// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package jpeg

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"image"
	"image/color"
	stdlibjpeg "image/jpeg"
	"io"
	"math/rand"
	"os"
	"runtime/debug"
	"strings"
	"testing"
	"time"

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

// TestDecodeProgressive tests that decoding the baseline and progressive
// versions of the same image result in exactly the same pixel data, in YCbCr
// space for color images, and Y space for grayscale images.
func TestDecodeProgressive(t *testing.T) {
	testCases := []string{
		"../testdata/video-001",
		"../testdata/video-001.q50.410",
		"../testdata/video-001.q50.411",
		"../testdata/video-001.q50.420",
		"../testdata/video-001.q50.422",
		"../testdata/video-001.q50.440",
		"../testdata/video-001.q50.444",
		"../testdata/video-005.gray.q50",
		"../testdata/video-005.gray.q50.2x2",
		"../testdata/video-001.separate.dc.progression",
	}
	for _, tc := range testCases {
		m0, err := decodeFile(tc + ".jpeg")
		if err != nil {
			t.Errorf("%s: %v", tc+".jpeg", err)
			continue
		}
		m1, err := decodeFile(tc + ".progressive.jpeg")
		if err != nil {
			t.Errorf("%s: %v", tc+".progressive.jpeg", err)
			continue
		}
		if m0.Bounds() != m1.Bounds() {
			t.Errorf("%s: bounds differ: %v and %v", tc, m0.Bounds(), m1.Bounds())
			continue
		}
		// All of the video-*.jpeg files are 150x103.
		if m0.Bounds() != image.Rect(0, 0, 150, 103) {
			t.Errorf("%s: bad bounds: %v", tc, m0.Bounds())
			continue
		}

		switch m0 := m0.(type) {
		case *image.YCbCr:
			m1 := m1.(*image.YCbCr)
			if err := check(m0.Bounds(), m0.Y, m1.Y, m0.YStride, m1.YStride); err != nil {
				t.Errorf("%s (Y): %v", tc, err)
				continue
			}
			if err := check(m0.Bounds(), m0.Cb, m1.Cb, m0.CStride, m1.CStride); err != nil {
				t.Errorf("%s (Cb): %v", tc, err)
				continue
			}
			if err := check(m0.Bounds(), m0.Cr, m1.Cr, m0.CStride, m1.CStride); err != nil {
				t.Errorf("%s (Cr): %v", tc, err)
				continue
			}
		case *image.Gray:
			m1 := m1.(*image.Gray)
			if err := check(m0.Bounds(), m0.Pix, m1.Pix, m0.Stride, m1.Stride); err != nil {
				t.Errorf("%s: %v", tc, err)
				continue
			}
		default:
			t.Errorf("%s: unexpected image type %T", tc, m0)
			continue
		}
	}
}

func decodeFile(filename string) (image.Image, error) {
	f, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return Decode(f)
}

type eofReader struct {
	data     []byte // deliver from Read without EOF
	dataEOF  []byte // then deliver from Read with EOF on last chunk
	lenAtEOF int
}

func (r *eofReader) Read(b []byte) (n int, err error) {
	if len(r.data) > 0 {
		n = copy(b, r.data)
		r.data = r.data[n:]
	} else {
		n = copy(b, r.dataEOF)
		r.dataEOF = r.dataEOF[n:]
		if len(r.dataEOF) == 0 {
			err = io.EOF
			if r.lenAtEOF == -1 {
				r.lenAtEOF = n
			}
		}
	}
	return
}

func TestDecodeEOF(t *testing.T) {
	// Check that if reader returns final data and EOF at same time, jpeg handles it.
	data, err := os.ReadFile("../testdata/video-001.jpeg")
	if err != nil {
		t.Fatal(err)
	}

	n := len(data)
	for i := 0; i < n; {
		r := &eofReader{data[:n-i], data[n-i:], -1}
		_, err := Decode(r)
		if err != nil {
			t.Errorf("Decode with Read() = %d, EOF: %v", r.lenAtEOF, err)
		}
		if i == 0 {
			i = 1
		} else {
			i *= 2
		}
	}
}

