newcode.kt

import android.text.Editable
import android.text.TextWatcher
import android.widget.EditText
import java.text.DecimalFormatSymbols

fun EditText.addThousandSeparator() {
    this.addTextChangedListener(object : TextWatcher {
        private var current = ""
        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}

        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}

        override fun afterTextChanged(s: Editable?) {
            if (s.toString() != current) {
                val userInput = s.toString().replace("[^\\d]".toRegex(), "")
                if (userInput.isNotEmpty()) {
                    val formatted = StringBuilder()
                    val symbols = DecimalFormatSymbols.getInstance()
                    val separator = symbols.groupingSeparator

                    var counter = 0
                    for (i in userInput.length - 1 downTo 0) {
                        formatted.append(userInput[i])
                        counter++
                        if (counter % 3 == 0 && i != 0) {
                            formatted.append(separator)
                        }
                    }
                    current = formatted.reverse().toString()

                    val selectionStart = this@addThousandSeparator.selectionStart
                    val selectionEnd = this@addThousandSeparator.selectionEnd

                    this@addThousandSeparator.removeTextChangedListener(this)
                    this@addThousandSeparator.setText(current)
                    this@addThousandSeparator.setSelection(calculateCursorPosition(selectionStart, selectionEnd, current))
                    this@addThousandSeparator.addTextChangedListener(this)
                }
            }
        }
    })
}

private fun calculateCursorPosition(start: Int, end: Int, text: String): Int {
    val symbols = DecimalFormatSymbols.getInstance()
    val separator = symbols.groupingSeparator
    var newPosition = start

    for (i in 0 until start) {
        if (text[i] == separator) {
            newPosition++
        }
    }

    return newPosition.coerceAtMost(text.length)
}