Calculate the days in a given year that are the most or least 'Blue'

BlueDays.swift

import UIKit

enum Blueness: String {
    case Most, Least
}

// Print out the days in a given year that are the most or least 'Blue'
func blueDays(`in` year: Int, blueness: Blueness) {
    
    // Generate dates for each day for the given year
    func days(inYear year: Int) -> [Date] {
        let calendar = Calendar(identifier: .gregorian)
        var comps = calendar.dateComponents([.day, .month, .year], from: Date())
        comps.year = year
        
        comps.day = 1
        comps.month = 1
        let jan1 = calendar.date(from: comps)!

        comps.day = 31
        comps.month = 12
        let dec31 = calendar.date(from: comps)!

        var days = [Date]()
        var head = jan1
        while head <= dec31 {
            days.append(head)
            head = Calendar.current.date(byAdding: .day, value: 1, to: head)!
        }
        return days
    }

    // Data type to wrap up all information about a colour
    struct ColourComponenets {
        let hex: String
        let amountOfBlue: CGFloat
        let colour: UIColor
        
        var hexSixDigits: String {
            let index = hex.index(hex.startIndex, offsetBy: 6)
            return String(hex[..<index])
        }
    }

    // Convert a hex into a color, capturing the blue RBG value in the componenets
    // Assumes hex is 8 digits long
    func colourComponenets(from hex: String) -> ColourComponenets {
        let r, g, b, a: CGFloat
        
        let scanner = Scanner(string: hex)
        var hexNumber: UInt64 = 0
        
        scanner.scanHexInt64(&hexNumber)
        
        r = CGFloat((hexNumber & 0xff000000) >> 24)
        g = CGFloat((hexNumber & 0x00ff0000) >> 16)
        b = CGFloat((hexNumber & 0x0000ff00) >> 8)
        a = CGFloat(hexNumber & 0x000000ff)
        
        let colour = UIColor(red: r / 255, green: g / 255, blue: b / 255, alpha: a / 255)
        
        return ColourComponenets(hex: hex, amountOfBlue: b, colour: colour)
    }
    
    // Lightweight type to bind a date to it's colour componenets
    typealias DatAndColourComponents = (date: Date, colourComponenets: ColourComponenets)
    
    // MAIN ALGORITHM
    // Get all the days in the given year
    let daysThisYear = days(inYear: year)
    
    // Get the colour value for each day by converting the unix time stamp into a hex value
    let colouredDays: [DatAndColourComponents] = daysThisYear.map { day in
        let hex = String(Int(day.timeIntervalSince1970), radix: 16)
        let comps = colourComponenets(from: hex)
        return (day, comps)
    }

    // Find the days that have the most / least blueness
    let sortedByBlue = colouredDays.sorted { a, b in
        switch blueness {
        case .Least: return a.colourComponenets.amountOfBlue < b.colourComponenets.amountOfBlue
        case .Most : return a.colourComponenets.amountOfBlue > b.colourComponenets.amountOfBlue
        }
    }
    let maxValue = sortedByBlue.first!.colourComponenets.amountOfBlue
    let blueDays = sortedByBlue.filter { $0.colourComponenets.amountOfBlue == maxValue } // could be multiple days with the same blue value

    // Print out the days
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "E d MMM"
    print("\(blueness.rawValue) 'Blue' Days in \(year)")
    for day in blueDays {
        print("\t\(dateFormatter.string(from: day.date)). Blue \(day.colourComponenets.amountOfBlue), #\(day.colourComponenets.hexSixDigits)")
    }
    print("")
}


// Most and Least 'Blue' days in the next 5 years
blueDays(in: 2022, blueness: .Least)
blueDays(in: 2022, blueness: .Most)
blueDays(in: 2023, blueness: .Least)
blueDays(in: 2023, blueness: .Most)
blueDays(in: 2024, blueness: .Least)
blueDays(in: 2024, blueness: .Most)
blueDays(in: 2025, blueness: .Most)
blueDays(in: 2025, blueness: .Most)
blueDays(in: 2026, blueness: .Least)
blueDays(in: 2026, blueness: .Most)
blueDays(in: 2027, blueness: .Least)
blueDays(in: 2027, blueness: .Most)

Running this in a Swift Playground you get:

Least 'Blue' Days in 2022
	Sun 9 Oct. Blue 0.0, #634200

Most 'Blue' Days in 2022
	Sat 17 Sep. Blue 255.0, #6324ff

Least 'Blue' Days in 2023
	Sun 11 Jun. Blue 0.0, #648500

Most 'Blue' Days in 2023
	Sat 18 Mar. Blue 255.0, #6414ff
	Sat 20 May. Blue 255.0, #6467ff
	Sun 10 Dec. Blue 255.0, #6574ff

Least 'Blue' Days in 2024
	Mon 1 Jan. Blue 0.0, #659200

Most 'Blue' Days in 2024
	Sun 13 Oct. Blue 255.0, #670aff

Most 'Blue' Days in 2025
	Mon 7 Jul. Blue 255.0, #686aff

Most 'Blue' Days in 2025
	Mon 7 Jul. Blue 255.0, #686aff

Least 'Blue' Days in 2026
	Tue 27 Jan. Blue 0.0, #697800
	Tue 31 Mar. Blue 0.0, #69cb00

Most 'Blue' Days in 2026
	Mon 5 Jan. Blue 255.0, #695aff

Least 'Blue' Days in 2027
	Wed 25 Aug. Blue 0.0, #6c6e00

Most 'Blue' Days in 2027
	Tue 3 Aug. Blue 255.0, #6c50ff