3 files changed, 196 insertions, 0 deletions
diff --git a/pkg/stack/min.go b/pkg/stack/min.go
new file mode 100644
index 0000000..e97aaed
--- /dev/null
+++ b/pkg/stack/min.go
@@ -0,0 +1,8 @@
+package stack
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
diff --git a/pkg/stack/stack.go b/pkg/stack/stack.go
new file mode 100644
index 0000000..c307133
--- /dev/null
+++ b/pkg/stack/stack.go
@@ -0,0 +1,105 @@
+package stack
+
+type Stack struct {
+	size   int
+	height int
+	data   []int
+	next   *Stack // Pointer to the next element in the stack stack
+}
+
+func NewStack(size int, next *Stack) *Stack {
+	return &Stack{
+		size:   size,
+		height: 0,
+		data:   make([]int, size),
+		next:   next,
+	}
+}
+
+func (s *Stack) Clear() {
+	s.height = 0
+}
+
+func (s *Stack) Duplicate() {
+	if s.height > 0 {
+		s.Push(s.data[s.height-1])
+	} else {
+		s.Push(0)
+		s.Push(0)
+	}
+}
+
+func (s *Stack) Pop() int {
+	if s.height > 0 {
+		s.height--
+		return s.data[s.height]
+	}
+	return 0
+}
+
+func (s *Stack) Push(value int) {
+	if s.height >= s.size {
+		s.size += 32
+		s.data = append(s.data, make([]int, 32)...)
+	}
+	s.data[s.height] = value
+	s.height++
+}
+
+func (s *Stack) Swap() {
+	a := s.Pop()
+	b := s.Pop()
+	s.Push(a)
+	s.Push(b)
+}
+
+func (s Stack) GetHeights() []int {
+	if s.next != nil {
+		return append(s.next.GetHeights(), s.height)
+	} else {
+		return []int{s.height}
+	}
+}
+
+func (toss *Stack) Transfert(soss *Stack, n int) {
+	// Implements a value transfert between two stacks, intended for use with the '{'
+	// (aka begin) and '}' (aka end) stackstack commands
+	toss.height += n
+	if toss.height > toss.size {
+		toss.data = append(toss.data, make([]int, toss.height-toss.size)...)
+		toss.size = toss.height
+	}
+	for i := 1; i <= min(soss.height, n); i++ {
+		toss.data[toss.height-i] = soss.data[soss.height-i]
+		for i := min(soss.height, n) + 1; i <= n; i++ {
+			toss.data[toss.height-i] = 0
+		}
+	}
+	soss.height -= n
+	if soss.height < 0 {
+		soss.height = 0
+	}
+}
+
+func (s Stack) Next() *Stack {
+	return s.next
+}
+
+func (s *Stack) Discard(n int) {
+	// Implements a discard mechanism intended for use with the '}'(aka end) stackstack command
+	s.height -= n
+	if s.height < 0 {
+		s.height = 0
+	}
+}
+
+func (s *Stack) YCommandPick(n int, h int) {
+	if n > s.height {
+		s.height = 1
+		s.data[0] = 0
+	} else {
+		v := s.data[s.height-n]
+		s.height = h
+		s.Push(v)
+	}
+}
diff --git a/pkg/stack/stack_test.go b/pkg/stack/stack_test.go
new file mode 100644
index 0000000..2f15d3a
--- /dev/null
+++ b/pkg/stack/stack_test.go
@@ -0,0 +1,83 @@
+package stack
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestClear(t *testing.T) {
+	s := NewStack(32, nil)
+	s.Clear()
+	require.Equal(t, 0, s.height)
+}
+
+func TestDupicate(t *testing.T) {
+	expected := NewStack(32, nil)
+	expected.height = 2
+	s := NewStack(32, nil)
+	s.Duplicate()
+	require.Equal(t, expected.height, s.height)
+	s.Push(12)
+	s.Duplicate()
+	expected.Push(12)
+	expected.Push(12)
+	require.Equal(t, expected.height, s.height)
+	require.Equal(t, expected.data, s.data)
+}
+
+func TestPop(t *testing.T) {
+	s := NewStack(32, nil)
+	v := s.Pop()
+	require.Equal(t, 0, v)
+	s.Push(12)
+	s.Push(14)
+	v = s.Pop()
+	require.Equal(t, 14, v)
+	v = s.Pop()
+	require.Equal(t, 12, v)
+	v = s.Pop()
+	require.Equal(t, 0, v)
+}
+
+func TestPush(t *testing.T) {
+	s := NewStack(32, nil)
+	for i := 0; i < 32; i++ {
+		s.Push(i)
+	}
+	require.Equal(t, 32, s.size)
+	s.Push(-1)
+	require.Equal(t, 64, s.size)
+}
+
+func TestSwap(t *testing.T) {
+	s := NewStack(32, nil)
+	s2 := NewStack(32, nil)
+	s.Swap()
+	s2.Push(0)
+	s2.Push(0)
+	require.Equal(t, s2, s)
+	s.Clear()
+	s.Push(1)
+	s.Swap()
+	s2.Clear()
+	s2.Push(1)
+	s2.Push(0)
+	require.Equal(t, s2, s)
+	s.Clear()
+	s.Push(1)
+	s.Push(2)
+	s2.Clear()
+	s2.Push(2)
+	s2.Push(1)
+	s.Swap()
+	require.Equal(t, s2, s)
+}
+
+func TestHeights(t *testing.T) {
+	// TODO
+}
+
+func TestTransfert(t *testing.T) {
+	// TODO
+}