Add better error messages for Image Upload fail states (#1062)

Classes/Image Upload/ImageUploadTableViewController.swift

@@ -155,10 +155,21 @@ class ImageUploadTableViewController: UITableViewController {
         }
 
         // Check that we have enough "tokens" to actually upload the image
-        client.canUploadImage { [weak self] success in
+        client.canUploadImage { [weak self] error in
             // Ensure that we do have enough tokens, otherwise remove the upload button
-            guard success else {
-                ToastManager.showError(message: NSLocalizedString("Rate Limit reached, cannot upload!", comment: ""))
+            if let error = error as? ImgurClient.ImgurError {
+                
+                switch error {
+                case .endpointError(let response):
+                    ToastManager.showError(message: response)
+                    
+                case .rateLimitExceeded:
+                    ToastManager.showError(message: NSLocalizedString("Rate Limit reached, cannot upload!", comment: ""))
+                    
+                default:
+                    ToastManager.showGenericError()
+                }
+                
                 self?.navigationItem.rightBarButtonItem = nil
                 return
             }

Classes/Image Upload/ImgurClient.swift

@@ -14,6 +14,15 @@ final class ImgurClient {
     enum ImgurError: Error {
         // missingLink: - Received a valid response, but no link was available in the payload
         case missingLink
+        
+        // endpointError: - We got an error back from Imgur, where the parameter is their response
+        case endpointError(String)
+        
+        // malformedResponse: - We got a response back from Imgur, but it did not contain values we expected
+        case malformedResponse
+        
+        // rateLimitExceeded: - We are too close to the Imgur rate limit, so no images are being permitted
+        case rateLimitExceeded
     }
 
     private static let hostpath = "https://api.imgur.com/3/"
@@ -39,23 +48,33 @@ final class ImgurClient {
     }
 
     func canUploadImage(
-        completion: @escaping (Bool) -> Void
+        completion: @escaping (Error?) -> Void
         ) {
 
         request("credits") { response in
             guard let dict = response.value as? [String: Any], let data = dict["data"] as? [String: Any] else {
-                completion(false)
+                completion(ImgurError.malformedResponse)
+                return
+            }
+            
+            if let error = data["error"] as? String {
+                completion(ImgurError.endpointError(error))
                 return
             }
 
             guard let userRemaining = data["UserRemaining"] as? Int, let clientRemaining = data["ClientRemaining"] as? Int else {
-                completion(false)
+                completion(ImgurError.malformedResponse)
                 return
             }
 
             // Takes 10 tokens to upload an image, a buffer has been added to prevent us using 100% of our allowance as this
             // will mean our app gets temporarily blocked from Imgur!
-            completion(userRemaining > 20 && clientRemaining > 100)
+            guard userRemaining > 20, clientRemaining > 100 else {
+                completion(ImgurError.rateLimitExceeded)
+                return
+            }
+            
+            completion(nil)
         }
     }