From da8493cf8d5652664822afed88f073c683278d5f Mon Sep 17 00:00:00 2001
From: Eugene Crosser <crosser@average.org>
Date: Mon, 2 May 2022 19:48:34 +0200
Subject: [PATCH] Change LocEvt to use json encoding

---
 gps303/zmsg.py | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/gps303/zmsg.py b/gps303/zmsg.py
index 80cf000..898918c 100644
--- a/gps303/zmsg.py
+++ b/gps303/zmsg.py
@@ -1,6 +1,7 @@
 """ Zeromq messages """
 
 from datetime import datetime, timezone
+from json import dumps, loads
 import ipaddress as ip
 from struct import pack, unpack
 
@@ -59,15 +60,20 @@ class _Zmsg:
             ),
         )
 
+    def __eq__(self, other):
+        return all(
+            [getattr(self, k) == getattr(other, k) for k, _ in self.KWARGS]
+        )
+
     def decode(self, buffer):
-        raise RuntimeError(
-            self.__class__.__name__ + "must implement `encode()` method"
+        raise NotImplementedError(
+            self.__class__.__name__ + "must implement `decode()` method"
         )
 
     @property
     def packed(self):
-        raise RuntimeError(
-            self.__class__.__name__ + "must implement `encode()` method"
+        raise NotImplementedError(
+            self.__class__.__name__ + "must implement `packed()` property"
         )
 
 
@@ -133,18 +139,27 @@ class LocEvt(_Zmsg):
         ("is_gps", True),
     )
 
+    # This message is for external consumption, so use json encoding,
+    # except imei that forms 16 byte prefix that can be used as the
+    # topic to subscribe.
     @property
     def packed(self):
-        return self.imei.encode() + pack(
-            "!dddB",
-            self.devtime.replace(tzinfo=timezone.utc).timestamp(),
-            self.lat,
-            self.lon,
-            int(self.is_gps),
+        return (
+            self.imei.encode()
+            + dumps(
+                {
+                    "devtime": str(self.devtime),
+                    "latitude": self.lat,
+                    "longitude": self.lon,
+                    "is-gps": self.is_gps,
+                }
+            ).encode()
         )
 
     def decode(self, buffer):
         self.imei = buffer[:16].decode()
-        when, self.lat, self.lon, is_gps = unpack("!dddB", buffer[16:])
-        self.devtime = datetime.fromtimestamp(when).astimezone(tz=timezone.utc)
-        self.is_gps = bool(is_gps)
+        json_data = loads(buffer[16:])
+        self.devtime = datetime.fromisoformat(json_data["devtime"])
+        self.lat = json_data["latitude"]
+        self.lon = json_data["longitude"]
+        self.is_gps = json_data["is-gps"]
-- 
2.39.2