Formats URLSpans with a %s placeholder into new URLSpans with vararg URLs

SpannedStringFormatter

// usage:
// spannedStringFormatter.format(context.getText(R.string.mystring), "url1", "url2"))
// where R.string.mystring is <string name="mystring"><![CDATA[ Link one <a href="%s"><b> Link one</b></a> and link two <a href="%s"><b>Link two</b></a>.]]></string>
class SpannedStringFormatter {
    /**
     * replace all the %s in the spanned string with corresponding URLs
     */
    fun format(format: CharSequence, vararg urls: String?): SpannedString {
        // make a spannable copy so that we can change the spans (Spanned is immutable)
        val spannableString = SpannableStringBuilder(String.format(format.toString(), *urls).toHtmlSpan())

        val oldUrlSpans = spannableString.getSpans(
            0, spannableString.length,
            URLSpan::class.java
        )

        oldUrlSpans.forEachIndexed { index, urlSpan ->
            // get the span range
            val start = spannableString.getSpanStart(urlSpan)
            val end = spannableString.getSpanEnd(urlSpan)

            // remove the old span
            spannableString.removeSpan(urlSpan)

            // add the new url span in the same place
            val underlineSpan = URLSpan(urls[index])
            spannableString.setSpan(underlineSpan, start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
        }

        return SpannedString(spannableString)
    }
}