package probe

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

// buildJpegWithOrientation 拼一个带 Exif 方向标记的最小 JPEG：
// SOI + APP1(Exif) + EOI，APP1 里只放 TIFF 头 + IFD0 一条 Orientation。
func buildJpegWithOrientation(t *testing.T, orientation uint16, bigEndian bool) []byte {
	t.Helper()
	var order binary.ByteOrder = binary.LittleEndian
	if bigEndian {
		order = binary.BigEndian
	}
	bom := []byte("II")
	if bigEndian {
		bom = []byte("MM")
	}
	// TIFF 头(8) + IFD0 计数(2) + 一条目(12)
	tiff := make([]byte, 0, 8+2+12)
	tiff = append(tiff, bom...)
	magic := make([]byte, 2)
	order.PutUint16(magic, 42)
	tiff = append(tiff, magic...)
	ifdOff := make([]byte, 4)
	order.PutUint32(ifdOff, 8)
	tiff = append(tiff, ifdOff...)
	count := make([]byte, 2)
	order.PutUint16(count, 1)
	tiff = append(tiff, count...)
	// 一条目：tag=0x0112 type=SHORT count=1 value=orientation
	entry := make([]byte, 12)
	order.PutUint16(entry[0:2], 0x0112)
	order.PutUint16(entry[2:4], 3) // SHORT
	order.PutUint32(entry[4:8], 1) // count
	order.PutUint16(entry[8:10], orientation)
	tiff = append(tiff, entry...)

	app1Data := append([]byte("Exif\x00\x00"), tiff...)
	segLen := len(app1Data) + 2
	out := []byte{0xFF, 0xD8} // SOI
	out = append(out, 0xFF, 0xE1)
	lenB := make([]byte, 2)
	binary.BigEndian.PutUint16(lenB, uint16(segLen))
	out = append(out, lenB...)
	out = append(out, app1Data...)
	out = append(out, 0xFF, 0xD9) // EOI
	return out
}

func TestReadExifOrientation(t *testing.T) {
	dir := t.TempDir()
	cases := []struct {
		name    string
		ori     uint16
		bigEnd  bool
		want    int
	}{
		{"le6", 6, false, 6},
		{"be8", 8, true, 8},
		{"le1", 1, false, 1},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			p := filepath.Join(dir, c.name+".jpg")
			if err := os.WriteFile(p, buildJpegWithOrientation(t, c.ori, c.bigEnd), 0644); err != nil {
				t.Fatal(err)
			}
			if got := ReadExifOrientation(p); got != c.want {
				t.Fatalf("ReadExifOrientation = %d, want %d", got, c.want)
			}
		})
	}

	// 非 JPEG 返回 0
	p := filepath.Join(dir, "notjpeg.txt")
	if err := os.WriteFile(p, []byte("hello"), 0644); err != nil {
		t.Fatal(err)
	}
	if got := ReadExifOrientation(p); got != 0 {
		t.Fatalf("non-jpeg ReadExifOrientation = %d, want 0", got)
	}
	// 不存在的文件返回 0
	if got := ReadExifOrientation(filepath.Join(dir, "missing.jpg")); got != 0 {
		t.Fatalf("missing ReadExifOrientation = %d, want 0", got)
	}
}

func TestNeedsDimensionSwap(t *testing.T) {
	cases := map[int]bool{
		1: false, 2: false, 3: false, 4: false,
		5: true, 6: true, 7: true, 8: true,
		0: false, 9: false,
	}
	for ori, want := range cases {
		if got := NeedsDimensionSwap(ori); got != want {
			t.Fatalf("NeedsDimensionSwap(%d) = %v, want %v", ori, got, want)
		}
	}
}