WIP

app/graphql/resolvers/rdf.ts

@@ -16,6 +16,7 @@ import { truthy } from "@/domain/types";
 import { Loaders } from "@/graphql/context";
 import {
   DataCubeComponentFilter,
+  DataCubeObservationFilter,
   DataCubeResolvers,
   DimensionResolvers,
   QueryResolvers,
@@ -323,9 +324,15 @@ export const dataCubesMetadata: NonNullable<
 export const dataCubesObservations: NonNullable<
   QueryResolvers["dataCubesObservations"]
 > = async (_, { locale, filters }, { setup }, info) => {
+  if (filters.length > 1 && filters.some((f) => f.joinBy === undefined)) {
+    throw new Error("Can't query multiple cubes observations without joinBy!");
+  }
+
   const { loaders, sparqlClient, cache } = await setup(info);
+  // If the cube was updated, we need to also update the filter with the correct iri.
+  const filtersWithCorrectIri: DataCubeObservationFilter[] = [];
 
-  const data: Observation[] = [];
+  const dataByCubeIri: Record<string, Observation[]> = {};
   const sparqlEditorUrls: DataCubesObservations["sparqlEditorUrls"] = [];
 
   await Promise.all(
@@ -340,6 +347,11 @@ export const dataCubesObservations: NonNullable<
       const cube = latest ? await getLatestCube(rawCube) : rawCube;
       // TODO: optimize to avoid fetching the shape at all
       await cube.fetchShape();
+      filtersWithCorrectIri.push({
+        ...filter,
+        iri: cube.term?.value!,
+      });
+
       const { query, observations } = await getCubeObservations({
         cube,
         locale,
@@ -348,7 +360,8 @@ export const dataCubesObservations: NonNullable<
         componentIris,
         cache,
       });
-      data.push(...observations);
+
+      dataByCubeIri[cube.term?.value!] = observations;
       sparqlEditorUrls.push({
         cubeIri: cube.term?.value!,
         url: getSparqlEditorUrl({
@@ -362,8 +375,59 @@ export const dataCubesObservations: NonNullable<
     })
   );
 
+  const joinBys = filtersWithCorrectIri.reduce((acc, f) => {
+    acc[f.iri] = f.joinBy!;
+
+    return acc;
+  }, {} as Record<string, string>);
+
+  // FIXME: handle situation where we have column of the same name in multiple cubes
+  const observations: Observation[] = [];
+  const allKeys = Object.entries(dataByCubeIri).flatMap(([_, obs]) => {
+    return Object.keys(obs[0]);
+  });
+
+  Object.entries(dataByCubeIri).forEach(([cubeIri, obs], i) => {
+    const rest = Object.entries(dataByCubeIri)
+      .filter((_, j) => j !== i)
+      .map((c) =>
+        c[1].map((d) => ({ ...d, cubeIri: c[0] } as Record<string, any>))
+      );
+
+    [...obs].forEach((ob) => {
+      for (const r of rest.length === 0 ? [[]] : [...rest]) {
+        const base = allKeys.reduce((acc, d) => {
+          acc[d] = null;
+
+          return acc;
+        }, {} as Record<string, any>);
+
+        const toMergeId = r.findIndex(
+          (o) => o[joinBys[o.cubeIri]] === ob[joinBys[cubeIri]]
+        );
+
+        if (toMergeId !== -1) {
+          const { cubeIri: otherCubeIri, ...other } = r[toMergeId];
+          const toPush = Object.assign(base, ob, other, {
+            joinBy: ob[joinBys[cubeIri]] ?? other[joinBys[otherCubeIri]],
+          });
+          rest.splice(toMergeId, 1);
+          observations.push(toPush);
+        } else {
+          observations.push(
+            Object.assign(base, ob, { joinBy: ob[joinBys[cubeIri]] })
+          );
+        }
+      }
+      obs.splice(obs.indexOf(ob), 1);
+    });
+  });
+
+  console.log(observations);
+
   return {
-    data,
+    // data: Object.values(dataByCubeIri).flat(),
+    data: observations,
     sparqlEditorUrls,
   };
 };