fix: separate historical source methodologies

frontend/src/components/datasets/SourceCatalogPanel.tsx

@@ -66,12 +66,42 @@ function datasetTheme(dataset: DatasetCreateResponse): string | null {
   return null
 }
 
+function timelineSummary(
+  temporalCount: number,
+  temporalSeriesCount: number,
+  otherMethodCount: number,
+  firstYear: number | null,
+  lastYear: number | null,
+): string {
+  if (temporalCount < 2 || !firstYear || !lastYear) {
+    return 'Alleen de huidige toestand is vergelijkbaar beschikbaar.'
+  }
+  const seriesNote = temporalSeriesCount > 1
+    ? ` in ${temporalSeriesCount} afzonderlijke reeksen`
+    : ''
+  const methodNote = otherMethodCount > 0
+    ? `plus ${otherMethodCount} andere bronmethode${otherMethodCount === 1 ? '' : 'n'}`
+    : null
+  return [
+    `${temporalCount} vergelijkbare meetmomenten${seriesNote}`,
+    `${firstYear}-${lastYear}`,
+    methodNote,
+  ].filter(Boolean).join(' · ')
+}
+
 export function SourceCatalogPanel({ datasets }: SourceCatalogPanelProps): JSX.Element {
   const ready = datasets.filter((dataset) => dataset.status === 'ready')
   const themes = Object.keys(THEME_LABELS).map((theme) => {
     const matches = ready.filter((dataset) => datasetTheme(dataset) === theme)
     const temporal = matches.filter((dataset) => dataset.temporal_series_key && dataset.observed_at)
-    const years = temporal.map((dataset) => new Date(dataset.observed_at as string).getUTCFullYear())
+    const seriesGroups = new Map<string, DatasetCreateResponse[]>()
+    temporal.forEach((dataset) => {
+      const seriesKey = dataset.temporal_series_key as string
+      seriesGroups.set(seriesKey, [...(seriesGroups.get(seriesKey) ?? []), dataset])
+    })
+    const comparableSeries = [...seriesGroups.values()].filter((series) => series.length >= 2)
+    const comparableObservations = comparableSeries.flat()
+    const years = comparableObservations.map((dataset) => new Date(dataset.observed_at as string).getUTCFullYear())
     const latest = [...matches].sort(
       (left, right) => new Date(right.observed_at ?? right.imported_at ?? 0).getTime() - new Date(left.observed_at ?? left.imported_at ?? 0).getTime(),
     )[0]
@@ -79,7 +109,9 @@ export function SourceCatalogPanel({ datasets }: SourceCatalogPanelProps): JSX.E
       theme,
       label: THEME_LABELS[theme],
       datasetCount: matches.length,
-      temporalCount: temporal.length,
+      temporalCount: comparableObservations.length,
+      temporalSeriesCount: comparableSeries.length,
+      otherMethodCount: matches.length - comparableObservations.length,
       firstYear: years.length ? Math.min(...years) : null,
       lastYear: years.length ? Math.max(...years) : null,
       source: latest?.source_name ?? latest?.source ?? null,
@@ -105,11 +137,13 @@ export function SourceCatalogPanel({ datasets }: SourceCatalogPanelProps): JSX.E
               <span>{theme.source ? theme.source.replaceAll('_', ' ') : 'Nog niet ingeladen'}</span>
             </div>
             <b>{theme.datasetCount > 0 ? 'Beschikbaar' : 'Ontbreekt'}</b>
-            <p>
-              {theme.temporalCount >= 2 && theme.firstYear && theme.lastYear
-                ? `${theme.temporalCount} officiële meetmomenten · ${theme.firstYear}-${theme.lastYear}`
-                : 'Alleen de huidige toestand is vergelijkbaar beschikbaar.'}
-            </p>
+            <p>{timelineSummary(
+              theme.temporalCount,
+              theme.temporalSeriesCount,
+              theme.otherMethodCount,
+              theme.firstYear,
+              theme.lastYear,
+            )}</p>
           </article>
         ))}
       </div>