Textmanip now operates on a dot instead of a cursor

textmanip/textmanip.go

@@ -2,7 +2,40 @@ package textmanip
 
 import "unicode"
 
-func WordToLeft (text []rune, cursor int) (length int) {
+type Dot struct { Start, End int }
+
+func EmptyDot (position int) Dot {
+	return Dot { position, position }
+}
+
+func (dot Dot) Canon () Dot {
+	if dot.Start > dot.End {
+		return Dot { dot.End, dot.Start }
+	} else {
+		return dot
+	}
+}
+
+func (dot Dot) Empty () bool {
+	return dot.Start == dot.End
+}
+
+func (dot Dot) Add (delta int) Dot {
+	return Dot {
+		dot.Start + delta,
+		dot.End   + delta,
+	}
+}
+
+func (dot Dot) Sub (delta int) Dot {
+	return Dot {
+		dot.Start - delta,
+		dot.End   - delta,
+	}
+}
+
+func WordToLeft (text []rune, dot Dot) (length int) {
+	cursor := dot.End
 	if cursor < 1 { return }
 	if cursor > len(text) { cursor = len(text) }
 
@@ -18,7 +51,8 @@ func WordToLeft (text []rune, cursor int) (length int) {
 	return
 }
 
-func WordToRight (text []rune, cursor int) (length int) {
+func WordToRight (text []rune, dot Dot) (length int) {
+	cursor := dot.End
 	if cursor < 0 { return }
 	if cursor > len(text) { cursor = len(text) }
 
@@ -34,66 +68,93 @@ func WordToRight (text []rune, cursor int) (length int) {
 	return
 }
 
-func Backspace (text []rune, cursor int, word bool) (result []rune, moved int) {
-	if cursor < 1         { return text, cursor }
-	if cursor > len(text) { cursor = len(text) }
+func Backspace (text []rune, dot Dot, word bool) (result []rune, moved Dot) {
+	if dot.Empty() {
+		cursor := dot.End
+		if cursor < 1         { return text, dot }
+		if cursor > len(text) { cursor = len(text) }
 
-	moved = 1
-	if word {
-		moved = WordToLeft(text, cursor)
-	}
-	result = append(result, text[:cursor - moved]...)
-	result = append(result, text[cursor:]...)
-	moved = cursor - moved
-	return
-}
-
-func Delete (text []rune, cursor int, word bool) (result []rune, moved int) {
-	if cursor < 0         { return text, cursor }
-	if cursor > len(text) { cursor = len(text) }
-
-	moved = 1
-	if word {
-		moved = WordToRight(text, cursor)
-	}
-	result = append(result, text[:cursor]...)
-	result = append(result, text[cursor + moved:]...)
-	moved = cursor
-	return
-}
-
-func Type (text []rune, cursor int, character rune) (result []rune, moved int) {
-	if cursor < 0         { cursor = 0 }
-	if cursor > len(text) { cursor = len(text) }
-	result = append(result, text[:cursor]...)
-	result = append(result, character)
-	if cursor < len(text) {
+		distance := 1
+		if word {
+			distance = WordToLeft(text, dot)
+		}
+		result = append(result, text[:cursor - distance]...)
 		result = append(result, text[cursor:]...)
+		moved = EmptyDot(cursor - distance)
+	} else {
+		return Delete(text, dot, word)
 	}
-	moved = cursor + 1
+
 	return
 }
 
-func MoveLeft (text []rune, cursor int, word bool) (moved int) {
-	if cursor < 1         { return cursor }
+func Delete (text []rune, dot Dot, word bool) (result []rune, moved Dot) {
+	if dot.Empty() {
+		cursor := dot.End
+		if cursor < 0         { return text, dot }
+		if cursor > len(text) { cursor = len(text) }
+
+		distance := 1
+		if word {
+			distance = WordToRight(text, dot)
+		}
+		result = append(result, text[:cursor]...)
+		result = append(result, text[cursor + distance:]...)
+		moved = dot
+		return	
+	} else {
+		result = append(result, text[:dot.Start]...)
+		result = append(result, text[dot.End:]...)
+		moved = EmptyDot(dot.Start)
+		return
+	}
+}
+
+func Type (text []rune, dot Dot, character rune) (result []rune, moved Dot) {
+	if dot.Empty() {
+		cursor := dot.End
+		if cursor < 0         { cursor = 0 }
+		if cursor > len(text) { cursor = len(text) }
+		result = append(result, text[:cursor]...)
+		result = append(result, character)
+		if cursor < len(text) {
+			result = append(result, text[cursor:]...)
+		}
+		moved = EmptyDot(cursor + 1)
+		return
+	} else {
+		result = append(result, text[:dot.Start]...)
+		result = append(result, character)
+		result = append(result, text[dot.End:]...)
+		moved = EmptyDot(dot.Start)
+		return
+	}
+}
+
+func MoveLeft (text []rune, dot Dot, word bool) (moved Dot) {
+	cursor := dot.Start
+
+	if cursor < 1         { return EmptyDot(cursor) }
 	if cursor > len(text) { cursor = len(text) }
 
-	moved = 1
+	distance := 1
 	if word {
-		moved = WordToLeft(text, cursor)
+		distance = WordToLeft(text, dot)
 	}
-	moved = cursor - moved
+	moved = EmptyDot(cursor - distance)
 	return
 }
 
-func MoveRight (text []rune, cursor int, word bool) (moved int) {
-	if cursor < 0         { return cursor }
+func MoveRight (text []rune, dot Dot, word bool) (moved Dot) {
+	cursor := dot.End
+	
+	if cursor < 0         { return EmptyDot(cursor) }
 	if cursor > len(text) { cursor = len(text) }
 
-	moved = 1
+	distance := 1
 	if word {
-		moved = WordToRight(text, cursor)
+		distance = WordToRight(text, dot)
 	}
-	moved = cursor + moved
+	moved = EmptyDot(cursor + distance)
 	return
 }