Parse TZN timezone headers

__snapshots__/test.ts.snap

@@ -180,6 +180,7 @@ Object {
     ],
     "taskNumber": 2,
   },
+  "timezone": 0,
 }
 `;
 

fixtures/20241007TZN.igc

@@ -0,0 +1,216 @@
+AXSX004 SKYTRAXX
+HFPLTPILOT:Stefan Walter
+HFDTM100GPSDATUM:WGS-84
+HFRFWFIRMWAREVERSION:202401301017
+HFRHWHARDWAREVERSION:2.1
+HFTZNTIMEZONE:+5.50
+HFSITSITE:Bir_Billing_Golf Cour
+HFDTE071024
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index.ts

@@ -16,6 +16,7 @@ const RE_SIT_HEADER = /^H(\w)SIT(?:.{0,}?:(.*)|(.*))$/;
 const RE_FTY_HEADER = /^H(\w)FTY(?:.{0,}?:(.*)|(.*))$/;
 const RE_RFW_HEADER = /^H(\w)RFW(?:.{0,}?:(.*)|(.*))$/;
 const RE_RHW_HEADER = /^H(\w)RHW(?:.{0,}?:(.*)|(.*))$/;
+const RE_TZN_HEADER = /^H(\w)TZN(?:.{0,}?:([-+]?[\d.]+))$/;
 const RE_B = /^B(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})(\d{3})([NS])(\d{3})(\d{2})(\d{3})([EW])([AV])(-\d{4}|\d{5})(-\d{4}|\d{5})/;
 const RE_K = /^K(\d{2})(\d{2})(\d{2})/;
 const RE_IJ = /^[IJ](\d{2})(?:\d{2}\d{2}[A-Z]{3})+/;
@@ -34,6 +35,7 @@ declare namespace IGCParser {
     /** UTC date of the flight in ISO 8601 format */
     date: string;
     numFlight: number | null;
+    timezone: number | null;
 
     pilot: string | null;
     copilot: string | null;
@@ -269,6 +271,8 @@ class IGCParser {
       this._result.competitionClass = this.parseCompetitionClass(line);
     } else if (headerType === 'SIT') {
       this._result.site = this.parseSite(line);
+    } else if (headerType === 'TZN') {
+      this._result.timezone = this.parseTimezone(line);
     } else if (headerType === 'FTY') {
       this._result.loggerType = this.parseLoggerType(line);
     } else if (headerType === 'RFW') {
@@ -354,6 +358,14 @@ class IGCParser {
     return this.parseTextHeader('SIT', RE_SIT_HEADER, line);
   }
 
+  private parseTimezone(line: string): number {
+    let result = this.parseTextHeader('TZN', RE_TZN_HEADER, line);
+    let hours = parseFloat(result);
+    if (isNaN(hours))
+       throw new Error(`Invalid TZN header at line ${this.lineNumber}: ${line}`);
+    return hours;
+  }
+
   private parseLoggerType(line: string): string {
     return this.parseTextHeader('FTY', RE_FTY_HEADER, line);
   }

test.ts

@@ -104,6 +104,14 @@ describe('IGCParser', () => {
       expect(result).toMatchSnapshot();
     });
 
+    /* Test timezone parsing */
+    test('20241007TZN.igc', () => {
+      let content = fs.readFileSync(`${__dirname}/fixtures/20241007TZN.igc`, 'utf8');
+      let result = IGCParser.parse(content);
+
+      expect(result.timezone).toEqual(5.5);
+    });
+
     test('MD_85ugkjj1.IGC', () => {
       let content = fs.readFileSync(`${__dirname}/fixtures/MD_85ugkjj1.IGC`, 'utf8');
       let result = IGCParser.parse(content, { lenient: true });