ft: ZENKO-1144 redis wrapper for sorted sets

Changes in this commit:
- Add wrapper for Redis sorted set methods: ZADD, ZCARD,
  ZRANGE, ZRANGEBYSCORE, ZREM, ZSCORE
- Add wrapper for Redis methods: EXISTS

lib/metrics/RedisClient.js

@@ -68,6 +68,20 @@ class RedisClient {
         return this._client.incrby(key, amount, cb);
     }
 
+    /**
+     * increment value of a key by a given amount and set a ttl
+     * @param {string} key - key holding the value
+     * @param {number} amount - amount to increase by
+     * @param {number} expiry - expiry in seconds
+     * @param {callback} cb - callback
+     * @return {undefined}
+     */
+    incrbyEx(key, amount, expiry, cb) {
+        return this._client
+            .multi([['incrby', key, amount], ['expire', key, expiry]])
+            .exec(cb);
+    }
+
     /**
      * decrement value of a key by a given amount
      * @param {string} key - key holding the value
@@ -90,17 +104,15 @@ class RedisClient {
     }
 
     /**
-     * increment value of a key by a given amount and set a ttl
-     * @param {string} key - key holding the value
-     * @param {number} amount - amount to increase by
-     * @param {number} expiry - expiry in seconds
-     * @param {callback} cb - callback
+     * Checks if a key exists
+     * @param {string} key - name of key
+     * @param {function} cb - callback
+     *   If cb response returns 0, key does not exist.
+     *   If cb response returns 1, key exists.
      * @return {undefined}
      */
-    incrbyEx(key, amount, expiry, cb) {
-        return this._client
-            .multi([['incrby', key, amount], ['expire', key, expiry]])
-            .exec(cb);
+    exists(key, cb) {
+        return this._client.exists(key, cb);
     }
 
     /**
@@ -113,6 +125,85 @@ class RedisClient {
         return this._client.pipeline(cmds).exec(cb);
     }
 
+    /**
+     * Add a value and its score to a sorted set. If no sorted set exists, this
+     * will create a new one for the given key.
+     * @param {string} key - name of key
+     * @param {integer} score - score used to order set
+     * @param {string} value - value to store
+     * @param {callback} cb - callback
+     * @return {undefined}
+     */
+    zadd(key, score, value, cb) {
+        return this._client.zadd(key, score, value, cb);
+    }
+
+    /**
+     * Get number of elements in a sorted set.
+     * Note: using this on a key that does not exist will return 0.
+     * Note: using this on an existing key that isn't a sorted set will
+     * return an error WRONGTYPE.
+     * @param {string} key - name of key
+     * @param {function} cb - callback
+     * @return {undefined}
+     */
+    zcard(key, cb) {
+        return this._client.zcard(key, cb);
+    }
+
+    /**
+     * Get the score for given value in a sorted set
+     * Note: using this on a key that does not exist will return nil.
+     * Note: using this on a value that does not exist in a valid sorted set key
+     *       will return nil.
+     * @param {string} key - name of key
+     * @param {string} value - value within sorted set
+     * @param {function} cb - callback
+     * @return {undefined}
+     */
+    zscore(key, value, cb) {
+        return this._client.zscore(key, value, cb);
+    }
+
+    /**
+     * Remove a value from a sorted set
+     * @param {string} key - name of key
+     * @param {string|array} value - value within sorted set. Can specify
+     *   multiple values within an array
+     * @param {function} cb - callback
+     *   The cb response returns number of values removed
+     * @return {undefined}
+     */
+    zrem(key, value, cb) {
+        return this._client.zrem(key, value, cb);
+    }
+
+    /**
+     * Get specified range of elements in a sorted set
+     * @param {string} key - name of key
+     * @param {integer} start - start index (inclusive)
+     * @param {integer} end - end index (inclusive) (can use -1)
+     * @param {function} cb - callback
+     * @return {undefined}
+     */
+    zrange(key, start, end, cb) {
+        return this._client.zrange(key, start, end, cb);
+    }
+
+    /**
+     * Get range of elements in a sorted set based off score
+     * @param {string} key - name of key
+     * @param {integer|string} min - min score value (inclusive)
+     *   (can use "-inf")
+     * @param {integer|string} max - max score value (inclusive)
+     *   (can use "+inf")
+     * @param {function} cb - callback
+     * @return {undefined}
+     */
+    zrangebyscore(key, min, max, cb) {
+        return this._client.zrangebyscore(key, min, max, cb);
+    }
+
     clear(cb) {
         return this._client.flushdb(cb);
     }