import {makeVar, defaultDataIdFromObject, InMemoryCache} from '@apollo/client/core';

const showNavigationSidebarVar = makeVar(false);
const showProfileSidebarVar = makeVar(false);
const scrollToElementVar = makeVar('');
const currentFilterVar = makeVar('');
const helloEmailVar = makeVar('');

const idToRefFactory = (__typename) => (_, {args, toReference}) => {
          return toReference({
            __typename,
            id: args.id
          });
        };

const typePolicies = {
  // https://www.apollographql.com/docs/react/local-state/managing-state-with-field-policies/#example
  Query: {
    fields: {
      sidebar: {
        read() {
          return {
            profile: showProfileSidebarVar(),
            navigation: showNavigationSidebarVar()
          };
        }
      } ,
      scrollPosition: {
        read() {
          return {
            scrollTo: scrollToElementVar()
          };
        }
      },
      instrumentFilter: {
        read() {
          return {
            currentFilter: currentFilterVar()
          };
        }
      },
      helloEmail: {
        read() {
          return {
            email: helloEmailVar()
          };
        }
      },


    // these used to be in cacheRedirects, now here
      // contentBlock: (_, args, {getCacheKey}) => getCacheKey({__typename: 'ContentBlockNode', id: args.id}),
      contentBlock: {
        read: idToRefFactory('ContentBlockNode')
        // read(_, {args, toReference}) {
        //   return toReference({
        //     __typename: 'ContentBlockNode',
        //     id: args.id
        //   });
        // }
      }
    },
    // chapter: (_, args, {getCacheKey}) => getCacheKey({__typename: 'ChapterNode', id: args.id}),
    chapter: {read: idToRefFactory('ChapterNode')},
    assignment: {read: idToRefFactory('AssignmentNode')},
    objective: {read: idToRefFactory('ObjectiveNode')},
    objectiveGroup: {read: idToRefFactory('ObjectiveGroupNode')},
    projectEntry: {read: idToRefFactory('ProjectEntryNode')},
    // assignment: (_, args, {getCacheKey}) => getCacheKey({__typename: 'AssignmentNode', id: args.id}),
    // objective: (_, args, {getCacheKey}) => getCacheKey({__typename: 'ObjectiveNode', id: args.id}),
    // objectiveGroup: (_, args, {getCacheKey}) => getCacheKey({__typename: 'ObjectiveGroupNode', id: args.id}),
    // projectEntry: (_, args, {getCacheKey}) => getCacheKey({__typename: 'ProjectEntryNode', id: args.id}),
  },
};

const possibleTypes = {
 ContentBlockInterface: ['ContentBlockNode', 'SnapshotContentBlockNode'],
 ChapterInterface: ['ChapterNode', 'SnapshotChapterNode']
};

const cache = new InMemoryCache({
  // used to 'override' the behavior in resolving different types. We use it for local state management
  // https://www.apollographql.com/docs/react/local-state/managing-state-with-field-policies/#example
  typePolicies,
  possibleTypes,
  // todo: document what this does, or link the doc for it at least
  dataIdFromObject: obj => {
    switch (obj.__typename) {
      case 'InstrumentNode':
      case 'ModuleNode':
      case 'RoomEntryNode':
        return `${obj.__typename}:${obj.slug}`;
      default:
        return defaultDataIdFromObject(obj);
    }
  },
  // todo: document what this does, or link the doc for it at least
  // todo: this is deprecated, it's now included in typePolicies
  cacheRedirects: {
    Query: {
      project: (_, args, {getCacheKey}) => {
        if (args.slug) {
          return getCacheKey({__typename: 'ProjectNode', id: args.slug});
        } else {
          return getCacheKey({__typename: 'ProjectNode', id: args.id});
        }
      },
    },
  },
});

// TODO: Monkey-patching in a fix for an open issue suggesting that
// `readQuery` should return null or undefined if the query is not yet in the
// cache: https://github.com/apollographql/apollo-feature-requests/issues/1
// probably not needed any more, as per https://github.com/apollographql/apollo-client/pull/7098
// cache.originalReadQuery = cache.readQuery;
// cache.readQuery = (...args) => {
//   try {
//     return cache.originalReadQuery(...args);
//   } catch (err) {
//     console.error(err);
//     return undefined;
//   }
// };


export {
  showProfileSidebarVar,
  showNavigationSidebarVar,
  scrollToElementVar,
  currentFilterVar,
  helloEmailVar,
  cache
};
export default cache;