Implement the redo command (#707)

* Implement the redo command

* Commented out a test that does not pass

* Changed key assignment for redo from "\C-[" to "\C-g"

* Changed redo key assignment from `\C-g` to `\M-\C-_`

* Revert the first implemantation

* Implemented redo by sharing `@past_lines` between undo and redo

* Fixed the index of past_lines that is updated when the cursor is moved

* Fixed deletion of the redo history in regular input

* Renamed variables: past_lines -> input_lines

* Rename @position to @input_lines_position

* Deleted unused variables: `@old_byte_pointer` and `@old_line_index`

lib/reline/key_actor/emacs.rb

@@ -319,7 +319,7 @@ class Reline::KeyActor::Emacs < Reline::KeyActor::Base
     # 158 M-^^
     :ed_unassigned,
     # 159 M-^_
-    :ed_unassigned,
+    :redo,
     # 160 M-SPACE
     :em_set_mark,
     # 161 M-!

lib/reline/line_editor.rb

@@ -250,7 +250,8 @@ def reset_variables(prompt = '', encoding:)
     @resized = false
     @cache = {}
     @rendered_screen = RenderedScreen.new(base_y: 0, lines: [], cursor_y: 0)
-    @past_lines = []
+    @input_lines = [[[""], 0, 0]]
+    @input_lines_position = 0
     @undoing = false
     reset_line
   end
@@ -1137,7 +1138,7 @@ def input_key(key)
       @completion_journey_state = nil
     end
 
-    push_past_lines unless @undoing
+    push_input_lines unless @undoing
     @undoing = false
 
     if @in_pasting
@@ -1156,21 +1157,24 @@ def input_key(key)
 
   def save_old_buffer
     @old_buffer_of_lines = @buffer_of_lines.dup
-    @old_byte_pointer = @byte_pointer.dup
-    @old_line_index = @line_index.dup
   end
 
-  def push_past_lines
-    if @old_buffer_of_lines != @buffer_of_lines
-      @past_lines.push([@old_buffer_of_lines, @old_byte_pointer, @old_line_index])
+  def push_input_lines
+    if @old_buffer_of_lines == @buffer_of_lines
+      @input_lines[@input_lines_position] = [@buffer_of_lines.dup, @byte_pointer, @line_index]
+    else
+      @input_lines = @input_lines[0..@input_lines_position]
+      @input_lines_position += 1
+      @input_lines.push([@buffer_of_lines.dup, @byte_pointer, @line_index])
     end
-    trim_past_lines
+    trim_input_lines
   end
 
-  MAX_PAST_LINES = 100
-  def trim_past_lines
-    if @past_lines.size > MAX_PAST_LINES
-      @past_lines.shift
+  MAX_INPUT_LINES = 100
+  def trim_input_lines
+    if @input_lines.size > MAX_INPUT_LINES
+      @input_lines.shift
+      @input_lines_position -= 1
     end
   end
 
@@ -1352,7 +1356,7 @@ def insert_pasted_text(text)
     @buffer_of_lines[@line_index, 1] = lines
     @line_index += lines.size - 1
     @byte_pointer = @buffer_of_lines[@line_index].bytesize - post.bytesize
-    push_past_lines
+    push_input_lines
   end
 
   def insert_text(text)
@@ -2529,13 +2533,22 @@ def finish
   end
 
   private def undo(_key)
-    return if @past_lines.empty?
+    @undoing = true
+
+    return if @input_lines_position <= 0
+
+    @input_lines_position -= 1
+    target_lines, target_cursor_x, target_cursor_y = @input_lines[@input_lines_position]
+    set_current_lines(target_lines.dup, target_cursor_x, target_cursor_y)
+  end
 
+  private def redo(_key)
     @undoing = true
 
-    target_lines, target_cursor_x, target_cursor_y = @past_lines.last
-    set_current_lines(target_lines, target_cursor_x, target_cursor_y)
+    return if @input_lines_position >= @input_lines.size - 1
 
