Defines an Expander.

An expander is a wrapper around an adapter that makes it easy for you to swap the cache adapter without having to change your code.

It is also responsible for doing some sanity checks before handing down the url to the adapter.

When used, the expander expects :otp_app as an option. The :otp_app should point to an OTP application that has the expander configuration. For example, the expander:

defmodule Sample.Expander do
  use Expander.Expand, otp_app: :sample
end

Could be configured with:

config :sample, Sample.Expander,
  adapter: Expander.Cache.Adapter.Local,
  api_key: "x.x.x"

Most of the configuration that goes into the config is specific to the adapter, so check the adapter’s documentation for more information.

Note that the configuration is set into your expander at compile time. If you need to reference config at runtime you can use a tuple like {:system, "ENV_VAR"}.

config :sample, Sample.LocalCacheExpander,
  adapter: Expander.Cache.Adapter.Local

Examples

Once configured you can use your expander like this:

# in an IEx console
iex> url = new() |> short_url("http://amzn.to/2w9oM5d")
%Expander.Url{long_url: nil, short_url: "http://amzn.to/2w9oM5d"}
iex> Expander.expand(url)
{:ok, {%Expander.Url{long_url: "http://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/create_dashboard.html?sc_channel=sm&sc_campaign=Docs&sc_publisher=TWITTER&sc_country=Global&sc_geo=GLOBAL&sc_outcome=[GLOBAL]&sc_content=Docs&linkId=40350988", short_url: "http://amzn.to/2w9oM5d"}, []}}

You can also pass an extra config argument to expand/2 that will be merged with your Expander’s config:

# in an IEx console
iex> url = new() |> short_url("http://amzn.to/2w9oM5d")
%Expander.Url{long_url: nil, short_url: "http://amzn.to/2w9oM5d"}
iex> Expander.expand(url, tls: 100)
{%Expander.Url{long_url: "http://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/create_dashboard.html?sc_channel=sm&sc_campaign=Docs&sc_publisher=TWITTER&sc_country=Global&sc_geo=GLOBAL&sc_outcome=[GLOBAL]&sc_content=Docs&linkId=40350988", short_url: "http://amzn.to/2w9oM5d"}, []}}