class Day6 {

    companion object {
        const val COM = "COM"
        const val YOU = "YOU"
        const val SANTA = "SAN"
    }

    /**
     * PART #1
     */
    fun doPart1(input: Array<String>): Int? {
        val dataMap = buildMap(input)
        return dataMap.map { countOrbits(it.value, dataMap) }.sum()
    }

    private fun buildMap(input: Array<String>) = input.map { it.split(')') }.associateBy({ it[1] }, { it[0] })

    private tailrec fun countOrbits(value: String, dataMap: Map<String, String>, orbits: Int = 1): Int {
        if (value == COM) return orbits
        return countOrbits(dataMap.getValue(value), dataMap, orbits + 1)
    }

    /**
     * PART #2
     */
    fun doPart2(input: Array<String>): Int? {
        val dataMap = buildMap(input)
        return listOf(YOU, SANTA)
            .map { buildPath(dataMap.getValue(it), dataMap) }
            .zipWithNext(function()).first().split(',').count()
    }

    private fun function(): (a: String, b: String) -> String {
        return { you, santa ->
            val commonPrefix = you.zip(santa).takeWhile { it.first == it.second }.map { it.first }.joinToString("")
            listOf(you, santa).joinToString(",") { it.removePrefix(commonPrefix) }
        }
    }

    private tailrec fun buildPath(value: String, dataMap: Map<String, String>, way: String = ""): String {
        if (value == COM) return way.dropLast(1)
        return buildPath(dataMap.getValue(value), dataMap, "$value,$way")
    }

}