implement a cache

so we don't hammer the overpass API as much

streets.ps1

@@ -4,6 +4,47 @@ param (
     $DataSource = './Gesamtergebnis-Gemeinderatswahl-2019_stripped.csv'
 )
 
+function Get-OverpassStreet {
+    param (
+        [string]
+        $Name
+    )
+
+    if (!$cache.$Name) {
+        $query = @'
+<osm-script>
+  <query into="_" type="area">
+    <has-kv k="name" modv="" v="Öhringen"/>
+  </query>
+  <query into="_" type="way">
+    <has-kv k="name" modv="" v="{0}"/>
+    <area-query/>
+  </query>
+  <union into="_">
+    <item from="_" into="_"/>
+    <recurse type="way-node"/>
+  </union>
+  <print e="" from="_" geometry="skeleton" ids="yes" limit="" mode="body" n="" order="id" s="" w=""/>
+</osm-script>
+'@ -f $Name
+
+        $overpassSplat = @{
+            Method = 'Post'
+            Uri = 'https://overpass-api.de/api/interpreter'
+            Body = $query
+        }
+        $cache.$Name = Invoke-RestMethod @overpassSplat
+    }
+
+    $cache.$Name
+}
+
+if (Test-Path ./cache.xml) {
+    $cache = Import-Clixml ./cache.xml
+} else {
+    $cache = @{}
+}
+
 
 $data = Import-Csv $DataSource
 
@@ -81,29 +122,7 @@ $featureList = Import-Csv ./polling_stations.csv
         $description += "`n`n"
         $description += $electionResultString
 
-        $query = @'
-<osm-script>
-  <query into="_" type="area">
-    <has-kv k="name" modv="" v="Öhringen"/>
-  </query>
-  <query into="_" type="way">
-    <has-kv k="name" modv="" v="{0}"/>
-    <area-query/>
-  </query>
-  <union into="_">
-    <item from="_" into="_"/>
-    <recurse type="way-node"/>
-  </union>
-  <print e="" from="_" geometry="skeleton" ids="yes" limit="" mode="body" n="" order="id" s="" w=""/>
-</osm-script>
-'@ -f $street
-
-        $overpassSplat = @{
-            Method = 'Post'
-            Uri = 'https://overpass-api.de/api/interpreter'
-            Body = $query
-        }
-        $overpassResult = Invoke-RestMethod @overpassSplat
+        $overpassResult = Get-OverpassStreet -Name $street
 
         if (!$overpassResult.osm.way.nd) {
             Write-Error ('way "{0}" for polling station "{1}" probably not found' -f $street,$pollingStation.name)
@@ -141,3 +160,5 @@ $output = [PSCustomObject]@{
 }
 
 $output | ConvertTo-Json -Depth 99 | Out-File output.geojson
+
+$cache | Export-Clixml ./cache.xml