package navigation_test

import (
	"testing"

	"github.com/nebara/nebara-os/internal/model"
	"github.com/nebara/nebara-os/internal/ui/navigation"
)

func sampleItems() []model.MenuItem {
	return []model.MenuItem{
		{Label: "Item A", Description: "Desc A", Children: []model.MenuItem{
			{Label: "Child A1", Description: "Desc A1"},
			{Label: "Child A2", Description: "Desc A2"},
		}},
		{Label: "Item B", Description: "Desc B"},
		{Label: "Item C", Description: "Desc C"},
	}
}

func TestNewNavigator_InitialIndex(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 1)
	if nav.Current().SelectedIdx != 1 {
		t.Errorf("expected initial index 1, got %d", nav.Current().SelectedIdx)
	}
}

func TestNewNavigator_InvalidIndex(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 99)
	if nav.Current().SelectedIdx != 0 {
		t.Errorf("out-of-range index should clamp to 0, got %d", nav.Current().SelectedIdx)
	}
}

func TestMoveDown(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	nav.MoveDown()
	if nav.Current().SelectedIdx != 1 {
		t.Errorf("expected index 1 after MoveDown, got %d", nav.Current().SelectedIdx)
	}
}

func TestMoveDown_Clamps(t *testing.T) {
	items := sampleItems()
	nav := navigation.NewNavigator(items, len(items)-1)
	nav.MoveDown()
	if nav.Current().SelectedIdx != len(items)-1 {
		t.Errorf("MoveDown should clamp at last item")
	}
}

func TestMoveUp(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 2)
	nav.MoveUp()
	if nav.Current().SelectedIdx != 1 {
		t.Errorf("expected index 1 after MoveUp, got %d", nav.Current().SelectedIdx)
	}
}

func TestMoveUp_Clamps(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	nav.MoveUp()
	if nav.Current().SelectedIdx != 0 {
		t.Errorf("MoveUp should clamp at 0")
	}
}

func TestMoveFirst(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 2)
	nav.MoveFirst()
	if nav.Current().SelectedIdx != 0 {
		t.Errorf("MoveFirst should jump to 0")
	}
}

func TestMoveLast(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	nav.MoveLast()
	last := len(sampleItems()) - 1
	if nav.Current().SelectedIdx != last {
		t.Errorf("MoveLast should jump to %d, got %d", last, nav.Current().SelectedIdx)
	}
}

func TestEnter_HasChildren(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0) // Item A has children
	ok := nav.Enter()
	if !ok {
		t.Fatal("Enter on item with children should return true")
	}
	if nav.Depth() != 1 {
		t.Errorf("expected depth 1, got %d", nav.Depth())
	}
	if nav.Current().Items[0].Label != "Child A1" {
		t.Errorf("expected Child A1, got %s", nav.Current().Items[0].Label)
	}
}

func TestEnter_NoChildren(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 1) // Item B has no children
	ok := nav.Enter()
	if ok {
		t.Fatal("Enter on leaf item should return false")
	}
	if nav.Depth() != 0 {
		t.Errorf("depth should remain 0 for leaf enter")
	}
}

func TestBack(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	nav.Enter()
	ok := nav.Back()
	if !ok {
		t.Fatal("Back from submenu should return true")
	}
	if nav.Depth() != 0 {
		t.Errorf("expected depth 0 after back, got %d", nav.Depth())
	}
}

func TestBack_AtRoot(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	ok := nav.Back()
	if ok {
		t.Fatal("Back at root should return false")
	}
}

func TestIsAtRoot(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	if !nav.IsAtRoot() {
		t.Error("should be at root initially")
	}
	nav.Enter()
	if nav.IsAtRoot() {
		t.Error("should not be at root after Enter")
	}
	nav.Back()
	if !nav.IsAtRoot() {
		t.Error("should be at root after Back")
	}
}

func TestSelectionPreservedAfterBack(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	nav.MoveDown() // idx=1
	nav.MoveDown() // idx=2
	nav.Back()     // at root, nothing changes
	if nav.Current().SelectedIdx != 2 {
		t.Errorf("selection should be 2, got %d", nav.Current().SelectedIdx)
	}
	nav.MoveFirst() // idx=0
	nav.Enter()     // into Item A's children
	nav.Back()      // back to root, parent should restore idx=0
	if nav.Current().SelectedIdx != 0 {
		t.Errorf("after returning from submenu, root selection should be 0, got %d", nav.Current().SelectedIdx)
	}
}

func TestBreadcrumbTitle(t *testing.T) {
	nav := navigation.NewNavigator(sampleItems(), 0)
	if nav.BreadcrumbTitle() != "" {
		t.Error("breadcrumb should be empty at root")
	}
	nav.Enter()
	if nav.BreadcrumbTitle() != "Item A" {
		t.Errorf("breadcrumb should be 'Item A', got %q", nav.BreadcrumbTitle())
	}
}