// check checks that the two pix data are equal, within the given bounds.
func check(bounds image.Rectangle, pix0, pix1 []byte, stride0, stride1 int) error {
	if stride0 <= 0 || stride0%8 != 0 {
		return fmt.Errorf("bad stride %d", stride0)
	}
	if stride1 <= 0 || stride1%8 != 0 {
		return fmt.Errorf("bad stride %d", stride1)
	}
	// Compare the two pix data, one 8x8 block at a time.
	for y := 0; y < len(pix0)/stride0 && y < len(pix1)/stride1; y += 8 {
		for x := 0; x < stride0 && x < stride1; x += 8 {
			if x >= bounds.Max.X || y >= bounds.Max.Y {
				// We don't care if the two pix data differ if the 8x8 block is
				// entirely outside of the image's bounds. For example, this can
				// occur with a 4:2:0 chroma subsampling and a 1x1 image. Baseline
				// decoding works on the one 16x16 MCU as a whole; progressive
				// decoding's first pass works on that 16x16 MCU as a whole but
				// refinement passes only process one 8x8 block within the MCU.
				continue
			}

			for j := range 8 {
				for i := range 8 {
					index0 := (y+j)*stride0 + (x + i)
					index1 := (y+j)*stride1 + (x + i)
					if pix0[index0] != pix1[index1] {
						return fmt.Errorf("blocks at (%d, %d) differ:\n%sand\n%s", x, y,
							pixString(pix0, stride0, x, y),
							pixString(pix1, stride1, x, y),
						)
					}
				}
			}
		}
	}
	return nil
}

func pixString(pix []byte, stride, x, y int) string {
	s := &strings.Builder{}
	for j := range 8 {
		fmt.Fprintf(s, "\t")
		for i := range 8 {
			fmt.Fprintf(s, "%02x ", pix[(y+j)*stride+(x+i)])
		}
		fmt.Fprintf(s, "\n")
	}
	return s.String()
}

func TestTruncatedSOSDataDoesntPanic(t *testing.T) {
	b, err := os.ReadFile("../testdata/video-005.gray.q50.jpeg")
	if err != nil {
		t.Fatal(err)
	}
	sosMarker := []byte{0xff, 0xda}
	i := bytes.Index(b, sosMarker)
	if i < 0 {
		t.Fatal("SOS marker not found")
	}
	i += len(sosMarker)
	j := min(i+10, len(b))
	for ; i < j; i++ {
		Decode(bytes.NewReader(b[:i]))
	}
}

