feat: implemented 'X', tested

X and x are the same in visual mode I think

FEATURES.md

@@ -104,7 +104,7 @@
 ### Delete Actions
 - [x] `x` - Delete character under cursor
 - [x] `D` - Delete to end of line
-- [ ] `X` - Delete character before cursor
+- [x] `X` - Delete character before cursor
 - [ ] `J` - Join lines
 - [ ] `gJ` - Join lines without space
 

internal/action/delete.go

@@ -27,6 +27,35 @@ func (a DeleteChar) WithCount(n int) Action {
 	return DeleteChar{Count: n}
 }
 
+// DeletePrevChar implements Action (x)
+type DeletePrevChar struct {
+	Count int
+}
+
+// DeletePrevChar.Execute: Deletes Count characters before the cursor position (x key).
+func (a DeletePrevChar) Execute(m Model) tea.Cmd {
+	win := m.ActiveWindow()
+	buf := m.ActiveBuffer()
+
+	pos := win.Cursor.Col
+	line := buf.Lines[win.Cursor.Line]
+	for i := 0; i < a.Count && pos <= len(line); i++ {
+		if pos > 0 {
+			line = line[:pos-1] + line[pos:]
+			buf.SetLine(win.Cursor.Line, line)
+			pos--
+			win.SetCursorCol(pos)
+		}
+	}
+
+	return nil
+}
+
+// DeletePrevChar.WithCount: Returns a new DeletePrevChar with the given count.
+func (a DeletePrevChar) WithCount(n int) Action {
+	return DeletePrevChar{Count: n}
+}
+
 // DeleteToEndOfLine implements Action (D) - deletes from cursor to end of line
 // and optionally Count-1 additional lines below.
 type DeleteToEndOfLine struct {

