FontManager+FontScaling.swift

//
//  FontManager.swift
//
//  Created by http://www.popcornomnom.com
//  Copyright © 2020 Marharyta Lytvynenko. All rights reserved.
//

import UIKit

///optional type in case if you don't want to support scaled font yet
private let autoScaleSettings: AutoScaleSettings? = AutoScaleSettings()

private class AutoScaleSettings {
    let mostPopularScreenWidth: CGFloat = 375
    let maxScreenWidth: CGFloat = 460 //use to prevent huge font scalinh on iPad
    let minScaleFactor: CGFloat = 0.93 //to protect scalling of very small sizes
}

//MARK: - Font Parts

public extension UIFont {
    
    enum Family: String, CaseIterable {
        case system = ".SFUIText" //".SFUI"
        case inter = "Inter"
        
        //easy to change default app fonts family
        public static let defaultFamily = Family.inter
    }
    
    enum CustomWeight: String, CaseIterable {
        case regular = "", medium, light, heavy, bold, semibold, black
    }
    
    enum Size: CGFloat, CaseIterable {
        case h1 = 36, h2 = 28, h3 = 20
        case bodyL = 17, bodyM = 15, bodyS = 13
        var doesSupportMinScalling: Bool { return rawValue > Size.bodyM.rawValue } //readability bounds
    }
    
    private class func stringName(_ family: Family, _ weight: CustomWeight) -> String {
        /**
         Define incompatible family, weight here
         in this case set defaults compatible values
         */
        let fontWeight: String
        switch (family, weight) {
        case (.inter, .heavy): fontWeight = CustomWeight.bold.rawValue
        case (.inter, .light): fontWeight = "\(weight.rawValue)BETA"
        default:               fontWeight = weight.rawValue
        }
        //put Family and Weight together
        let familyName = family.rawValue
        return fontWeight.isEmpty ? "\(familyName)" : "\(familyName)-\(fontWeight)"
    }
}

//MARK: - Initializers

public extension UIFont {
    
    convenience init(_ size: Size, _ weight: CustomWeight) {
        self.init(.defaultFamily, size, weight)
    }
    
    convenience init(_ family: Family = .defaultFamily,
                     _ size: Size, _ weight: CustomWeight) {
        var _size = size.rawValue
        if let autoScaleSettings = autoScaleSettings {
            var ratio = (min(UIScreen.main.bounds.width,
                             autoScaleSettings.maxScreenWidth)
                / autoScaleSettings.mostPopularScreenWidth)
            ratio = max(autoScaleSettings.minScaleFactor, ratio)
            if ratio > 1 || (ratio < 1 && size.doesSupportMinScalling) {
                _size = round(ratio * _size)
            }
        }
        self.init(name: UIFont.stringName(family, weight), size: _size)!
    }
}

// *DEBUG* https://gist.github.com/popcornomnom/a677d549aa216b071ac92d336557c63b