodash')
+
+// Prints all the items.
+_.forEach(col.all, function (value, key) {
+ console.log('- %s: %j', key, value)
+})
+
+// Finds all the items which are objects and have a property
+// `active` which equals `true`.
+var results = _.where(col.all, { active: true })
+```
+
+**Getting the number of items**
+
+```javascript
+var size = col.size
+```
+
+### Events
+
+> The events are emitted asynchronously (at the next turn/tick of the
+> event loop) and are deduplicated which means, for instance, that an
+> addition followed by an update will result only in a single
+> addition.
+
+**New items**
+
+```javascript
+col.on('add', (added) => {
+ forEach(added, (value, key) => {
+ console.log('+ %s: %j', key, value)
+ })
+})
+```
+
+**Updated items**
+
+```javascript
+col.on('update', (updated) => {
+ forEach(updated, (value, key) => {
+ console.log('± %s: %j', key, value)
+ })
+})
+```
+
+**Removed items**
+
+```javascript
+col.on('remove', (removed) => {
+ // For consistency, `removed` is also a map but contrary to `added`
+ // and `updated`, the values associated to the keys are not
+ // significant since the items have already be removed.
+
+ forEach(removed, (value, key) => {
+ console.log('- %s', key)
+ })
+})
+```
+
+**End of update**
+
+> Emitted when all the update process is finished and all the update
+> events has been emitted.
+
+```javascript
+col.on('finish', () => {
+ console.log('the collection has been updated')
+})
+```
+
+### Iteration
+
+```javascript
+for (const [key, value] of col) {
+ console.log('- %s: %j', key, value)
+}
+
+for (const key of col.keys()) {
+ console.log('- %s', key)
+}
+
+for (const value of col.values()) {
+ console.log('- %j', value)
+}
+```
+
+### Views
+
+```javascript
+const View = require('xo-collection/view')
+```
+
+> A view is a read-only collection which contains only the items of a
+> parent collection which satisfy a predicate.
+>
+> It is updated at most once per turn of the event loop and therefore
+> can be briefly invalid.
+
+```javascript
+const myView = new View(parentCollection, function predicate (value, key) {
+ // This function should return a boolean indicating whether the
+ // current item should be in this view.
+})
+```
+
+## Development
+
+```
+# Install dependencies
+> npm install
+
+# Run the tests
+> npm test
+
+# Continuously compile
+> npm run dev
+
+# Continuously run the tests
+> npm run dev-test
+
+# Build for production (automatically called by npm install)
+> npm run build
+```
+
+## Contributions
+
+Contributions are *very* welcomed, either on the documentation or on
+the code.
+
+You may:
+
+- report any [issue](https://github.com/marsaud/collection/issues)
+ you've encountered;
+- fork and create a pull request.
+
+## License
+
+ISC © [Vates SAS](http://vates.fr)
diff --git a/packages/xo-collection/index.js b/packages/xo-collection/index.js
new file mode 100644
index 000000000..aae59039c
--- /dev/null
+++ b/packages/xo-collection/index.js
@@ -0,0 +1 @@
+module.exports = require('./dist/index')
diff --git a/packages/xo-collection/package.json b/packages/xo-collection/package.json
new file mode 100644
index 000000000..987658be0
--- /dev/null
+++ b/packages/xo-collection/package.json
@@ -0,0 +1,87 @@
+{
+ "name": "xo-collection",
+ "version": "0.4.1",
+ "license": "ISC",
+ "description": "Generic in-memory collection with events",
+ "keywords": [],
+ "homepage": "https://github.com/marsaud/collection",
+ "bugs": "https://github.com/marsaud/collection/issues",
+ "repository": {
+ "type": "git",
+ "url": "https://github.com/marsaud/collection.git"
+ },
+ "author": {
+ "name": "Fabrice Marsaud",
+ "email": "fabrice.marsaud@vates.fr"
+ },
+ "preferGlobal": false,
+ "main": "dist/collection",
+ "bin": {},
+ "files": [
+ "dist/",
+ "*.js"
+ ],
+ "engines": {
+ "node": ">=4"
+ },
+ "dependencies": {
+ "babel-runtime": "^6.18.0",
+ "kindof": "^2.0.0",
+ "lodash": "^4.17.2",
+ "make-error": "^1.0.2"
+ },
+ "devDependencies": {
+ "babel-cli": "^6.18.0",
+ "babel-eslint": "^7.1.0",
+ "babel-plugin-lodash": "^3.2.9",
+ "babel-plugin-transform-runtime": "^6.15.0",
+ "babel-preset-latest": "^6.16.0",
+ "babel-preset-stage-0": "^6.16.0",
+ "clarify": "^2.0.0",
+ "cross-env": "^3.1.3",
+ "dependency-check": "^2.6.0",
+ "event-to-promise": "^0.7.0",
+ "ghooks": "^1.3.2",
+ "mocha": "^3.1.2",
+ "must": "^0.13.2",
+ "rimraf": "^2.4.3",
+ "sinon": "^1.14.1",
+ "source-map-support": "^0.4.6",
+ "standard": "^8.5.0",
+ "trace": "^2.3.3"
+ },
+ "scripts": {
+ "build": "cross-env NODE_ENV=production babel --source-maps --out-dir=dist/ src/",
+ "clean": "rimraf dist/",
+ "depcheck": "dependency-check ./package.json --entry dist/collection.js index.js unique-index.js view.js",
+ "dev": "cross-env NODE_ENV=development babel --watch --source-maps --out-dir=dist/ src/",
+ "lint": "standard",
+ "posttest": "npm run lint && npm run depcheck",
+ "prebuild": "npm run clean",
+ "predev": "npm run clean",
+ "prepublish": "npm run build",
+ "test": "npm run lint && mocha --opts .mocha.opts \"dist/**/*.spec.js\"",