internal/editor/integration_delete_test.go

@@ -194,6 +194,274 @@ func TestDeleteCharEdgeCases(t *testing.T) {
 	})
 }
 
+func TestDeleteCharBackward(t *testing.T) {
+	t.Run("test 'X' deletes character before cursor", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 1, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "ello" {
+			t.Errorf("lines[0] = %q, want 'ello'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' in middle of line", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 3, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "helo" {
+			t.Errorf("lines[0] = %q, want 'helo'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' at end of line", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 4, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "helo" {
+			t.Errorf("lines[0] = %q, want 'helo'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'XX' deletes two characters backward", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 2, Line: 0})
+		sendKeys(tm, "X", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "llo" {
+			t.Errorf("lines[0] = %q, want 'llo'", m.ActiveBuffer().Lines[0])
+		}
+	})
+}
+
+func TestDeleteCharBackwardWithCount(t *testing.T) {
+	t.Run("test '3X' deletes three characters backward", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 3, Line: 0})
+		sendKeys(tm, "3", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "lo" {
+			t.Errorf("lines[0] = %q, want 'lo'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test '10X' with overflow", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 4, Line: 0})
+		sendKeys(tm, "1", "0", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "o" {
+			t.Errorf("lines[0] = %q, want 'o'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test '2X' from middle", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 3, Line: 0})
+		sendKeys(tm, "2", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "hlo" {
+			t.Errorf("lines[0] = %q, want 'hlo'", m.ActiveBuffer().Lines[0])
+		}
+	})
+}
+
+func TestDeleteCharBackwardEdgeCases(t *testing.T) {
+	t.Run("test 'X' at start of line does nothing", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLines(t, lines)
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "hello" {
+			t.Errorf("Line(0) = %q, want 'hello'", m.ActiveBuffer().Lines[0])
+		}
+		if m.ActiveWindow().Cursor.Col != 0 {
+			t.Errorf("CursorX() = %d, want 0", m.ActiveWindow().Cursor.Col)
+		}
+	})
+
+	t.Run("test 'X' on empty line does nothing", func(t *testing.T) {
+		lines := []string{""}
+		tm := newTestModelWithLines(t, lines)
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "" {
+			t.Errorf("Line(0) = %q, want ''", m.ActiveBuffer().Lines[0])
+		}
+		if m.ActiveWindow().Cursor.Col != 0 {
+			t.Errorf("CursorX() = %d, want 0", m.ActiveWindow().Cursor.Col)
+		}
+	})
+
+	t.Run("test 'X' on single character line from end", func(t *testing.T) {
+		lines := []string{"a"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 0, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "a" {
+			t.Errorf("Line(0) = %q, want 'a'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' at second char deletes first", func(t *testing.T) {
+		lines := []string{"ab"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 1, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "b" {
+			t.Errorf("Line(0) = %q, want 'b'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' with whitespace", func(t *testing.T) {
+		lines := []string{"a b c"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 2, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "ab c" {
+			t.Errorf("Line(0) = %q, want 'ab c'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' preserves other lines", func(t *testing.T) {
+		lines := []string{"hello", "world"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 1, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().LineCount() != 2 {
+			t.Errorf("LineCount() = %d, want 2", m.ActiveBuffer().LineCount())
+		}
+		if m.ActiveBuffer().Lines[1] != "world" {
+			t.Errorf("Line(1) = %q, want 'world'", m.ActiveBuffer().Lines[1])
+		}
+	})
+
+	t.Run("test 'X' multiple times deletes multiple chars backward", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 3, Line: 0})
+		sendKeys(tm, "X", "X", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "lo" {
+			t.Errorf("Line(0) = %q, want 'lo'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' on line with tabs", func(t *testing.T) {
+		lines := []string{"a\tb"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 2, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "ab" {
+			t.Errorf("Line(0) = %q, want 'ab'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test '5X' with only 3 chars available before cursor", func(t *testing.T) {
+		lines := []string{"abc"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 2, Line: 0})
+		sendKeys(tm, "5", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "c" {
+			t.Errorf("Line(0) = %q, want 'c'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' in middle preserves surrounding chars", func(t *testing.T) {
+		lines := []string{"abcde"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 3, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "abde" {
+			t.Errorf("Line(0) = %q, want 'abde'", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' cursor position after delete", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 3, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		// Cursor should move back one position after deleting char before it
+		if m.ActiveWindow().Cursor.Col != 2 {
+			t.Errorf("CursorX() = %d, want 2", m.ActiveWindow().Cursor.Col)
+		}
+	})
+
+	t.Run("test '3X' cursor position after delete", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 4, Line: 0})
+		sendKeys(tm, "3", "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "ho" {
+			t.Errorf("Line(0) = %q, want 'ho'", m.ActiveBuffer().Lines[0])
+		}
+		// Cursor should be at position 1 after deleting 3 chars backward from position 4
+		if m.ActiveWindow().Cursor.Col != 1 {
+			t.Errorf("CursorX() = %d, want 1", m.ActiveWindow().Cursor.Col)
+		}
+	})
+
+	t.Run("test 'X' at start of second line does nothing", func(t *testing.T) {
+		lines := []string{"hello", "world"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 0, Line: 1})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "hello" {
+			t.Errorf("Line(0) = %q, want 'hello'", m.ActiveBuffer().Lines[0])
+		}
+		if m.ActiveBuffer().Lines[1] != "world" {
+			t.Errorf("Line(1) = %q, want 'world'", m.ActiveBuffer().Lines[1])
+		}
+	})
+
+	t.Run("test 'X' on whitespace-only line", func(t *testing.T) {
+		lines := []string{"    "}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 2, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "   " {
+			t.Errorf("Line(0) = %q, want '   '", m.ActiveBuffer().Lines[0])
+		}
+	})
+
+	t.Run("test 'X' from end of line deletes last char", func(t *testing.T) {
+		lines := []string{"hello"}
+		tm := newTestModelWithLinesAndCursorPos(t, lines, core.Position{Col: 4, Line: 0})
+		sendKeys(tm, "X")
+
+		m := getFinalModel(t, tm)
+		if m.ActiveBuffer().Lines[0] != "helo" {
+			t.Errorf("Line(0) = %q, want 'helo'", m.ActiveBuffer().Lines[0])
+		}
+		if m.ActiveWindow().Cursor.Col != 3 {
+			t.Errorf("CursorX() = %d, want 3", m.ActiveWindow().Cursor.Col)
+		}
+	})
+}
+
 func TestDeleteToEndOfLine(t *testing.T) {
 	t.Run("test 'D' deletes to end of line", func(t *testing.T) {
 		lines := []string{"hello world"}

internal/input/keymap.go

@@ -55,6 +55,7 @@ func NewNormalKeymap() *Keymap {
 			"o":      action.OpenLineBelow{},
 			"O":      action.OpenLineAbove{},
 			"x":      action.DeleteChar{Count: 1},
+			"X":      action.DeletePrevChar{Count: 1},
 			":":      action.EnterComandMode{},
 			"v":      action.EnterVisualMode{},
 			"V":      action.EnterVisualLineMode{},