package web

import (
	"bytes"
	"encoding/binary"
	"hash/crc32"
	"image"
	"image/jpeg"
	"image/png"
	"strings"
	"testing"
)

func TestTruncateRunes(t *testing.T) {
	tests := []struct {
		in   string
		max  int
		want string
	}{
		{"abc", 10, "abc"},
		{"abcdef", 3, "abc"},
		{"héllo", 3, "hél"},
		{"🙂🙂🙂", 2, "🙂🙂"},
		{"世界和平", 2, "世界"},
		{"abc", 0, ""},
		{"abc", -1, ""},
		{"", 5, ""},
	}
	for _, tc := range tests {
		if got := truncateRunes(tc.in, tc.max); got != tc.want {
			t.Fatalf("truncateRunes(%q, %d)=%q want %q", tc.in, tc.max, got, tc.want)
		}
	}
}

func TestPrepareAvatar(t *testing.T) {
	var pngBuf bytes.Buffer
	if err := png.Encode(&pngBuf, image.NewRGBA(image.Rect(0, 0, 2, 2))); err != nil {
		t.Fatal(err)
	}
	var jpegBuf bytes.Buffer
	if err := jpeg.Encode(&jpegBuf, image.NewRGBA(image.Rect(0, 0, 2, 2)), &jpeg.Options{Quality: 90}); err != nil {
		t.Fatal(err)
	}
	var largePNG bytes.Buffer
	if err := png.Encode(&largePNG, image.NewRGBA(image.Rect(0, 0, 800, 600))); err != nil {
		t.Fatal(err)
	}

	oversized := bytes.Repeat([]byte{0x89}, (2<<20)+2)

	tests := []struct {
		name    string
		in      []byte
		max     int64
		wantExt string
		wantErr string
	}{
		{name: "png", in: pngBuf.Bytes(), max: 2 << 20, wantExt: ".png"},
		{name: "jpeg", in: jpegBuf.Bytes(), max: 2 << 20, wantExt: ".jpg"},
		{name: "resize large", in: largePNG.Bytes(), max: 2 << 20, wantExt: ".png"},
		{name: "empty", in: nil, max: 2 << 20, wantErr: "empty"},
		{name: "invalid", in: []byte("not-an-image"), max: 2 << 20, wantErr: "unsupported"},
		{name: "oversized", in: oversized, max: 2 << 20, wantErr: "too large"},
		{name: "huge dims", in: pngWithDims(100000, 100000), max: 2 << 20, wantErr: "dimensions"},
		{name: "over decode cap", in: pngWithDims(2048, 2048), max: 2 << 20, wantErr: "dimensions"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			body, ext, ct, err := prepareAvatar(bytes.NewReader(tc.in), tc.max)
			if tc.wantErr != "" {
				if err == nil || !strings.Contains(err.Error(), tc.wantErr) {
					t.Fatalf("err=%v want substring %q", err, tc.wantErr)
				}
				return
			}
			if err != nil {
				t.Fatal(err)
			}
			if ext != tc.wantExt {
				t.Fatalf("ext=%q want %q", ext, tc.wantExt)
			}
			if len(body) == 0 || ct == "" {
				t.Fatalf("empty output body/ct")
			}
			if int64(len(body)) > tc.max {
				t.Fatalf("encoded size %d exceeds max %d", len(body), tc.max)
			}
			cfg, _, err := image.DecodeConfig(bytes.NewReader(body))
			if err != nil {
				t.Fatal(err)
			}
			if cfg.Width > 512 || cfg.Height > 512 {
				t.Fatalf("avatar dims %dx%d exceed 512", cfg.Width, cfg.Height)
			}
		})
	}
}

func pngWithDims(w, h int) []byte {
	var buf bytes.Buffer
	buf.Write([]byte{0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a})
	var ihdr bytes.Buffer
	_ = binary.Write(&ihdr, binary.BigEndian, uint32(w))
	_ = binary.Write(&ihdr, binary.BigEndian, uint32(h))
	ihdr.Write([]byte{8, 2, 0, 0, 0}) // bit depth, color type, compression, filter, interlace
	writePNGChunk(&buf, "IHDR", ihdr.Bytes())
	writePNGChunk(&buf, "IDAT", []byte{0x08, 0xd7, 0x63, 0xf8, 0xcf, 0xc0, 0x00, 0x00, 0x00, 0x03, 0x00, 0x01})
	writePNGChunk(&buf, "IEND", nil)
	return buf.Bytes()
}

func writePNGChunk(buf *bytes.Buffer, name string, data []byte) {
	_ = binary.Write(buf, binary.BigEndian, uint32(len(data)))
	buf.WriteString(name)
	buf.Write(data)
	crc := crc32.NewIEEE()
	_, _ = crc.Write([]byte(name))
	_, _ = crc.Write(data)
	_ = binary.Write(buf, binary.BigEndian, crc.Sum32())
}