Helper for writing simple csv files

CsvFileHelper.kt

package at.triply.eventoverview.api

import java.io.File

class CsvFileHelper(val file: File) {

    companion object {
        val SEPERATOR = ";"
    }

    private fun createIfNotExists() {
        if (!file.exists()) {
            file.mkdirs()
            file.createNewFile()
        }
    }

    init {
        createIfNotExists()
    }

    fun <T> writeData(data: List<T>, columns: List<CsvColumn<T>>, seperator: String = SEPERATOR) {
        val headers = columns.map(CsvColumn<T>::header).joinToString(seperator)
        val lines = data.map { item ->
            columns.joinToString(seperator) {
                it.encodeValue(item).run {
                    this as? String ?: it.toString()
                }
            }
        }

        file.bufferedWriter()
                .apply {
                    write(headers)
                    newLine()
                    lines.forEach {
                        write(it)
                        newLine()
                    }
                    flush()
                }
                .close()
    }


    class CsvColumn<in T>(val header: String, private val encoder: (T) -> Any) {
        fun encodeValue(value: T): Any {
            return encoder(value)
        }
    }
}