Change project layout and use go.mod

internal/buffer/stack.go

@@ -0,0 +1,43 @@
+package buffer
+
+// TEStack is a simple implementation of a LIFO stack for text events
+type TEStack struct {
+	Top  *Element
+	Size int
+}
+
+// An Element which is stored in the Stack
+type Element struct {
+	Value *TextEvent
+	Next  *Element
+}
+
+// Len returns the stack's length
+func (s *TEStack) Len() int {
+	return s.Size
+}
+
+// Push a new element onto the stack
+func (s *TEStack) Push(value *TextEvent) {
+	s.Top = &Element{value, s.Top}
+	s.Size++
+}
+
+// Pop removes the top element from the stack and returns its value
+// If the stack is empty, return nil
+func (s *TEStack) Pop() (value *TextEvent) {
+	if s.Size > 0 {
+		value, s.Top = s.Top.Value, s.Top.Next
+		s.Size--
+		return
+	}
+	return nil
+}
+
+// Peek returns the top element of the stack without removing it
+func (s *TEStack) Peek() *TextEvent {
+	if s.Size > 0 {
+		return s.Top.Value
+	}
+	return nil
+}