func TestLargeImageWithShortData(t *testing.T) {
	// This input is an invalid JPEG image, based on the fuzzer-generated image
	// in issue 10413. It is only 504 bytes, and shouldn't take long for Decode
	// to return an error. The Start Of Frame marker gives the image dimensions
	// as 8192 wide and 8192 high, so even if an unreadByteStuffedByte bug
	// doesn't technically lead to an infinite loop, such a bug can still cause
	// an unreasonably long loop for such a short input.
	const input = "" +
		"\xff\xd8\xff\xe0\x00\x10\x4a\x46\x49\x46\x00\x01\x01\x00\x00\x01" +
		"\x00\x01\x00\x00\xff\xdb\x00\x43\x00\x10\x0b\x0c\x0e\x0c\x0a\x10" +
		"\x0e\x89\x0e\x12\x11\x10\x13\x18\xff\xd8\xff\xe0\x00\x10\x4a\x46" +
		"\x49\x46\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00\x43" +
		"\x00\x10\x0b\x0c\x0e\x0c\x0a\x10\x0e\x0d\x0e\x12\x11\x10\x13\x18" +
		"\x28\x1a\x18\x16\x16\x18\x31\x23\x25\x1d\x28\x3a\x33\x3d\x3c\x39" +
		"\x33\x38\x37\x40\x48\x5c\x4e\x40\x44\x57\x45\x37\x38\x50\x6d\x51" +
		"\x57\x5f\x62\x67\x68\x67\x3e\x4d\x71\x79\x70\x64\x78\x5c\x65\x67" +
		"\x63\xff\xc0\x00\x0b\x08\x20\x00\x20\x00\x01\x01\x11\x00\xff\xc4" +
		"\x00\x1f\x00\x00\x01\x05\x01\x01\x01\x01\x01\x01\x00\x00\x00\x00" +
		"\x00\x00\x00\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\xff" +
		"\xc4\x00\xb5\x10\x00\x02\x01\x03\x03\x02\x04\x03\x05\x05\x04\x04" +
		"\x00\x00\x01\x7d\x01\x02\x03\x00\x04\x11\x05\x12\x21\x31\x01\x06" +
		"\x13\x51\x61\x07\x22\x71\x14\x32\x81\x91\xa1\x08\x23\xd8\xff\xdd" +
		"\x42\xb1\xc1\x15\x52\xd1\xf0\x24\x33\x62\x72\x82\x09\x0a\x16\x17" +
		"\x18\x19\x1a\x25\x26\x27\x28\x29\x2a\x34\x35\x36\x37\x38\x39\x3a" +
		"\x43\x44\x45\x46\x47\x48\x49\x4a\x53\x54\x55\x56\x57\x58\x59\x5a" +
		"\x00\x63\x64\x65\x66\x67\x68\x69\x6a\x73\x74\x75\x76\x77\x78\x79" +
		"\x7a\x83\x84\x85\x86\x87\x88\x89\x8a\x92\x93\x94\x95\x96\x97\x98" +
		"\x99\x9a\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xb2\xb3\xb4\xb5\xb6" +
		"\xb7\xb8\xb9\xba\xc2\xc3\xc4\xc5\xc6\xc7\xff\xd8\xff\xe0\x00\x10" +
		"\x4a\x46\x49\x46\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb" +
		"\x00\x43\x00\x10\x0b\x0c\x0e\x0c\x0a\x10\x0e\x0d\x0e\x12\x11\x10" +
		"\x13\x18\x28\x1a\x18\x16\x16\x18\x31\x23\x25\x1d\xc8\xc9\xca\xd2" +
		"\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8" +
		"\xe9\xea\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xff\xda\x00\x08" +
		"\x01\x01\x00\x00\x3f\x00\xb9\xeb\x50\xb0\xdb\xc8\xa8\xe4\x63\x80" +
		"\xdd\x31\xd6\x9d\xbb\xf2\xc5\x42\x1f\x6c\x6f\xf4\x34\xdd\x3c\xfc" +
		"\xac\xe7\x3d\x80\xa9\xcc\x87\x34\xb3\x37\xfa\x2b\x9f\x6a\xad\x63" +
		"\x20\x36\x9f\x78\x64\x75\xe6\xab\x7d\xb2\xde\x29\x70\xd3\x20\x27" +
		"\xde\xaf\xa4\xf0\xca\x9f\x24\xa8\xdf\x46\xa8\x24\x84\x96\xe3\x77" +
		"\xf9\x2e\xe0\x0a\x62\x7f\xdf\xd9"

	timer := time.AfterFunc(30*time.Second, func() {
		debug.SetTraceback("all")
		panic("TestLargeImageWithShortData stuck in Decode")
	})
	defer timer.Stop()

	_, err := Decode(strings.NewReader(input))
	if err == nil {
		t.Fatalf("got nil error, want non-nil")
	}
}

func TestPaddedRSTMarker(t *testing.T) {
	// This test image comes from golang.org/issue/28717
	const base64EncodedImage = `
/9j/4AAhQVZJMQABAQEAeAB4AAAAAAAAAAAAAAAAAAAAAAAAAP/bAEMABAIDAwMCBAMDAwQEBAQGCgYG
BQUGDAgJBwoODA8PDgwODxASFxMQERURDQ4UGhQVFxgZGhkPExweHBkeFxkZGP/bAEMBBAQEBgUGCwYG
CxgQDhAYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGP/EAaIA
AAEFAQEBAQEBAAAAAAAAAAABAgMEBQYHCAkKCxAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1Fh
ByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNk
ZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT
1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6AQADAQEBAQEBAQEBAAAAAAAAAQIDBAUGBwgJCgsRAAIB
AgQEAwQHBQQEAAECdwABAgMRBAUhMQYSQVEHYXETIjKBCBRCkaGxwQkjM1LwFWJy0QoWJDThJfEXGBka
JicoKSo1Njc4OTpDREVGR0hJSlNUVVZXWFlaY2RlZmdoaWpzdHV2d3h5eoKDhIWGh4iJipKTlJWWl5iZ
mqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uLj5OXm5+jp6vLz9PX29/j5+v/dAAQA
Cv/gAAQAAP/AABEIALABQAMBIQACEQEDEQH/2gAMAwEAAhEDEQA/APnCFTk5BPPGKliAB718W7H2j3Ip
VUuwJxzTfKXacde9VBhYRUBAyO3pTmUAbSMU5WGmybywzHGAMdelPVFC+n1qXZCuyaJADxjj2qzbBMAP
xz1rKaVib6ltLcFvlIx2pLy0dwuAMMBnH1rFON9RNsszAZPFEYHldPzrOy3KewmBk9qUABugxjtTVmiW
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CS1Q/wDte4Trip49ecA7g3FSqMW9zlqZandxJ4/EKADcSPqKni8QQMT865qOSUNjiqZdNbFiHWYXz84N
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`

