//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

import CoreFoundation

/**
 `DateComponents` encapsulates the components of a date in an extendable, structured manner.
 
 It is used to specify a date by providing the temporal components that make up a date and time in a particular calendar: hour, minutes, seconds, day, month, year, and so on. It can also be used to specify a duration of time, for example, 5 hours and 16 minutes. A `DateComponents` is not required to define all the component fields.
 
 When a new instance of `DateComponents` is created, the date components are set to `nil`.
 */
public struct DateComponents : ReferenceConvertible, Hashable, Equatable, _MutableBoxing {
    public typealias ReferenceType = NSDateComponents
    
    internal var _handle: _MutableHandle<NSDateComponents>
    
    /// Initialize a `DateComponents`, optionally specifying values for its fields.
    public init(calendar: Calendar? = nil,
                timeZone: TimeZone? = nil,
                era: Int? = nil,
                year: Int? = nil,
                month: Int? = nil,
                day: Int? = nil,
                hour: Int? = nil,
                minute: Int? = nil,
                second: Int? = nil,
                nanosecond: Int? = nil,
                weekday: Int? = nil,
                weekdayOrdinal: Int? = nil,
                quarter: Int? = nil,
                weekOfMonth: Int? = nil,
                weekOfYear: Int? = nil,
                yearForWeekOfYear: Int? = nil) {
        _handle = _MutableHandle(adoptingReference: NSDateComponents())
        if let _calendar = calendar { self.calendar = _calendar }
        if let _timeZone = timeZone { self.timeZone = _timeZone }
        if let _era = era { self.era = _era }
        if let _year = year { self.year = _year }
        if let _month = month { self.month = _month }
        if let _day = day { self.day = _day }
        if let _hour = hour { self.hour = _hour }
        if let _minute = minute { self.minute = _minute }
        if let _second = second { self.second = _second }
        if let _nanosecond = nanosecond { self.nanosecond = _nanosecond }
        if let _weekday = weekday { self.weekday = _weekday }
        if let _weekdayOrdinal = weekdayOrdinal { self.weekdayOrdinal = _weekdayOrdinal }
        if let _quarter = quarter { self.quarter = _quarter }
        if let _weekOfMonth = weekOfMonth { self.weekOfMonth = _weekOfMonth }
        if let _weekOfYear = weekOfYear { self.weekOfYear = _weekOfYear }
        if let _yearForWeekOfYear = yearForWeekOfYear { self.yearForWeekOfYear = _yearForWeekOfYear }
    }
    
    
    // MARK: - Properties
    
    /// Translate from the NSDateComponentUndefined value into a proper Swift optional
    private func _getter(_ x : Int) -> Int? { return x == NSDateComponentUndefined ? nil : x }
    
    /// Translate from the proper Swift optional value into an NSDateComponentUndefined
    private func _setter(_ x : Int?) -> Int { if let xx = x { return xx } else { return NSDateComponentUndefined } }
    
    /// The `Calendar` used to interpret the other values in this structure.
    ///
    /// - note: API which uses `DateComponents` may have different behavior if this value is `nil`. For example, assuming the current calendar or ignoring certain values.
    public var calendar: Calendar? {
        get { return _handle.map { $0.calendar } }
        set { _applyMutation { $0.calendar = newValue } }
    }
    
    /// A time zone.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var timeZone: TimeZone? {
        get { return _handle.map { $0.timeZone } }
        set { _applyMutation { $0.timeZone = newValue } }
    }
    
    /// An era or count of eras.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var era: Int? {
        get { return _handle.map { _getter($0.era) } }
        set { _applyMutation { $0.era = _setter(newValue) } }
    }
    
    /// A year or count of years.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var year: Int? {
        get { return _handle.map { _getter($0.year) } }
        set { _applyMutation { $0.year = _setter(newValue) } }
    }
    
    /// A month or count of months.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var month: Int? {
        get { return _handle.map { _getter($0.month) } }
        set { _applyMutation { $0.month = _setter(newValue) } }
    }
    
    /// A day or count of days.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var day: Int? {
        get { return _handle.map { _getter($0.day) } }
        set { _applyMutation { $0.day = _setter(newValue) } }
    }
    
    /// An hour or count of hours.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var hour: Int? {
        get { return _handle.map { _getter($0.hour) } }
        set { _applyMutation { $0.hour = _setter(newValue) } }
    }
    
