From f94d3074e1f0d1fbae56ad0cb266d434cab8ed42 Mon Sep 17 00:00:00 2001
From: ingalls <nick@ingalls.ca>
Date: Tue, 24 Sep 2024 12:45:16 -0600
Subject: [PATCH] Fallback Syntax and Tests

---
 api/lib/style.ts       |  4 ++++
 api/test/style.test.ts | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/api/lib/style.ts b/api/lib/style.ts
index 0a03f9fee..34b974dac 100644
--- a/api/lib/style.ts
+++ b/api/lib/style.ts
@@ -4,6 +4,10 @@ import type { Feature } from '@tak-ps/node-cot';
 import handlebars from 'handlebars';
 import Err from '@openaddresses/batch-error';
 
+handlebars.registerHelper('fallback', (...params: Array<unknown>) => {
+    return params.find(el => !!el)
+})
+
 interface ValidateStyle {
     id?: string;
     callsign?: string;
diff --git a/api/test/style.test.ts b/api/test/style.test.ts
index 2d77fd09a..4e48f908a 100644
--- a/api/test/style.test.ts
+++ b/api/test/style.test.ts
@@ -734,3 +734,45 @@ test('Style: Invalid Templates', async () => {
         })
     }, /Expecting/);
 });
+
+test('Style: {{fallback p1 p2 ...}}', async () => {
+    const style = new Style({
+        stale: 123,
+        enabled_styles: true,
+        styles: {
+            callsign: '{{fallback none1 none2 yes1 none3 yes2}}'
+        }
+    });
+
+    assert.deepEqual(await style.feat({
+        type: 'Feature',
+        properties: {
+            metadata: {
+                yes1: 'I exist',
+                yes2: 'I exist but shouldn\'t be picked'
+            }
+        },
+        geometry: {
+            type: 'Point',
+            coordinates: [0, 0]
+        }
+    }), {
+        type: 'Feature',
+        properties: {
+            callsign: 'I exist',
+            metadata: {                                                                                                                                                          
+                yes1: 'I exist',                                                             
+                yes2: "I exist but shouldn't be picked"                                    
+            },                   
+            stale: 123000       
+        },               
+        geometry: {
+            coordinates: [
+                0,
+                0          
+            ],
+            type: 'Point'
+        },                     
+    });
+});
+