AppVersionHelper.swift

enum AppVersionComparisonResult {
    case greater
    case smaller
    case equal
    case unknown
}

class AppVersion {
    var major: Int?
    var minor: Int?
    var patch: Int?
    
    init(_ versionString: String) {
        let array: [Int?] = versionString.split(separator: ".").map{ Int(String($0)) }
        
        if array.indices.contains(0), let value = array[0] {
            major = value
        }
        
        if array.indices.contains(1), let value = array[1] {
            minor = value
        }
        
        if array.indices.contains(2), let value = array[2] {
            patch = value
        }
    }
    
    func compare(to version: AppVersion) -> AppVersionComparisonResult {
        // Major
        guard let major1 = major else {
            if version.major != nil {
                return .smaller
            } else {
                return .unknown
            }
        }
        guard let major2 = version.major else { return .greater }
        
        if major1 > major2 { return .greater } else if major2 > major1 { return .smaller }
        
        // Minor
        guard let minor1 = minor else {
            if version.minor != nil {
                return .smaller
            } else {
                return .equal
            }
        }
        guard let minor2 = version.minor else { return .greater }
        
        if minor1 > minor2 { return .greater } else if minor2 > minor1 { return .smaller }
        
        // Patch
        guard let patch1 = patch else {
            if version.patch != nil {
                return .smaller
            } else {
                return .equal
            }
        }
        guard let patch2 = version.patch else { return .greater }
        
        if patch1 > patch2 { return .greater } else if patch2 > patch1 { return .smaller } else { return .equal }
    }
}