3 files changed, 102 insertions, 0 deletions

diff --git a/services/data-broadcaster.js b/services/data-broadcaster.js
index 60c2368..4905eda 100644
--- a/services/data-broadcaster.js
+++ b/services/data-broadcaster.js
@@ -16,6 +16,10 @@ function broadcastPowerStateUpdate(deviceId, data) {
   broadcast(generatePayload('powerState', deviceId, data));
 }
 
+function broadcastNewLogEntry(deviceId, data) {
+  broadcast(generatePayload('newLogEntry', deviceId, data));
+}
+
 function broadcast(payload) {
   app.getWsClients().forEach(client => {
     client.send(payload);
@@ -39,5 +43,6 @@ module.exports = {
   broadcastDailyUsageUpdate: broadcastDailyUsageUpdate,
   broadcastMonthlyUsageUpdate: broadcastMonthlyUsageUpdate,
   broadcastPowerStateUpdate: broadcastPowerStateUpdate,
+  broadcastNewLogEntry: broadcastNewLogEntry,
   generatePayload: generatePayload
 }
diff --git a/services/data-logger.js b/services/data-logger.js
new file mode 100644
index 0000000..9c23de1
--- /dev/null
+++ b/services/data-logger.js
@@ -0,0 +1,94 @@
+const fs = require('fs');
+const dataBroadcaster = require('./data-broadcaster');
+
+let logIntervalMs;
+let maxLogEntries;
+
+loadLogConfig();
+
+function loadLogConfig() {
+  try {
+    let config  = JSON.parse(fs.readFileSync('logger-config.json', 'utf8'));
+    logIntervalMs = (config.logIntervalSeconds * 1000);
+    maxLogEntries = config.maxLogEntries;
+
+  }
+  catch (err) {
+    console.warn('Error reading logger config. Reverting to defaults.', err);
+    logIntervalMs = 60000 // 1 min
+    maxLogEntries = 1440  // 24 hrs at 1/min
+ }  
+}
+
+function startLogging(device) {
+  setInterval(() => { log(device); }, logIntervalMs);
+  console.log('Logging started for ' + device.alias + ' [' + device.deviceId + '] every ' + (logIntervalMs/1000) + ' seconds');
+}
+
+function writeLog(filePath, log) {
+  fs.writeFile(filePath, JSON.stringify(log), { flag: 'w' }, (err) => {
+    if (err) {
+      console.warn('Error writing log for ' + device.alias + ' [' + device.deviceId + ']', err);
+    }
+  });
+}
+
+function getLogEntries(filePath, callback) {
+  
+  fs.access(filePath, fs.constants.F_OK, (err) => {
+    if(err) {
+      // No log file, init empty one
+      writeLog(filePath, []);
+      callback([]);
+    }
+    else {
+      fs.readFile(filePath, 'utf8', (err, data) => {
+        if (err) {
+          console.warn('Error reading usage log ' + filePath, err);
+          callback([]);
+        }
+        else {
+          callback(JSON.parse(data));
+        }
+      });
+    }
+  });
+}
+
+function log(device) {
+
+  device.emeter.getRealtime().then(response => {
+
+    let logEntry = {
+      ts: Date.now(),
+      pw: (('power_mw' in response) ? (response.power_mw / 1000) : response.power)
+    }
+
+    let filePath = getLogPath(device.deviceId);
+
+    getLogEntries(filePath, (entries) => {
+      entries.push(logEntry)
+      
+      // Remove old entries
+      entries.splice(0, entries.length - maxLogEntries);
+
+      writeLog(filePath, entries);
+      dataBroadcaster.broadcastNewLogEntry(device.deviceId, logEntry);
+    })
+
+  });
+}
+
+function getLogPath(deviceId) {
+  return deviceId + '-log.json';
+}
+
+function getLogEntriesForDevice(deviceId, callback) {
+  return getLogEntries(getLogPath(deviceId), callback);
+}
+
+module.exports = {
+  startLogging: startLogging,
+  log: log,
+  getLogEntriesForDevice: getLogEntriesForDevice
+}
\ No newline at end of file
diff --git a/services/device-manager.js b/services/device-manager.js
index e4d18f3..1e17f75 100644
--- a/services/device-manager.js
+++ b/services/device-manager.js
@@ -1,4 +1,5 @@
 const { Client } = require('tplink-smarthome-api');
+const dataLogger = require('./data-logger');
 
 const client = new Client();
 var devices = [];
@@ -9,6 +10,8 @@ client.startDiscovery({
   }).on('plug-new', plug => {
   console.log('Found device: ' + plug.alias + ' [' + plug.deviceId + ']');
   devices.push(plug);
+
+  dataLogger.startLogging(plug);
 });
 
 module.exports.getDevice = function(deviceId) {