package dev.inmo.krontab.internal

import com.soywiz.klock.*
import dev.inmo.krontab.*
import dev.inmo.krontab.collection.plus

/**
 * Cron-oriented realisation of [KronScheduler] with taking into account [offset] for list of [cronDateTimes]
 *
 * @see CronDateTime
 */
internal data class CronDateTimeSchedulerTz internal constructor(
    internal val cronDateTimes: List<CronDateTime>,
    internal val offset: TimezoneOffset
) : KronSchedulerTz {
    override suspend fun next(relatively: DateTimeTz): DateTimeTz? {
        val dateTimeWithActualOffset = relatively.utc.toOffset(offset).local
        return cronDateTimes.mapNotNull {
            it.toNearDateTime(dateTimeWithActualOffset)
        }.minOrNull() ?.toOffset(relatively.offset)
    }
}

internal fun mergeCronDateTimeSchedulers(
    schedulers: List<CronDateTimeSchedulerTz>
) = schedulers.groupBy {
    it.offset
}.map { (offset, schedulers) ->
    CronDateTimeSchedulerTz(schedulers.flatMap { it.cronDateTimes }, offset)
}