/**
 * You can edit, run, and share this code.
 * play.kotlinlang.org
 */

import java.time.LocalDateTime
import java.time.temporal.ChronoUnit
import java.time.format.DateTimeFormatter

fun main() {
    val a = listOf("2017-03-10 08:13:11", "2017-03-10 19:01:27", "2017-03-11 07:35:55", "2017-03-11 16:15:11", "2017-03-12 08:01:41", "2017-03-12 17:19:08")
    val b = listOf("2017-03-10 18:58:11", "2017-03-10 19:01:27", "2017-03-11 07:35:55", "2017-03-11 16:15:11", "2017-03-12 08:01:41", "2017-03-12 17:19:08")
    val c = listOf("2017-03-08 17:11:13", "2017-03-11 17:22:47", "2017-03-11 19:23:51", "2017-03-11 22:03:12", "2017-03-12 08:32:04", "2017-03-12 13:19:08", "2017-03-12 17:19:08")

    val requiredLastDaysCount = 3
    val requiredSessionCount = 6

    val hasEnoughSessions = hasEnoughSessions(requiredSessionCount, c)
    val wasUsedForEnoughLastDays = wasUsedForLastDays(requiredLastDaysCount, c.asReversed())

    if (hasEnoughSessions and wasUsedForEnoughLastDays) {
        println("Ask user for the opinion")
    }
}

private fun wasUsedForLastDays(requiredLastDaysCount : Int, dates: List<String>) : Boolean {
    val format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")
    val lastOpenDate = LocalDateTime.parse(dates[0], format)

    for (day in 0..requiredLastDaysCount - 1) {
        var usedThatDay = false
        for (dateIndex in 1 until dates.size) {
            val currentDate = LocalDateTime.parse(dates[dateIndex], format)
            val dayDifference = Math.abs(ChronoUnit.DAYS.between(lastOpenDate, currentDate)).toInt()
            if (dayDifference == day){
                usedThatDay = true
            }
        }

        if (!usedThatDay) return false
    }

    return true
}

private fun hasEnoughSessions(requiredSessionCount: Int, dates: List<String>) : Boolean{
    var sessionCount = 0
    val indexesToExclude = mutableListOf<Int>()

    dates.forEachIndexed { index, date ->
        if (!indexesToExclude.contains(index)) {
            indexesToExclude.addAll(session(date, dates))
            sessionCount = sessionCount + 1
        }
    }

    return sessionCount >= requiredSessionCount
}

/**
 * Checks for the dates associated with the given session
 *
 * @date to check all of the other dates against
 * @dates list of all dates
 *
 * @returns indexes of the dates that are considered to be the same session
 */
private fun session(date: String, dates: List<String>): List<Int>{
    val sessionIndexes = mutableListOf<Int>()
    val format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")

    val date =  LocalDateTime.parse(date, format)
    dates.forEachIndexed { index, otherDateString ->
        val otherDate = LocalDateTime.parse(otherDateString, format)
        if (date.isSameSession(otherDate)) {
            sessionIndexes.add(index)
        }
    }

    return sessionIndexes
}

private fun LocalDateTime.isSameSession(otherDate: LocalDateTime) : Boolean {
     if (this != otherDate) {
          val difference = ChronoUnit.MINUTES.between(this, otherDate)
          if (difference <= 30) return true
        }
     return false
}