package generator

import (
	"image"
	"image/color"
	"testing"
)

func TestBuildLogoPlane(t *testing.T) {
	// 8x4 logo: white left half, near-75% red right half (8-bit 191 is
	// 0.749, a hair under the exact-0.75 bars value, hence Y=203 not 204),
	// one transparent pixel at (2,1).
	img := image.NewRGBA(image.Rect(0, 0, 8, 4))
	for yy := 0; yy < 4; yy++ {
		for xx := 0; xx < 8; xx++ {
			if xx < 4 {
				img.Set(xx, yy, color.RGBA{255, 255, 255, 255})
			} else {
				img.Set(xx, yy, color.RGBA{191, 0, 0, 255})
			}
		}
	}
	img.Set(2, 1, color.RGBA{0, 0, 0, 0})

	plane, err := BuildLogoPlane(img)
	if err != nil {
		t.Fatalf("BuildLogoPlane: %v", err)
	}
	if len(plane) != 1+8*4 {
		t.Fatalf("plane len=%d, want 33", len(plane))
	}
	if hdr := plane[0]; hdr != 8|4<<16 {
		t.Fatalf("header=%#x, want w=8 h=4", hdr)
	}
	cases := []struct {
		dx, dy    int
		opaque    bool
		y, cb, cr uint32
	}{
		{1, 1, true, 940, 512, 512}, // white
		{5, 2, true, 203, 435, 848}, // near-75% red
		{2, 1, false, 0, 0, 0},      // transparent
	}
	for _, c := range cases {
		s := plane[1+c.dy*8+c.dx]
		if got := (s >> 30) & 1; got != boolToBit(c.opaque) {
			t.Fatalf("pixel (%d,%d): opaque=%d, want %v", c.dx, c.dy, got, c.opaque)
		}
		if !c.opaque {
			continue
		}
		if s&0x3FF != c.y || (s>>10)&0x3FF != c.cb || (s>>20)&0x3FF != c.cr {
			t.Fatalf("pixel (%d,%d): got %d/%d/%d, want %d/%d/%d",
				c.dx, c.dy, s&0x3FF, (s>>10)&0x3FF, (s>>20)&0x3FF, c.y, c.cb, c.cr)
		}
	}
}

func boolToBit(b bool) uint32 {
	if b {
		return 1
	}
	return 0
}