package generator

import (
	"errors"
	"strings"
	"testing"
)

func fillFrame(value byte) FrameRenderer {
	return func(dst []byte, _, _, _ int) error {
		for i := range dst {
			dst[i] = value
		}
		return nil
	}
}

func TestNewCPUGeneratorValidation(t *testing.T) {
	renderer := fillFrame(0)
	tests := []struct {
		name       string
		width      uint
		height     uint
		renderer   FrameRenderer
		wantErrSub string
	}{
		{name: "zero width", height: 1, renderer: renderer, wantErrSub: "greater than zero"},
		{name: "zero height", width: 6, renderer: renderer, wantErrSub: "greater than zero"},
		{name: "odd width", width: 7, height: 1, renderer: renderer, wantErrSub: "even"},
		{name: "nil renderer", width: 6, height: 1, wantErrSub: "renderer is nil"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			_, err := NewCPUGenerator(tc.width, tc.height, tc.renderer, nil)
			if err == nil || !strings.Contains(err.Error(), tc.wantErrSub) {
				t.Fatalf("error = %v, want substring %q", err, tc.wantErrSub)
			}
		})
	}
}

func TestCPUGeneratorCopiesBaseAndRestoresBeforePatch(t *testing.T) {
	patch := func(dst []byte, _, _, frameIndex int) error {
		switch frameIndex {
		case 1:
			dst[0] = 0x22
		case 2:
			dst[16] = 0x33
		}
		return nil
	}
	g, err := NewCPUGenerator(12, 1, fillFrame(0x11), patch)
	if err != nil {
		t.Fatalf("NewCPUGenerator: %v", err)
	}

	frame := make([]byte, V210FrameSize(12, 1))
	if err := g.GenerateFrame(frame, 1); err != nil {
		t.Fatalf("GenerateFrame(1): %v", err)
	}
	if frame[0] != 0x22 {
		t.Fatalf("frame 1 patch byte = %#x, want 0x22", frame[0])
	}

	if err := g.GenerateFrame(frame, 2); err != nil {
		t.Fatalf("GenerateFrame(2): %v", err)
	}
	if frame[0] != 0x11 {
		t.Fatalf("old patch byte = %#x, want restored base 0x11", frame[0])
	}
	if frame[16] != 0x33 {
		t.Fatalf("frame 2 patch byte = %#x, want 0x33", frame[16])
	}
}

func TestPackV210Block(t *testing.T) {
	var pixels [6]YCbCr10
	for i := range pixels {
		pixels[i] = YCbCr10{
			Y:  uint32(100 + i),
			Cb: uint32(200 + i),
			Cr: uint32(300 + i),
		}
	}
	frame := make([]byte, 16)
	packV210Block(frame, pixels)

	for x := range pixels {
		y, cb, cr := sampleV210(frame, 6, x, 0)
		chromaX := x - x%2
		if y != pixels[x].Y || cb != pixels[chromaX].Cb || cr != pixels[chromaX].Cr {
			t.Fatalf("pixel %d: got %d/%d/%d, want %d/%d/%d",
				x, y, cb, cr, pixels[x].Y, pixels[chromaX].Cb, pixels[chromaX].Cr)
		}
	}
}

func TestPackV210BlockMasksComponents(t *testing.T) {
	pixel := YCbCr10{Y: 0xC01, Cb: 0xC02, Cr: 0xC03}
	frame := make([]byte, 16)
	packV210Block(frame, [6]YCbCr10{pixel, pixel, pixel, pixel, pixel, pixel})
	y, cb, cr := sampleV210(frame, 6, 0, 0)
	if y != 1 || cb != 2 || cr != 3 {
		t.Fatalf("masked components = %d/%d/%d, want 1/2/3", y, cb, cr)
	}
}

func TestCPUGeneratorErrors(t *testing.T) {
	wantErr := errors.New("patch failed")
	g, err := NewCPUGenerator(6, 1, fillFrame(0), func([]byte, int, int, int) error {
		return wantErr
	})
	if err != nil {
		t.Fatalf("NewCPUGenerator: %v", err)
	}
	if err := g.GenerateFrame(make([]byte, V210FrameSize(6, 1)-1), 0); err == nil || !strings.Contains(err.Error(), "too small") {
		t.Fatalf("small destination error = %v", err)
	}
	if err := g.GenerateFrame(make([]byte, V210FrameSize(6, 1)), 4); !errors.Is(err, wantErr) {
		t.Fatalf("patch error = %v, want wrapped %v", err, wantErr)
	}
}

func TestCPUGeneratorUsesPaddedV210Rows(t *testing.T) {
	const width, height = 100, 2
	g, err := NewCPUPatternGenerator(width, height, "gray-ramp")
	if err != nil {
		t.Fatalf("NewCPUPatternGenerator: %v", err)
	}
	frame := make([]byte, V210FrameSize(width, height))
	if err := g.GenerateFrame(frame, 0); err != nil {
		t.Fatalf("GenerateFrame: %v", err)
	}

	for y := 0; y < height; y++ {
		gotY, gotCb, gotCr := sampleV210(frame, width, 0, y)
		if gotY != 64 || gotCb != 512 || gotCr != 512 {
			t.Fatalf("row %d first pixel = %d/%d/%d, want 64/512/512", y, gotY, gotCb, gotCr)
		}
		padding := frame[y*V210LineSize(width)+V210ActiveLineSize(width) : (y+1)*V210LineSize(width)]
		for i, b := range padding {
			if b != 0 {
				t.Fatalf("row %d padding byte %d = %#x, want 0", y, i, b)
			}
		}
	}
}