Add Reline as a fallback library for Readline

* lib/reine.rb, lib/reline/*: Reline is a readline stdlib compatible
  library.
* lib/readline.rb: Readline uses a fallback to Reline when ext/readline
  doesn't exist.
* tool/sync_default_gems.rb: add ruby/reline as a default gem.
* appveyor.yml: add "set RELINE_TEST_ENCODING=Windows-31J" for test suit
  of Reline, and add "--exclude readline" to "nmake test-all" on Visual
  Studio builds because of strange behavior.
* spec/ruby/library/readline/spec_helper.rb: skip Reline as with
  RbReadline.

1 files changed, 74 insertions, 0 deletions

diff --git a/lib/reline/key_stroke.rb b/lib/reline/key_stroke.rb
new file mode 100644
index 0000000000..ac0a820759
--- /dev/null
+++ b/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