Foundation+TimeAgo.swift

//
//  Foundation+TimeAgo.swift
//
//  The MIT License (MIT)
//
//  Copyright (c) 2015-present patrick piemonte (http://patrickpiemonte.com/)
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

extension Date {

    public var millisecondsSince1970: Int {
        Int((self.timeIntervalSince1970 * 1000.0).rounded())
    }

    public var yesterday: Date {
        Calendar.current.date(byAdding: .day, value: -1, to: self)!
    }

    public func hoursFromNow() -> Int {
        let date = Date()
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }

    public func minutesFromNow() -> Int {
        let date = Date()
        return Calendar.current.dateComponents([.minute], from: date, to: self).hour ?? 0
    }

    public func hours(from date: Date) -> Int {
        Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }

    public func minutes(from date: Date) -> Int {
        Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }

    private static let shortPrettyDateFormatter = DateFormatter()
    /// Returns a short pretty date.
    /// - Returns: Formatted date string.
    public func shortPrettyDate() -> String {
        Date.shortPrettyDateFormatter.dateFormat = "M/d/yy"
        return Date.shortPrettyDateFormatter.string(from: self)
    }

    private static let shortPrettyDateAndTimeFormatter = DateFormatter()
    /// Returns a short pretty date and time.
    /// - Returns: Formatted date and time string.
    public func shortPrettyDateTime() -> String {
        Date.shortPrettyDateAndTimeFormatter.dateFormat = "M/d/yyyy h:mma"
        return Date.shortPrettyDateAndTimeFormatter.string(from: self)
    }

    private static let prettyDateFormatter = DateFormatter()
    /// Return a short pretty date.
    /// - Returns: Formatted date string.
    public func prettyDate() -> String {
        Date.prettyDateFormatter.dateFormat = "MMMM yyyy"
        return Date.prettyDateFormatter.string(from: self)
    }

    private static let fullPrettyDateFormatter = DateFormatter()
    /// Return a short pretty date.
    /// - Returns: Formatted date string.
    public func fullPrettyDate() -> String {
        Date.prettyDateFormatter.dateFormat = "MMMM d, yyyy"
        return Date.prettyDateFormatter.string(from: self)
    }

    /// Create a pretty formatted string of time passed based on the date components, ex: "Last month", "2 weeks ago", "Just now"
    /// - Parameter numericDates: A flag to determine if a numerical string should be used, ex: "An hour ago" vs "1 hour ago".
    /// - Returns: Formatted string of time passed.
    public func timeAgo(numericDates: Bool = true) -> String {
        let calendar = Calendar.current
        let now = Date()
        let earliest = self < now ? self : now
        let latest =  self > now ? self : now

        let unitFlags: Set<Calendar.Component> = [.minute, .hour, .day, .weekOfMonth, .month, .year, .second]
        let components: DateComponents = calendar.dateComponents(unitFlags, from: earliest, to: latest)

        let year = components.year ?? 0
        let month = components.month ?? 0
        let weekOfMonth = components.weekOfMonth ?? 0
        let day = components.day ?? 0
        let hour = components.hour ?? 0
        let minute = components.minute ?? 0
        let second = components.second ?? 0

