package generator

import (
	"encoding/binary"
	"path/filepath"
	"testing"
)

func TestWGPUMoveSquare(t *testing.T) {
	const width, height = 1920, 1080
	g, err := NewWGPUGenerator(width, height, filepath.Join("..", "..", "kernels", "v210_bars_move.wgsl"))
	if err != nil {
		t.Fatalf("init: %v", err)
	}
	defer g.Close()

	buf := make([]byte, width*height*8/3)
	sample := func(x, y int) (yc, cb, cr uint32) {
		p := y*width + x
		off := (p / 6) * 16
		w0 := binary.LittleEndian.Uint32(buf[off:])
		w1 := binary.LittleEndian.Uint32(buf[off+4:])
		w2 := binary.LittleEndian.Uint32(buf[off+8:])
		w3 := binary.LittleEndian.Uint32(buf[off+12:])
		switch p % 6 {
		case 0:
			return (w0 >> 10) & 0x3FF, w0 & 0x3FF, (w0 >> 20) & 0x3FF
		case 1:
			return w1 & 0x3FF, w0 & 0x3FF, (w0 >> 20) & 0x3FF
		case 2:
			return (w1 >> 20) & 0x3FF, (w1 >> 10) & 0x3FF, w2 & 0x3FF
		case 3:
			return (w2 >> 10) & 0x3FF, (w1 >> 10) & 0x3FF, w2 & 0x3FF
		case 4:
			return w3 & 0x3FF, (w2 >> 20) & 0x3FF, (w3 >> 10) & 0x3FF
		default:
			return (w3 >> 20) & 0x3FF, (w2 >> 20) & 0x3FF, (w3 >> 10) & 0x3FF
		}
	}

	// square center x=960 sits on the green bar (534/253/207):
	// inverted -> Y=1004-534=470, Cb=1024-253=771, Cr=1024-207=817
	const invY, invCb, invCr = 470, 771, 817
	const greenY = 534 // bar 3 covers x in [823,1098)

	// tick 0: offset = 0, square centered at (960,540), half = 75
	if err := g.GenerateFrame(buf, 0); err != nil {
		t.Fatalf("tick 0: %v", err)
	}
	if y, cb, cr := sample(960, 540); y != invY || cb != invCb || cr != invCr {
		t.Fatalf("tick 0 center: got %d/%d/%d, want inverted green 470/771/817", y, cb, cr)
	}
	if y, _, _ := sample(860, 540); y != greenY {
		t.Fatalf("tick 0 left of square: Y=%d, want green %d", y, greenY)
	}

	// amplitude = centerX - half = 885: tick 79 (sin~1) puts the square at
	// the far right, x in [1770,1920), over the blue bar (111/848/481):
	// inverted -> Y=1004-111=893, Cb=1024-848=176, Cr=1024-481=543
	const invBlueY, invBlueCb, invBlueCr = 893, 176, 543
	if err := g.GenerateFrame(buf, 79); err != nil {
		t.Fatalf("tick 79: %v", err)
	}
	if y, cb, cr := sample(1840, 540); y != invBlueY || cb != invBlueCb || cr != invBlueCr {
		t.Fatalf("tick 79 shifted center: got %d/%d/%d, want inverted blue 893/176/543", y, cb, cr)
	}
	if y, _, _ := sample(960, 540); y != greenY {
		t.Fatalf("tick 79 old center: Y=%d, want green %d (square moved away)", y, greenY)
	}
	// bars untouched far from the square
	if y, _, _ := sample(100, 100); y != 721 {
		t.Fatalf("tick 79 bars: Y=%d, want white 721", y)
	}
}