+ "test-dev": "mocha --opts .mocha.opts --watch --reporter=min \"dist/**/*.spec.js\""
+ },
+ "babel": {
+ "plugins": [
+ "lodash",
+ "transform-runtime"
+ ],
+ "presets": [
+ "latest",
+ "stage-0"
+ ]
+ },
+ "standard": {
+ "ignore": [
+ "dist"
+ ],
+ "parser": "babel-eslint"
+ },
+ "config": {
+ "ghooks": {
+ "commit-msg": "npm test"
+ }
+ }
+}
diff --git a/packages/xo-collection/src/clear-object.js b/packages/xo-collection/src/clear-object.js
new file mode 100644
index 000000000..0250f65c2
--- /dev/null
+++ b/packages/xo-collection/src/clear-object.js
@@ -0,0 +1,5 @@
+export default function clearObject (object) {
+ for (const key in object) {
+ delete object[key]
+ }
+}
diff --git a/packages/xo-collection/src/collection.js b/packages/xo-collection/src/collection.js
new file mode 100644
index 000000000..d65e8d7d6
--- /dev/null
+++ b/packages/xo-collection/src/collection.js
@@ -0,0 +1,363 @@
+import kindOf from 'kindof'
+import {BaseError} from 'make-error'
+import {EventEmitter} from 'events'
+import {forEach} from 'lodash'
+
+import isEmpty from './is-empty'
+import isObject from './is-object'
+
+// ===================================================================
+
+const {
+ create: createObject,
+ prototype: { hasOwnProperty }
+} = Object
+
+export const ACTION_ADD = 'add'
+export const ACTION_UPDATE = 'update'
+export const ACTION_REMOVE = 'remove'
+
+// ===================================================================
+
+export class BufferAlreadyFlushed extends BaseError {
+ constructor () {
+ super('buffer flush already requested')
+ }
+}
+
+export class DuplicateIndex extends BaseError {
+ constructor (name) {
+ super('there is already an index with the name ' + name)
+ }
+}
+
+export class DuplicateItem extends BaseError {
+ constructor (key) {
+ super('there is already a item with the key ' + key)
+ }
+}
+
+export class IllegalTouch extends BaseError {
+ constructor (value) {
+ super('only an object value can be touched (found a ' + kindOf(value) + ')')
+ }
+}
+
+export class InvalidKey extends BaseError {
+ constructor (key) {
+ super('invalid key of type ' + kindOf(key))
+ }
+}
+
+export class NoSuchIndex extends BaseError {
+ constructor (name) {
+ super('there is no index with the name ' + name)
+ }
+}
+
+export class NoSuchItem extends BaseError {
+ constructor (key) {
+ super('there is no item with the key ' + key)
+ }
+}
+
+// -------------------------------------------------------------------
+
+export default class Collection extends EventEmitter {
+ constructor () {
+ super()
+
+ this._buffer = createObject(null)
+ this._buffering = 0
+ this._indexes = createObject(null)
+ this._indexedItems = createObject(null)
+ this._items = {} // createObject(null)
+ this._size = 0
+ }
+
+ // Overridable method used to compute the key of an item when
+ // unspecified.
+ //
+ // Default implementation returns the `id` property.
+ getKey (value) {
+ return value && value.id
+ }
+
+ // -----------------------------------------------------------------
+ // Properties
+ // -----------------------------------------------------------------
+
+ get all () {
+ return this._items
+ }
+
+ get indexes () {
+ return this._indexedItems
+ }
+
+ get size () {
+ return this._size
+ }
+
+ // -----------------------------------------------------------------
+ // Manipulation
+ // -----------------------------------------------------------------
+
+ add (keyOrObjectWithId, valueIfKey = undefined) {
+ const [key, value] = this._resolveItem(keyOrObjectWithId, valueIfKey)
+ this._assertHasNot(key)
+
+ this._items[key] = value
+ this._size++
+ this._touch(ACTION_ADD, key)
+ }
+
+ clear () {
+ forEach(this._items, (_, key) => this._remove(key))
+ }
+
+ remove (keyOrObjectWithId) {
+ const [key] = this._resolveItem(keyOrObjectWithId)
+ this._assertHas(key)
+
+ this._remove(key)
+ }
+
+ set (keyOrObjectWithId, valueIfKey = undefined) {
+ const [key, value] = this._resolveItem(keyOrObjectWithId, valueIfKey)
+
+ const action = this.has(key) ? ACTION_UPDATE : ACTION_ADD
+ this._items[key] = value
+ if (action === ACTION_ADD) {
+ this._size++
+ }
+ this._touch(action, key)
+ }
+
+ touch (keyOrObjectWithId) {
+ const [key] = this._resolveItem(keyOrObjectWithId)
+ this._assertHas(key)
+ const value = this.get(key)
+ if (!isObject(value)) {
+ throw new IllegalTouch(value)
+ }
+
+ this._touch(ACTION_UPDATE, key)
+
+ return this.get(key)
+ }
+
+ unset (keyOrObjectWithId) {
+ const [key] = this._resolveItem(keyOrObjectWithId)
+
+ if (this.has(key)) {
+ this._remove(key)
+ }
+ }
+
+ update (keyOrObjectWithId, valueIfKey = undefined) {
+ const [key, value] = this._resolveItem(keyOrObjectWithId, valueIfKey)
+ this._assertHas(key)
+
+ this._items[key] = value
+ this._touch(ACTION_UPDATE, key)
+ }
+
+ // -----------------------------------------------------------------
+ // Query
+ // -----------------------------------------------------------------
+
+ get (key, defaultValue) {
+ if (this.has(key)) {
+ return this._items[key]
+ }
+
+ if (arguments.length > 1) {
+ return defaultValue
+ }
+
+ // Throws a NoSuchItem.
