editor: add ^W delete word binding

It allows to delete the current word (any string of characters until a
space). Also, all spaces at the start are cleared to allow doing
something like:

    Hello world|
    Hello | <- the cursor is at a space
    | <- nothing left

3 files changed, 40 insertions, 0 deletions

diff --git a/app.go b/app.go
index 6809a04..13d77ab 100644
--- a/app.go
+++ b/app.go
@@ -448,6 +448,12 @@ func (app *App) handleKeyEvent(ev *tcell.EventKey) {
 			app.typing()
 			app.updatePrompt()
 		}
+	case tcell.KeyCtrlW:
+		ok := app.win.InputDeleteWord()
+		if ok {
+			app.typing()
+			app.updatePrompt()
+		}
 	case tcell.KeyTab:
 		ok := app.win.InputAutoComplete(1)
 		if ok {
diff --git a/ui/editor.go b/ui/editor.go
index 66774e0..5419eaa 100644
--- a/ui/editor.go
+++ b/ui/editor.go
@@ -116,6 +116,36 @@ func (e *Editor) remRuneAt(idx int) {
 	e.text[e.lineIdx] = e.text[e.lineIdx][:len(e.text[e.lineIdx])-1]
 }
 
+func (e *Editor) RemWord() (ok bool) {
+	ok = 0 < e.cursorIdx
+	if !ok {
+		return
+	}
+
+	line := e.text[e.lineIdx]
+
+	// To allow doing something like this (| is the cursor):
+	// Hello world|
+	// Hello |
+	// |
+	for line[e.cursorIdx - 1] == ' ' {
+		e.remRuneAt(e.cursorIdx - 1)
+		e.Left()
+	}
+
+	for i := e.cursorIdx - 1; i >= 0; i -= 1 {
+		if line[i] == ' ' {
+			break
+		}
+		e.remRuneAt(i)
+		e.Left()
+	}
+
+	e.autoCache = nil
+	return
+}
+
+
 func (e *Editor) Flush() (content string) {
 	content = string(e.text[e.lineIdx])
 	if len(e.text[len(e.text)-1]) == 0 {
diff --git a/ui/ui.go b/ui/ui.go
index e527f8e..50ddab5 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -192,6 +192,10 @@ func (ui *UI) InputDelete() (ok bool) {
 	return ui.e.RemRuneForward()
 }
 
+func (ui *UI) InputDeleteWord() (ok bool) {
+	return ui.e.RemWord()
+}
+
 func (ui *UI) InputAutoComplete(offset int) (ok bool) {
 	return ui.e.AutoComplete(offset)
 }