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+<!-- markdownlint-disable MD013 MD024 -->
+
+# MQEmitter
+
+![ci](https://github.com/mcollina/mqemitter/workflows/ci/badge.svg)
+[![Known Vulnerabilities](https://snyk.io/test/github/mcollina/mqemitter/badge.svg)](https://snyk.io/test/github/mcollina/mqemitter)
+[![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](http://standardjs.com/)\
+[![Dependencies Status](https://david-dm.org/mcollina/mqemitter/status.svg)](https://david-dm.org/mcollina/mqemitter)
+[![devDependencies Status](https://david-dm.org/mcollina/mqemitter/dev-status.svg)](https://david-dm.org/mcollina/mqemitter?type=dev)\
+[![NPM version](https://img.shields.io/npm/v/mqemitter.svg?style=flat)](https://www.npmjs.com/mqemitter)
+[![NPM downloads](https://img.shields.io/npm/dm/mqemitter.svg?style=flat)](https://www.npmjs.com/mqemitter)
+
+An Opinionated Message Queue with an emitter-style API, but with callbacks.
+
+If you need a multi process MQEmitter, check out the table below:
+
+- [mqemitter-redis]: Redis-powered mqemitter
+- [mqemitter-mongodb]: Mongodb based mqemitter
+- [mqemitter-child-process]: Share the same mqemitter between a hierarchy of child processes
+- [mqemitter-cs]: Expose a MQEmitter via a simple client/server protocol
+- [mqemitter-p2p]: A P2P implementation of MQEmitter, based on HyperEmitter and a Merkle DAG
+- [mqemitter-aerospike]: Aerospike mqemitter
+
+## Installation
+
+```sh
+npm install mqemitter
+```
+
+## Examples
+
+```js
+const mq = require('mqemitter')
+const emitter = mq({ concurrency: 5 })
+const message
+
+emitter.on('hello world', function (message, cb) {
+  // call callback when you are done
+  // do not pass any errors, the emitter cannot handle it.
+  cb()
+})
+
+// topic is mandatory
+message = { topic: 'hello world', payload: 'or any other fields' }
+emitter.emit(message, function () {
+  // emitter will never return an error
+})
+```
+
+## API
+
+- [new MQEmitter ([options])](#new-mqemitter-options)
+- [emitter.emit (message, callback)](#emitteremit-message-callback)
+- [emitter.on (topic, listener, [callback])](#emitteron-topic-listener-callback)
+- [emitter.removeListener (topic, listener, [callback])](#emitterremovelistener-topic-listener-callback)
+- [emitter.close (callback)](#emitterclose-callback)
+
+## new MQEmitter ([options])
+
+- options `<object>`
+  - `concurrency` `<number>` maximum number of concurrent messages that can be on concurrent delivery. __Default__: `0`
+  - `wildcardOne` `<string>` a char to use for matching exactly one _non-empty_ level word. __Default__: `+`
+  - `wildcardSome` `<string>` a char to use for matching multiple level wildcards. __Default__: #`
+  - `matchEmptyLevels` `<boolean>` If true then `wildcardOne` also matches an empty word. __Default__: `true`
+  - `separator` `<string>`  a separator character to use for separating words. __Default__: `/`
+
+Create a new MQEmitter class.
+
+MQEmitter is the class and function exposed by this module.
+It can be created by `MQEmitter()` or using `new MQEmitter()`.
+
+For more information on wildcards, see [this explanation](#wildcards) or [Qlobber](https://www.npmjs.com/qlobber).
+
+## emitter.emit (message, callback)
+
+- `message` `<object>`
+- `callback` `<Function>` `(error) => void`
+  - error `<Error>` | `null`
+
+Emit the given message, which must have a `topic` property, which can contain wildcards as defined on creation.
+
+## emitter.on (topic, listener, [callback])
+
+- `topic` `<string>`
+- `listener` `<Function>` `(message, done) => void`
+- `callback` `<Function>` `() => void`
+
+Add the given listener to the passed topic. Topic can contain wildcards, as defined on creation.
+
+The `listener` __must never error__ and `done` must not be called with an __`err`__ object.
+
+`callback` will be called when the event subscribe is done correctly.
+
+## emitter.removeListener (topic, listener, [callback])
+
+The inverse of `on`.
+
+## emitter.close (callback)
+
+- `callback` `<Function>` `() => void`
+
+Close the given emitter. After, all writes will return an error.
+
+## Wildcards
+
+__MQEmitter__ supports the use of wildcards: every topic is splitted according to `separator`.
+
+The wildcard character `+` matches exactly _non-empty_ one word:
+
+```js
+const mq = require('mqemitter')
+const emitter = mq()
+
+emitter.on('hello/+/world', function(message, cb) {
+  // will ONLY capture { topic: 'hello/my/world', 'something': 'more' }
+  console.log(message)
+  cb()
+})
+emitter.on('hello/+', function(message, cb) {
+  // will not be called
+  console.log(message)
+  cb()
+})
+
+emitter.emit({ topic: 'hello/my/world', something: 'more' })
+emitter.emit({ topic: 'hello//world', something: 'more' })
+```
+
+The wildcard character `+` matches one word:
+
+```js
+const mq = require('mqemitter')
+const emitter = mq({ matchEmptyLevels: true })
+
+emitter.on('hello/+/world', function(message, cb) {
+  // will capture { topic: 'hello/my/world', 'something': 'more' }
+  // and capture { topic: 'hello//world', 'something': 'more' }
+  console.log(message)
+  cb()
+})
+
+emitter.on('hello/+', function(message, cb) {
+  // will not be called
+  console.log(message)
+  cb()
+})
+
+emitter.emit({ topic: 'hello/my/world', something: 'more' })
+emitter.emit({ topic: 'hello//world', something: 'more' })
+```
+
+The wildcard character `#` matches zero or more words:
+
+```js
+const mq = require('mqemitter')
+const emitter = mq()
+
+emitter.on('hello/#', function(message, cb) {
+  // this will print { topic: 'hello/my/world', 'something': 'more' }
+  console.log(message)
+  cb()
+})
+
+emitter.on('#', function(message, cb) {
+  // this will print { topic: 'hello/my/world', 'something': 'more' }
+  console.log(message)
+  cb()
+})
+
+emitter.on('hello/my/world/#', function(message, cb) {
+  // this will print { topic: 'hello/my/world', 'something': 'more' }
+  console.log(message)
+  cb()
+})
+
+emitter.emit({ topic: 'hello/my/world', something: 'more' })
+```
+
+Of course, you can mix `#` and `+` in the same subscription.
+
+## LICENSE
+
+MIT
+
+[mqemitter-redis]: https://www.npmjs.com/mqemitter-redis
+[mqemitter-mongodb]: https://www.npmjs.com/mqemitter-mongodb
+[mqemitter-child-process]: https://www.npmjs.com/mqemitter-child-process
+[mqemitter-cs]: https://www.npmjs.com/mqemitter-cs
+[mqemitter-p2p]: https://www.npmjs.com/mqemitter-p2p
+[mqemitter-aerospike]: https://www.npmjs.com/mqemitter-aerospike