From 4bb1fdb5051df53e3e2d8c5eb7facb8c10fdcf7b Mon Sep 17 00:00:00 2001
From: Andre Paquette <andrepaquette@andres.laptop.lan>
Date: Tue, 21 Apr 2026 20:34:21 -0400
Subject: [PATCH] Add Label 52 decoder plugin

New plugin registered in official.ts and MessageDecoder.ts.
---
 lib/MessageDecoder.ts       |   1 +
 lib/plugins/Label_52_AGM.ts | 121 ++++++++++++++++++++++++++++++++++++
 lib/plugins/official.ts     |   1 +
 3 files changed, 123 insertions(+)
 create mode 100644 lib/plugins/Label_52_AGM.ts

diff --git a/lib/MessageDecoder.ts b/lib/MessageDecoder.ts
index b40f43af..05888619 100644
--- a/lib/MessageDecoder.ts
+++ b/lib/MessageDecoder.ts
@@ -78,6 +78,7 @@ const pluginClasses = [
   Plugins.Label_QQ,
   Plugins.Label_QR,
   Plugins.Label_QS,
+  Plugins.Label_52_AGM,
 ];
 
 export class MessageDecoder {
diff --git a/lib/plugins/Label_52_AGM.ts b/lib/plugins/Label_52_AGM.ts
new file mode 100644
index 00000000..5f7dc1cd
--- /dev/null
+++ b/lib/plugins/Label_52_AGM.ts
@@ -0,0 +1,121 @@
+import { DecoderPlugin } from '../DecoderPlugin';
+import { DecodeResult, Message, Options } from '../DecoderPluginInterface';
+
+/**
+ * Label 52 — AGM (Ground UTC Request)
+ *
+ * Ground-to-air uplink asking the aircraft's ACARS Management Unit (MU)
+ * to report / synchronise its UTC clock. Paired with label 51 (Ground
+ * GMT Request response).
+ *
+ * Wire format (only the first three fields — the calendar date in
+ * YYMMDD — are decoded here; the remaining characters carry an
+ * anomalous time portion and a trailing byte that are not formally
+ * documented and are intentionally left unparsed per analyst guidance):
+ *
+ *   26 04 20 1091039
+ *   |  |  |  |
+ *   |  |  |  └ (ignored — undocumented time / status portion)
+ *   |  |  └─── Day of month (DD)
+ *   |  └────── Month (MM)
+ *   └───────── Year (YY, 20YY)
+ */
+export class Label_52_AGM extends DecoderPlugin {
+  name = 'label-52-agm';
+
+  qualifiers() {
+    return {
+      labels: ['52'],
+    };
+  }
+
+  decode(message: Message, options: Options = {}): DecodeResult {
+    const decodeResult = this.initResult(
+      message,
+      'AGM — Ground UTC Request',
+    );
+
+    const text = (message.text || '').trim();
+    if (!text || text.length < 6) {
+      this.setDecodeLevel(decodeResult, false);
+      return decodeResult;
+    }
+
+    // First 6 chars must be YYMMDD digits.
+    const m = text.match(/^(?<yy>\d{2})(?<mm>\d{2})(?<dd>\d{2})/);
+    if (!m?.groups) {
+      this.setDecodeLevel(decodeResult, false);
+      return decodeResult;
+    }
+
+    const { yy, mm, dd } = m.groups;
+    const monthN = Number(mm);
+    const dayN = Number(dd);
+    if (monthN < 1 || monthN > 12 || dayN < 1 || dayN > 31) {
+      this.setDecodeLevel(decodeResult, false);
+      return decodeResult;
+    }
+
+    const isoDate = `20${yy}-${mm}-${dd}`;
+    const monthNames = [
+      'January',
+      'February',
+      'March',
+      'April',
+      'May',
+      'June',
+      'July',
+      'August',
+      'September',
+      'October',
+      'November',
+      'December',
+    ];
+    const monthName = monthNames[monthN - 1];
+
+    // ── raw ──
+    decodeResult.raw.year = Number(`20${yy}`);
+    decodeResult.raw.month = monthN;
+    decodeResult.raw.day = dayN;
+    decodeResult.raw.date = isoDate;
+
+    // ── formatted ──
+    decodeResult.formatted.items.unshift(
+      {
+        type: 'message_type',
+        code: 'MSGTYP',
+        label: 'Message Type',
+        value: 'AGM — Ground UTC Request',
+      },
+      {
+        type: 'direction',
+        code: 'DIR',
+        label: 'Direction',
+        value: 'Uplink (ground → aircraft)',
+      },
+    );
+    decodeResult.formatted.items.push(
+      {
+        type: 'year',
+        code: 'YEAR',
+        label: 'Year',
+        value: `20${yy}`,
+      },
+      {
+        type: 'month',
+        code: 'MONTH',
+        label: 'Month',
+        value: `${mm} (${monthName})`,
+      },
+      {
+        type: 'day',
+        code: 'DAY',
+        label: 'Day',
+        value: dd,
+      },
+    );
+
+    this.setDecodeLevel(decodeResult, true, 'full');
+    return decodeResult;
+  }
+}
diff --git a/lib/plugins/official.ts b/lib/plugins/official.ts
index 0d3d6fac..f73b2df6 100644
--- a/lib/plugins/official.ts
+++ b/lib/plugins/official.ts
@@ -64,3 +64,4 @@ export * from './Label_QR';
 export * from './Label_QP';
 export * from './Label_QS';
 export * from './Label_QQ';
+export * from './Label_52_AGM';