1 files changed, 67 insertions, 0 deletions
diff --git a/app/assets/javascripts/lib/apollo/persistence_mapper.js b/app/assets/javascripts/lib/apollo/persistence_mapper.js
new file mode 100644
index 00000000000..8fc7c69c79d
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+++ b/app/assets/javascripts/lib/apollo/persistence_mapper.js
@@ -0,0 +1,67 @@
+// this file is based on https://github.com/apollographql/apollo-cache-persist/blob/master/examples/react-native/src/utils/persistence/persistenceMapper.ts
+// with some heavy refactororing
+
+/* eslint-disable @gitlab/require-i18n-strings */
+/* eslint-disable no-underscore-dangle */
+/* eslint-disable no-param-reassign */
+/* eslint-disable dot-notation */
+export const persistenceMapper = async (data) => {
+  const parsed = JSON.parse(data);
+
+  const mapped = {};
+  const persistEntities = [];
+  const rootQuery = parsed['ROOT_QUERY'];
+
+  // cache entities that have `__persist: true`
+  Object.keys(parsed).forEach((key) => {
+    if (parsed[key]['__persist']) {
+      persistEntities.push(key);
+    }
+  });
+
+  // cache root queries that have `@persist` directive
+  mapped['ROOT_QUERY'] = Object.keys(rootQuery).reduce(
+    (obj, key) => {
+      if (key === '__typename') return obj;
+
+      if (/@persist$/.test(key)) {
+        obj[key] = rootQuery[key];
+
+        if (Array.isArray(rootQuery[key])) {
+          const entities = rootQuery[key].map((item) => item.__ref);
+          persistEntities.push(...entities);
+        } else {
+          const entity = rootQuery[key].__ref;
+          persistEntities.push(entity);
+        }
+      }
+
+      return obj;
+    },
+    { __typename: 'Query' },
+  );
+
+  persistEntities.reduce((obj, key) => {
+    const parsedEntity = parsed[key];
+
+    // check for root queries and only cache root query properties that have `__persist: true`
+    // we need this to prevent overcaching when we fetch the same entity (e.g. project) more than once
+    // with different set of fields
+
+    if (Object.values(rootQuery).some((value) => value.__ref === key)) {
+      const mappedEntity = {};
+      Object.entries(parsedEntity).forEach(([parsedKey, parsedValue]) => {
+        if (!parsedValue || typeof parsedValue !== 'object' || parsedValue['__persist']) {
+          mappedEntity[parsedKey] = parsedValue;
+        }
+      });
+      obj[key] = mappedEntity;
+    } else {
+      obj[key] = parsed[key];
+    }
+
+    return obj;
+  }, mapped);
+
+  return JSON.stringify(mapped);
+};