+ this._assertHas(key)
+ }
+
+ has (key) {
+ return hasOwnProperty.call(this._items, key)
+ }
+
+ // -----------------------------------------------------------------
+ // Indexes
+ // -----------------------------------------------------------------
+
+ createIndex (name, index) {
+ const {_indexes: indexes} = this
+ if (hasOwnProperty.call(indexes, name)) {
+ throw new DuplicateIndex(name)
+ }
+
+ indexes[name] = index
+ this._indexedItems[name] = index.items
+
+ index._attachCollection(this)
+ }
+
+ deleteIndex (name) {
+ const {_indexes: indexes} = this
+ if (!hasOwnProperty.call(indexes, name)) {
+ throw new NoSuchIndex(name)
+ }
+
+ const index = indexes[name]
+ delete indexes[name]
+ delete this._indexedItems[name]
+
+ index._detachCollection(this)
+ }
+
+ // -----------------------------------------------------------------
+ // Iteration
+ // -----------------------------------------------------------------
+
+ * [Symbol.iterator] () {
+ const {_items: items} = this
+
+ for (const key in items) {
+ yield [key, items[key]]
+ }
+ }
+
+ * keys () {
+ const {_items: items} = this
+
+ for (const key in items) {
+ yield key
+ }
+ }
+
+ * values () {
+ const {_items: items} = this
+
+ for (const key in items) {
+ yield items[key]
+ }
+ }
+
+ // -----------------------------------------------------------------
+ // Events buffering
+ // -----------------------------------------------------------------
+
+ bufferEvents () {
+ ++this._buffering
+
+ let called = false
+ return () => {
+ if (called) {
+ throw new BufferAlreadyFlushed()
+ }
+ called = true
+
+ if (--this._buffering) {
+ return
+ }
+
+ const {_buffer: buffer} = this
+
+ // Due to deduplication there could be nothing in the buffer.
+ if (isEmpty(buffer)) {
+ return
+ }
+
+ const data = {
+ add: createObject(null),
+ remove: createObject(null),
+ update: createObject(null)
+ }
+
+ for (const key in this._buffer) {
+ data[buffer[key]][key] = this._items[key]
+ }
+
+ forEach(data, (items, action) => {
+ if (!isEmpty(items)) {
+ this.emit(action, items)
+ }
+ })
+
+ // Indicates the end of the update.
+ //
+ // This name has been chosen because it is used in Node writable
+ // streams when the data has been successfully committed.
+ this.emit('finish')
+
+ this._buffer = createObject(null)
+ }
+ }
+
+ // =================================================================
+
+ _assertHas (key) {
+ if (!this.has(key)) {
+ throw new NoSuchItem(key)
+ }
+ }
+
+ _assertHasNot (key) {
+ if (this.has(key)) {
+ throw new DuplicateItem(key)
+ }
+ }
+
+ _assertValidKey (key) {
+ if (!this._isValidKey(key)) {
+ throw new InvalidKey(key)
+ }
+ }
+
+ _isValidKey (key) {
+ return typeof key === 'number' || typeof key === 'string'
+ }
+
+ _remove (key) {
+ delete this._items[key]
+ this._size--
+ this._touch(ACTION_REMOVE, key)
+ }
+
+ _resolveItem (keyOrObjectWithId, valueIfKey = undefined) {
+ if (valueIfKey !== undefined) {
+ this._assertValidKey(keyOrObjectWithId)
+
+ return [keyOrObjectWithId, valueIfKey]
+ }
+
+ if (this._isValidKey(keyOrObjectWithId)) {
+ return [keyOrObjectWithId]
+ }
+
+ const key = this.getKey(keyOrObjectWithId)
+ this._assertValidKey(key)
+
+ return [key, keyOrObjectWithId]
+ }
+
+ _touch (action, key) {
+ if (this._buffering === 0) {
+ const flush = this.bufferEvents()
+
+ process.nextTick(flush)
+ }
+
+ if (action === ACTION_ADD) {
+ this._buffer[key] = this._buffer[key] ? ACTION_UPDATE : ACTION_ADD
+ } else if (action === ACTION_REMOVE) {
+ if (this._buffer[key] === ACTION_ADD) {
+ delete this._buffer[key]
+ } else {
+ this._buffer[key] = ACTION_REMOVE
+ }
+ } else { // update
+ if (!this._buffer[key]) {
+ this._buffer[key] = ACTION_UPDATE
+ }
+ }
+ }
+}
diff --git a/packages/xo-collection/src/collection.spec.js b/packages/xo-collection/src/collection.spec.js
new file mode 100644
index 000000000..28c639a99
--- /dev/null
+++ b/packages/xo-collection/src/collection.spec.js
@@ -0,0 +1,346 @@
+/* eslint-env mocha */
+
+import eventToPromise from 'event-to-promise'
+import expect from 'must'
+import sinon from 'sinon'
+import { forEach } from 'lodash'
+
+// ===================================================================
+
+import Collection, {DuplicateItem, NoSuchItem} from '..'
+
+// ===================================================================
+
+function waitTicks (n = 1) {
+ const {nextTick} = process
+
+ return new Promise(function (resolve) {
+ (function waitNextTick () {
+ // The first tick is handled by Promise#then()
+ if (--n) {
+ nextTick(waitNextTick)
+ } else {
+ resolve()
+ }
+ })()
+ })
+}
+
+describe('Collection', function () {
+ beforeEach(function () {
+ this.col = new Collection()
+ this.col.add('bar', 0)
+
+ return waitTicks()
+ })
+
+ it('is iterable', function () {
+ const iterator = this.col[Symbol.iterator]()
+
+ expect(iterator.next()).to.eql({done: false, value: ['bar', 0]})
+ expect(iterator.next()).to.eql({done: true, value: undefined})
+ })
+
+ describe('#keys()', function () {
+ it('returns an iterator over the keys', function () {
+ const iterator = this.col.keys()
+
+ expect(iterator.next()).to.eql({done: false, value: 'bar'})
+ expect(iterator.next()).to.eql({done: true, value: undefined})
+ })
+ })
+
+ describe('#values()', function () {
+ it('returns an iterator over the values', function () {
+ const iterator = this.col.values()
+
+ expect(iterator.next()).to.eql({done: false, value: 0})
+ expect(iterator.next()).to.eql({done: true, value: undefined})
+ })
+ })
+
+ describe('#add()', function () {
+ it('adds item to the collection', function () {
+ const spy = sinon.spy()
+ this.col.on('add', spy)
+
+ this.col.add('foo', true)
+
+ expect(this.col.get('foo')).to.be.true()
+
+ // No sync events.
