Finished basic features of the line editor

lib/line_editor.go

@@ -29,50 +29,40 @@ func (self *LineEditor) Prompt(command rune) {
 
 //-----------------------------------------------------------------------------
 func (self *LineEditor) Handle(ev termbox.Event) bool {
+	defer termbox.Flush()
+
 	switch ev.Key {
 	case termbox.KeyEsc:
 		ClearLine(0, 3)
 		termbox.HideCursor()
-		termbox.Flush()
 		return true
+
 	case termbox.KeyEnter:
 		ClearLine(0, 3)
 		termbox.HideCursor()
-		termbox.Flush()
 		return true
+
         case termbox.KeyBackspace, termbox.KeyBackspace2:
-		if len(self.input) > 0 {
-			self.input = self.input[:len(self.input)-1]
-			self.cursor -= 1
-			DrawLine(len(self.prompt), 3, self.input + " ")
-			termbox.SetCursor(len(self.prompt) + self.cursor, 3)
-			termbox.Flush()
-		}
+		self.delete_previous_character()
+
 	case termbox.KeyCtrlB, termbox.KeyArrowLeft:
-		if self.cursor > 0 {
-			self.cursor -= 1
-			termbox.SetCursor(len(self.prompt) + self.cursor, 3)
-			termbox.Flush()
-		}
+		self.move_left()
+
 	case termbox.KeyCtrlF, termbox.KeyArrowRight:
-		if self.cursor < len(self.input) {
-			self.cursor += 1
-			termbox.SetCursor(len(self.prompt) + self.cursor, 3)
-			termbox.Flush()
-		}
-	case termbox.KeyCtrlA: // Jump to the beginning of line.
-		self.cursor = 0
-		termbox.SetCursor(len(self.prompt) + self.cursor, 3)
-		termbox.Flush()
-	case termbox.KeyCtrlE: // Jump to the end of line.
-		self.cursor = len(self.input)
-		termbox.SetCursor(len(self.prompt) + self.cursor, 3)
-		termbox.Flush()
+		self.move_right()
+
+	case termbox.KeyCtrlA:
+		self.jump_to_beginning()
+
+	case termbox.KeyCtrlE:
+		self.jump_to_end()
+
 	case termbox.KeySpace:
-		self.append_character(' ')
+		self.insert_character(' ')
+
 	default:
 		if ev.Ch != 0 {
-			self.append_character(ev.Ch)
+			self.insert_character(ev.Ch)
 		}
 	}
 	DrawLine(20,20, fmt.Sprintf("cursor: %02d [%s] %08d", self.cursor, self.input, ev.Ch))
@@ -80,11 +70,57 @@ func (self *LineEditor) Handle(ev termbox.Event) bool {
 }
 
 //-----------------------------------------------------------------------------
-func (self *LineEditor) append_character(ch rune) {
+func (self *LineEditor) delete_previous_character() {
+	if self.cursor > 0 {
+		if self.cursor < len(self.input) {
+			// Remove character in the middle of the input string.
+			self.input = self.input[0 : self.cursor-1] + self.input[self.cursor : len(self.input)]
+		} else {
+			// Remove last input character.
+			self.input = self.input[ : len(self.input)-1]
+		}
+		DrawLine(len(self.prompt), 3, self.input + " ") // Erase last character.
+		self.move_left()
+	}
+}
+
+//-----------------------------------------------------------------------------
+func (self *LineEditor) insert_character(ch rune) {
+	if self.cursor < len(self.input) {
+		// Insert the character in the middle of the input string.
+		self.input = self.input[0 : self.cursor] + string(ch) + self.input[self.cursor : len(self.input)]
+	} else {
+		// Append the character to the end of the input string.
 		self.input += string(ch)
-	self.cursor += 1
+	}
 	DrawLine(len(self.prompt), 3, self.input)
+	self.move_right()
+}
+
+//-----------------------------------------------------------------------------
+func (self *LineEditor) move_left() {
+	if self.cursor > 0 {
+		self.cursor -= 1
 		termbox.SetCursor(len(self.prompt) + self.cursor, 3)
-	termbox.Flush()
+	}
 }
 
+//-----------------------------------------------------------------------------
+func (self *LineEditor) move_right() {
+	if self.cursor < len(self.input) {
+		self.cursor += 1
+		termbox.SetCursor(len(self.prompt) + self.cursor, 3)
+	}
+}
+
+//-----------------------------------------------------------------------------
+func (self *LineEditor) jump_to_beginning() {
+	self.cursor = 0
+	termbox.SetCursor(len(self.prompt) + self.cursor, 3)
+}
+
+//-----------------------------------------------------------------------------
+func (self *LineEditor) jump_to_end() {
+	self.cursor = len(self.input)
+	termbox.SetCursor(len(self.prompt) + self.cursor, 3)
+}