"Time ago" em Swift

Timeago-ahead.swift

/// Based on https://gist.github.com/jinthagerman/009c85b7bbd0a40dcbba747e89a501bf
import UIKit

struct DateComponentUnitFormatter {
    
    private struct DateComponentUnitFormat {
        let unit: Calendar.Component
        
        let singularUnit: String
        let pluralUnit: String
        
        let futureSingular: String
        let pastSingular: String
    }
    
    private let formats: [DateComponentUnitFormat] = [
        
        DateComponentUnitFormat(unit: .day,
                                singularUnit: "dia",
                                pluralUnit: "dias",
                                futureSingular: "amanhã",
                                pastSingular: "ontem"),
        
        DateComponentUnitFormat(unit: .hour,
                                singularUnit: "hora",
                                pluralUnit: "horas",
                                futureSingular: "em 1 hora",
                                pastSingular: "há 1 hora"),
        
        DateComponentUnitFormat(unit: .minute,
                                singularUnit: "minuto",
                                pluralUnit: "minutos",
                                futureSingular: "em 1 minuto",
                                pastSingular: "há 1 minuto"),
        
        ]
    
    func string(_ date: Date, forDateComponents dateComponents: DateComponents, useNumericDates: Bool) -> String {
        for format in self.formats {
            
            let unitValue: Int
            
            // MARK: - Get difference, in case.
            
            switch format.unit {
            case .day:
                unitValue = dateComponents.day ?? 0
            case .hour:
                unitValue = dateComponents.hour ?? 0
            case .minute:
                unitValue = dateComponents.minute ?? 0
            default:
                assertionFailure("Date does not have requried components")
                return ""
            }
            
            // MARK: - 1 day difference handling
            
            // Set formatter
            let formatter = DateFormatter()
            // Portuguese-BR
            formatter.locale = Locale(identifier: "pt_BR")
            let absoluteUnitValue = abs(unitValue)
            
            // Checks if is 1 day difference
            let todayDay = Calendar.current.component(.day, from: Date())
            let dateDay = Calendar.current.component(.day, from: date)
            
            if abs(todayDay - dateDay) == 1 {
                
                let day = todayDay > dateDay ? "ontem" : "amanhã"
                
                formatter.dateFormat = "'\(day) às' HH:mm"
                
                return formatter.string(from: date)
            }
            
            // MARK: - Handle date difference
            
            switch (format.unit, absoluteUnitValue){
            case (_, 0):
                break
                
            // Over 7 days
            case (.day, 7...Int.max):
                
                // Same year?
                let todayYear = Calendar.current.component(.year, from: Date())
                let dateYear = Calendar.current.component(.year, from: date)
                
                if todayYear != dateYear{
                    // Different years, change date to "EEEEEE, dd/MM/yy".
                    formatter.dateFormat = "EEEEEE, dd/MM/yy"
                }else {
                    // Same year, more detail on date difference
                    formatter.dateFormat = "dd 'de' MMMM 'às' HH:mm"
                }
                
                return formatter.string(from: date)
                
            // 1 to 7 days
            case (.day, 1..<7):
                
                formatter.dateFormat = "EEEE, 'às' HH:mm"
                return formatter.string(from: date)
                
            case (.hour, 0...Int.max), (.minute, 5...Int.max):
                // Same day
                let prefix = unitValue > 0 ? "há" : "em"
                
                return "\(prefix) \(absoluteUnitValue) \(absoluteUnitValue == 1 ? format.singularUnit : format.pluralUnit)"
                
            default:
                break
            }
            
        }
        // Under 5 minutes.
        return "agora"
    }
    
}

extension Date {
    
    func timeAgoSinceNow(useNumericDates: Bool = false) -> String {
        
        let calendar = Calendar.current
        let unitFlags: Set<Calendar.Component> = [.minute, .hour, .day]
        let now = Date()
        let components = calendar.dateComponents(unitFlags, from: self, to: now)
        
        let formatter = DateComponentUnitFormatter()
        return formatter.string(self, forDateComponents: components, useNumericDates: useNumericDates)
    }
}