1 files changed, 103 insertions, 0 deletions
diff --git a/lib/declarative_policy/dsl.rb b/lib/declarative_policy/dsl.rb
new file mode 100644
index 00000000000..b26807a7622
--- /dev/null
+++ b/lib/declarative_policy/dsl.rb
@@ -0,0 +1,103 @@
+module DeclarativePolicy
+  # The DSL evaluation context inside rule { ... } blocks.
+  # Responsible for creating and combining Rule objects.
+  #
+  # See Base.rule
+  class RuleDsl
+    def initialize(context_class)
+      @context_class = context_class
+    end
+
+    def can?(ability)
+      Rule::Ability.new(ability)
+    end
+
+    def all?(*rules)
+      Rule::And.make(rules)
+    end
+
+    def any?(*rules)
+      Rule::Or.make(rules)
+    end
+
+    def none?(*rules)
+      ~Rule::Or.new(rules)
+    end
+
+    def cond(condition)
+      Rule::Condition.new(condition)
+    end
+
+    def delegate(delegate_name, condition)
+      Rule::DelegatedCondition.new(delegate_name, condition)
+    end
+
+    def method_missing(m, *a, &b)
+      return super unless a.size == 0 && !block_given?
+
+      if @context_class.delegations.key?(m)
+        DelegateDsl.new(self, m)
+      else
+        cond(m.to_sym)
+      end
+    end
+  end
+
+  # Used when the name of a delegate is mentioned in
+  # the rule DSL.
+  class DelegateDsl
+    def initialize(rule_dsl, delegate_name)
+      @rule_dsl = rule_dsl
+      @delegate_name = delegate_name
+    end
+
+    def method_missing(m, *a, &b)
+      return super unless a.size == 0 && !block_given?
+
+      @rule_dsl.delegate(@delegate_name, m)
+    end
+  end
+
+  # The return value of a rule { ... } declaration.
+  # Can call back to register rules with the containing
+  # Policy class (context_class here). See Base.rule
+  #
+  # Note that the #policy method just performs an #instance_eval,
+  # which is useful for multiple #enable or #prevent callse.
+  #
+  # Also provides a #method_missing proxy to the context
+  # class's class methods, so that helper methods can be
+  # defined and used in a #policy { ... } block.
+  class PolicyDsl
+    def initialize(context_class, rule)
+      @context_class = context_class
+      @rule = rule
+    end
+
+    def policy(&b)
+      instance_eval(&b)
+    end
+
+    def enable(*abilities)
+      @context_class.enable_when(abilities, @rule)
+    end
+
+    def prevent(*abilities)
+      @context_class.prevent_when(abilities, @rule)
+    end
+
+    def prevent_all
+      @context_class.prevent_all_when(@rule)
+    end
+
+    def method_missing(m, *a, &b)
+      return super unless @context_class.respond_to?(m)
+
+      @context_class.__send__(m, *a, &b)
+    end
+
+    def respond_to_missing?(m)
+      @context_class.respond_to?(m) || super
+    end
+  end
+end