    /// A minute or count of minutes.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var minute: Int? {
        get { return _handle.map { _getter($0.minute) } }
        set { _applyMutation { $0.minute = _setter(newValue) } }
    }
    
    /// A second or count of seconds.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var second: Int? {
        get { return _handle.map { _getter($0.second) } }
        set { _applyMutation { $0.second = _setter(newValue) } }
    }
    
    /// A nanosecond or count of nanoseconds.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var nanosecond: Int? {
        get { return _handle.map { _getter($0.nanosecond) } }
        set { _applyMutation { $0.nanosecond = _setter(newValue) } }
    }
    
    /// A weekday or count of weekdays.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var weekday: Int? {
        get { return _handle.map { _getter($0.weekday) } }
        set { _applyMutation { $0.weekday = _setter(newValue) } }
    }
    
    /// A weekday ordinal or count of weekday ordinals.
    /// Weekday ordinal units represent the position of the weekday within the next larger calendar unit, such as the month. For example, 2 is the weekday ordinal unit for the second Friday of the month.///
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var weekdayOrdinal: Int? {
        get { return _handle.map { _getter($0.weekdayOrdinal) } }
        set { _applyMutation { $0.weekdayOrdinal = _setter(newValue) } }
    }
    
    /// A quarter or count of quarters.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var quarter: Int? {
        get { return _handle.map { _getter($0.quarter) } }
        set { _applyMutation { $0.quarter = _setter(newValue) } }
    }
    
    /// A week of the month or a count of weeks of the month.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var weekOfMonth: Int? {
        get { return _handle.map { _getter($0.weekOfMonth) } }
        set { _applyMutation { $0.weekOfMonth = _setter(newValue) } }
    }
    
    /// A week of the year or count of the weeks of the year.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var weekOfYear: Int? {
        get { return _handle.map { _getter($0.weekOfYear) } }
        set { _applyMutation { $0.weekOfYear = _setter(newValue) } }
    }
    
    /// The ISO 8601 week-numbering year of the receiver.
    ///
    /// The Gregorian calendar defines a week to have 7 days, and a year to have 356 days, or 366 in a leap year. However, neither 356 or 366 divide evenly into a 7 day week, so it is often the case that the last week of a year ends on a day in the next year, and the first week of a year begins in the preceding year. To reconcile this, ISO 8601 defines a week-numbering year, consisting of either 52 or 53 full weeks (364 or 371 days), such that the first week of a year is designated to be the week containing the first Thursday of the year.
    ///
    /// You can use the yearForWeekOfYear property with the weekOfYear and weekday properties to get the date corresponding to a particular weekday of a given week of a year. For example, the 6th day of the 53rd week of the year 2005 (ISO 2005-W53-6) corresponds to Sat 1 January 2005 on the Gregorian calendar.
    /// - note: This value is interpreted in the context of the calendar in which it is used.
    public var yearForWeekOfYear: Int? {
        get { return _handle.map { _getter($0.yearForWeekOfYear) } }
        set { _applyMutation { $0.yearForWeekOfYear = _setter(newValue) } }
    }
    
    /// Set to true if these components represent a leap month.
    public var isLeapMonth: Bool? {
        get { return _handle.map { $0.leapMonthSet ? $0.isLeapMonth : nil } }
        set {
            _applyMutation {
                // Technically, the underlying class does not support setting isLeapMonth to nil, but it could - so we leave the API consistent.
                if let b = newValue {
                    $0.isLeapMonth = b
                } else {
                    $0.isLeapMonth = false
                }
            }
        }
    }
    
    /// Returns a `Date` calculated from the current components using the `calendar` property.
    public var date: Date? {
        if let d = _handle.map({$0.date}) {
            return d as Date
        } else {
            return nil
        }
    }
    
    // MARK: - Generic Setter/Getters
    
    /// Set the value of one of the properties, using an enumeration value instead of a property name.
    ///
    /// The calendar and timeZone and isLeapMonth properties cannot be set by this method.
    public mutating func setValue(_ value: Int?, for component: Calendar.Component) {
        _applyMutation {
            $0.setValue(_setter(value), forComponent: Calendar._toCalendarUnit([component]))
        }
    }
    
