show last element in stack string

scanner/stack/stack.go

@@ -0,0 +1,61 @@
+package stack
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/sentriz/gonic/model"
+)
+
+type item struct {
+	value *model.Album
+	next  *item
+}
+
+type Stack struct {
+	top *item
+	len uint
+}
+
+func (s *Stack) Push(v *model.Album) {
+	s.top = &item{
+		value: v,
+		next:  s.top,
+	}
+	s.len++
+}
+
+func (s *Stack) Pop() *model.Album {
+	if s.len == 0 {
+		return nil
+	}
+	v := s.top.value
+	s.top = s.top.next
+	s.len--
+	return v
+}
+
+func (s *Stack) Peek() *model.Album {
+	if s.len == 0 {
+		return nil
+	}
+	return s.top.value
+}
+
+func (s *Stack) PeekID() int {
+	if s.len == 0 {
+		return 0
+	}
+	return s.top.value.ID
+}
+
+func (s *Stack) String() string {
+	var str strings.Builder
+	str.WriteString("[")
+	for i, f := uint(0), s.top; i < s.len; i++ {
+		str.WriteString(fmt.Sprintf("%d, ", f.value.ID))
+		f = f.next
+	}
+	str.WriteString("]")
+	return str.String()
+}

scanner/stack/stack_test.go

@@ -0,0 +1,40 @@
+package stack
+
+import (
+	"testing"
+
+	"github.com/sentriz/gonic/model"
+)
+
+func egAlbum(id int) *model.Album {
+	return &model.Album{IDBase: model.IDBase{id}}
+}
+
+func TestFolderStack(t *testing.T) {
+	sta := &Stack{}
+	sta.Push(egAlbum(3))
+	sta.Push(egAlbum(4))
+	sta.Push(egAlbum(5))
+	sta.Push(egAlbum(6))
+	expected := "[6, 5, 4, 3, ]"
+	actual := sta.String()
+	if expected != actual {
+		t.Errorf("first stack: expected string %q, got %q",
+			expected, actual)
+	}
+	//
+	sta = &Stack{}
+	sta.Push(egAlbum(27))
+	sta.Push(egAlbum(4))
+	sta.Peek()
+	sta.Push(egAlbum(5))
+	sta.Push(egAlbum(6))
+	sta.Push(egAlbum(7))
+	sta.Pop()
+	expected = "[6, 5, 4, 27, ]"
+	actual = sta.String()
+	if expected != actual {
+		t.Errorf("second stack: expected string %q, got %q",
+			expected, actual)
+	}
+}