# Disco

Simple, opinionated yet flexible library to build CQRS/ES driven systems.

Disco has been extracted from work done to build apps following the CQRS/ES pattern.
Several ideas come from other excellent examples such as [commanded](https://github.com/commanded/commanded).
However, the goal was to build something simpler and more flexible, because it's not always
possible to follow 100% CQRS/ES pattern neither anywhere in your apps. Disco tries to
solve this gap.

### Production ready?

Not yet. Well, this approach and code has been used to build several apps in production
without problems, however before being really usable, it might need some polishing. Expect
potential breaking changes until explicitly stated.

## Installation

The package is available in [Hex](https://hex.pm/packages/disco), follow these steps to install:

1.  Add `disco` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  # Get from hex
  [{:disco, "~> 0.1.0"}]
  # Or use the latest from master
  [{:disco, github: "andreapavoni/disco"}]
end
```

2.  Run setup to generate event store migrations:

```sh
mix do deps.get, compile, disco.install
```

## Usage

Quick and dirty console example, to show how it's supposed to work.

```
$ iex -S mix
# start Orchestrator process with the available aggregates
iex> Disco.Orchestrator.start_link [MyApp.Wallet]
{:ok, #PID<0.327.0>}

# get available commands
iex> Disco.Orchestrator.commands()
[:create_wallet]

# execute a command (sync)
iex> Disco.Orchestrator.dispatch(:create_wallet, %{user_id: UUID.uuid4(), balance: 100.0})
{:ok, %MyApp.Wallet.Aggregate{
  balance: 100.0,
  id: "4fd98a9e-8d6f-4e35-a8fc-aca5544596cb",
  user_id: "13bbece9-9bf3-4158-92b4-7e8a62d62361"
}}

# execute a command (async -> returns {:ok, aggregate_id})
iex> Disco.Orchestrator.dispatch(:create_wallet, %{user_id: UUID.uuid4(), balance: 100.0}, async: true)
{:ok, "ce998b0d-8d6f-4e35-a8fc-aca5544596cb"}

# execute invalid command
iex> Disco.Orchestrator.dispatch(:create_wallet, %{balance: 100.0})
{:error, %{user_id: ["must be a valid UUID string"]}}

# get available queries
iex> Disco.Orchestrator.queries()
[:list_wallets]

# list user wallets
iex> Disco.Orchestrator.query(:list_wallets, %{user_id: "13bbece9-9bf3-4158-92b4-7e8a62d62361"})
[%{
  balance: 100.0,
  id: "4fd98a9e-8d6f-4e35-a8fc-aca5544596cb",
  user_id: "13bbece9-9bf3-4158-92b4-7e8a62d62361"
}]

# execute invalid query
iex> Disco.Orchestrator.query(:list_wallets, %{})
{:error, %{user_id: ["must be a valid UUID string"]}}
```

## Documentation

The documentation is available at [https://hexdocs.pm/disco](https://hexdocs.pm/disco).

## TODO / SHORT TERM ROADMAP

* [x] improve overall documentation
* [ ] consolidate Event to be a struct and/or protocol
* [ ] consolidate API for aggregates or event consumer (mostly based on feedback, if any)
* [ ] adopt an adapter-based approach for event store database

## Contributing

Everyone is welcome to contribute to PlugEtsCache and help tackling existing issues!

Use the [issue tracker](https://github.com/andreapavoni/disco/issues) for bug reports or feature requests.

Please, do your best to follow the [Elixir's Code of Conduct](https://github.com/elixir-lang/elixir/blob/master/CODE_OF_CONDUCT.md).

## License

This source code is released under MIT License. Check [LICENSE](https://github.com/andreapavoni/disco/blob/master/LICENSE) file for more information.