        switch (year, month, weekOfMonth, day, hour, minute, second) {
        case (let year, _, _, _, _, _, _) where year >= 2: return NSLocalizedString("\(year) years ago", comment: "\(year) years ago")
        case (let year, _, _, _, _, _, _) where year == 1 && numericDates: return NSLocalizedString("1 year ago", comment: "1 year ago")
        case (let year, _, _, _, _, _, _) where year == 1 && !numericDates: return NSLocalizedString("Last year", comment: "Last year")
        case (_, let month, _, _, _, _, _) where month >= 2: return NSLocalizedString("\(month) months ago", comment: "\(month) months ago")
        case (_, let month, _, _, _, _, _) where month == 1 && numericDates: return NSLocalizedString("1 month ago", comment: "1 month ago")
        case (_, let month, _, _, _, _, _) where month == 1 && !numericDates: return NSLocalizedString("Last month", comment: "Last month")
        case (_, _, let weekOfMonth, _, _, _, _) where weekOfMonth >= 2: return NSLocalizedString("\(weekOfMonth) weeks ago", comment: "\(weekOfMonth) weeks ago")
        case (_, _, let weekOfMonth, _, _, _, _) where weekOfMonth == 1 && numericDates: return NSLocalizedString("1 week ago", comment: "1 week ago")
        case (_, _, let weekOfMonth, _, _, _, _) where weekOfMonth == 1 && !numericDates: return NSLocalizedString("Last week", comment: "Last week")
        case (_, _, _, let day, _, _, _) where day >= 2: return NSLocalizedString("\(day) days ago", comment: "\(day) days ago")
        case (_, _, _, let day, _, _, _) where day == 1 && numericDates: return NSLocalizedString("1 day ago", comment: "1 day ago")
        case (_, _, _, let day, _, _, _) where day == 1 && !numericDates: return NSLocalizedString("Yesterday", comment: "Yesterday")
        case (_, _, _, _, let hour, _, _) where hour >= 2: return NSLocalizedString("\(hour) hours ago", comment: "\(hour) hours ago")
        case (_, _, _, _, let hour, _, _) where hour == 1 && numericDates: return NSLocalizedString("1 hour ago", comment: "1 hour ago")
        case (_, _, _, _, let hour, _, _) where hour == 1 && !numericDates: return NSLocalizedString("An hour ago", comment: "An hour ago")
        case (_, _, _, _, _, let minute, _) where minute >= 2: return NSLocalizedString("\(minute) minutes ago", comment: "\(minute) minutes ago")
        case (_, _, _, _, _, let minute, _) where minute == 1 && numericDates: return NSLocalizedString("1 minute ago", comment: "1 minute ago")
        case (_, _, _, _, _, let minute, _) where minute == 1 && !numericDates: return NSLocalizedString("A minute ago", comment: "A minute ago")
        case (_, _, _, _, _, _, let second) where second >= 3: return NSLocalizedString("\(second) seconds ago", comment: "\(second) seconds ago")
        default: return NSLocalizedString("Just now", comment: "Just now")
        }
    }

    /// Create a short pretty formatted string of time passed based on the date components, ex: "2y", "2mo", "now".
    /// - Returns: Short formatted string of time passed.
    public func shortTimeAgo() -> String {
        let calendar = Calendar.current
        let now = Date()
        let earliest = self < now ? self : now
        let latest =  self > now ? self : now

        let unitFlags: Set<Calendar.Component> = [.minute, .hour, .day, .weekOfMonth, .month, .year, .second]
        let components: DateComponents = calendar.dateComponents(unitFlags, from: earliest, to: latest)

        let year = components.year ?? 0
        let month = components.month ?? 0
        let weekOfMonth = components.weekOfMonth ?? 0
        let day = components.day ?? 0
        let hour = components.hour ?? 0
        let minute = components.minute ?? 0
        let second = components.second ?? 0

        switch (year, month, weekOfMonth, day, hour, minute, second) {
        case (let year, _, _, _, _, _, _) where year >= 1: return NSLocalizedString("\(year)y", comment: "\(year)y")
        case (_, let month, _, _, _, _, _) where month >= 1: return NSLocalizedString("\(month)mo", comment: "\(month)mo")
        case (_, _, let weekOfMonth, _, _, _, _) where weekOfMonth >= 1: return NSLocalizedString("\(weekOfMonth)w", comment: "\(weekOfMonth)w")
        case (_, _, _, let day, _, _, _) where day >= 1: return NSLocalizedString("\(day)d", comment: "\(day)d")
        case (_, _, _, _, let hour, _, _) where hour >= 1: return NSLocalizedString("\(hour)h", comment: "\(hour)h")
        case (_, _, _, _, _, let minute, _) where minute >= 1: return NSLocalizedString("\(minute)m", comment: "\(minute)m")
        case (_, _, _, _, _, _, let second) where second >= 0: return NSLocalizedString("\(second)s", comment: "\(second)s")
        default: return NSLocalizedString("now", comment: "now")
        }
    }

}