import { ApolloClient, InMemoryCache, HttpLink, gql } from '@apollo/client';

const GET_CART_ITEMS = gql`
  query GetCartItems {
    cartItems @client
  }
`;

const cache = new InMemoryCache();
cache.writeQuery({
  query: GET_CART_ITEMS,
  data: {
    cartItems: [],
  },
});

const client = new ApolloClient({
  cache,
  link: new HttpLink({
    uri: 'http://localhost:4000/graphql',
  }),
  resolvers: {
    Launch: {
      isInCart: (launch, _args, { cache }) => {
        const { cartItems } = cache.readQuery({ query: GET_CART_ITEMS });
        return cartItems.includes(launch.id);
      },
    },
  },
});

const GET_LAUNCH_DETAILS = gql`
  query LaunchDetails($launchId: ID!) {
    launch(id: $launchId) {
      isInCart @client
      site
      rocket {
        type
      }
    }
  }
`;

// ... run the query using client.query, a <Query /> component, etc.

import { InMemoryCache } from '@apollo/client';

const cache = new InMemoryCache();
cache.writeQuery({
  query: gql`query MyQuery {
    isLoggedIn,
    cartItems
  }`,
  data: {
    isLoggedIn: !!localStorage.getItem('token'),
    cartItems: [],
  },
});

import { ApolloClient, InMemoryCache } from '@apollo/client';

const client = new ApolloClient({
  cache: new InMemoryCache({
    typePolicies: {
      Query: {
        fields: {
          book: {
            read(_, { args, toReference }) {
              return toReference({
                __typename: 'Book',
                id: args.id,
              });
            }
          }
        }
      }
    }
  })
});

import { ApolloClient, InMemoryCache, gql } from '@apollo/client';

let nextTodoId = 0;

const cache = new InMemoryCache();

cache.writeQuery({
  query: gql`query GetTodos { todos { ... } }`,
  data: { todos: [] },
});

const client = new ApolloClient({
  resolvers: {
    Mutation: {
      addTodo: (_, { text }, { cache }) => {
        const query = gql`
          query GetTodos {
            todos @client {
              id
              text
              completed
            }
          }
        `;

        const previous = cache.readQuery({ query });
        const newTodo = { id: nextTodoId++, text, completed: false, __typename: 'TodoItem' };
        const data = {
          todos: [...previous.todos, newTodo],
        };

        cache.writeQuery({ query, data });
        return newTodo;
      },
    },
  },
});

import { ApolloClient, InMemoryCache } from '@apollo/client';

const client = new ApolloClient({
  cache: new InMemoryCache(),
  resolvers: {
    Mutation: {
      updateVisibilityFilter: (_, { visibilityFilter }, { cache }) => {
        cache.writeQuery({
          query: gql`query GetVisibilityFilter { visibilityFilter }`,
          data: {
            __typename: 'Filter',
            visibilityFilter,
          },
        });
      },
    },
  },
};