Shopify Oauth strategy for Elixir

Shopify.Oauth.ex

defmodule Shopify.Oauth do
  @moduledoc """
  An OAuth2 strategy for Shopify.
  Based on the OAuth2 strategy for GitHub by Sonny Scroggin
  in https://github.com/scrogson/oauth2_example
  """
	use OAuth2.Strategy

	alias OAuth2.Strategy.AuthCode
	alias OAuth2.Request
	alias OAuth2.AccessToken

	# Public API

	def create(shopid) do
  OAuth2.Client.new([
		strategy: __MODULE__,
		client_id: System.get_env("CLIENT_ID"),
		client_secret: System.get_env("CLIENT_SECRET"),
		redirect_uri: System.get_env("REDIRECT_URI") <> "/auth/shopify/callback",
		site: "https://#{shopid}.myshopify.com/admin",
		authorize_url: "https://#{shopid}.myshopify.com/admin/oauth/authorize",
		token_url: "https://#{shopid}.myshopify.com/admin/oauth/access_token"
  ])
	end

	def authorize_url!(shopid, params \\ []) do
		OAuth2.Client.authorize_url!(create(shopid), params)
	end

	def get_token!(shopid, params \\ [], headers \\ []) do
		OAuth2.Client.get_token!(create(shopid), params)
	end

	# Strategy Callbacks

	def authorize_url(client, params) do
		AuthCode.authorize_url(client, params)
	end

	def get_token(client, params, headers) do
		client
		|> put_header("Accept", "application/json")
		|> AuthCode.get_token(params, headers)
	end

	defp prepare_url(token, url_) do
		case String.downcase(url_) do
			<<"http://":: utf8, _::binary>> -> url_
			<<"https://":: utf8, _::binary>> -> url_
			_ -> token.client.site <> url_
		end
	end

	defp req_headers(token, headers) do
		headers1 = [{"X-Shopify-Access-Token", token.access_token} | headers]
		[{"Authorization", "#{token.token_type} #{token.access_token}"}| headers1]
	end

	defp req_post_headers(headers) do
		[{"Content-Type", "application/json; charset=utf-8"} | headers]
	end

	def get!(token, url_, header \\ [], opts \\ []) do
		headers = req_headers(token, header)
		url = prepare_url(token, url_)
		resp = AccessToken.get!(token, url, headers, opts)
		resp.body
	end

	def post!(token, url_, data, header \\ [], opts \\ []) do
		headers = req_headers(token, header)
		|> req_post_headers
		url = prepare_url(token, url_)
		payload = Poison.Encoder.encode(data, [])
		case apply(Request, :post, [url, data, headers, opts]) do
			{:ok, response} -> {:ok, response.body}
			{:error, error} -> {:error, error}
		end
	end


	def put!(token, url_, data, header \\ [], opts \\ []) do
		headers = req_headers(token, header)
		|> req_post_headers
		url = prepare_url(token, url_)
		IO.inspect url
		IO.inspect headers
		payload = Poison.Encoder.encode(data, [])
		IO.inspect payload
		case apply(Request, :put, [url, data, headers, opts]) do
			{:ok, response} -> {:ok, response.body}
			{:error, error} -> {:error, error}
		end
	end

end