	data, err := base64.StdEncoding.DecodeString(base64EncodedImage)
	if err != nil {
		t.Fatalf("base64 DecodeString: %v", err)
	}
	if _, err = Decode(bytes.NewReader(data)); err != nil {
		t.Fatalf("Decode: %v", err)
	}
}

func delta(u0, u1 uint32) int64 {
	d := int64(u0) - int64(u1)
	if d < 0 {
		return -d
	}
	return d
}

// averageDelta returns the average delta in RGB space. The two images must
// have the same bounds.
func averageDelta(m0, m1 image.Image) int64 {
	b := m0.Bounds()
	var sum, n int64
	for y := b.Min.Y; y < b.Max.Y; y++ {
		for x := b.Min.X; x < b.Max.X; x++ {
			c0 := m0.At(x, y)
			c1 := m1.At(x, y)
			r0, g0, b0, _ := c0.RGBA()
			r1, g1, b1, _ := c1.RGBA()
			sum += delta(r0, r1)
			sum += delta(g0, g1)
			sum += delta(b0, b1)
			n += 3
		}
	}
	return sum / n
}

func TestExtraneousData(t *testing.T) {
	// Encode a 1x1 red image.
	src := image.NewRGBA(image.Rect(0, 0, 1, 1))
	src.Set(0, 0, color.RGBA{0xff, 0x00, 0x00, 0xff})
	buf := new(bytes.Buffer)
	if err := stdlibjpeg.Encode(buf, src, nil); err != nil {
		t.Fatalf("encode: %v", err)
	}
	enc := buf.String()
	// Sanity check that the encoded JPEG is long enough, that it ends in a
	// "\xff\xd9" EOI marker, and that it contains a "\xff\xda" SOS marker
	// somewhere in the final 64 bytes.
	if len(enc) < 64 {
		t.Fatalf("encoded JPEG is too short: %d bytes", len(enc))
	}
	if got, want := enc[len(enc)-2:], "\xff\xd9"; got != want {
		t.Fatalf("encoded JPEG ends with %q, want %q", got, want)
	}
	if s := enc[len(enc)-64:]; !strings.Contains(s, "\xff\xda") {
		t.Fatalf("encoded JPEG does not contain a SOS marker (ff da) near the end: % x", s)
	}
	// Test that adding some random junk between the SOS marker and the
	// EOI marker does not affect the decoding.
	rnd := rand.New(rand.NewSource(1))
	for i, nerr := 0, 0; i < 1000 && nerr < 10; i++ {
		buf.Reset()
		// Write all but the trailing "\xff\xd9" EOI marker.
		buf.WriteString(enc[:len(enc)-2])
		// Write some random extraneous data.
		for n := rnd.Intn(10); n > 0; n-- {
			if x := byte(rnd.Intn(256)); x != 0xff {
				buf.WriteByte(x)
			} else {
				// The JPEG format escapes a SOS 0xff data byte as "\xff\x00".
				buf.WriteString("\xff\x00")
			}
		}
		// Write the "\xff\xd9" EOI marker.
		buf.WriteString("\xff\xd9")

