[api] Add module Backend::ConnectionHelper

This module will hold http verbs like methods that help calculating
the endpoints and the query params that will end up in the backend
requests

src/api/lib/backend/connection_helper.rb

@@ -0,0 +1,79 @@
+# API for connecting to the backend
+module Backend
+  module ConnectionHelper
+    # Performs a get action
+    def get(endpoint, options = {})
+      Backend::Connection.get(calculate_url(endpoint, options), options[:headers] || {}).body.force_encoding("UTF-8")
+    end
+
+    # Performs a post action
+    def post(endpoint, options = {})
+      Backend::Connection.post(calculate_url(endpoint, options), options[:data], options[:headers] || {}).body.force_encoding("UTF-8")
+    end
+
+    # Performs a put action
+    def put(endpoint, options = {})
+      Backend::Connection.put(calculate_url(endpoint, options), options[:data], options[:headers] || {}).body.force_encoding("UTF-8")
+    end
+
+    # Performs a delete action
+    def delete(endpoint, options = {})
+      Backend::Connection.delete(calculate_url(endpoint, options), options[:headers] || {}).body.force_encoding("UTF-8")
+    end
+
+    private
+
+    def calculate_url(endpoint, options)
+      endpoint = calculate_endpoint(endpoint)
+      params = calculate_params(options)
+      [endpoint, params].compact.join('?')
+    end
+
+    def calculate_params(options)
+      return nil if options.blank?
+      params = rename_params(options[:params] || {}, options[:rename] || {})
+      params = accept_params(params, options[:accepted] || [])
+      params = merge_defaults(params, options[:defaults] || {})
+      params = expand_params(params, options[:expand] || [])
+      return nil if params.blank?
+      params.join('&')
+    end
+
+    def merge_defaults(params, defaults)
+      defaults.merge(params)
+    end
+
+    def accept_params(params, accepted)
+      params.slice!(*accepted) unless accepted.empty?
+      params
+    end
+
+    def rename_params(params, renames)
+      renames.each do |old_name, new_name|
+        params[new_name] = params.delete(old_name) if params.key?(old_name)
+      end
+      params
+    end
+
+    def expand_params(params, expand)
+      expanded_params = []
+      expand.each do |key|
+        expanded_params += params.delete(key).map { |value| value.to_query(key) } if params.key?(key)
+      end
+      expanded_params += [params.to_query] unless params.empty?
+      expanded_params
+    end
+
+    def calculate_endpoint(endpoint)
+      return endpoint if endpoint.is_a?(String)
+      template = endpoint.shift
+      values = endpoint.map { |x| CGI.escape(x.to_s) }
+      placeholders = template.scan(/(:\w+)/).flatten
+      raise "Endpoit not valid: different number of placeholders and values" if values.size != placeholders.size
+      placeholders.each_with_index do |placeholder, index|
+        template.gsub!(placeholder, values[index])
+      end
+      template
+    end
+  end
+end