# Cain
Camunda-REST-API-Interpreter to handle common Camunda specific workflow use cases for a more clearly usage by hiding the REST-Calls under the hood.
### Covered
- Handle external tasks
- Invoke DMN evaluations
## External Task Client
Use `Cain.ExternalWorker` for referencing your external task function implementation in your application.
```elixir
defmodule MyWorker do
use Cain.ExternalWorker, [
max_tasks: 5, # default: 3
use_priority: true, # default: false
polling_interval: 1000 # default: 3000
]
end
```
Add `register_topics/1` and create a list of a tuple with the following elements:
- Name of the topic that has been given in the BPMN-Process-Model
- Function implementation with a tuple of Module, function and args the topic refers to
- Setting lock duration in milliseconds, defaults to 3000ms
```elixir
def register_topics do
[{:my_topic, {MyTopicHandler, :handle_topic, [:my_arg], [lock_duration: 5000]}]
end
```
Response in the referenced function by using the provided API in `MyWorker`.
> Notice: The payload of a topic fetch is always provided as the first argument and needs to be considered on your function implementation
```elixir
defmodule MyTopicHandler do
def handle_topic(payload, :my_arg) do
do_something_with_payload(payload)
case an_external_service_call() do
:ok ->
# provide a map with atom keys to response with variables
MyWorker.success()
{:error, error} ->
MyWorker.retry("external_service_error", inspect(error), 3, 3000)
_unexpected ->
MyWorker.create_incident("unexpected_error", "See the logs")
end
end
end
```
## DMN Evaluation
Use `Cain.DecisionTable` and set the corresponding `definition_key` of the deployed table in the engine.
```elixir
defmodule MyDecisionTable do
use Cain.DecisionTable, definition_key: "MY_TABLE"
end
```
And evaluate.
```elixir
MyDecisionTable.evaluate(%{first: 1, second: "Second"})
# {:ok, [%{is_valid: true}]}
```
The return value depends on the output definition of the table.
## Installation
<!-- If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `cain` to your list of dependencies in `mix.exs`: -->
```elixir
def deps do
[
{:cain, "~> 0.3.0"}
]
end
```
<!--
Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at [https://hexdocs.pm/cain](https://hexdocs.pm/cain). -->
