IRB is improved with Reline and RDoc

Reline is a readline stdlib compatible library. It also supports
multiline input. IRB is improved with Reline and supports multiline.
Besides, supports showing documents when completed.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67645 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/reline/key_stroke.rb

@@ -0,0 +1,74 @@
+class Reline::KeyStroke
+  using Module.new {
+    refine Array do
+      def start_with?(other)
+        other.size <= size && other == self.take(other.size)
+      end
+
+      def bytes
+        self
+      end
+    end
+  }
+
+  def initialize(config)
+    @config = config
+    @buffer = []
+  end
+
+  def input_to(bytes)
+    case match_status(bytes)
+    when :matching
+      nil
+    when :matched
+      expand(bytes)
+    when :unmatched
+      bytes
+    end
+  end
+
+  def input_to!(bytes)
+    @buffer.concat Array(bytes)
+    input_to(@buffer)&.tap { clear }
+  end
+
+  private
+
+  def match_status(input)
+    key_mapping.keys.select { |lhs|
+      lhs.start_with? input
+    }.tap { |it|
+      return :matched  if it.size == 1 && (it.max_by(&:size)&.size&.== input.size)
+      return :matching if it.size == 1 && (it.max_by(&:size)&.size&.!= input.size)
+      return :matched  if it.max_by(&:size)&.size&.< input.size
+      return :matching if it.size > 1
+    }
+    key_mapping.keys.select { |lhs|
+      input.start_with? lhs
+    }.tap { |it|
+      return it.size > 0 ? :matched : :unmatched
+    }
+  end
+
+  def expand(input)
+    lhs = key_mapping.keys.select { |lhs| input.start_with? lhs }.sort_by(&:size).reverse.first
+    return input unless lhs
+    rhs = key_mapping[lhs]
+
+    case rhs
+    when String
+      rhs_bytes = rhs.bytes
+      expand(expand(rhs_bytes) + expand(input.drop(lhs.size)))
+    when Symbol
+      [rhs] + expand(input.drop(lhs.size))
+    end
+  end
+
+  def key_mapping
+    @config[:key_mapping].transform_keys(&:bytes)
+  end
+
+  def clear
+    @buffer = []
+  end
+end