feat: Add gasUsage topic (#12)

Support for gas usage by @zegerk 

Co-authored-by: Zeger Knops <15801866+zegerk@users.noreply.github.com>

src/output/debug-output.ts

@@ -18,6 +18,9 @@ export default class DebugOutput extends Output {
     p1Reader.on(P1ReaderEvents.UsageChanged, (result) => {
       console.log(' - usageChange %s', result.message);
     });
+    p1Reader.on(P1ReaderEvents.GasUsageChanged, (result) => {
+      console.log(' - gasUsageChange %s', result.message);
+    });
     p1Reader.on(P1ReaderEvents.ErrorMessage, (message) => {
       console.log(' - errorMessage %s', message);
     });

src/output/interval-output.ts

@@ -28,6 +28,9 @@ export default class IntervalOutput extends Output {
     p1Reader.on(P1ReaderEvents.UsageChanged, (result) => {
       this.emit(P1ReaderEvents.UsageChanged, result);
     });
+    p1Reader.on(P1ReaderEvents.GasUsageChanged, (result) => {
+      this.emit(P1ReaderEvents.GasUsageChanged, result);
+    });
 
     this.timer = setInterval(() => {
       this.publishNextEvent = true;

src/output/mqtt-output.ts

@@ -34,6 +34,10 @@ export default class MqttOutput extends Output {
       this.publishUsage(data);
     });
 
+    p1Reader.on(P1ReaderEvents.GasUsageChanged, (data) => {
+      this.publishGasUsage(data);
+    });
+
     p1Reader.on(P1ReaderEvents.SolarResult, (data) => {
       this.publishSolar(data);
     });
@@ -68,6 +72,14 @@ export default class MqttOutput extends Output {
     this.mqtt?.publish(this.getTopic('usage'), JSON.stringify(message), { qos: 0, retain: false });
   }
 
+  private publishGasUsage(data: any): void {
+    const message = data;
+    message.val = data.currentUsage;
+    delete message.currentUsage;
+    message.tc = Date.now();
+    this.mqtt?.publish(this.getTopic('gasUsage'), JSON.stringify(message), { qos: 0, retain: false });
+  }
+
   private publishData(data: DsmrMessage): void {
     if (this.config.distinct) {
       this.config.distinctFields.forEach((element) => {

src/p1-reader-events.ts

@@ -14,5 +14,7 @@ export default class P1ReaderEvents {
   /** Usage change is emitted after the parsed result. It keeps the last result to compare. */
   static get UsageChanged(): string { return 'usageChanged'; }
 
+  static get GasUsageChanged(): string { return 'gasUsageChanged'; }
+
   static get SolarResult(): string { return 'solar'; }
 }

src/p1-reader.ts

@@ -5,10 +5,17 @@ import P1Parser from './p1-parser';
 import P1ReaderEvents from './p1-reader-events';
 import DsmrMessage from './dsmr-message';
 import SolarInput from './solar-input';
+import GasValue from './gas-value';
 
 export default class P1Reader extends EventEmitter {
   private usage: number;
 
+  private gasUsage: number;
+
+  private gasReadingTimestamp: number;
+
+  private gasReading: number;
+
   private reading: boolean;
 
   private parsing: boolean;
@@ -31,6 +38,9 @@ export default class P1Reader extends EventEmitter {
   constructor() {
     super();
     this.usage = 0;
+    this.gasUsage = 0;
+    this.gasReading = 0;
+    this.gasReadingTimestamp = 0;
     this.reading = false;
     this.parsing = false;
   }
@@ -120,6 +130,44 @@ export default class P1Reader extends EventEmitter {
       });
       this.usage = newUsage;
     }
+
+    /**
+     * Handle the gas value - this is a bit different from electricity usage, the meter does not
+     * indicate the actual gas usage in m3/hour but only submits the meter reading every XX minutes
+     */
+    const gas = result.xGas ?? result.gas;
+    if (gas) {
+      const currentGasReadingTimestamp = (new Date(((gas as GasValue)).ts ?? 0).getTime() / 1000);
+      const period = currentGasReadingTimestamp - this.gasReadingTimestamp;
+      /**
+       * Report for every new timestamp
+       */
+      if (period) {
+        const newGasReading = ((gas as GasValue).totalUse ?? 0);
+        const relative = this.gasReading ? (newGasReading - this.gasReading) : 0;
+        let newGasUsage = 0;
+
+        /**
+         * Gas usage in m3 per hour
+         */
+        newGasUsage = relative * (3600 / period);
+
+        /**
+         * Gas usage is measured in thousands (0.001) - round the numbers
+         * accordingly
+         */
+        this.emit(P1ReaderEvents.GasUsageChanged, {
+          previousUsage: parseFloat(this.gasUsage.toFixed(3)),
+          currentUsage: parseFloat(newGasUsage.toFixed(3)),
+          relative: parseFloat(relative.toFixed(3)),
+          message: `Reading increased +${relative} to ${newGasReading}`,
+        });
+
+        this.gasReadingTimestamp = currentGasReadingTimestamp;
+        this.gasReading = newGasReading;
+        this.gasUsage = newGasUsage;
+      }
+    }
   }
 
   public close(): Promise<void> {