Harden service catalogue loading against malformed data

ios/AWSary/resources/Info.plist

@@ -4,7 +4,7 @@
 <dict>
 	<key>ITSAppUsesNonExemptEncryption</key>
 	<false/>
-	<key>NSCalendarsWriteOnlyAccessUsageDescription</key>
-	<string></string>
+        <key>NSCalendarsWriteOnlyAccessUsageDescription</key>
+        <string>Calendar access is only used to add the classroom schedules you request.</string>
 </dict>
 </plist>

ios/Shared/DataModels/AwsServices.swift

@@ -8,7 +8,6 @@
 import Foundation
 
 var fm = FileManager.default
-var subUrl: URL?
 var mainUrl: URL? = Bundle.main.url(forResource: "aws_services", withExtension: "json")
 var lastRandom: awsService = awsService(id: 10, name: "DeepRacer", longName: "AWS DeepRacer", shortDesctiption: "DeepRacer", imageURL: "https://static.tig.pt/awsary/logos/Arch_AWS-DeepRacer_64.svg", youtube_id: "")
 
@@ -23,47 +22,78 @@ class AwsServices: ObservableObject {
       return lastRandom
    }
 
-   func getRandomElement() -> awsService{
-      lastRandom = services.randomElement()!
-      return lastRandom
+   func getRandomElement() -> awsService {
+      if services.isEmpty {
+         refresh()
+      }
+
+      guard let randomService = services.randomElement() else {
+         return lastRandom
+      }
+
+      lastRandom = randomService
+      return randomService
+   }
+
+   init() {
+      refresh()
+   }
+
+   private func servicesFromDocuments() -> [awsService] {
+      do {
+         let documentDirectory = try fm.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
+         let documentURL = documentDirectory.appendingPathComponent("aws_services.json")
+
+         guard fm.fileExists(atPath: documentURL.path) else {
+            return []
+         }
+
+         return decodeData(pathName: documentURL)
+      } catch {
+         print("Failed to resolve documents directory for aws_services.json: \(error)")
+         return []
+      }
+   }
+
+   private func servicesFromBundle() -> [awsService] {
+      guard let bundleURL = mainUrl else {
+         print("Missing bundled aws_services.json")
+         return []
+      }
+
+      return decodeData(pathName: bundleURL)
+   }
+
+   private func decodeData(pathName: URL) -> [awsService] {
+      do {
+         let jsonData = try Data(contentsOf: pathName)
+         let decoder = JSONDecoder()
+         let decoded = try decoder.decode([awsService].self, from: jsonData)
+
+         if decoded.isEmpty {
+            print("Decoded zero services from \(pathName.lastPathComponent)")
+         }
+
+         return decoded
+      } catch {
+         print("Failed to decode aws_services.json from \(pathName): \(error)")
+         return []
+      }
+   }
+
+   func refresh() {
+      var loadedServices = servicesFromDocuments()
+
+      if loadedServices.isEmpty {
+         loadedServices = servicesFromBundle()
+      }
+
+      if loadedServices.isEmpty {
+         print("Falling back to last known service to prevent empty catalogue")
+         services = [lastRandom]
+      } else {
+         loadedServices.sort { $0.name < $1.name }
+         services = loadedServices
+      }
    }
-    init() {
-       refresh()
-    }
-
-   func getData() {
-           do {
-               let documentDirectory = try fm.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
-               subUrl = documentDirectory.appendingPathComponent("aws_services.json")
-               loadFile(mainPath: mainUrl!, subPath: subUrl!)
-           } catch {
-               print(error)
-           }
-       }
-
-   func loadFile(mainPath: URL, subPath: URL){
-           if fm.fileExists(atPath: subPath.path){
-               decodeData(pathName: subPath)
-
-               if services.isEmpty{
-                   decodeData(pathName: mainPath)
-               }
-
-           }else{
-               decodeData(pathName: mainPath)
-           }
-       }
-
-   func decodeData(pathName: URL){
-           do{
-               let jsonData = try Data(contentsOf: pathName)
-               let decoder = JSONDecoder()
-              services = try decoder.decode([awsService].self, from: jsonData)
-           } catch {}
-       }
-
-    func refresh(){
-       getData()
-       services.sort {$0.name < $1.name}
-    }
 }