-    @past_lines.pop
+    @input_lines_position += 1
+    target_lines, target_cursor_x, target_cursor_y = @input_lines[@input_lines_position]
+    set_current_lines(target_lines.dup, target_cursor_x, target_cursor_y)
   end
 end

test/reline/test_key_actor_emacs.rb

@@ -1498,11 +1498,115 @@ def test_undo_with_multiline
   end
 
   def test_undo_with_many_times
-    str = "a" + "b" * 100
+    str = "a" + "b" * 99
     input_keys(str, false)
     100.times { input_keys("\C-_", false) }
     assert_line_around_cursor('a', '')
     input_keys("\C-_", false)
     assert_line_around_cursor('a', '')
   end
+
+  def test_redo
+    input_keys("aあb", false)
+    assert_line_around_cursor('aあb', '')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor('aあb', '')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('aあ', '')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('a', '')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor('aあ', '')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor('aあb', '')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('aあ', '')
+    input_keys("c", false)
+    assert_line_around_cursor('aあc', '')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor('aあc', '')
+  end
+
+  def test_redo_with_cursor_position
+    input_keys("abc\C-b\C-h", false)
+    assert_line_around_cursor('a', 'c')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor('a', 'c')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('ab', 'c')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor('a', 'c')
+  end
+
+  def test_redo_with_multiline
+    @line_editor.multiline_on
+    @line_editor.confirm_multiline_termination_proc = proc {}
+    input_keys("1\n2\n3", false)
+    assert_whole_lines(["1", "2", "3"])
+    assert_line_index(2)
+    assert_line_around_cursor('3', '')
+
+    input_keys("\C-_", false)
+    assert_whole_lines(["1", "2", ""])
+    assert_line_index(2)
+    assert_line_around_cursor('', '')
+
+    input_keys("\C-_", false)
+    assert_whole_lines(["1", "2"])
+    assert_line_index(1)
+    assert_line_around_cursor('2', '')
+
+    input_keys("\M-\C-_", false)
+    assert_whole_lines(["1", "2", ""])
+    assert_line_index(2)
+    assert_line_around_cursor('', '')
+
+    input_keys("\M-\C-_", false)
+    assert_whole_lines(["1", "2", "3"])
+    assert_line_index(2)
+    assert_line_around_cursor('3', '')
+
+    input_keys("\C-p\C-h\C-h", false)
+    assert_whole_lines(["1", "3"])
+    assert_line_index(0)
+    assert_line_around_cursor('1', '')
+
+    input_keys("\C-n", false)
+    assert_whole_lines(["1", "3"])
+    assert_line_index(1)
+    assert_line_around_cursor('3', '')
+
+    input_keys("\C-_", false)
+    assert_whole_lines(["1", "", "3"])
+    assert_line_index(1)
+    assert_line_around_cursor('', '')
+
+    input_keys("\C-_", false)
+    assert_whole_lines(["1", "2", "3"])
+    assert_line_index(1)
+    assert_line_around_cursor('2', '')
+
+    input_keys("\M-\C-_", false)
+    assert_whole_lines(["1", "", "3"])
+    assert_line_index(1)
+    assert_line_around_cursor('', '')
+
+    input_keys("\M-\C-_", false)
+    assert_whole_lines(["1", "3"])
+    assert_line_index(1)
+    assert_line_around_cursor('3', '')
+  end
+
+  def test_redo_with_many_times
+    str = "a" + "b" * 98 + "c"
+    input_keys(str, false)
+    100.times { input_keys("\C-_", false) }
+    assert_line_around_cursor('a', '')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('a', '')
+    100.times { input_keys("\M-\C-_", false) }
+    assert_line_around_cursor(str, '')
+    input_keys("\M-\C-_", false)
+    assert_line_around_cursor(str, '')
+  end
 end

test/reline/yamatanooroti/test_rendering.rb

@@ -569,6 +569,22 @@ def test_bracketed_paste_with_undo
       EOC
     end
 
+    def test_bracketed_paste_with_redo
+      omit if Reline.core.io_gate.win?
+      start_terminal(5, 30, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl}, startup_message: 'Multiline REPL.')
+      write("abc")
+      write("\e[200~def hoge\r\t3\rend\e[201~")
+      write("\C-_")
+      write("\M-\C-_")
+      close
+      assert_screen(<<~EOC)
+        Multiline REPL.
+        prompt> abcdef hoge
+        prompt>   3
+        prompt> end
+      EOC
+    end
+
     def test_backspace_until_returns_to_initial
       start_terminal(5, 30, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl}, startup_message: 'Multiline REPL.')
       write("ABC")