add general filter utility for resources

lib/utils/filter.rb

@@ -0,0 +1,43 @@
+# encoding: utf-8
+# author: Dominik Richter
+# author: Christoph Hartmann
+
+module Inspec
+  module Filter
+    module Show; end
+
+    def add_filter(field_name)
+      fail "Called add_filter in resource #{self} with field name nil!" if field_name.nil?
+      method_name = field_name.to_s
+      # methods will alwas target plurals; this is why the suffix 's' is mandatory
+      method_name += 's' unless method_name.end_with? 's'
+
+      define_method method_name.to_sym do |condition = Show|
+        return get_fields(field_name) if condition == Show
+        where({ field_name => condition })
+      end
+    end
+
+    def self.where(table, conditions = {})
+      return self if !conditions.is_a?(Hash) || conditions.empty?
+      filters = ''
+      conditions.each do |field, condition|
+        filters += " #{field} = #{condition.inspect}"
+        table = filter_lines(table, field, condition)
+      end
+      [table, filters]
+    end
+
+    def self.filter_lines(table, field, condition)
+      table.find_all do |line|
+        next unless line.key?(field)
+        case line[field]
+        when condition
+          true
+        else
+          false
+        end
+      end
+    end
+  end
+end