package xyz.driver.core

import java.text.SimpleDateFormat
import java.time.{Clock, Instant, ZoneId, ZoneOffset}
import java.util._
import java.util.concurrent.TimeUnit

import xyz.driver.core.date.Month

import scala.concurrent.duration._
import scala.language.implicitConversions
import scala.util.Try

object time {

  // The most useful time units
  val Second  = 1000L
  val Seconds = Second
  val Minute  = 60 * Seconds
  val Minutes = Minute
  val Hour    = 60 * Minutes
  val Hours   = Hour
  val Day     = 24 * Hours
  val Days    = Day
  val Week    = 7 * Days
  val Weeks   = Week

  final case class Time(millis: Long) extends AnyVal {

    def isBefore(anotherTime: Time): Boolean = implicitly[Ordering[Time]].lt(this, anotherTime)

    def isAfter(anotherTime: Time): Boolean = implicitly[Ordering[Time]].gt(this, anotherTime)

    def advanceBy(duration: Duration): Time = Time(millis + duration.toMillis)

    def durationTo(anotherTime: Time): Duration = Duration.apply(anotherTime.millis - millis, TimeUnit.MILLISECONDS)

    def durationFrom(anotherTime: Time): Duration = Duration.apply(millis - anotherTime.millis, TimeUnit.MILLISECONDS)

    def toDate(timezone: TimeZone): date.Date = {
      val cal = Calendar.getInstance(timezone)
      cal.setTimeInMillis(millis)
      date.Date(cal.get(Calendar.YEAR), date.Month(cal.get(Calendar.MONTH)), cal.get(Calendar.DAY_OF_MONTH))
    }

    def toInstant: Instant = Instant.ofEpochMilli(millis)
  }

  object Time {
    implicit def timeOrdering: Ordering[Time] = Ordering.by(_.millis)

    implicit def apply(instant: Instant): Time = Time(instant.toEpochMilli)
  }

  /**
    * Encapsulates a time and timezone without a specific date.
    */
  final case class TimeOfDay(localTime: java.time.LocalTime, timeZone: TimeZone) {

    /**
      * Is this time before another time on a specific day. Day light savings safe. These are zero-indexed
      * for month/day.
      */
    def isBefore(other: TimeOfDay, day: Int, month: Month, year: Int): Boolean = {
      toCalendar(day, month, year).before(other.toCalendar(day, month, year))
    }

    /**
      * Is this time after another time on a specific day. Day light savings safe.
      */
    def isAfter(other: TimeOfDay, day: Int, month: Month, year: Int): Boolean = {
      toCalendar(day, month, year).after(other.toCalendar(day, month, year))
    }

    def sameTimeAs(other: TimeOfDay, day: Int, month: Month, year: Int): Boolean = {
      toCalendar(day, month, year).equals(other.toCalendar(day, month, year))
    }

    /**
      * Enforces the same formatting as expected by [[java.sql.Time]]
      * @return string formatted for `java.sql.Time`
      */
    def timeString: String = {
      localTime.format(TimeOfDay.getFormatter)
    }

    /**
      * @return a string parsable by [[java.util.TimeZone]]
      */
    def timeZoneString: String = {
      timeZone.getID
    }

    /**
      * @return this [[TimeOfDay]] as [[java.sql.Time]] object, [[java.sql.Time.valueOf]] will
      *         throw when the string is not valid, but this is protected by [[timeString]] method.
      */
    def toTime: java.sql.Time = {
      java.sql.Time.valueOf(timeString)
    }

    private def toCalendar(day: Int, month: Int, year: Int): Calendar = {
      val cal = Calendar.getInstance(timeZone)
      cal.set(year, month, day, localTime.getHour, localTime.getMinute, localTime.getSecond)
      cal.clear(Calendar.MILLISECOND)
      cal
    }
  }

  object TimeOfDay {
    def now(): TimeOfDay = {
      TimeOfDay(java.time.LocalTime.now(), TimeZone.getDefault)
    }

    /**
      * Throws when [s] is not parsable by [[java.time.LocalTime.parse]], uses default [[java.util.TimeZone]]
      */
    def parseTimeString(tz: TimeZone = TimeZone.getDefault)(s: String): TimeOfDay = {
      TimeOfDay(java.time.LocalTime.parse(s), tz)
    }

    def fromString(tz: TimeZone)(s: String): Option[TimeOfDay] = {
      val op = Try(java.time.LocalTime.parse(s)).toOption
      op.map(lt => TimeOfDay(lt, tz))
    }

    def fromStrings(zoneId: String)(s: String): Option[TimeOfDay] = {
      val op = Try(TimeZone.getTimeZone(zoneId)).toOption
      op.map(tz => TimeOfDay.parseTimeString(tz)(s))
    }

    /**
      * Formatter that enforces `HH:mm:ss` which is expected by [[java.sql.Time]]
      */
    def getFormatter: java.time.format.DateTimeFormatter = {
      java.time.format.DateTimeFormatter.ofPattern("HH:mm:ss")
    }
  }

  final case class TimeRange(start: Time, end: Time) {
    def duration: Duration = FiniteDuration(end.millis - start.millis, MILLISECONDS)
  }

  def startOfMonth(time: Time) = {
    Time(make(new GregorianCalendar()) { cal =>
      cal.setTime(new Date(time.millis))
      cal.set(Calendar.DAY_OF_MONTH, cal.getActualMinimum(Calendar.DAY_OF_MONTH))
    }.getTime.getTime)
  }

  def textualDate(timezone: TimeZone)(time: Time): String =
    make(new SimpleDateFormat("MMMM d, yyyy"))(_.setTimeZone(timezone)).format(new Date(time.millis))

  def textualTime(timezone: TimeZone)(time: Time): String =
    make(new SimpleDateFormat("MMM dd, yyyy hh:mm:ss a"))(_.setTimeZone(timezone)).format(new Date(time.millis))

  class ChangeableClock(@volatile var instant: Instant, val zone: ZoneId = ZoneOffset.UTC) extends Clock {

    def tick(duration: FiniteDuration): Unit =
      instant = instant.plusNanos(duration.toNanos)

    val getZone: ZoneId = zone

    def withZone(zone: ZoneId): Clock = new ChangeableClock(instant, zone = zone)

    override def toString: String = "ChangeableClock(" + instant + "," + zone + ")"
  }

  object provider {

    /**
      * Time providers are supplying code with current times
      * and are extremely useful for testing to check how system is going
      * to behave at specific moments in time.
      *
      * All the calls to receive current time must be made using time
      * provider injected to the caller.
      */
    @deprecated(
      "Use java.time.Clock instead. Note that xyz.driver.core.Time and xyz.driver.core.date.Date will also be deprecated soon!",
      "0.13.0")
    trait TimeProvider {
      def currentTime(): Time
      def toClock: Clock
    }

    final implicit class ClockTimeProvider(clock: Clock) extends TimeProvider {
      def currentTime(): Time = Time(clock.instant().toEpochMilli)

      val toClock: Clock = clock
    }

    final class SystemTimeProvider extends TimeProvider {
      def currentTime() = Time(System.currentTimeMillis())

      lazy val toClock: Clock = Clock.systemUTC()
    }

    final val SystemTimeProvider = new SystemTimeProvider

    final class SpecificTimeProvider(time: Time) extends TimeProvider {

      def currentTime(): Time = time

      lazy val toClock: Clock = Clock.fixed(time.toInstant, ZoneOffset.UTC)
    }

  }
}