From 49c96d01e7d4e16542009c476fc57ad62d8b8d38 Mon Sep 17 00:00:00 2001
From: Tim Cowlishaw <tim@timcowlishaw.co.uk>
Date: Fri, 11 Oct 2024 07:53:45 +0200
Subject: [PATCH] ensure null values are elided

---
 app/grammars/raw_message.tt              | 24 +++++++++++++++++++-----
 spec/lib/raw_mqtt_message_parser_spec.rb |  6 ++++++
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/app/grammars/raw_message.tt b/app/grammars/raw_message.tt
index 3c904d90..96cfc8b0 100644
--- a/app/grammars/raw_message.tt
+++ b/app/grammars/raw_message.tt
@@ -14,9 +14,11 @@ grammar RawMessage
           pair = pair_node.to_value
           if pair[:key] == :t
             accum.merge(recorded_at: pair[:value])
-          else
+          elsif pair && pair[:value]
             new_sensors_list = accum[:sensors] + [{id: pair[:key], value: pair[:value]}]
             accum.merge(sensors: new_sensors_list)
+          else
+            accum
           end
         }
       end
@@ -34,23 +36,35 @@ grammar RawMessage
   rule timestamp_pair
     't' whitespace ':' timestamp {
       def to_value
-        { key: :t, value: timestamp.text_value }
+        { key: :t, value: timestamp.to_value }
       end
     }
   end
 
   rule value_pair
-    number whitespace ':' whitespace value {
+    number whitespace ':' whitespace optional_value {
       def to_value
-         { key: number.text_value, value: value.text_value }
+         { key: number.to_value, value: optional_value.to_value }
       end
     }
   end
 
+  rule optional_value
+    value / null
+  end
+
   rule value
     float / number
   end
 
+  rule null
+    "null" {
+      def to_value
+        nil
+      end
+    }
+  end
+
   rule float
     float:(number decimal_part) {
       def to_value
@@ -74,7 +88,7 @@ grammar RawMessage
   rule timestamp
     timestamp:([0-9] 4..4 '-' [0-9] 2..2 '-' [0-9] 2..2 'T' [0-9] 2..2 ':' [0-9] 2..2 ':' [0-9] 2..2 'Z') {
       def to_value
-        Time.parse(timestamp.text_value)
+        timestamp.text_value
       end
     }
   end
diff --git a/spec/lib/raw_mqtt_message_parser_spec.rb b/spec/lib/raw_mqtt_message_parser_spec.rb
index 97817fbe..7e3d798a 100644
--- a/spec/lib/raw_mqtt_message_parser_spec.rb
+++ b/spec/lib/raw_mqtt_message_parser_spec.rb
@@ -53,6 +53,12 @@
     expect(parsed).to eq({ data: [ { recorded_at: "2024-09-25T13:19:38Z", sensors: [{id: "100", value: "-2000.12345"}, { id: "21", value: "12345.23450"}] }]})
   end
 
+  it "strips null vales from messages" do
+    message = "{t:2024-09-25T13:19:38Z,100:-2000.12345,21:null}"
+    parsed = parser.parse(message)
+    expect(parsed).to eq({ data: [ { recorded_at: "2024-09-25T13:19:38Z", sensors: [{id: "100", value: "-2000.12345"}] }]})
+  end
+
   it "returns nil if no valid message parsed" do
     message = "ceci n'est pas un message"
     parsed = parser.parse(message)