Add mc-players.js plugin

apps/monitor/src/plugins/mc-players.js

@@ -0,0 +1,44 @@
+const { readFileSync } = require('fs');
+const { log } = require('../node-common')(['log']);
+const { updateMetrics } = require('../modules/metrics');
+
+const JOINED_TAG = 'joined the game';
+const LEFT_TAG = 'left the game';
+
+/**
+ * Log metrics for logging Minecraft players online.
+ *
+ * @param {object} args - Plugin args.
+ */
+module.exports = async (args = {}) => {
+  const { LOG_PATH = '/home/pi/hom-mc-server.log' } = args;
+  try {
+    const mcPlayers = [];
+
+    // Load log file
+    const lines = readFileSync(LOG_PATH, 'utf-8')
+      .split('\n')
+      .map((p) => p.trim())
+      .filter((p) => p.includes(JOINED_TAG) || p.includes(LEFT_TAG))
+      .map((p) => p.split(': ')[1]);
+
+    // Get all names mentioned
+    const names = lines.reduce((acc, p) => {
+      const [name] = p.split(' ');
+      return acc.includes(name) ? acc : [...acc, name];
+    }, []);
+    log.debug(`Found MC players: ${names.join(', ')}`);
+
+    // Determine who's still there
+    names.forEach((p) => {
+      const joinCount = lines.filter((l) => l.includes(p) && l.includes(JOINED_TAG)).length;
+      const leftCount = lines.filter((l) => l.includes(p) && l.includes(LEFT_TAG)).length;
+
+      if (joinCount > leftCount) mcPlayers.push(p);
+    });
+
+    updateMetrics({ mcPlayers });
+  } catch (e) {
+    log.error(e);
+  }
+};