+ sinon.assert.notCalled(spy)
+
+ // Async event.
+ return eventToPromise(this.col, 'add').then(function (added) {
+ expect(added).to.have.keys(['foo'])
+ expect(added.foo).to.be.true()
+ })
+ })
+
+ it('throws an exception if the item already exists', function () {
+ expect(() => this.col.add('bar', true)).to.throw(DuplicateItem)
+ })
+
+ it('accepts an object with an id property', function () {
+ const foo = { id: 'foo' }
+
+ this.col.add(foo)
+
+ expect(this.col.get(foo.id)).to.equal(foo)
+ })
+ })
+
+ describe('#update()', function () {
+ it('updates an item of the collection', function () {
+ const spy = sinon.spy()
+ this.col.on('update', spy)
+
+ this.col.update('bar', 1)
+ expect(this.col.get('bar')).to.equal(1) // Will be forgotten by de-duplication
+ this.col.update('bar', 2)
+ expect(this.col.get('bar')).to.equal(2)
+
+ // No sync events.
+ sinon.assert.notCalled(spy)
+
+ // Async event.
+ return eventToPromise(this.col, 'update').then(function (updated) {
+ expect(updated).to.have.keys(['bar'])
+ expect(updated.bar).to.equal(2)
+ })
+ })
+
+ it('throws an exception if the item does not exist', function () {
+ expect(() => this.col.update('baz', true)).to.throw(NoSuchItem)
+ })
+
+ it('accepts an object with an id property', function () {
+ const bar = { id: 'bar' }
+
+ this.col.update(bar)
+
+ expect(this.col.get(bar.id)).to.equal(bar)
+ })
+ })
+
+ describe('#remove()', function () {
+ it('removes an item of the collection', function () {
+ const spy = sinon.spy()
+ this.col.on('remove', spy)
+
+ this.col.update('bar', 1)
+ expect(this.col.get('bar')).to.equal(1) // Will be forgotten by de-duplication
+ this.col.remove('bar')
+
+ // No sync events.
+ sinon.assert.notCalled(spy)
+
+ // Async event.
+ return eventToPromise(this.col, 'remove').then(function (removed) {
+ expect(removed).to.have.keys(['bar'])
+ expect(removed.bar).to.not.exist()
+ })
+ })
+
+ it('throws an exception if the item does not exist', function () {
+ expect(() => this.col.remove('baz', true)).to.throw(NoSuchItem)
+ })
+
+ it('accepts an object with an id property', function () {
+ const bar = { id: 'bar' }
+
+ this.col.remove(bar)
+
+ expect(this.col.has(bar.id)).to.be.false()
+ })
+ })
+
+ describe('#set()', function () {
+ it('adds item if collection has not key', function () {
+ const spy = sinon.spy()
+ this.col.on('add', spy)
+
+ this.col.set('foo', true)
+
+ expect(this.col.get('foo')).to.be.true()
+
+ // No sync events.
+ sinon.assert.notCalled(spy)
+
+ // Async events.
+ return eventToPromise(this.col, 'add').then(function (added) {
+ expect(added).to.have.keys(['foo'])
+ expect(added.foo).to.be.true()
+ })
+ })
+
+ it('updates item if collection has key', function () {
+ const spy = sinon.spy()
+ this.col.on('udpate', spy)
+
+ this.col.set('bar', 1)
+
+ expect(this.col.get('bar')).to.equal(1)
+
+ // No sync events.
+ sinon.assert.notCalled(spy)
+
+ // Async events.
+ return eventToPromise(this.col, 'update').then(function (updated) {
+ expect(updated).to.have.keys(['bar'])
+ expect(updated.bar).to.equal(1)
+ })
+ })
+
+ it('accepts an object with an id property', function () {
+ const foo = { id: 'foo' }
+
+ this.col.set(foo)
+
+ expect(this.col.get(foo.id)).to.equal(foo)
+ })
+ })
+
+ describe('#unset()', function () {
+ it('removes an existing item', function () {
+ this.col.unset('bar')
+
+ expect(this.col.has('bar')).to.be.false()
+
+ return eventToPromise(this.col, 'remove').then(function (removed) {
+ expect(removed).to.have.keys(['bar'])
+ expect(removed.bar).to.not.exist()
+ })
+ })
+
+ it('does not throw if the item does not exists', function () {
+ this.col.unset('foo')
+ })
+
+ it('accepts an object with an id property', function () {
+ this.col.unset({id: 'bar'})
+
+ expect(this.col.has('bar')).to.be.false()
+
+ return eventToPromise(this.col, 'remove').then(function (removed) {
+ expect(removed).to.have.keys(['bar'])
+ expect(removed.bar).to.not.exist()
+ })
+ })
+ })
+
+ describe('touch()', function () {
+ it('can be used to signal an indirect update', function () {
+ const foo = { id: 'foo' }
+ this.col.add(foo)
+
+ return waitTicks().then(() => {
+ this.col.touch(foo)
+
+ return eventToPromise(this.col, 'update', (items) => {
+ expect(items).to.have.keys(['foo'])
+ expect(items.foo).to.equal(foo)
+ })
+ })
+ })
+ })
+
+ describe('clear()', function () {
+ it('removes all items from the collection', function () {
+ this.col.clear()
+
+ expect(this.col.size).to.equal(0)
