Add error handling

Sources/ResgenSwift/Analytics/Analytics.swift

@@ -35,6 +35,9 @@ struct Analytics: ParsableCommand {
         print("[\(Self.toolName)] Will use inputFile \(options.inputFile) to generate analytics for target: \(options.target)")
         print("[\(Self.toolName)] Will generate analytics")
         
+        // Check requirements
+        guard checkRequirements() else { return }
+        
         // Parse input file
         let sections = AnalyticsFileParser.parse(options.inputFile, target: options.target)
         
@@ -48,6 +51,29 @@ struct Analytics: ParsableCommand {
         
         print("[\(Self.toolName)] Analytics generated")
     }
+    
+    // MARK: - Requirements
+    
+    private func checkRequirements() -> Bool {
+        let fileManager = FileManager()
+        
+        // Input file
+        guard fileManager.fileExists(atPath: options.inputFile) else {
+            let error = AnalyticsError.fileNotExists(options.inputFile)
+            print(error.description)
+            Analytics.exit(withError: error)
+        }
+        
+        // Check if needed to regenerate
+        guard GeneratorChecker.shouldGenerate(force: options.forceGeneration,
+                                              inputFilePath: options.inputFile,
+                                              extensionFilePath: options.extensionFilePath) else {
+            print("[\(Self.toolName)] Analytics are already up to date :) ")
+            return false
+        }
+        
+        return true
+    }
 }
 
 extension Analytics {