Refactor to use version object #59

Enable writing safer version aware logic.

src/domain/Version.ts

@@ -0,0 +1,24 @@
+export class Version {
+  public readonly major: number;
+
+  public readonly minor: number;
+
+  public readonly patch: number;
+
+  public constructor(semanticVersion: string) {
+    if (!semanticVersion) {
+      throw new Error('empty version');
+    }
+    if (!semanticVersion.match(/^\d+\.\d+\.\d+$/g)) {
+      throw new Error(`invalid version: ${semanticVersion}`);
+    }
+    const [major, minor, patch] = semanticVersion.split('.');
+    this.major = parseInt(major, 10);
+    this.minor = parseInt(minor, 10);
+    this.patch = parseInt(patch, 10);
+  }
+
+  public toString(): string {
+    return `${this.major}.${this.minor}.${this.patch}`;
+  }
+}