+
+ return eventToPromise(this.col, 'remove').then((items) => {
+ expect(items).to.have.keys(['bar'])
+ expect(items.bar).to.not.exist()
+ })
+ })
+ })
+
+ describe('deduplicates events', function () {
+ forEach({
+ 'add & update → add': [
+ [
+ ['add', 'foo', 0],
+ ['update', 'foo', 1]
+ ],
+ {
+ add: {
+ foo: 1
+ }
+ }
+ ],
+
+ 'add & remove → ∅': [
+ [
+ ['add', 'foo', 0],
+ ['remove', 'foo']
+ ],
+ {}
+ ],
+
+ 'update & update → update': [
+ [
+ ['update', 'bar', 1],
+ ['update', 'bar', 2]
+ ],
+ {
+ update: {
+ bar: 2
+ }
+ }
+ ],
+
+ 'update & remove → remove': [
+ [
+ ['update', 'bar', 1],
+ ['remove', 'bar']
+ ],
+ {
+ remove: {
+ bar: undefined
+ }
+ }
+ ],
+
+ 'remove & add → update': [
+ [
+ ['remove', 'bar'],
+ ['add', 'bar', 0]
+ ],
+ {
+ update: {
+ bar: 0
+ }
+ }
+ ]
+ }, ([operations, results], label) => {
+ it(label, function () {
+ const {col} = this
+
+ forEach(operations, ([method, ...args]) => {
+ col[method](...args)
+ })
+
+ const spies = Object.create(null)
+ forEach(['add', 'update', 'remove'], event => {
+ col.on(event, (spies[event] = sinon.spy()))
+ })
+
+ return waitTicks(2).then(() => {
+ forEach(spies, (spy, event) => {
+ const items = results[event]
+ if (items) {
+ sinon.assert.calledOnce(spy)
+ expect(spy.args[0][0]).to.eql(items)
+ } else {
+ sinon.assert.notCalled(spy)
+ }
+ })
+ })
+ })
+ })
+ })
+})
diff --git a/packages/xo-collection/src/index.js b/packages/xo-collection/src/index.js
new file mode 100644
index 000000000..5c5dd01bc
--- /dev/null
+++ b/packages/xo-collection/src/index.js
@@ -0,0 +1,149 @@
+import { bind, iteratee } from 'lodash'
+
+import clearObject from './clear-object'
+import isEmpty from './is-empty'
+import NotImplemented from './not-implemented'
+import {
+ ACTION_ADD,
+ ACTION_UPDATE,
+ ACTION_REMOVE
+} from './collection'
+
+// ===================================================================
+
+export default class Index {
+ constructor (computeHash) {
+ if (computeHash) {
+ this.computeHash = iteratee(computeHash)
+ }
+
+ this._itemsByHash = Object.create(null)
+ this._keysToHash = Object.create(null)
+
+ // Bound versions of listeners.
+ this._onAdd = bind(this._onAdd, this)
+ this._onUpdate = bind(this._onUpdate, this)
+ this._onRemove = bind(this._onRemove, this)
+ }
+
+ // This method is used to compute the hash under which an item must
+ // be saved.
+ computeHash (value, key) {
+ throw new NotImplemented('this method must be overridden')
+ }
+
+ // Remove empty items lists.
+ sweep () {
+ const {_itemsByHash: itemsByHash} = this
+ for (const hash in itemsByHash) {
+ if (isEmpty(itemsByHash[hash])) {
+ delete itemsByHash[hash]
+ }
+ }
+ }
+
+ // -----------------------------------------------------------------
+
+ get items () {
+ return this._itemsByHash
+ }
+
+ // -----------------------------------------------------------------
+
+ _attachCollection (collection) {
+ // Add existing entries.
+ //
+ // FIXME: I think there may be a race condition if the `add` event
+ // has not been emitted yet.
+ this._onAdd(collection.all)
+
+ collection.on(ACTION_ADD, this._onAdd)
+ collection.on(ACTION_UPDATE, this._onUpdate)
+ collection.on(ACTION_REMOVE, this._onRemove)
+ }
+
+ _detachCollection (collection) {
+ collection.removeListener(ACTION_ADD, this._onAdd)
+ collection.removeListener(ACTION_UPDATE, this._onUpdate)
+ collection.removeListener(ACTION_REMOVE, this._onRemove)
+
+ clearObject(this._itemsByHash)
+ clearObject(this._keysToHash)
+ }
+
+ // -----------------------------------------------------------------
+
+ _onAdd (items) {
+ const {
+ computeHash,
+ _itemsByHash: itemsByHash,
+ _keysToHash: keysToHash
+ } = this
+
+ for (const key in items) {
+ const value = items[key]
+
+ const hash = computeHash(value, key)
+
+ if (hash != null) {
+ (
+ itemsByHash[hash] ||
+
+ // FIXME: We do not use objects without prototype for now
+ // because it breaks Angular in xo-web, change it back when
+ // this is fixed.
+ (itemsByHash[hash] = {})
+ )[key] = value
+
+ keysToHash[key] = hash
+ }
+ }
+ }
+
+ _onUpdate (items) {
+ const {
+ computeHash,
+ _itemsByHash: itemsByHash,
+ _keysToHash: keysToHash
+ } = this
+
+ for (const key in items) {
+ const value = items[key]
+
+ const prev = keysToHash[key]
+ const hash = computeHash(value, key)
+
+ // Removes item from the previous hash's list if any.
+ if (prev != null) delete itemsByHash[prev][key]
+
+ // Inserts item into the new hash's list if any.
