diff --git a/lib/reline.rb b/lib/reline.rb
index b233a85838..d079e13c9a 100644
--- a/lib/reline.rb
+++ b/lib/reline.rb
@@ -2,6 +2,7 @@
 require 'reline/version'
 require 'reline/config'
 require 'reline/key_actor'
+require 'reline/key_stroke'
 require 'reline/line_editor'
 
 module Reline
@@ -85,11 +86,24 @@ def self.readline(prompt = '', add_hist = false)
     @line_editor.completion_proc = @completion_proc
     @line_editor.retrieve_completion_block = method(:retrieve_completion_block)
     @line_editor.rerender
+    config = {
+      key_mapping: {
+        # TODO
+        # "a" => "bb",
+        # "z" => "aa",
+        # "y" => "ak",
+      }
+    }
+    key_stroke = Reline::KeyStroke.new(config)
     begin
       while c = getc
-        @line_editor.input_key(c)
-        @line_editor.rerender
-        break if @line_editor.finished?
+        key_stroke.input_to!(c)&.then { |inputs|
+          inputs.each { |c|
+            @line_editor.input_key(c)
+            @line_editor.rerender
+            break if @line_editor.finished?
+          }
+        }
       end
       move_cursor_column(0)
       if add_hist and @line_editor.line and @line_editor.line.chomp.size > 0
diff --git a/lib/reline/key_stroke.rb b/lib/reline/key_stroke.rb
new file mode 100644
index 0000000000..2fec45b667
--- /dev/null
+++ b/lib/reline/key_stroke.rb
@@ -0,0 +1,70 @@
+class Reline::KeyStroke
+  using Module.new {
+    refine Array do
+      def start_with?(other)
+        other.size <= size && other == self.take(other.size)
+      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
diff --git a/test/key_stroke_test.rb b/test/key_stroke_test.rb
new file mode 100644
index 0000000000..65d24cadb1
--- /dev/null
+++ b/test/key_stroke_test.rb
@@ -0,0 +1,51 @@
+require 'helper'
+
+class Reline::KeyStroke::Test < Reline::TestCase
+  using Module.new {
+    refine Array do
+      def as_s
+        map(&:chr).join
+      end
+    end
+  }
+
+  def test_input_to!
+    config = {
+      key_mapping: {
+        "a" => "xx",
+        "ab" => "y",
+        "abc" => "z",
+        "x" => "rr"
+      }
+    }
+    stroke = Reline::KeyStroke.new(config)
+    result = ("abzwabk".bytes).map { |char|
+      stroke.input_to!(char)&.then { |result|
+        "#{result.as_s}"
+      }
+    }
+    assert_equal(result, [nil, nil, "yz", "w", nil, nil, "yk"])
+  end
+
+  def test_input_to
+    config = {
+      key_mapping: {
+        "a" => "xx",
+        "ab" => "y",
+        "abc" => "z",
+        "x" => "rr"
+      }
+    }
+    stroke = Reline::KeyStroke.new(config)
+    assert_equal(stroke.input_to("a".bytes)&.as_s, nil)
+    assert_equal(stroke.input_to("ab".bytes)&.as_s, nil)
+    assert_equal(stroke.input_to("abc".bytes)&.as_s, "z")
+    assert_equal(stroke.input_to("abz".bytes)&.as_s, "yz")
+    assert_equal(stroke.input_to("abx".bytes)&.as_s, "yrr")
+    assert_equal(stroke.input_to("ac".bytes)&.as_s, "rrrrc")
+    assert_equal(stroke.input_to("aa".bytes)&.as_s, "rrrrrrrr")
+    assert_equal(stroke.input_to("x".bytes)&.as_s, "rr")
+    assert_equal(stroke.input_to("m".bytes)&.as_s, "m")
+    assert_equal(stroke.input_to("abzwabk".bytes)&.as_s, "yzwabk")
+  end
+end