/*

Generic mutation wrapper to insert a new document in a collection and update
a related query on the client with the new item and a new total item count. 

Sample mutation: 

  mutation moviesNew($document: MoviesInput) {
    moviesNew(document: $document) {
      ...MoviesNewFormFragment
    }
  }

Arguments: 

  - document: the document to insert

Child Props:

  - newMutation(document)
    
*/

import React, { Component } from 'react';
import { graphql } from 'react-apollo';
import gql from 'graphql-tag';
import update from 'immutability-helper';

export default function withNew(options) {

  // get options
  const { collection, fragment, queryToUpdate } = options,
        fragmentName = fragment.definitions[0].name.value,
        collectionName = collection._name,
        mutationName = collection.options.mutations.new.name,
        listResolverName = collection.options.resolvers.list.name,
        totalResolverName = collection.options.resolvers.total.name;

  // wrap component with graphql HoC
  return graphql(gql`
    mutation ${mutationName}($document: ${collectionName}Input) {
      ${mutationName}(document: $document) {
        ...${fragmentName}
      }
    }
    ${fragment}
  `, {
    props: ({ownProps, mutate}) => ({
      newMutation: ({document}) => {

        // if a queryToUpdate is passed as prop, generate updateQueries function
        let updateQueries = {};
        if (queryToUpdate) {
          updateQueries = {
            [queryToUpdate]: (prev, { mutationResult }) => {

              // get new document to insert
              const newDocument = mutationResult.data[mutationName];

              // generate new list with updated total count and document inserted at top
              const newList = update(prev, {
                [listResolverName]: { $unshift: [newDocument] },
                [totalResolverName]: { $set: prev[totalResolverName] + 1 }
              });

              return newList;
            }
          };
        }

        return mutate({ 
          variables: { document },
          updateQueries: options.updateQueries || updateQueries
        });
      }
    }),
  });

}