+ if (hash != null) {
+ (
+ itemsByHash[hash] ||
+
+ // FIXME: idem: change back to Object.create(null)
+ (itemsByHash[hash] = {})
+ )[key] = value
+
+ keysToHash[key] = hash
+ } else {
+ delete keysToHash[key]
+ }
+ }
+ }
+
+ _onRemove (items) {
+ const {
+ _itemsByHash: itemsByHash,
+ _keysToHash: keysToHash
+ } = this
+
+ for (const key in items) {
+ const prev = keysToHash[key]
+ if (prev != null) {
+ delete itemsByHash[prev][key]
+ delete keysToHash[key]
+ }
+ }
+ }
+}
diff --git a/packages/xo-collection/src/index.spec.js b/packages/xo-collection/src/index.spec.js
new file mode 100644
index 000000000..352708051
--- /dev/null
+++ b/packages/xo-collection/src/index.spec.js
@@ -0,0 +1,183 @@
+/* eslint-env mocha */
+
+import eventToPromise from 'event-to-promise'
+import expect from 'must'
+import { forEach } from 'lodash'
+
+// ===================================================================
+
+import Collection from '..'
+import Index from '../index'
+
+// ===================================================================
+
+const waitTicks = (n = 1) => {
+ const {nextTick} = process
+
+ return new Promise(resolve => {
+ (function waitNextTick () {
+ // The first tick is handled by Promise#then()
+ if (--n) {
+ nextTick(waitNextTick)
+ } else {
+ resolve()
+ }
+ })()
+ })
+}
+
+// ===================================================================
+
+describe('Index', function () {
+ let col, byGroup
+ const item1 = {
+ id: '2ccb8a72-dc65-48e4-88fe-45ef541f2cba',
+ group: 'foo'
+ }
+ const item2 = {
+ id: '7d21dc51-4da8-4538-a2e9-dd6f4784eb76',
+ group: 'bar'
+ }
+ const item3 = {
+ id: '668c1274-4442-44a6-b99a-512188e0bb09',
+ group: 'foo'
+ }
+ const item4 = {
+ id: 'd90b7335-e540-4a44-ad22-c4baae9cd0a9'
+ }
+
+ beforeEach(function () {
+ col = new Collection()
+ forEach([item1, item2, item3, item4], item => {
+ col.add(item)
+ })
+
+ byGroup = new Index('group')
+
+ col.createIndex('byGroup', byGroup)
+
+ return waitTicks()
+ })
+
+ it('works with existing items', function () {
+ expect(col.indexes).to.eql({
+ byGroup: {
+ foo: {
+ [item1.id]: item1,
+ [item3.id]: item3
+ },
+ bar: {
+ [item2.id]: item2
+ }
+ }
+ })
+ })
+
+ it('works with added items', function () {
+ const item5 = {
+ id: '823b56c4-4b96-4f3a-9533-5d08177167ac',
+ group: 'baz'
+ }
+
+ col.add(item5)
+
+ return waitTicks(2).then(() => {
+ expect(col.indexes).to.eql({
+ byGroup: {
+ foo: {
+ [item1.id]: item1,
+ [item3.id]: item3
+ },
+ bar: {
+ [item2.id]: item2
+ },
+ baz: {
+ [item5.id]: item5
+ }
+ }
+ })
+ })
+ })
+
+ it('works with updated items', function () {
+ const item1bis = {
+ id: item1.id,
+ group: 'bar'
+ }
+
+ col.update(item1bis)
+
+ return waitTicks(2).then(() => {
+ expect(col.indexes).to.eql({
+ byGroup: {
+ foo: {
+ [item3.id]: item3
+ },
+ bar: {
+ [item1.id]: item1bis,
+ [item2.id]: item2
+ }
+ }
+ })
+ })
+ })
+
+ it('works with removed items', function () {
+ col.remove(item2)
+
+ return waitTicks(2).then(() => {
+ expect(col.indexes).to.eql({
+ byGroup: {
+ foo: {
+ [item1.id]: item1,
+ [item3.id]: item3
+ },
+ bar: {}
+ }
+ })
+ })
+ })
+
+ it('correctly updates the value even the same object has the same hash', function () {
+ const item1bis = {
+ id: item1.id,
+ group: item1.group,
+ newProp: true
+ }
+
+ col.update(item1bis)
+
+ return eventToPromise(col, 'finish').then(() => {
+ expect(col.indexes).to.eql({
+ byGroup: {
+ foo: {
+ [item1.id]: item1bis,
+ [item3.id]: item3
+ },
+ bar: {
+ [item2.id]: item2
+ }
+ }
+ })
+ })
+ })
+
+ describe('#sweep()', function () {
+ it('removes empty items lists', function () {
+ col.remove(item2)
+
+ return waitTicks(2).then(() => {
+ byGroup.sweep()
+
+ expect(col.indexes).to.eql({
+ byGroup: {
+ foo: {
+ [item1.id]: item1,
+ [item3.id]: item3
+ }
+ }
+ })
+ })
+ })
+ })
+})
diff --git a/packages/xo-collection/src/is-empty.js b/packages/xo-collection/src/is-empty.js
new file mode 100644
index 000000000..9e688ac7c
--- /dev/null
+++ b/packages/xo-collection/src/is-empty.js
@@ -0,0 +1,7 @@
+export default function isEmpty (object) {
+ /* eslint no-unused-vars: 0 */
+ for (const key in object) {
+ return false
+ }
+ return true
+}
diff --git a/packages/xo-collection/src/is-object.js b/packages/xo-collection/src/is-object.js
new file mode 100644
index 000000000..92961e81c
--- /dev/null
+++ b/packages/xo-collection/src/is-object.js
@@ -0,0 +1,3 @@
+export default function isObject (value) {
+ return (value !== null) && (typeof value === 'object')
+}
diff --git a/packages/xo-collection/src/not-implemented.js b/packages/xo-collection/src/not-implemented.js
new file mode 100644
index 000000000..52e507e37
--- /dev/null
+++ b/packages/xo-collection/src/not-implemented.js
@@ -0,0 +1,7 @@
+import {BaseError} from 'make-error'
+
+export default class NotImplemented extends BaseError {
+ constructor (message) {
+ super(message || 'this method is not implemented')
+ }
+}
diff --git a/packages/xo-collection/src/unique-index.js b/packages/xo-collection/src/unique-index.js
new file mode 100644
index 000000000..45735b10b
--- /dev/null
+++ b/packages/xo-collection/src/unique-index.js
@@ -0,0 +1,124 @@
+import { bind, iteratee } from 'lodash'
+
+import clearObject from './clear-object'
+import NotImplemented from './not-implemented'
+import {
+ ACTION_ADD,
+ ACTION_UPDATE,
+ ACTION_REMOVE
+} from './collection'
+
+// ===================================================================
+
+export default class UniqueIndex {
+ constructor (computeHash) {
+ if (computeHash) {
+ this.computeHash = iteratee(computeHash)
+ }
+
+ this._itemByHash = Object.create(null)
+ this._keysToHash = Object.create(null)
+
+ // Bound versions of listeners.
