show remaining attempts

internal/storage/memstore/messages.go

@@ -108,11 +108,11 @@ func (s *memMessageStore) GetFullMessage(id string, pin string) (*storage.Messag
 				return &msg, nil
 			}
 
-			msg.Attempt += 1
+			msg.AttemptsRemaining -= 1
 			s.messages.Store(id, msg)
 
 			// If the pin was wrong then start tracking attempts
-			if msg.Attempt >= storage.MAX_PIN_ATTEMPTS {
+			if msg.AttemptsRemaining <= 0 {
 				s.messages.Delete(id)
 			}
 		} else {

internal/storage/messages.go

@@ -19,9 +19,9 @@ type MessageStore interface {
 
 type Message struct {
 	aztables.Entity
-	Content string `json:"content,omitempty"`
-	Pin     string `json:"pin,omitempty"`
-	Attempt int    `json:"Attempt,omitempty"`
+	Content           string `json:"content,omitempty"`
+	Pin               string `json:"pin,omitempty"`
+	AttemptsRemaining int    `json:"remaining,omitempty"`
 }
 
 func NewMessage(username string, ciphertext string, pin string) (Message, error) {
@@ -36,8 +36,8 @@ func NewMessage(username string, ciphertext string, pin string) (Message, error)
 			RowKey:       username,
 			Timestamp:    aztables.EDMDateTime(t),
 		},
-		Content: ciphertext,
-		Pin:     pinHash,
-		Attempt: 0,
+		Content:           ciphertext,
+		Pin:               pinHash,
+		AttemptsRemaining: MAX_PIN_ATTEMPTS,
 	}, nil
 }

web/message.show.tmpl

@@ -35,6 +35,9 @@
                 <input type="password" name="pin" class="form-control" aria-describedby="pinHelp" id="pin" placeholder="secret PIN" />
                 <div id="pinHelp" class="form-text">Provide a PIN to unlock content</div>
               </div>
+              <div class="mb-3">
+                <div class="form-text">Remaining attempts: {{ .data.AttemptsRemaining }}</div>
+              </div>
               <button type="submit" class="btn btn-primary">Validate and decrypt</button>
             </form>
           {{end}}