		// Check that we can still decode the resultant image.
		got, err := Decode(buf)
		if err != nil {
			t.Errorf("could not decode image #%d: %v", i, err)
			nerr++
			continue
		}
		if got.Bounds() != src.Bounds() {
			t.Errorf("image #%d, bounds differ: %v and %v", i, got.Bounds(), src.Bounds())
			nerr++
			continue
		}
		if averageDelta(got, src) > 2<<8 {
			t.Errorf("image #%d changed too much after a round trip", i)
			nerr++
			continue
		}
	}
}

func TestIssue56724(t *testing.T) {
	b, err := os.ReadFile("../testdata/video-001.jpeg")
	if err != nil {
		t.Fatal(err)
	}

	b = b[:24] // truncate image data

	_, err = Decode(bytes.NewReader(b))
	if err != io.ErrUnexpectedEOF {
		t.Errorf("got: %v, want: %v", err, io.ErrUnexpectedEOF)
	}
}

func TestBadRestartMarker(t *testing.T) {
	b, err := os.ReadFile("../testdata/video-001.restart2.jpeg")
	if err != nil {
		t.Fatal(err)
	} else if len(b) != 4855 {
		t.Fatal("test image had unexpected length")
	} else if (b[2816] != 0xff) || (b[2817] != 0xd1) {
		t.Fatal("test image did not have FF D1 restart marker at expected offset")
	}
	prefix, suffix := b[:2816], b[2816:]

	testCases := []string{
		"PASS:",
		"PASS:\x00",
		"PASS:\x61",
		"PASS:\x61\x62\x63\xff\x00\x64",
		"PASS:\xff",
		"PASS:\xff\x00",
		"PASS:\xff\xff\xff\x00\xff\x00\x00\xff\xff\xff",

		"FAIL:\xff\x03",
		"FAIL:\xff\xd5",
		"FAIL:\xff\xff\xd5",
	}

	for _, tc := range testCases {
		want := tc[:5] == "PASS:"
		infix := tc[5:]

		data := []byte(nil)
		data = append(data, prefix...)
		data = append(data, infix...)
		data = append(data, suffix...)
		_, err := Decode(bytes.NewReader(data))
		got := err == nil

		if got != want {
			t.Errorf("%q: got %v, want %v", tc, got, want)
		}
	}
}

func require_images_equal(t *testing.T, a, b *image.YCbCr) {
	require.Equal(t, a.Bounds(), b.Bounds())
	for y := a.Bounds().Min.Y; y < a.Bounds().Max.Y; y++ {
		for x := a.Bounds().Min.X; x < a.Bounds().Max.X; x++ {
			ac := a.YCbCrAt(x, y)
			bc := b.YCbCrAt(x, y)
			require.Equal(t, ac, bc, fmt.Sprintf("pixel at: (%d, %d)", x-a.Bounds().Min.X, y-a.Bounds().Min.Y))
		}
	}
}

func test_flex(t *testing.T, path string) {
	t.Run(path, func(t *testing.T) {
		t.Parallel()
		data, err := os.ReadFile(path)
		require.NoError(t, err)
		expected, err := stdlibjpeg.Decode(bytes.NewReader(data))
		require.NoError(t, err)
		d := decoder{force_flex: true}
		actual, err := d.decode(bytes.NewReader(data), false)
		require.NoError(t, err)
		require.True(t, d.flex)
		require_images_equal(t, expected.(*image.YCbCr), actual.(*image.YCbCr))
	})
}

func TestNonStandardSubSampling(t *testing.T) {
	for _, path := range []string{
		"../testdata/video-001",
		"../testdata/video-001.q50.410",
		"../testdata/video-001.q50.411",
		"../testdata/video-001.q50.420",
		"../testdata/video-001.q50.422",
		"../testdata/video-001.q50.440",
		"../testdata/video-001.q50.444"} {
		test_flex(t, path+".jpeg")
	}

}

func benchmarkDecode(b *testing.B, filename string) {
	data, err := os.ReadFile(filename)
	if err != nil {
		b.Fatal(err)
	}
	cfg, err := DecodeConfig(bytes.NewReader(data))
	if err != nil {
		b.Fatal(err)
	}
	b.SetBytes(int64(cfg.Width * cfg.Height * 4))
	b.ReportAllocs()

	for b.Loop() {
		Decode(bytes.NewReader(data))
	}
}

func BenchmarkDecodeBaseline(b *testing.B) {
	benchmarkDecode(b, "../testdata/video-001.jpeg")
}

func BenchmarkDecodeProgressive(b *testing.B) {
	benchmarkDecode(b, "../testdata/video-001.progressive.jpeg")
}