+ this._onAdd = bind(this._onAdd, this)
+ this._onUpdate = bind(this._onUpdate, this)
+ this._onRemove = bind(this._onRemove, this)
+ }
+
+ // This method is used to compute the hash under which an item must
+ // be saved.
+ computeHash (value, key) {
+ throw new NotImplemented('this method must be overridden')
+ }
+
+ // -----------------------------------------------------------------
+
+ get items () {
+ return this._itemByHash
+ }
+
+ // -----------------------------------------------------------------
+
+ _attachCollection (collection) {
+ // Add existing entries.
+ //
+ // FIXME: I think there may be a race condition if the `add` event
+ // has not been emitted yet.
+ this._onAdd(collection.all)
+
+ collection.on(ACTION_ADD, this._onAdd)
+ collection.on(ACTION_UPDATE, this._onUpdate)
+ collection.on(ACTION_REMOVE, this._onRemove)
+ }
+
+ _detachCollection (collection) {
+ collection.removeListener(ACTION_ADD, this._onAdd)
+ collection.removeListener(ACTION_UPDATE, this._onUpdate)
+ collection.removeListener(ACTION_REMOVE, this._onRemove)
+
+ clearObject(this._itemByHash)
+ clearObject(this._keysToHash)
+ }
+
+ // -----------------------------------------------------------------
+
+ _onAdd (items) {
+ const {
+ computeHash,
+ _itemByHash: itemByHash,
+ _keysToHash: keysToHash
+ } = this
+
+ for (const key in items) {
+ const value = items[key]
+
+ const hash = computeHash(value, key)
+
+ if (hash != null) {
+ itemByHash[hash] = value
+ keysToHash[key] = hash
+ }
+ }
+ }
+
+ _onUpdate (items) {
+ const {
+ computeHash,
+ _itemByHash: itemByHash,
+ _keysToHash: keysToHash
+ } = this
+
+ for (const key in items) {
+ const value = items[key]
+
+ const prev = keysToHash[key]
+ const hash = computeHash(value, key)
+
+ // Removes item from the previous hash's list if any.
+ if (prev != null) delete itemByHash[prev]
+
+ // Inserts item into the new hash's list if any.
+ if (hash != null) {
+ itemByHash[hash] = value
+ keysToHash[key] = hash
+ } else {
+ delete keysToHash[key]
+ }
+ }
+ }
+
+ _onRemove (items) {
+ const {
+ _itemByHash: itemByHash,
+ _keysToHash: keysToHash
+ } = this
+
+ for (const key in items) {
+ const prev = keysToHash[key]
+ if (prev != null) {
+ delete itemByHash[prev]
+ delete keysToHash[key]
+ }
+ }
+ }
+}
diff --git a/packages/xo-collection/src/unique-index.spec.js b/packages/xo-collection/src/unique-index.spec.js
new file mode 100644
index 000000000..d972050b2
--- /dev/null
+++ b/packages/xo-collection/src/unique-index.spec.js
@@ -0,0 +1,134 @@
+/* eslint-env mocha */
+
+import eventToPromise from 'event-to-promise'
+import expect from 'must'
+import { forEach } from 'lodash'
+
+// ===================================================================
+
+import Collection from '..'
+import Index from '../unique-index'
+
+// ===================================================================
+
+const waitTicks = (n = 1) => {
+ const {nextTick} = process
+
+ return new Promise(resolve => {
+ (function waitNextTick () {
+ // The first tick is handled by Promise#then()
+ if (--n) {
+ nextTick(waitNextTick)
+ } else {
+ resolve()
+ }
+ })()
+ })
+}
+
+// ===================================================================
+
+describe('UniqueIndex', function () {
+ let col, byKey
+ const item1 = {
+ id: '2ccb8a72-dc65-48e4-88fe-45ef541f2cba',
+ key: '036dee1b-9a3b-4fb5-be8a-4f535b355581'
+ }
+ const item2 = {
+ id: '7d21dc51-4da8-4538-a2e9-dd6f4784eb76',
+ key: '103cd893-d2cc-4d37-96fd-c259ad04c0d4'
+ }
+ const item3 = {
+ id: '668c1274-4442-44a6-b99a-512188e0bb09'
+ }
+
+ beforeEach(function () {
+ col = new Collection()
+ forEach([item1, item2, item3], item => {
+ col.add(item)
+ })
+
+ byKey = new Index('key')
+
+ col.createIndex('byKey', byKey)
+
+ return waitTicks()
+ })
+
+ it('works with existing items', function () {
+ expect(col.indexes).to.eql({
+ byKey: {
+ [item1.key]: item1,
+ [item2.key]: item2
+ }
+ })
+ })
+
+ it('works with added items', function () {
+ const item4 = {
+ id: '823b56c4-4b96-4f3a-9533-5d08177167ac',
+ key: '1437af14-429a-40db-8a51-8a2f5ed03201'
+ }
+
+ col.add(item4)
+
+ return waitTicks(2).then(() => {
+ expect(col.indexes).to.eql({
+ byKey: {
+ [item1.key]: item1,
+ [item2.key]: item2,
+ [item4.key]: item4
+ }
+ })
+ })
+ })
+
+ it('works with updated items', function () {
+ const item1bis = {
+ id: item1.id,
+ key: 'e03d4a3a-0331-4aca-97a2-016bbd43a29b'
+ }
+
+ col.update(item1bis)
+
+ return waitTicks(2).then(() => {
+ expect(col.indexes).to.eql({
+ byKey: {
+ [item1bis.key]: item1bis,
+ [item2.key]: item2
+ }
+ })
+ })
+ })
+
+ it('works with removed items', function () {
+ col.remove(item2)
+
+ return waitTicks(2).then(() => {
+ expect(col.indexes).to.eql({
+ byKey: {
+ [item1.key]: item1
+ }
+ })
+ })
+ })
+
+ it('correctly updates the value even the same object has the same hash', function () {
+ const item1bis = {
+ id: item1.id,
+ key: item1.key,
+ newProp: true
+ }
+
+ col.update(item1bis)
+
+ return eventToPromise(col, 'finish').then(() => {
+ expect(col.indexes).to.eql({
+ byKey: {
+ [item1.key]: item1bis,
+ [item2.key]: item2
+ }
+ })
+ })
+ })
+})
diff --git a/packages/xo-collection/src/view.example.js b/packages/xo-collection/src/view.example.js
new file mode 100644
index 000000000..c7f546e60
--- /dev/null
+++ b/packages/xo-collection/src/view.example.js
@@ -0,0 +1,56 @@
+import { forEach } from 'lodash'
+
+import Collection from '..'
