//
//  Version.swift
//  KeymanEngine
//
//  Created by Gabriel Wong on 2017-11-23.
//  Copyright © 2017 SIL International. All rights reserved.
//

import Foundation

/// Dotted-decimal version.
public struct Version: Comparable {
  public static let fallback = Version("1.0")!
  public static let current = Version("13.0.65")!

  // The Engine first started tracking the 'last loaded version' in 12.0.
  public static let firstTracked = Version("12.0")!

  // The Keyman App's file browser was first added in 13.0 alpha;
  // this prompted a mild rework of KMP installation file management,
  // since this exposed byproducts to the users in the Files app.
  public static let fileBrowserImplemented = Version("13.0")!
  public static let defaultsNeedBackup = Version("13.0.65")!

  private let components: [Int]
  public let string: String

  public init?(_ string: String) {
    let stringComponents = string.components(separatedBy: ".")
    var components: [Int] = []
    for s in stringComponents {
      guard let i = Int(s), i >= 0 else {
        return nil
      }
      components.append(i)
    }

    self.string = string
    self.components = components
  }

  public static func <(lhs: Version, rhs: Version) -> Bool {
    let len = max(lhs.components.count, rhs.components.count)
    for i in 0..<len {
      let leftComponent = lhs.components[safe: i] ?? 0
      let rightComponent = rhs.components[safe: i] ?? 0
      if leftComponent < rightComponent {
        return true
      }
      if leftComponent > rightComponent {
        return false
      }
    }
    return false
  }

  public static func ==(lhs: Version, rhs: Version) -> Bool {
    return lhs.components == rhs.components
  }

  // For nice logging output.
  public var description: String {
    return self.string
  }
}