*.kt

import java.nio.file.Path
import kotlin.io.path.*

class PrefixPair(
    val indent: String = "",
    val before: String = "",
)

class Prefix(
    val pre: PrefixPair = PrefixPair(),
    val post: PrefixPair = PrefixPair(),
)

val NO_PREFIX = Prefix(
    PrefixPair("", ""),
    PrefixPair("", "")
)

val PIPES_PREFIX = Prefix(
    PrefixPair("│   ", "├── "),
    PrefixPair("    ", "└── ")
)

fun drawFileTree(
    prefix: Prefix,
    dir: Path,
    margin: String,
    out: StringBuilder
) {
    val entries = dir.listDirectoryEntries()

    entries.forEachIndexed { ix, entry ->
        val p = if (ix < entries.size - 1) prefix.pre else prefix.post

        out.append("$margin${p.before}${entry.name}")

        if (entry.isDirectory()) {
            out.append("/\n")

            drawFileTree(PIPES_PREFIX, entry, "$margin${p.indent}", out)
        } else {
            out.append("\n")
        }
    }
}

fun drawFileTree(output: Path): String =
    "${StringBuilder().also { drawFileTree(NO_PREFIX, output, "", it) }}"

fun main() {
    println(drawFileTree(
        Path(".")
    ))
}