package world

import (
	"testing"

	"github.com/stretchr/testify/require"
)

func TestRender_PanSmall_UsesCopyShiftAndRendersOnlyDirtyStrips(t *testing.T) {
	t.Parallel()

	w := NewWorld(10, 10)
	w.resetGrid(2 * SCALE)

	_, err := w.AddPoint(5, 5)
	require.NoError(t, err)
	_, err = w.AddCircle(2, 2, 1)
	require.NoError(t, err)
	_, err = w.AddLine(9, 5, 1, 5)
	require.NoError(t, err)

	for _, obj := range w.objects {
		w.indexObject(obj)
	}

	params := RenderParams{
		ViewportWidthPx:  10,
		ViewportHeightPx: 10,
		MarginXPx:        4, // threshold=2
		MarginYPx:        4, // threshold=2
		CameraXWorldFp:   5 * SCALE,
		CameraYWorldFp:   5 * SCALE,
		CameraZoom:       1.0,
	}

	// First render initializes state (full redraw).
	d0 := &fakePrimitiveDrawer{}
	require.NoError(t, w.Render(d0, params))

	// Pan right by 1 unit => dx=-1 => incremental shift expected.
	params2 := params
	params2.CameraXWorldFp += 1 * SCALE

	d := &fakePrimitiveDrawer{}
	err = w.Render(d, params2)
	require.NoError(t, err)

	// Must contain CopyShift for incremental path.
	require.NotEmpty(t, d.CommandsByName("CopyShift"))

	// All clip rects should be "small": width <= 1 for dx=-1 strip.
	clipCmds := d.CommandsByName("ClipRect")
	require.NotEmpty(t, clipCmds)
	for _, c := range clipCmds {
		wPx := int(c.Args[2])
		hPx := int(c.Args[3])
		require.LessOrEqual(t, wPx, 2)
		require.LessOrEqual(t, hPx, params2.CanvasHeightPx())
	}

	require.NotEmpty(t, d.CommandsByName("AddPoint"))
	require.NotEmpty(t, d.CommandsByName("AddCircle"))
	require.NotEmpty(t, d.CommandsByName("AddLine"))
}

func TestRender_PanTooLarge_FallsBackToFullRedraw(t *testing.T) {
	t.Parallel()

	w := NewWorld(10, 10)
	w.resetGrid(2 * SCALE)

	_, err := w.AddPoint(5, 5)
	require.NoError(t, err)
	for _, obj := range w.objects {
		w.indexObject(obj)
	}

	params := RenderParams{
		ViewportWidthPx:  10,
		ViewportHeightPx: 10,
		MarginXPx:        4, // threshold=2
		MarginYPx:        4,
		CameraXWorldFp:   5 * SCALE,
		CameraYWorldFp:   5 * SCALE,
		CameraZoom:       1.0,
	}

	d0 := &fakePrimitiveDrawer{}
	require.NoError(t, w.Render(d0, params))

	// Pan right by 3 units => abs(dx)=3 > threshold(2) => full redraw expected.
	params2 := params
	params2.CameraXWorldFp += 3 * SCALE

	d := &fakePrimitiveDrawer{}
	err = w.Render(d, params2)
	require.NoError(t, err)

	// Full redraw should NOT call CopyShift.
	require.Empty(t, d.CommandsByName("CopyShift"))

	// Full redraw should clear the entire canvas.
	require.NotEmpty(t, d.CommandsByName("ClearAllTo"))

	// And should draw something (at least the point).
	// Depending on your implementation, it might be AddPoint or AddCircle/AddLine as well.
	require.NotEmpty(t, d.CommandsByName("AddPoint"))
}