display results as color and opacity gradient

party colors were not really useful, when there are only two winning parties

streets.ps1

@@ -4,12 +4,58 @@ 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
 
 $greenParty = ($data[0].PSObject.Properties.Name -like '*Grüne*')[0]
 
-$partyMapping = $data | Where-Object Description -eq 'Color'
+$dataMeasure = $data.$greenParty
+| Where-Object {$_ -match '%$'}
+| ForEach-Object {$_ -replace '%$'}
+| Measure-Object -Minimum -Maximum
+$minimumResultValue = $dataMeasure.Minimum
+$maximumResultValue = $dataMeasure.Maximum
 
 # nested array instead of hashtable, because hashtable keys are case-insensitive
 $replacementList = @(
@@ -47,27 +93,21 @@ $featureList = Import-Csv ./polling_stations.csv
             $_.Formatted + "`t" + $_.Party
         }) -join "`n"
 
-        $greenResult = ($electionResultArray | Where-Object Party -eq $greenParty).ResultValue
+        $greenResultValue = ($electionResultArray | Where-Object Party -eq $greenParty).ResultValue
 
-        $opacity = ($greenResult - 20) / 5 * 0.6 + 0.4
-        $opacity = $opacity -gt 1.0 ? 1.0 : $opacity
-        $opacity = $opacity -lt 0.4 ? 0.4 : $opacity
+        $colorGreen = (($greenResultValue - $minimumResultValue) * (100 - 220)) / ($maximumResultValue - $minimumResultValue) + 220
+        $color = "rgb(0, $colorGreen, 0)"
 
-        $weight = ($greenResult - 20) / 5 * 10 + 5
-        $weight = $weight -gt 15 ? 15 : $weight
-        $weight = $weight -lt  5 ?  5 : $weight
-
-        $party = $electionResultArray[0].Party
+        $opacity = (($greenResultValue - $minimumResultValue) * (1.0 - 0.4)) / ($maximumResultValue - $minimumResultValue) + 0.4
     } else {
         $electionResultString = 'no data available'
         $opacity = 0.5
-        $party = $null
+        $color = '#ff00ff'
     }
 
     $umapOptiones = [PSCustomObject]@{
-        #color = ($using:partyMapping).$party
-        color = $partyMapping.$party ?? '#ff00ff'
-        weight = $weight
+        color = $color
+        weight = 10
         opacity = $opacity
     }
 
@@ -81,29 +121,7 @@ $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 +159,5 @@ $output = [PSCustomObject]@{
 }
 
 $output | ConvertTo-Json -Depth 99 | Out-File output.geojson
+
+$cache | Export-Clixml ./cache.xml