Implement the undo command (#701)

* Refactor send

* Implement the undo command

* Fix @past_lines initialization

* Improve assertion

* Hide to save buffer in insert_pasted_text

* Replace @using_delete_command with @undoing

* Refactor `@past_lines`

lib/reline/key_actor/emacs.rb

@@ -63,7 +63,7 @@ class Reline::KeyActor::Emacs < Reline::KeyActor::Base
     #  30 ^^
     :ed_unassigned,
     #  31 ^_
-    :ed_unassigned,
+    :undo,
     #  32 SPACE
     :ed_insert,
     #  33 !

lib/reline/line_editor.rb

@@ -4,7 +4,6 @@
 require 'tempfile'
 
 class Reline::LineEditor
-  # TODO: undo
   # TODO: Use "private alias_method" idiom after drop Ruby 2.5.
   attr_reader :byte_pointer
   attr_accessor :confirm_multiline_termination_proc
@@ -251,6 +250,8 @@ def reset_variables(prompt = '', encoding:)
     @resized = false
     @cache = {}
     @rendered_screen = RenderedScreen.new(base_y: 0, lines: [], cursor_y: 0)
+    @past_lines = []
+    @undoing = false
     reset_line
   end
 
@@ -948,7 +949,8 @@ def dialog_proc_scope_completion_journey_data
         unless @waiting_proc
           byte_pointer_diff = @byte_pointer - old_byte_pointer
           @byte_pointer = old_byte_pointer
-          send(@vi_waiting_operator, byte_pointer_diff)
+          method_obj = method(@vi_waiting_operator)
+          wrap_method_call(@vi_waiting_operator, method_obj, byte_pointer_diff)
           cleanup_waiting
         end
       else
@@ -1009,7 +1011,8 @@ def wrap_method_call(method_symbol, method_obj, key, with_operator = false)
       if @vi_waiting_operator
         byte_pointer_diff = @byte_pointer - old_byte_pointer
         @byte_pointer = old_byte_pointer
-        send(@vi_waiting_operator, byte_pointer_diff)
+        method_obj = method(@vi_waiting_operator)
+        wrap_method_call(@vi_waiting_operator, method_obj, byte_pointer_diff)
         cleanup_waiting
       end
       @kill_ring.process
@@ -1106,6 +1109,7 @@ def update(key)
   end
 
   def input_key(key)
+    save_old_buffer
     @config.reset_oneshot_key_bindings
     @dialogs.each do |dialog|
       if key.char.instance_of?(Symbol) and key.char == dialog.name
@@ -1120,7 +1124,6 @@ def input_key(key)
       finish
       return
     end
-    old_lines = @buffer_of_lines.dup
     @first_char = false
     @completion_occurs = false
 
@@ -1134,12 +1137,15 @@ def input_key(key)
       @completion_journey_state = nil
     end
 
+    push_past_lines unless @undoing
+    @undoing = false
+
     if @in_pasting
       clear_dialogs
       return
     end
 
-    modified = old_lines != @buffer_of_lines
+    modified = @old_buffer_of_lines != @buffer_of_lines
     if !@completion_occurs && modified && !@config.disable_completion && @config.autocompletion
       # Auto complete starts only when edited
       process_insert(force: true)
@@ -1148,6 +1154,26 @@ def input_key(key)
     modified
   end
 
+  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])
+    end
+    trim_past_lines
+  end
+
+  MAX_PAST_LINES = 100
+  def trim_past_lines
+    if @past_lines.size > MAX_PAST_LINES
+      @past_lines.shift
+    end
+  end
+
   def scroll_into_view
     _wrapped_cursor_x, wrapped_cursor_y = wrapped_cursor_position
     if wrapped_cursor_y < screen_scroll_top
@@ -1224,6 +1250,18 @@ def set_current_line(line, byte_pointer = nil)
     process_auto_indent
   end
 
+  def set_current_lines(lines, byte_pointer = nil, line_index = 0)
+    cursor = current_byte_pointer_cursor
+    @buffer_of_lines = lines
+    @line_index = line_index
+    if byte_pointer
+      @byte_pointer = byte_pointer
+    else
+      calculate_nearest_cursor(cursor)
+    end
+    process_auto_indent
+  end
+
   def retrieve_completion_block(set_completion_quote_character = false)
     if Reline.completer_word_break_characters.empty?
       word_break_regexp = nil
@@ -1306,13 +1344,15 @@ def confirm_multiline_termination
   end
 
   def insert_pasted_text(text)
+    save_old_buffer
     pre = @buffer_of_lines[@line_index].byteslice(0, @byte_pointer)
     post = @buffer_of_lines[@line_index].byteslice(@byte_pointer..)
     lines = (pre + text.gsub(/\r\n?/, "\n") + post).split("\n", -1)
     lines << '' if lines.empty?
     @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
   end
 
   def insert_text(text)
@@ -2487,4 +2527,15 @@ def finish
   private def vi_editing_mode(key)
     @config.editing_mode = :vi_insert
   end
+
+  private def undo(_key)
+    return if @past_lines.empty?
+
+    @undoing = true
+
+    target_lines, target_cursor_x, target_cursor_y = @past_lines.last
+    set_current_lines(target_lines, target_cursor_x, target_cursor_y)
+
+    @past_lines.pop
+  end
 end

test/reline/test_key_actor_emacs.rb

@@ -1437,4 +1437,72 @@ def test_vi_editing_mode
     @line_editor.__send__(:vi_editing_mode, nil)
     assert(@config.editing_mode_is?(:vi_insert))
   end
+
+  def test_undo
+    input_keys("\C-_", false)
+    assert_line_around_cursor('', '')
+    input_keys("aあb\C-h\C-h\C-h", false)
+    assert_line_around_cursor('', '')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('a', '')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('aあ', '')
+    input_keys("\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("\C-_", false)
+    assert_line_around_cursor('', '')
+  end
+
+  def test_undo_with_cursor_position
+    input_keys("abc\C-b\C-h", false)
+    assert_line_around_cursor('a', 'c')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('ab', 'c')
+    input_keys("あいう\C-b\C-h", false)
+    assert_line_around_cursor('abあ', 'うc')
+    input_keys("\C-_", false)
+    assert_line_around_cursor('abあい', 'うc')
+  end
+
+  def test_undo_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-p\C-h\C-h", false)
+    assert_whole_lines(["1", "3"])
+    assert_line_index(0)
+    assert_line_around_cursor('1', '')
+    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("\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', '')
+  end
+
+  def test_undo_with_many_times
+    str = "a" + "b" * 100
+    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
 end

test/reline/yamatanooroti/test_rendering.rb

@@ -556,6 +556,19 @@ def test_bracketed_paste
       EOC
     end
 
+    def test_bracketed_paste_with_undo
+      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-_")
+      close
+      assert_screen(<<~EOC)
+        Multiline REPL.
+        prompt> abc
+      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")