1 files changed, 53 insertions, 22 deletions

diff --git a/actionpack/lib/action_dispatch/http/headers.rb b/actionpack/lib/action_dispatch/http/headers.rb
index bc5410dc38..3c03976f03 100644
--- a/actionpack/lib/action_dispatch/http/headers.rb
+++ b/actionpack/lib/action_dispatch/http/headers.rb
@@ -2,9 +2,23 @@ module ActionDispatch
   module Http
     # Provides access to the request's HTTP headers from the environment.
     #
-    #   env     = { "CONTENT_TYPE" => "text/plain" }
-    #   headers = ActionDispatch::Http::Headers.new(env)
+    #   env     = { "CONTENT_TYPE" => "text/plain", "HTTP_USER_AGENT" => "curl/7.43.0" }
+    #   headers = ActionDispatch::Http::Headers.from_hash(env)
     #   headers["Content-Type"] # => "text/plain"
+    #   headers["User-Agent"] # => "curl/7.43.0"
+    #
+    # Also note that when headers are mapped to CGI-like variables by the Rack
+    # server, both dashes and underscores are converted to underscores. This
+    # ambiguity cannot be resolved at this stage anymore. Both underscores and
+    # dashes have to be interpreted as if they were originally sent as dashes.
+    #
+    #   # GET / HTTP/1.1
+    #   # ...
+    #   # User-Agent: curl/7.43.0
+    #   # X_Custom_Header: token
+    #
+    #   headers["X_Custom_Header"] # => nil
+    #   headers["X-Custom-Header"] # => "token"
     class Headers
       CGI_VARIABLES = Set.new(%W[
         AUTH_TYPE
@@ -30,27 +44,37 @@ module ActionDispatch
       HTTP_HEADER = /\A[A-Za-z0-9-]+\z/
 
       include Enumerable
-      attr_reader :env
 
-      def initialize(env = {}) # :nodoc:
-        @env = env
+      def self.from_hash(hash)
+        new ActionDispatch::Request.new hash
+      end
+
+      def initialize(request) # :nodoc:
+        @req = request
       end
 
       # Returns the value for the given key mapped to @env.
       def [](key)
-        @env[env_name(key)]
+        @req.get_header env_name(key)
       end
 
       # Sets the given value for the key mapped to @env.
       def []=(key, value)
-        @env[env_name(key)] = value
+        @req.set_header env_name(key), value
+      end
+
+      # Add a value to a multivalued header like Vary or Accept-Encoding.
+      def add(key, value)
+        @req.add_header env_name(key), value
       end
 
       def key?(key)
-        @env.key? env_name(key)
+        @req.has_header? env_name(key)
       end
       alias :include? :key?
 
+      DEFAULT = Object.new # :nodoc:
+
       # Returns the value for the given key mapped to @env.
       #
       # If the key is not found and an optional code block is not provided,
@@ -58,18 +82,22 @@ module ActionDispatch
       #
       # If the code block is provided, then it will be run and
       # its result returned.
-      def fetch(key, *args, &block)
-        @env.fetch env_name(key), *args, &block
+      def fetch(key, default = DEFAULT)
+        @req.fetch_header(env_name(key)) do
+          return default unless default == DEFAULT
+          return yield if block_given?
+          raise KeyError, key
+        end
       end
 
       def each(&block)
-        @env.each(&block)
+        @req.each_header(&block)
       end
 
       # Returns a new Http::Headers instance containing the contents of
       # <tt>headers_or_env</tt> and the original instance.
       def merge(headers_or_env)
-        headers = Http::Headers.new(env.dup)
+        headers = @req.dup.headers
         headers.merge!(headers_or_env)
         headers
       end
@@ -79,21 +107,24 @@ module ActionDispatch
       # <tt>headers_or_env</tt>.
       def merge!(headers_or_env)
         headers_or_env.each do |key, value|
-          self[env_name(key)] = value
+          @req.set_header env_name(key), value
         end
       end
 
+      def env; @req.env.dup; end
+
       private
-      # Converts a HTTP header name to an environment variable name if it is
-      # not contained within the headers hash.
-      def env_name(key)
-        key = key.to_s
-        if key =~ HTTP_HEADER
-          key = key.upcase.tr('-', '_')
-          key = "HTTP_" + key unless CGI_VARIABLES.include?(key)
+
+        # Converts an HTTP header name to an environment variable name if it is
+        # not contained within the headers hash.
+        def env_name(key)
+          key = key.to_s
+          if key =~ HTTP_HEADER
+            key = key.upcase.tr("-", "_")
+            key = "HTTP_" + key unless CGI_VARIABLES.include?(key)
+          end
+          key
         end
-        key
-      end
     end
   end
 end