# Multiverse
[](https://beta.hexfaktor.org/github/Nebo15/multiverse) [](https://hex.pm/packages/multiverse) [](https://hex.pm/packages/multiverse) [](https://hex.pm/packages/multiverse) [](https://travis-ci.org/Nebo15/multiverse) [](https://coveralls.io/github/Nebo15/multiverse?branch=master) [](https://ebertapp.io/github/Nebo15/multiverse)
This plug helps to manage multiple API versions based on request and response gateways. This is an awesome practice to hide your backward compatibility. It allows to have your code in a latest possible version, without duplicating controllers or models.
Inspired by Stripe API. Read more at [MOVE FAST, DON'T BREAK YOUR API](http://amberonrails.com/move-fast-dont-break-your-api/) or [API versioning](https://stripe.com/blog/api-versioning).
## Goals
- reduce changes required to support multiple API versions;
- provide a way to test and schedule API version releases;
- to have minimum dependencies and low performance hit;
- to be flexible enough for most of projects to adopt it.
## Adapters
Multiverse allows you to use a custom adapter which can, for eg.:
- store consumer version upon his first request and re-use it as default each time consumer is using your API, eliminating need of passing version headers for them (a.k.a. version pinning). Change this version when consumer has explicitly set it;
- use _other than ISO date_ version types, eg. incremental counters (`v1`, `v2`);
- handle malformed versions by responding with JSON errors.
Default adapter works with ISO-8601 date from `x-api-version` header (configurable). For malformed versions it would log a warning and fallback to the current date.
Also, it allows to use channel name instead of date, where:
- `latest` channel would fallback to the current date;
- `edge` channel would disable all changes altogether.
Channels allow you to plan version releases upfront and test them without affecting users,
just set future date for a change and pass it explicitly or use `edge` channel to test latest
application version.
## Installation
The package (take look at [hex.pm](https://hex.pm/packages/multiverse)) can be installed as:
1. Add `multiverse` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[{:multiverse, "~> 2.0.0"}]
end
```
2. Make sure that `multiverse` is available at runtime in your production:
```elixir
def application do
[applications: [:multiverse]]
end
```
## How to use
1. Insert this plug into your API pipeline (in your ```router.ex```):
```elixir
pipeline :api do
plug :accepts, ["json"]
plug :put_secure_browser_headers
plug Multiverse, default_version: :latest
end
```
2. Define module that handles change
```elixir
defmodule AccountTypeChange do
@behaviour Multiverse.Change
def handle_request(%Plug.Conn{} = conn) do
# Mutate your request here
IO.inspect "AccountTypeChange.handle_request applied to request"
conn
end
def handle_response(%Plug.Conn{} = conn) do
# Mutate your response here
IO.inspect "AccountTypeChange.handle_response applied to response"
conn
end
end
```
3. Enable the change:
```elixir
pipeline :api do
plug :accepts, ["json"]
plug :put_secure_browser_headers
plug Multiverse,
default_version: :latest,
gates: %{
~D[2016-07-21] => [AccountTypeChange]
}
end
```
4. Send your API requests with ```X-API-Version``` header with version lower or equal to ```2016-07-20```.
### Overriding version header
You can use any version headers by passing option to Multiverse:
```elixir
pipeline :api do
plug :accepts, ["json"]
plug :put_secure_browser_headers
plug Multiverse,
default_version: :latest,
version_header: "x-my-version-header",
gates: %{
~D[2016-07-21] => [AccountTypeChange]
}
end
```
### Using custom adapters
You can use your own adapter which implements `Multiverse.Adapter` behaviour:
```elixir
pipeline :api do
plug :accepts, ["json"]
plug :put_secure_browser_headers
plug Multiverse,
default_version: :latest,
adapter: MyApp.SmartMultiverseAdapter,
gates: %{
~D[2016-07-21] => [AccountTypeChange]
}
end
```
## Structuring your tests
1. Split your tests into versions:
$ ls -l test/acceptance
total 0
drwxr-xr-x 2 andrew staff 68 Aug 1 19:23 AccountTypeChange
drwxr-xr-x 2 andrew staff 68 Aug 1 19:24 OlderChange
2. Avoid touching request or response in old tests. Create API gates and matching folder in acceptance tests.
## Other things you might want to do
1. Store Multiverse configuration in `config.ex`:
```elixir
use Mix.Config
config :multiverse, MyApp.Endpoint,
default_version: :latest,
gates: %{
~D[2016-07-21] => [AccountTypeChange]
}
```
```elixir
plug Multiverse, endpoint: __MODULE__
```
2. Generate API documentation from changes `@moduledoc`'s.
3. Other awesome stuff. Open an issue and tell me about it! :).
# License
See [LICENSE.md](LICENSE.md).
