Add overflow functionality Input component

Fixes #7

components/input.go

@@ -8,17 +8,21 @@ import (
 
 // Input is the definition of an Input component
 type Input struct {
-	Par            *termui.Par
-	Text           []rune
-	CursorPosition int
+	Par                  *termui.Par
+	Text                 []rune
+	CursorPositionScreen int
+	CursorPositionText   int
+	Offset               int
 }
 
 // CreateInput is the constructor of the Input struct
 func CreateInputComponent() *Input {
 	input := &Input{
-		Par:            termui.NewPar(""),
-		Text:           make([]rune, 0),
-		CursorPosition: 0,
+		Par:                  termui.NewPar(""),
+		Text:                 make([]rune, 0),
+		CursorPositionScreen: 0,
+		CursorPositionText:   0,
+		Offset:               0,
 	}
 
 	input.Par.Height = 3
@@ -31,9 +35,9 @@ func (i *Input) Buffer() termui.Buffer {
 	buf := i.Par.Buffer()
 
 	// Set visible cursor
-	char := buf.At(i.Par.InnerX()+i.CursorPosition, i.Par.Block.InnerY())
+	char := buf.At(i.Par.InnerX()+i.CursorPositionScreen, i.Par.Block.InnerY())
 	buf.Set(
-		i.Par.InnerX()+i.CursorPosition,
+		i.Par.InnerX()+i.CursorPositionScreen,
 		i.Par.Block.InnerY(),
 		termui.Cell{
 			Ch: char.Ch,
@@ -70,49 +74,81 @@ func (i *Input) SendMessage(svc *service.SlackService, channel string, message s
 	svc.SendMessage(channel, message)
 }
 
-// Insert will insert a given key at the place of the current CursorPosition
+// Insert will insert a given key at the place of the current CursorPositionText
 func (i *Input) Insert(key rune) {
-	if len(i.Text) < i.Par.InnerBounds().Dx()-1 {
+	// Append key to the left side
+	left := make([]rune, len(i.Text[0:i.CursorPositionText]))
+	copy(left, i.Text[0:i.CursorPositionText])
+	left = append(left, key)
 
-		left := make([]rune, len(i.Text[0:i.CursorPosition]))
-		copy(left, i.Text[0:i.CursorPosition])
-		left = append(left, key)
+	// Combine left and right side
+	i.Text = append(left, i.Text[i.CursorPositionText:]...)
 
-		i.Text = append(left, i.Text[i.CursorPosition:]...)
-
-		i.Par.Text = string(i.Text)
-		i.MoveCursorRight()
-	}
+	// Set visible range of component
+	i.MoveCursorRight()
 }
 
-// Backspace will remove a character in front of the CursorPosition
+// Backspace will remove a character in front of the CursorPositionText
 func (i *Input) Backspace() {
-	if i.CursorPosition > 0 {
-		i.Text = append(i.Text[0:i.CursorPosition-1], i.Text[i.CursorPosition:]...)
-		i.Par.Text = string(i.Text)
+	if i.CursorPositionText > 0 {
+		i.Text = append(i.Text[0:i.CursorPositionText-1], i.Text[i.CursorPositionText:]...)
+		i.Par.Text = string(i.Text[i.Offset:])
 		i.MoveCursorLeft()
 	}
 }
 
-// Delete will remove a character at the CursorPosition
+// Delete will remove a character at the CursorPositionText
 func (i *Input) Delete() {
-	if i.CursorPosition < len(i.Text) {
-		i.Text = append(i.Text[0:i.CursorPosition], i.Text[i.CursorPosition+1:]...)
-		i.Par.Text = string(i.Text)
+	if i.CursorPositionText < len(i.Text) {
+		i.Text = append(i.Text[0:i.CursorPositionText], i.Text[i.CursorPositionText+1:]...)
+		i.Par.Text = string(i.Text[i.Offset:])
 	}
 }
 
-// MoveCursorRight will increase the current CursorPosition with 1
+// MoveCursorRight will increase the current CursorPositionText with 1
 func (i *Input) MoveCursorRight() {
-	if i.CursorPosition < len(i.Text) {
-		i.CursorPosition++
+	if i.CursorPositionText < len(i.Text) {
+		i.CursorPositionText++
+		i.ScrollRight()
+	}
+
+	i.Par.Text = string(i.Text[i.Offset:])
+}
+
+// MoveCursorLeft will decrease the current CursorPositionText with 1
+func (i *Input) MoveCursorLeft() {
+	if i.CursorPositionText > 0 {
+		i.CursorPositionText--
+		i.ScrollLeft()
+	}
+
+	i.Par.Text = string(i.Text[i.Offset:])
+}
+
+func (i *Input) ScrollLeft() {
+	// Is the cursor at the far left of the Input component?
+	if i.CursorPositionScreen == 0 {
+
+		// Decrease offset to show what is on the left side
+		if i.Offset > 0 {
+			i.Offset--
+		}
+	} else {
+		i.CursorPositionScreen--
 	}
 }
 
-// MoveCursorLeft will decrease the current CursorPosition with 1
-func (i *Input) MoveCursorLeft() {
-	if i.CursorPosition > 0 {
-		i.CursorPosition--
+func (i *Input) ScrollRight() {
+	// Is the cursor at the far right of the Input component, cursor
+	// isn't at the end of the text
+	if i.CursorPositionScreen == i.Par.InnerBounds().Dx()-1 {
+
+		// Increase offset to show what is on the right side
+		if i.Offset < len(i.Text) {
+			i.Offset++
+		}
+	} else {
+		i.CursorPositionScreen++
 	}
 }
 
@@ -128,7 +164,8 @@ func (i *Input) IsEmpty() bool {
 func (i *Input) Clear() {
 	i.Text = make([]rune, 0)
 	i.Par.Text = ""
-	i.CursorPosition = 0
+	i.CursorPositionScreen = 0
+	i.CursorPositionText = 0
 }
 
 // GetText returns the text currently in the input