package captcha

import (
	"bytes"
	"encoding/base64"
	"image/png"
	"strings"
	"testing"
)

func TestDrawImageValidPNG(t *testing.T) {
	img := drawImage("ABCD")
	b64 := encodeToBase64(img)
	data, err := base64.StdEncoding.DecodeString(b64)
	if err != nil {
		t.Fatalf("base64 decode failed: %v", err)
	}

	decoded, err := png.Decode(bytes.NewReader(data))
	if err != nil {
		t.Fatalf("png decode failed: %v", err)
	}

	bounds := decoded.Bounds()
	if bounds.Dx() != 120 || bounds.Dy() != 40 {
		t.Fatalf("expected 120x40, got %dx%d", bounds.Dx(), bounds.Dy())
	}

	// Verify all characters in chars set can be drawn without panic
	for _, ch := range chars {
		_ = drawImage(strings.Repeat(string(ch), 4))
	}
}