InputParser.kt

package calculator.model.input

object InputParser {
    const val NON_NUMERIC_DEFAULT_VALUE = -1
    private val DEFAULT_DELIMITERS = arrayOf(",", ":")
    private val customDelimiterRegex: Regex by lazy {
        Regex("//(.)\n(.*)")
    }
    private val nonNumericCharacterRegex: Regex by lazy {
        Regex("-?\\d+")
    }

    fun parse(input: String?): List<Int> {
        if (input.isNullOrEmpty()) return listOf(0)
        val (customDelimiter, numberInput) = extractDelimiterAndNumbers(input)
        val delimiters = combineDelimiters(customDelimiter)
        val tokens = splitInputByDelimiters(numberInput, delimiters)
        val numbers = parseNonNegativeNumbers(tokens)
        val nonNumeric = extractNonNumericCharacters(numberInput)
        InputValidator.validateDelimiters(nonNumeric, delimiters)
        InputValidator.validateNumbers(numbers)
        return numbers
    }

    private fun extractDelimiterAndNumbers(input: String): DelimiterAndNumbers {
        val result = customDelimiterRegex.find(input)
        return if (result != null) {
            val customDelimiter = result.groupValues[1]
            val numbers = result.groupValues[2]
            DelimiterAndNumbers(customDelimiter, numbers)
        } else {
            DelimiterAndNumbers(null, input)
        }
    }

    private fun combineDelimiters(customDelimiter: String?): Array<String> {
        return mutableListOf(*DEFAULT_DELIMITERS).apply {
            customDelimiter?.let(::add)
        }.toTypedArray()
    }

    private fun splitInputByDelimiters(
        numberInput: String,
        delimiters: Array<String>,
    ): List<String> {
        return numberInput.split(*delimiters)
    }

    private fun parseNonNegativeNumbers(tokens: List<String>): List<Int> {
        return tokens.map { token ->
            token.toIntOrNull() ?: NON_NUMERIC_DEFAULT_VALUE
        }
    }

    private fun extractNonNumericCharacters(input: String): List<String> {
        return input.replace(nonNumericCharacterRegex, "").trim()
            .map { "$it" }
    }
}