+import View from '../view'
+
+// ===================================================================
+
+// Create the collection.
+const users = new Collection()
+users.getKey = (user) => user.name
+
+// Inserts some data.
+users.add({
+ name: 'bob'
+})
+users.add({
+ name: 'clara',
+ active: true
+})
+users.add({
+ name: 'ophelia'
+})
+users.add({
+ name: 'Steve',
+ active: true
+})
+
+// -------------------------------------------------------------------
+
+// Create the view.
+const activeUsers = new View(users, 'active')
+
+// Register some event listeners to see the changes.
+activeUsers.on('add', users => {
+ forEach(users, (_, id) => {
+ console.log('+ active user:', id)
+ })
+})
+activeUsers.on('remove', users => {
+ forEach(users, (_, id) => {
+ console.log('- active user:', id)
+ })
+})
+
+// Make some changes in the future.
+setTimeout(function () {
+ console.log('-----')
+
+ users.set({
+ name: 'ophelia',
+ active: true
+ })
+ users.set({
+ name: 'Steve'
+ })
+}, 10)
diff --git a/packages/xo-collection/src/view.js b/packages/xo-collection/src/view.js
new file mode 100644
index 000000000..c0fe4741f
--- /dev/null
+++ b/packages/xo-collection/src/view.js
@@ -0,0 +1,88 @@
+import { bind, forEach, iteratee as createCallback } from 'lodash'
+
+import Collection, {
+ ACTION_ADD,
+ ACTION_UPDATE,
+ ACTION_REMOVE
+} from './collection'
+
+// ===================================================================
+
+export default class View extends Collection {
+ constructor (collection, predicate) {
+ super()
+
+ this._collection = collection
+ this._predicate = createCallback(predicate)
+
+ // Handles initial items.
+ this._onAdd(this._collection.all)
+
+ // Bound versions of listeners.
+ this._onAdd = bind(this._onAdd, this)
+ this._onUpdate = bind(this._onUpdate, this)
+ this._onRemove = bind(this._onRemove, this)
+
+ // Register listeners.
+ this._collection.on(ACTION_ADD, this._onAdd)
+ this._collection.on(ACTION_UPDATE, this._onUpdate)
+ this._collection.on(ACTION_REMOVE, this._onRemove)
+ }
+
+ // This method is necessary to free the memory of the view if its
+ // life span is shorter than the collection.
+ destroy () {
+ this._collection.removeListener(ACTION_ADD, this._onAdd)
+ this._collection.removeListener(ACTION_UPDATE, this._onUpdate)
+ this._collection.removeListener(ACTION_REMOVE, this._onRemove)
+ }
+
+ add () {
+ throw new Error('a view is read only')
+ }
+
+ clear () {
+ throw new Error('a view is read only')
+ }
+
+ set () {
+ throw new Error('a view is read only')
+ }
+
+ update () {
+ throw new Error('a view is read only')
+ }
+
+ _onAdd (items) {
+ const {_predicate: predicate} = this
+
+ forEach(items, (value, key) => {
+ if (predicate(value, key, this)) {
+ // super.add() cannot be used because the item may already be
+ // in the view if it was already present at the creation of
+ // the view and its event not already emitted.
+ super.set(key, value)
+ }
+ })
+ }
+
+ _onUpdate (items) {
+ const {_predicate: predicate} = this
+
+ forEach(items, (value, key) => {
+ if (predicate(value, key, this)) {
+ super.set(key, value)
+ } else if (super.has(key)) {
+ super.remove(key)
+ }
+ })
+ }
+
+ _onRemove (items) {
+ forEach(items, (value, key) => {
+ if (super.has(key)) {
+ super.remove(key)
+ }
+ })
+ }
+}
diff --git a/packages/xo-collection/unique-index.js b/packages/xo-collection/unique-index.js
new file mode 100644
index 000000000..9f9d92cd5
--- /dev/null
+++ b/packages/xo-collection/unique-index.js
@@ -0,0 +1 @@
+module.exports = require('./dist/unique-index')
diff --git a/packages/xo-collection/view.js b/packages/xo-collection/view.js
new file mode 100644
index 000000000..6e691e6c2
--- /dev/null
+++ b/packages/xo-collection/view.js
@@ -0,0 +1 @@
+module.exports = require('./dist/view')