add WaintUntilForSeconds yield instruction

Runtime/Scripts/Helpers/WaitUntilForSeconds.cs

@@ -0,0 +1,70 @@
+using System;
+using UnityEngine;
+
+namespace TezosSDK.Helpers
+{
+    public class WaitUntilForSeconds: CustomYieldInstruction
+    {
+        float pauseTime;
+        float timer;
+        bool waitingForFirst;
+        Func<bool> myChecker;
+        Action<float> onInterrupt;
+        bool alwaysTrue;
+
+        public WaitUntilForSeconds(Func<bool> myChecker, float pauseTime, 
+            Action<float> onInterrupt = null)
+        {
+            this.myChecker = myChecker;
+            this.pauseTime = pauseTime;
+            this.onInterrupt = onInterrupt;
+
+            waitingForFirst = true;
+        }
+
+        public override bool keepWaiting
+        {
+            get
+            {
+                bool checkThisTurn = myChecker();
+                if (waitingForFirst) 
+                {
+                    if (checkThisTurn)
+                    {
+                        waitingForFirst = false;
+                        timer = pauseTime;
+                        alwaysTrue = true;
+                    }
+                }
+                else
+                {
+                    timer -= Time.deltaTime;
+
+                    if (onInterrupt != null && !checkThisTurn && alwaysTrue)
+                    {
+                        onInterrupt(timer);
+                    }
+                    alwaysTrue &= checkThisTurn;
+
+                    // Alternate version: Interrupt the timer on false, 
+                    // and restart the wait
+                    // if (!alwaysTrue || timer <= 0)
+
+                    if (timer <= 0)
+                    {
+                        if (alwaysTrue)
+                        {
+                            return false;
+                        }
+                        else 
+                        {
+                            waitingForFirst = true;
+                        }
+                    }
+                }
+
+                return true;
+            }
+        }
+    }
+}