HoursPicker.swift

private struct OrderTime: Sequence, IteratorProtocol {
    
    struct DayHour {
        let date: Date
        let hours: [Date]
    }
    
    let minimumDate: Date
    let maximumDate: Date
    
    init(minimumDate: Date, maximumDate: Date) {
        self.minimumDate = minimumDate
        self.maximumDate = maximumDate
    }
    
    var underestimatedCount: Int {
        if let workOffDate = Date(hour: 17, minute: 0, second: 0, nanosecond: 0),
                  let endDate = Date()?.end(of: .day),
                  minimumDate > workOffDate, minimumDate < endDate {
            /// offset date 在当天下班时间之后
            return Swift.max(0, maximumDate.daysSince(minimumDate).int - 1)
        } else {
            return Swift.max(0, maximumDate.daysSince(minimumDate).int)
        }
    }
    
    private var offsetDay = 0
    private var offsetDate = Date()
    
    mutating func next() -> DayHour? {
        defer {
            offsetDay += 1
        }
        
        offsetDate = minimumDate.adding(.day, value: offsetDay)
        
        guard offsetDate < maximumDate else {
            return nil
        }
        
        if let workOnDate = Date(hour: 8, minute: 0, second: 0, nanosecond: 0),
           let workOffDate = Date(hour: 17, minute: 0, second: 0, nanosecond: 0),
           offsetDate > workOnDate, offsetDate < workOffDate {
            /// offset date 在当天工作时间内
            let hours = (Swift.max(workOnDate.hour, offsetDate.hour)...Swift.min(workOffDate.hour, offsetDate.hour))
                .compactMap({ Date(year: offsetDate.year, month: offsetDate.month, day: offsetDate.day, hour: $0, minute: 0, second: 0, nanosecond: 0) })
            return hours.isEmpty ? nil : DayHour(date: offsetDate, hours: hours)
        } else if let workOffDate = Date(hour: 17, minute: 0, second: 0, nanosecond: 0),
                  let endDate = Date()?.end(of: .day),
                  offsetDate > workOffDate, offsetDate < endDate {
            /// offset date 在当天下班时间之后
            return nil
        } else {
            let hours = (8...17).compactMap({ Date(year: offsetDate.year, month: offsetDate.month, day: offsetDate.day, hour: $0, minute: 0, second: 0, nanosecond: 0) })
            return hours.isEmpty ? nil : DayHour(date: offsetDate, hours: hours)
        }
    }
}