Temporarily connects mongodb

package.json

@@ -17,6 +17,7 @@
     "loopback-boot": "^2.6.5",
     "loopback-component-explorer": "^4.0.0",
     "loopback-connector-rest": "^2.1.0",
+    "mongodb": "^2.2.28",
     "mustache": "^2.3.0",
     "request-promise": "^4.2.0",
     "serve-favicon": "^2.0.1",

server/boot/routes.js

@@ -8,6 +8,7 @@ var sensor  = require('../dao/sensor.js'),
 	user    = require('../dao/user.js');
 
 var conn    = require('../dao/connection.js');
+var dbConn = require('../dao/db_conn');
 
 // Configuration
 var limit = 50;
@@ -139,6 +140,46 @@ module.exports = function(app) {
 			)
 	});
 
+	router.get('/data/:sensor_id/latest', function (req, res) {
+    const sensor_id = req.params.sensor_id;
+
+    dbConn.latest('First', sensor_id).then(function (data) {
+      res.send(data);
+    }).catch(function (err) {
+      res.send({err: err.message});
+    });
+  })
+
+  router.get('/data/:sensor_id/history', function (req, res) {
+    const sensor_id = req.params.sensor_id;
+
+    var since_ts   = +req.query.since;      // required
+    var until_ts   = +req.query.until;      // optional
+    var downsample = +req.query.downsample; // optional
+
+    if (!since_ts) {
+      throw 'Missing or invalid query: "since"';
+    }
+
+    if (!until_ts) {
+      // until now by default
+      until_ts = new Date().getTime();
+    }
+
+    var promise;
+    if (downsample) {
+      promise = dbConn.downsample('First', sensor_id, since_ts, until_ts, downsample);
+    } else {
+      promise = dbConn.history('First', sensor_id, since_ts, until_ts);
+    }
+
+    promise.then(function (arr) {
+      res.send(arr);
+    }).catch(function (err) {
+        res.send({err: err.message});
+    });
+  })
+
 	// Render Dashboard Index Template
 	router.get('/dashboard', function (req, res) {
     	return res.render(path.join(app.get('template') + '/index.html'));

server/dao/db_conn.js

@@ -0,0 +1,94 @@
+/**
+ * Created by gong on 2017/6/15.
+ *
+ * [[[ IMPORTANT NODE ]]]
+ *
+ * Scaffold code. Remove this file later.
+ * (Dashboard should not connect MongoDB directly. Use backend API instead.)
+ *
+ */
+'use strict';
+
+var mongodb = require('mongodb');
+var mongoUrl = 'mongodb://leaniot:leaniot@119.254.211.60:37017/leaniot?authSource=leaniot';
+
+var mongo;
+
+mongodb.MongoClient.connect(mongoUrl).then(function(db) {
+  console.log('MongoDB connected.');
+  mongo = db;
+}).catch(function(err) {
+  console.log('Failed to connect MongoDB: ' + err.message);
+});
+
+/**
+ * 取最近一条数据。
+ *
+ * @param {string} coll
+ * @param {string} sensor_id
+ * @return {Promise.<object>}
+ */
+exports.latest = function(coll, sensor_id) {
+  return mongo.collection(coll).find({
+    sensor_id: sensor_id
+  }, {
+    _id: false, timestamp: true, payload: true
+  }).sort({timestamp: -1}).limit(1).toArray().then(function(arr) {
+    return arr.length === 1 ? arr[0] : {};
+  });
+}
+
+/**
+ * 取一个时间段内的完整数据。
+ *
+ * @param {string} coll
+ * @param {string} sensor_id
+ * @param {number} start_ts
+ * @param {number} end_ts
+ * @return {Promise.<Array>}
+ */
+exports.history = function(coll, sensor_id, start_ts, end_ts) {
+  return mongo.collection(coll).find({
+    sensor_id: sensor_id,
+    timestamp: {
+      $gte: start_ts,
+      $lte: end_ts
+    }
+  }, {
+    _id: false, timestamp: true, payload: true
+  }).sort({timestamp: 1}).toArray()
+}
+
+/**
+ * 取一个时间段内的数据，下降采样。
+ *
+ * @param {string} coll
+ * @param {string} sensor_id
+ * @param {number} start_ts
+ * @param {number} end_ts
+ * @param {number} buckets
+ * @return {Promise.<Array>}
+ */
+exports.downsample = function (coll, sensor_id, start_ts, end_ts, buckets) {
+  return mongo.collection(coll).aggregate([
+    {
+      $match: {
+        sensor_id: sensor_id,
+        timestamp: {
+          $gte: start_ts,
+          $lte: end_ts
+        }
+      }
+    },
+    {
+      $bucketAuto: {
+        groupBy: "$timestamp",
+        buckets: buckets,
+        output: {
+          timestamp: { $last: "$timestamp" },
+          payload: { $last: "$payload" }   // $max, $min, $first, $last, $avg
+        }
+      }
+    }
+  ]).project({_id: false}).sort({timestamp: 1}).toArray();
+}