    /// Returns the value of one of the properties, using an enumeration value instead of a property name.
    ///
    /// The calendar and timeZone and isLeapMonth property values cannot be retrieved by this method.
    public func value(for component: Calendar.Component) -> Int? {
        return _handle.map {
            $0.value(forComponent: Calendar._toCalendarUnit([component]))
        }
    }
    
    // MARK: -
    
    /// Returns true if the combination of properties which have been set in the receiver is a date which exists in the `calendar` property.
    ///
    /// This method is not appropriate for use on `DateComponents` values which are specifying relative quantities of calendar components.
    ///
    /// Except for some trivial cases (e.g., 'seconds' should be 0 - 59 in any calendar), this method is not necessarily cheap.
    ///
    /// If the time zone property is set in the `DateComponents`, it is used.
    ///
    /// The calendar property must be set, or the result is always `false`.
    public var isValidDate: Bool {
        return _handle.map { $0.isValidDate }
    }
    
    /// Returns true if the combination of properties which have been set in the receiver is a date which exists in the specified `Calendar`.
    ///
    /// This method is not appropriate for use on `DateComponents` values which are specifying relative quantities of calendar components.
    ///
    /// Except for some trivial cases (e.g., 'seconds' should be 0 - 59 in any calendar), this method is not necessarily cheap.
    ///
    /// If the time zone property is set in the `DateComponents`, it is used.
    public func isValidDate(in calendar: Calendar) -> Bool {
        return _handle.map { $0.isValidDate(in: calendar) }
    }
    
    // MARK: -
    
    public var hashValue: Int {
        return _handle.map { $0.hash }
    }
    
    public static func ==(lhs: DateComponents, rhs: DateComponents) -> Bool {
        // Don't copy references here; no one should be storing anything
        return lhs._handle._uncopiedReference().isEqual(rhs._handle._uncopiedReference())
    }
    
    // MARK: - Bridging Helpers
    
    internal init(reference: NSDateComponents) {
        _handle = _MutableHandle(reference: reference)
    }
}

extension DateComponents : CustomStringConvertible, CustomDebugStringConvertible, CustomReflectable {
    public var description: String {
        return _handle.map { $0.description }
    }
    
    public var debugDescription: String {
        return _handle.map { $0.debugDescription }
    }
    
    public var customMirror: Mirror {
        var c: [(label: String?, value: Any)] = []
        if let r = calendar { c.append((label: "calendar", value: r)) }
        if let r = timeZone { c.append((label: "timeZone", value: r)) }
        if let r = era { c.append((label: "era", value: r)) }
        if let r = year { c.append((label: "year", value: r)) }
        if let r = month { c.append((label: "month", value: r)) }
        if let r = day { c.append((label: "day", value: r)) }
        if let r = hour { c.append((label: "hour", value: r)) }
        if let r = minute { c.append((label: "minute", value: r)) }
        if let r = second { c.append((label: "second", value: r)) }
        if let r = nanosecond { c.append((label: "nanosecond", value: r)) }
        if let r = weekday { c.append((label: "weekday", value: r)) }
        if let r = weekdayOrdinal { c.append((label: "weekdayOrdinal", value: r)) }
        if let r = quarter { c.append((label: "quarter", value: r)) }
        if let r = weekOfMonth { c.append((label: "weekOfMonth", value: r)) }
        if let r = weekOfYear { c.append((label: "weekOfYear", value: r)) }
        if let r = yearForWeekOfYear { c.append((label: "yearForWeekOfYear", value: r)) }
        if let r = isLeapMonth { c.append((label: "isLeapMonth", value: r)) }
        return Mirror(self, children: c, displayStyle: Mirror.DisplayStyle.struct)
    }
}

// MARK: - Bridging

extension DateComponents : _ObjectTypeBridgeable {
    public static func _isBridgedToObjectiveC() -> Bool {
        return true
    }
    
    public static func _getObjectiveCType() -> Any.Type {
        return NSDateComponents.self
    }
    
