Challenge redislabs-training#3

Optimized and correct implementation of update() for SiteStatsDaoRedisImpl.java.
1. Use Transaction wherever you can.
2. Perform the compare-and-update operations using Lua. The file CompareAndUpdateScript.java contains everything you need.

src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java

@@ -47,7 +47,7 @@ public void update(MeterReading reading) {
             ZonedDateTime day = reading.getDateTime();
             String key = RedisSchema.getSiteStatsKey(siteId, day);
 
-            updateBasic(jedis, key, reading);
+            updateOptimized(jedis, key, reading);
         }
     }
 
@@ -81,6 +81,20 @@ private void updateBasic(Jedis jedis, String key, MeterReading reading) {
     // Challenge #3
     private void updateOptimized(Jedis jedis, String key, MeterReading reading) {
         // START Challenge #3
+        String reportingTime = ZonedDateTime.now(ZoneOffset.UTC).toString();
+
+        Transaction t = jedis.multi();
+        CompareAndUpdateScript script = new CompareAndUpdateScript(jedisPool);
+
+        t.hset(key, SiteStats.reportingTimeField, reportingTime);
+        t.hincrBy(key, SiteStats.countField, 1);
+        t.expire(key, weekSeconds);
+
+        script.updateIfGreater(t, key,  SiteStats.maxWhField, reading.getWhGenerated());
+        script.updateIfLess(t, key,  SiteStats.minWhField, reading.getWhGenerated());
+        script.updateIfGreater(t, key,  SiteStats.maxCapacityField, getCurrentCapacity(reading));
+
+        t.exec();
         // END Challenge #3
     }