added googledatastore handler

lib/document_stores/googledatastore.js

@@ -0,0 +1,92 @@
+/*global require,module,process*/
+
+const datastore = require('@google-cloud/datastore');
+const winston = require('winston');
+
+class GoogleDatastoreDocumentStore {
+
+  // Create a new store with options
+  constructor(options) {
+    this.kind = "Haste";
+    this.expire = options.expire;
+    this.datastore = new Datastore();
+  }
+
+  // Save file in a key
+  set(key, data, callback, skipExpire) {
+    var now = new Date();
+    var expireTime = skipExpire ? null : new Date(now.getTime() + this.expire * 1000;
+    
+    var taskKey = this.datastore.key([this.kind, key])
+    var task = {
+      key: taskKey,
+      data: [
+        {
+          name: 'value',
+          value: data,
+          excludeFromIndexes: true
+        },
+        {
+          name: 'expiration',
+          value: expireTime
+        }
+      ]
+    };
+    
+    this.datastore.insert(task).then(() => {
+      callback(true); 
+    })
+    .catch(err => {
+      callback(false);
+    });
+  }
+
+  // Get a file from a key
+  get(key, callback, skipExpire) {
+    var taskKey = this.datastore.key([this.kind, key])
+    
+    this.datastore.get(taskKey).then((entity) => {
+      
+      if (skipExpire) {
+        callback(entity[0]["value"]);
+      }
+      else {
+        // check for expiry
+        if (entity[0]["expiration"] != null && entity[0]["expiration"] < new Date()) {
+          winston.info("document expired", {key: key});
+          callback(false);
+        }
+        else {
+        
+          // update expiry
+          var now = new Date();
+          var task = {
+            key: taskKey,
+            data: [
+              {
+                name: 'value',
+                value: entity[0]["value"],
+                excludeFromIndexes: true
+              },
+              {
+                name: 'expiration',
+                value: new Date(now.getTime() + this.expire * 1000;
+              }
+            ]
+          };
+          this.datastore.update(task).then(() => {
+          })
+          .catch(err => {
+            winston.error("failed to update expiration", {error: err});
+          });
+          callback(entity[0]["value"]);
+        }
+      }
+    })
+    .catch(err => {
+        winston.error("Error retrieving value from Google Datastore", {error: err});
+        callback(false);
+    });
+}
+
+module.exports = GoogleDatastoreDocumentStore;