Handle null values in characteristics (#20)

Apparently `characteristic.value` can also be null. Let’s handle it
properly. Fixes #19

src/boundaries/hap.ts

@@ -1,4 +1,4 @@
-import z from 'zod'
+import z, { type ZodNull, type ZodOptional, type ZodType, type ZodUnion } from 'zod'
 
 const NumericTypesBoundary = z.union([
     z.literal('bool'),
@@ -11,17 +11,21 @@ const NumericTypesBoundary = z.union([
 ])
 export type NumericTypes = z.infer<typeof NumericTypesBoundary>
 
+function optionalNullable<T extends ZodType>(type: T): ZodOptional<ZodUnion<[ZodNull, T]>> {
+    return z.optional(z.union([z.null(), type]))
+}
+
 export const CharacteristicBoundary = z.intersection(
     z.object({ type: z.string(), description: z.string() }),
     z.union([
         z.object({
             format: NumericTypesBoundary,
-            value: z.optional(z.number()),
             unit: z.optional(z.string()),
+            value: optionalNullable(z.number()),
         }),
-        z.object({ format: z.literal('string'), value: z.string() }),
+        z.object({ format: z.literal('string'), value: optionalNullable(z.string()) }),
-        z.object({ format: z.literal('data'), value: z.optional(z.string()) }),
+        z.object({ format: z.literal('data'), value: optionalNullable(z.string()) }),
-        z.object({ format: z.literal('tlv8'), value: z.string(z.string()) }),
+        z.object({ format: z.literal('tlv8'), value: optionalNullable(z.string()) }),
     ]),
 )
 export type Characteristic = z.infer<typeof CharacteristicBoundary>

src/metrics.ts

@@ -42,7 +42,7 @@ export function aggregate(devices: Device[], timestamp: Date): Metric[] {
                         case 'uint16':
                         case 'uint32':
                         case 'uint64':
-                            if (typeof characteristic.value !== 'undefined') {
+                            if (characteristic.value != null) {
                                 if (METRICS_FILTER.includes(characteristic.description)) {
                                     break
                                 }
@@ -108,6 +108,7 @@ function getServiceLabels(service: Service): Record<string, string> {
 
     for (const characteristic of service.characteristics) {
         if (
+            characteristic.value != null &&
             characteristic.format === 'string' &&
             [
                 'Name',

tests/aggregator.test.ts

@@ -6,6 +6,7 @@ import emptyData from './fixtures/empty.json'
 import tpLinkData from './fixtures/tp-link.json'
 import harmonyData from './fixtures/harmony.json'
 import unknownUuidData from './fixtures/issues/gh-9-unknown-uuid.json'
+import nullableValueData from './fixtures/issues/gh-19-nullable-value.json'
 
 describe('Metrics aggregator', () => {
     const timestamp = new Date('2000-01-01 00:00:00 UTC')
@@ -171,4 +172,10 @@ describe('Metrics aggregator', () => {
             new Metric('custom_restart', 0, timestamp, expectedLabels),
         ])
     })
+
+    test('Aggregates metrics with nullable values', () => {
+        const unknowmnValue = DeviceBoundary.parse(nullableValueData)
+
+        expect(aggregate([unknowmnValue], timestamp)).toEqual([])
+    })
 })

tests/fixtures/issues/gh-19-nullable-value.json

@@ -0,0 +1,48 @@
+{
+    "ipAddress": "192.168.0.1",
+    "instance": {
+        "host": "192.168.0.1",
+        "port": 51826,
+        "url": "http://192.168.0.1:51826",
+        "deviceID": "AA:AA:AA:AA:AA:AA",
+        "txt": {
+            "c#": "5",
+            "ff": "0",
+            "id": "AA:AA:AA:AA:AA:AA",
+            "md": "homebridge",
+            "pv": "1.1",
+            "s#": "1",
+            "sf": "0",
+            "ci": "2",
+            "sh": "Hv0v9A=="
+        },
+        "name": "Test bridge"
+    },
+    "accessories": {
+        "accessories": [
+            {
+                "aid": 3,
+                "services": [
+                    {
+                        "type": "00000012-0000-1000-8000-656261617577",
+                        "iid": 8,
+                        "characteristics": [
+                            {
+                                "type": "00000073-0000-1000-8000-0026BB765291",
+                                "iid": 11,
+                                "value": null,
+                                "perms": ["ev", "pr"],
+                                "description": "Programmable Switch Event",
+                                "format": "uint8",
+                                "minValue": 0,
+                                "maxValue": 2,
+                                "minStep": 1,
+                                "valid-values": [0]
+                            }
+                        ]
+                    }
+                ]
+            }
+        ]
+    }
+}