Helpful extensions for java.util.Date

DateExtensions.kt

import java.text.SimpleDateFormat
import java.util.*
import java.util.concurrent.TimeUnit
import kotlin.math.round

val now: Date = Date()

val Date.daysFromToday: Long
    get() {
        val msDiff = now.time - this.time
        return TimeUnit.MILLISECONDS.toDays(msDiff)
    }

fun Date.format(format: String): String = SimpleDateFormat(format, Locale.ENGLISH).format(this)

fun Date.startOfDay(): Date {
    return Calendar.getInstance().apply {
        this.add(Calendar.DATE, round(daysFromToday.toDouble()).toInt())
        this.setMin(Calendar.HOUR_OF_DAY)
        this.setMin(Calendar.MINUTE)
        this.setMin(Calendar.SECOND)
        this.setMin(Calendar.MILLISECOND)
    }.time
}

fun Date.endOfDay(): Date {
    return Calendar.getInstance().apply {
        this.add(Calendar.DATE, round(daysFromToday.toDouble()).toInt())
        this.setMax(Calendar.HOUR_OF_DAY)
        this.setMax(Calendar.MINUTE)
        this.setMax(Calendar.SECOND)
        this.setMax(Calendar.MILLISECOND)
    }.time
}

private fun Calendar.setMax(field: Int) {
    set(field, getMaximum(field))
}

private fun Calendar.setMin(field: Int) {
    set(field, getMinimum(field))
}

fun Date.minusHours(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@minusHours
        this.add(Calendar.HOUR, -count)
    }.time
}

fun Date.plusHours(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@plusHours
        this.add(Calendar.HOUR, count)
    }.time
}

fun Date.plusDays(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@plusDays
        this.add(Calendar.DATE, count)
    }.time
}

fun Date.minusDays(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@minusDays
        this.add(Calendar.DATE, -count)
    }.time
}

fun Date.minusMinutes(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@minusMinutes
        this.add(Calendar.MINUTE, -count)
    }.time
}

fun Date.plusMinutes(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@plusMinutes
        this.add(Calendar.MINUTE, count)
    }.time
}

fun Date.minusSeconds(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@minusSeconds
        this.add(Calendar.SECOND, -count)
    }.time
}

fun Date.plusSeconds(count: Int): Date {
    return Calendar.getInstance().apply {
        this.time = this@plusSeconds
        this.add(Calendar.SECOND, count)
    }.time
}

fun Date.hour(): Int {
    return Calendar.getInstance().apply {
        this.time = this@hour
    }.get(Calendar.HOUR_OF_DAY)
}

fun Date.minutes(): Int {
    return Calendar.getInstance().apply {
        this.time = this@minutes
    }.get(Calendar.MINUTE)
}

val Date.dayOfWeek: Int
    get() = Calendar.getInstance().get(Calendar.DAY_OF_WEEK)

fun Date.isSunday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Sunday
fun Date.isMonday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Monday
fun Date.isTuesday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Tuesday
fun Date.isWednesday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Wednesday
fun Date.isThursday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Thursday
fun Date.isFriday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Friday
fun Date.isSaturday(): Boolean = Weekday.fromPosition(dayOfWeek) == Weekday.Saturday

sealed class Weekday(val weekPosition: Int) {
    object Sunday : Weekday(0)
    object Monday : Weekday(1)
    object Tuesday : Weekday(2)
    object Wednesday : Weekday(3)
    object Thursday : Weekday(4)
    object Friday : Weekday(5)
    object Saturday : Weekday(6)
    object Unknown : Weekday(-1)

    companion object {
        fun fromPosition(pos: Int): Weekday {
            return Weekday::class.nestedClasses
                    .map { klass -> klass.objectInstance }
                    .filterIsInstance<Weekday>()
                    .find { it.weekPosition == pos } ?: Unknown
        }
    }
}