# Pears

Welcome to the readme of Pears. This library is used to consume configuration
in Ruby applications in a cascading way. It is named Pears because its a short,
rememberable word and wasn't taken on rubygem.

## Installation

Add this line to your application's Gemfile:

```ruby
gem 'pears'
```

And then execute:

    $ bundle install

Or install it yourself as:

    $ gem install pears

## Usage

Examples:

```ruby
# You can load a dynamic config file like this
dynamic_config = Pears.subject(:settings) do |provider|
  provider.subscription do
    provider.remote_file "https://raw.githubusercontent.com/codefresh-io/yaml-examples/master/codefresh-build-1.yml"
  end
end

# You can "Cascade" data like this
cascading_config = Pears.subject(:settings) do |provider|
  provider.local_file Rails.root.join('config', 'settings.concrete.yml') # defines foo: 'foo'
  provider.local_file Rails.root.join('config', 'settings.default.yml') # defines foo: 'bar', baz: 'baz'
end

cascading_config[:foo] # => foo
cascading_config[:baz] # => baz

# And you can combine these
combined_config = Pears.subject(:settings) do |provider|
  provider.subscription { provider.remote_file "https://admin/configuration.yml" }
  provider.local_file Rails.root.join('config', 'default.yml')
end
```


## Terminology

- A Subject is a grouping of configuration items with a single interface
- A Subject contains at least a single "Layer" that wraps a "Provider"
- A Provider is an adapter(YAML OR REDIS).
- That wraps it up

##### Providers:

- LocalFile - read a yaml file identified by a path into a "Subject"
- RemoteFile - read a yaml file identified by a URI into a "Subject"
- Subscription - Read a yaml file identified by a URI as a segment and update it whenever the the provided redis channel gets an update.

You can create a custom povider like this:

```ruby
class GcloudProvider < Pears::Provider::LocalFile
  def initialize
    @data = parse_yaml Faraday.get(url, {}, authorization: token )
  end

  private

  def url
    'https://velogica-portal-admin.ey.r.appspot.com/settings/' \
    "#{Rails.application.secrets.settings_file}"
  end

  def token
    path = 'http://metadata.google.internal/computeMetadata/v1/instance/'

    'Bearer ' + Faraday.get(path, {}, { metadata_flavor: 'Google' }).body
  end
end
```

And register it like this:

```ruby
# config/initializers/pears.rb
Pears::Provider::Builder.enable_provider Pears::GcloudProvider
```


## Todo


## Development

After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and the created tag, and push the `.gem` file to [rubygems.org](https://rubygems.org).


## Future

- Factor subject as a distinct, non-provider entitity.
- Add Loco as a provider.
- Add ENV as a provider.
- Figure out if there is a sensible tie in with kubernetes.
- Add support for different file-types.
- Add different ways to trigger updates from redis subscriptions.

We want to add the following providers:
- ENV - read the ENV and overwrite keys found on lower layers of the segment. **
- LOCO - read a loco file into a segment.
- Redis - consume data drom a redis key.


## Contributing

Hit me up on slack, jira or Bitbucket!

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).