Allow inserting new lines

internal/editor/document/document.go

@@ -87,6 +87,41 @@ func (d *Document) AppendRow(s string) {
 	d.dirty = true
 }
 
+func (d *Document) InsertRow(at int, s string) {
+	if at < 0 || at > d.RowCount() {
+		return
+	}
+
+	var newRows []*Row
+
+	// Split the array of rows at the specified index
+	start := d.rows[0:at]
+	end := d.rows[at : d.RowCount()]
+
+	// Splice it back together
+	newRows = append(newRows, start...)
+	newRows = append(newRows, newRow(s))
+	newRows = append(newRows, end...)
+
+	d.rows = newRows
+	d.dirty = true
+}
+
+func (d *Document) InsertNewline(at *gilo.Point) {
+	if at.X == 0 {
+		d.InsertRow(at.Y, "")
+	} else {
+		row := d.rows[at.Y]
+
+		// Insert the characters right of the cursor to the next line
+		d.InsertRow(at.Y + 1, string(row.chars[at.X:row.Size()]))
+
+		// Remove the characters copied to the next line
+		row.chars = row.chars[0:at.X]
+		row.update()
+	}
+}
+
 func (d *Document) MergeRows(to int, from int) {
 	d.rows[to].appendString(d.rows[from].toString())
 	d.delRow(from)

internal/editor/input.go

@@ -45,6 +45,9 @@ func (e *editor) processKeypressChar(ch rune) bool {
 		e.Save()
 
 	case key.Enter:
+		e.document.InsertNewline(e.cursor)
+		e.cursor.Y += 1
+		e.cursor.X = 0
 
 	case key.Backspace, key.Ctrl('h'):
 		e.delChar()