Break up Brief + Document (#311)

Sources/Packages/Sources/Brief/SemVer.swift

@@ -0,0 +1,43 @@
+import Foundation
+
+/// A representation of a Semantic Version.
+public struct SemVer {
+
+    /// The SemVer broken into an array of integers.
+    let versionNumbers: [Int]
+
+    /// Initializes a SemVer from a string representation.
+    /// - Parameter version: A string representation of the SemVer, formatted as "major.minor.patch".
+    public init(_ version: String) {
+        // Betas have the format 1.2.3_beta1
+        let strippedBeta = version.split(separator: "_").first!
+        var split = strippedBeta.split(separator: ".").compactMap { Int($0) }
+        while split.count < 3 {
+            split.append(0)
+        }
+        versionNumbers = split
+    }
+
+    /// Initializes a SemVer from an ``OperatingSystemVersion`` representation.
+    /// - Parameter version: An  ``OperatingSystemVersion`` representation of the SemVer.
+    public init(_ version: OperatingSystemVersion) {
+        versionNumbers = [version.majorVersion, version.minorVersion, version.patchVersion]
+    }
+
+}
+
+extension SemVer: Comparable {
+
+    public static func < (lhs: SemVer, rhs: SemVer) -> Bool {
+        for (latest, current) in zip(lhs.versionNumbers, rhs.versionNumbers) {
+            if latest < current {
+                return true
+            } else if latest > current {
+                return false
+            }
+        }
+        return false
+    }
+
+
+}