package dataext

import (
	"errors"
	"sync"
	"testing"
)

func TestStack_PushPop(t *testing.T) {
	s := NewStack[int](false, 4)
	s.Push(1)
	s.Push(2)
	s.Push(3)

	if s.Length() != 3 {
		t.Fatalf("Length=%d", s.Length())
	}
	if s.Empty() {
		t.Fatal("should not be empty")
	}

	v, err := s.Pop()
	if err != nil || v != 3 {
		t.Fatalf("Pop got (%d,%v)", v, err)
	}
	v, err = s.Pop()
	if err != nil || v != 2 {
		t.Fatalf("Pop got (%d,%v)", v, err)
	}
	v, err = s.Pop()
	if err != nil || v != 1 {
		t.Fatalf("Pop got (%d,%v)", v, err)
	}
}

func TestStack_PopEmpty(t *testing.T) {
	s := NewStack[int](false, 0)
	_, err := s.Pop()
	if !errors.Is(err, ErrEmptyStack) {
		t.Fatalf("expected ErrEmptyStack, got %v", err)
	}
	if !s.Empty() {
		t.Fatal("should be empty")
	}
}

func TestStack_Peek(t *testing.T) {
	s := NewStack[string](false, 0)
	if _, err := s.Peek(); !errors.Is(err, ErrEmptyStack) {
		t.Fatalf("expected ErrEmptyStack got %v", err)
	}
	s.Push("a")
	s.Push("b")
	v, err := s.Peek()
	if err != nil || v != "b" {
		t.Fatalf("Peek got (%q,%v)", v, err)
	}
	if s.Length() != 2 {
		t.Fatal("Peek must not pop")
	}
}

func TestStack_OptPopOptPeek(t *testing.T) {
	s := NewStack[int](false, 0)
	if s.OptPop() != nil {
		t.Fatal("OptPop on empty should return nil")
	}
	if s.OptPeek() != nil {
		t.Fatal("OptPeek on empty should return nil")
	}
	s.Push(7)
	if p := s.OptPeek(); p == nil || *p != 7 {
		t.Fatalf("OptPeek bad")
	}
	if p := s.OptPop(); p == nil || *p != 7 {
		t.Fatalf("OptPop bad")
	}
	if !s.Empty() {
		t.Fatal("should be empty after OptPop")
	}
}

func TestStack_ThreadSafe(t *testing.T) {
	s := NewStack[int](true, 0)
	var wg sync.WaitGroup
	const n = 200
	wg.Add(n)
	for i := 0; i < n; i++ {
		go func(v int) {
			defer wg.Done()
			s.Push(v)
		}(i)
	}
	wg.Wait()
	if s.Length() != n {
		t.Fatalf("Length=%d want %d", s.Length(), n)
	}
}