    @_semantics("convertToObjectiveC")
    public func _bridgeToObjectiveC() -> NSDateComponents {
        return _handle._copiedReference()
    }
    
    public static func _forceBridgeFromObjectiveC(_ dateComponents: NSDateComponents, result: inout DateComponents?) {
        if !_conditionallyBridgeFromObjectiveC(dateComponents, result: &result) {
            fatalError("Unable to bridge \(DateComponents.self) to \(self)")
        }
    }
    
    public static func _conditionallyBridgeFromObjectiveC(_ dateComponents: NSDateComponents, result: inout DateComponents?) -> Bool {
        result = DateComponents(reference: dateComponents)
        return true
    }
    
    public static func _unconditionallyBridgeFromObjectiveC(_ source: NSDateComponents?) -> DateComponents {
        var result: DateComponents? = nil
        _forceBridgeFromObjectiveC(source!, result: &result)
        return result!
    }
}

extension DateComponents : Codable {
    private enum CodingKeys : Int, CodingKey {
        case calendar
        case timeZone
        case era
        case year
        case month
        case day
        case hour
        case minute
        case second
        case nanosecond
        case weekday
        case weekdayOrdinal
        case quarter
        case weekOfMonth
        case weekOfYear
        case yearForWeekOfYear
    }

    public init(from decoder: Decoder) throws {
        let container  = try decoder.container(keyedBy: CodingKeys.self)
        let calendar   = try container.decodeIfPresent(Calendar.self, forKey: .calendar)
        let timeZone   = try container.decodeIfPresent(TimeZone.self, forKey: .timeZone)
        let era        = try container.decodeIfPresent(Int.self, forKey: .era)
        let year       = try container.decodeIfPresent(Int.self, forKey: .year)
        let month      = try container.decodeIfPresent(Int.self, forKey: .month)
        let day        = try container.decodeIfPresent(Int.self, forKey: .day)
        let hour       = try container.decodeIfPresent(Int.self, forKey: .hour)
        let minute     = try container.decodeIfPresent(Int.self, forKey: .minute)
        let second     = try container.decodeIfPresent(Int.self, forKey: .second)
        let nanosecond = try container.decodeIfPresent(Int.self, forKey: .nanosecond)

        let weekday           = try container.decodeIfPresent(Int.self, forKey: .weekday)
        let weekdayOrdinal    = try container.decodeIfPresent(Int.self, forKey: .weekdayOrdinal)
        let quarter           = try container.decodeIfPresent(Int.self, forKey: .quarter)
        let weekOfMonth       = try container.decodeIfPresent(Int.self, forKey: .weekOfMonth)
        let weekOfYear        = try container.decodeIfPresent(Int.self, forKey: .weekOfYear)
        let yearForWeekOfYear = try container.decodeIfPresent(Int.self, forKey: .yearForWeekOfYear)

        self.init(calendar: calendar,
                  timeZone: timeZone,
                  era: era,
                  year: year,
                  month: month,
                  day: day,
                  hour: hour,
                  minute: minute,
                  second: second,
                  nanosecond: nanosecond,
                  weekday: weekday,
                  weekdayOrdinal: weekdayOrdinal,
                  quarter: quarter,
                  weekOfMonth: weekOfMonth,
                  weekOfYear: weekOfYear,
                  yearForWeekOfYear: yearForWeekOfYear)
    }

    public func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encodeIfPresent(self.calendar, forKey: .calendar)
        try container.encodeIfPresent(self.timeZone, forKey: .timeZone)
        try container.encodeIfPresent(self.era, forKey: .era)
        try container.encodeIfPresent(self.year, forKey: .year)
        try container.encodeIfPresent(self.month, forKey: .month)
        try container.encodeIfPresent(self.day, forKey: .day)
        try container.encodeIfPresent(self.hour, forKey: .hour)
        try container.encodeIfPresent(self.minute, forKey: .minute)
        try container.encodeIfPresent(self.second, forKey: .second)
        try container.encodeIfPresent(self.nanosecond, forKey: .nanosecond)

        try container.encodeIfPresent(self.weekday, forKey: .weekday)
        try container.encodeIfPresent(self.weekdayOrdinal, forKey: .weekdayOrdinal)
        try container.encodeIfPresent(self.quarter, forKey: .quarter)
        try container.encodeIfPresent(self.weekOfMonth, forKey: .weekOfMonth)
        try container.encodeIfPresent(self.weekOfYear, forKey: .weekOfYear)
        try container.encodeIfPresent(self.yearForWeekOfYear, forKey: .yearForWeekOfYear)
    }
}