README.md

# Debouncer [![Build Status](https://travis-ci.com/dominicletz/debouncer.svg?branch=master)](https://travis-ci.com/dominicletz/debouncer)

Debouncer module to reduce frequency of function calls to alerts, updates and similar. It supports four different modes:

* `apply()`      - For delayed triggers, e.g. to trigger an __autocomplete__ action
* `immediate()`  - For reducing frequency of events, the first event per interval is delivered immediately, e.g. trigger __data processing tasks__ 
* `immediate2()` - Similiar to immediate but never delays events, either forwards them or ignores them, e.g. to trigger __alert emails__ 
* `delay()`      - Only triggers an event after the timeout period, any further event delays the trigger. E.g. to detect data streams that __ended actvitiy__ 

## Usage Example

```elixir
  Debouncer.apply(SomeKey, fn() -> 
    IO.puts("Hello World, debounced will appear in 5 seconds") 
  end)
```

```elixir
  Debouncer.immediate(OtherKey, fn() -> 
    IO.puts("Hello World, will appear immediate, but not again within 5 seconds") 
  end)
```

## Behaviour Graph

```
EVENT        X1---X2------X3-------X4----------
TIMEOUT      ----------|----------|----------|-
===============================================
apply()      ----------X2---------X3---------X4
immediate()  X1--------X2---------X3---------X4
immediate2() X1-----------X3-------------------
delay()      --------------------------------X4
```

This graph represents when the different variants fire an event respectively on a timeline. In code the first line would look like this:

```elixir
fn ->
  Debouncer.apply(SomeKey, fn() -> IO.puts("X1") end, 1000)
  Process.sleep(500)
  Debouncer.apply(SomeKey, fn() -> IO.puts("X2") end, 1000)
  Process.sleep(800)
  Debouncer.apply(SomeKey, fn() -> IO.puts("X3") end, 1000)
  Process.sleep(900)
  Debouncer.apply(SomeKey, fn() -> IO.puts("X4") end, 1000)
  Process.sleep(1200)
end.()

> X2
> X3
> X4
```

## Installation

The debouncer can be installed by adding `debouncer` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:debouncer, "~> 0.1"}
  ]
end
```

The debouncer is an application and will start a GenServer to trigger the events. To include the Application in your release add it to your extra applications:

```elixir
  def application do
    [
      mod: {Your.Application, []},
      extra_applications: [:debouncer]
    ]
  end

```

If it's not started it will try to start itself on usage.

The docs can be found at [https://hexdocs.pm/debouncer](https://hexdocs.pm/debouncer).

## Remarks

The `delay()` behaviour should be the same as in Michal Muskalas Debounce implementation https://github.com/michalmuskala/debounce