package htmlimg_test

import (
	"bytes"
	"encoding/base64"
	"image"
	"image/color"
	"image/png"
	"math/rand/v2"
	"regexp"
	"testing"

	"github.com/stretchr/testify/require"

	"git.samanthony.xyz/htmlimg"
)

var tagExpr = regexp.MustCompile(`^<img src="data:image/png;base64,([A-Za-z0-9+/=]+)">$`)

func TestOutputMatchRegexp(t *testing.T) {
	t.Parallel()
	img := newImg(16)
	tag, err := htmlimg.Encode(img)
	require.NoError(t, err)
	require.Regexp(t, tagExpr, tag)
}

func TestDecodeImg(t *testing.T) {
	t.Parallel()

	img := newImg(16)

	// Encode <img> tag
	tag, err := htmlimg.Encode(img)
	require.NoError(t, err)
	t.Log(tag)

	// Extract and decode base64 data from tag to get png data
	groups := tagExpr.FindStringSubmatch(string(tag))
	require.Len(t, groups, 2)
	b64 := groups[1]
	decPng, err := base64.StdEncoding.DecodeString(b64)
	require.NoError(t, err)

	// Decoded png should match original image's png
	encPng := new(bytes.Buffer)
	err = png.Encode(encPng, img)
	require.NoError(t, err)
	require.Equal(t, encPng.Bytes(), decPng)
}

func BenchmarkEncode(b *testing.B) {
	img := newImg(1024)
	for b.Loop() {
		htmlimg.Encode(img)
	}
}

func newImg(size int) image.Image {
	w, h := size, size
	img := image.NewNRGBA(image.Rect(0, 0, w, h))
	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			img.Set(x, y, color.NRGBA{
				R: uint8(rand.IntN(256)),
				G: uint8(rand.IntN(256)),
				B: uint8(rand.IntN(256)),
				A: uint8(rand.IntN(256)),
			})
		}
	}
	return img
}