feat: add searchPagination resolver

Author: nodkz

README.md

@@ -52,12 +52,15 @@ Live demo of [Introspection of Elasticsearch API via Graphiql](https://graphql-c
 ---
 
 ## TypeComposer from Elastic mapping
-In other side this module is a plugin for [graphql-compose](https://github.com/nodkz/graphql-compose), which derives GraphQLType from your [elastic mapping](https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping.html) generates tons of types, provides all available methods in QueryDSL, Aggregations, Sorting with field autocompletion according to types in your mapping (like Dev Tools Console in Kibana).
+In other side this module is a plugin for [graphql-compose](https://github.com/graphql-compose/graphql-compose), which derives GraphQLType from your [elastic mapping](https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping.html) generates tons of types, provides all available methods in QueryDSL, Aggregations, Sorting with field autocompletion according to types in your mapping (like Dev Tools Console in Kibana).
 
 Generated TypeComposer model has several awesome resolvers:
 - `search` - greatly simplified elastic `search` method. According to GraphQL adaptation and its projection bunch of params setup automatically due your graphql query (eg `_source`, `explain`, `version`, `trackScores`), other rare fine tuning params moved to `opts` input field.  
 - `searchConnection` - elastic `search` method that implements Relay Cursor Connection [spec](https://facebook.github.io/relay/graphql/connections.htm) for infinite lists. Internally it uses cheap [search_after](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-search-after.html) API. One downside, Elastic does not support backward scrolling, so `before` argument will not work.
-- more resolvers will be later after my vacation: `suggest`, `getById`, `updateById` and others
+- `searchPagination` - elastic `search` method that has `page` and `perPage` arguments
+- `findById` - get elastic record by id
+- `updateById` - update elastic record by id
+- feel free to add your resolver or ask for a new one
 
 ```js
 import { GraphQLSchema, GraphQLObjectType } from 'graphql';
@@ -118,8 +121,9 @@ const Schema = new GraphQLSchema({
   query: new GraphQLObjectType({
     name: 'Query',
     fields: {
-      user: UserTC.get('$search').getFieldConfig(),
-      userConnection: UserTC.get('$searchConnection').getFieldConfig(),
+      user: UserTC.getResolver('search').getFieldConfig(),
+      userPagination: UserTC.getResolver('searchPagination').getFieldConfig(),
+      userConnection: UserTC.getResolver('searchConnection').getFieldConfig(),
     },
   }),
 });

src/composeWithElastic.js

@@ -4,6 +4,7 @@ import { TypeComposer } from 'graphql-compose';
 import { convertToSourceTC, inputPropertiesToGraphQLTypes } from './mappingConverter';
 import createSearchResolver from './resolvers/search';
 import createSearchConnectionResolver from './resolvers/searchConnection';
+import createSearchPaginationResolver from './resolvers/searchPagination';
 import createFindByIdResolver from './resolvers/findById';
 import createUpdateByIdResolver from './resolvers/updateById';
 
@@ -65,11 +66,13 @@ export function composeWithElastic(opts: composeWithElasticOptsT): TypeComposer
 
   const searchR = createSearchResolver(fieldMap, sourceTC, opts);
   const searchConnectionR = createSearchConnectionResolver(searchR, opts);
+  const searchPaginationR = createSearchPaginationResolver(searchR, opts);
   const findByIdR = createFindByIdResolver(fieldMap, sourceTC, opts);
   const updateByIdR = createUpdateByIdResolver(fieldMap, sourceTC, opts);
 
   sourceTC.addResolver(searchR);
   sourceTC.addResolver(searchConnectionR);
+  sourceTC.addResolver(searchPaginationR);
   sourceTC.addResolver(findByIdR);
   sourceTC.addResolver(updateByIdR);
 

src/resolvers/searchPagination.js

@@ -0,0 +1,116 @@
+/* @flow */
+
+import { Resolver, TypeComposer } from 'graphql-compose';
+import { getTypeName, getOrSetType } from '../utils';
+
+export default function createSearchPaginationResolver(
+  searchResolver: Resolver,
+  opts: mixed = {}
+): Resolver {
+  const resolver = searchResolver.clone({
+    name: `searchPagination`,
+  });
+
+  resolver
+    .addArgs({
+      page: 'Int',
+      perPage: {
+        type: 'Int',
+        defaultValue: 20,
+      },
+    })
+    .removeArg(['limit', 'skip'])
+    .reorderArgs(['q', 'query', 'sort', 'aggs', 'page', 'perPage']);
+
+  const searchTC = searchResolver.getTypeComposer();
+  if (!searchTC) {
+    throw new Error('Cannot get TypeComposer from resolver. Maybe resolver return Scalar?!');
+  }
+
+  const typeName = searchTC.getTypeName();
+  resolver.setType(
+    searchTC
+      .clone(`${typeName}Pagination`)
+      .addFields({
+        pageInfo: getPageInfoTC(opts),
+        items: [searchTC.get('hits')],
+      })
+      .removeField('hits')
+      .reorderFields(['items', 'count', 'pageInfo', 'aggregations'])
+  );
+
+  resolver.resolve = async rp => {
+    const { args = {}, projection = {} } = rp;
+
+    const page = args.page || 1;
+    if (page <= 0) {
+      throw new Error('Argument `page` should be positive number.');
+    }
+    const perPage = args.perPage || 20;
+    if (perPage <= 0) {
+      throw new Error('Argument `perPage` should be positive number.');
+    }
+    delete args.page;
+    delete args.perPage;
+    args.limit = perPage;
+    args.skip = (page - 1) * perPage;
+
+    if (projection.items) {
+      projection.hits = projection.items;
+      delete projection.items;
+    }
+
+    const res = await searchResolver.resolve(rp);
+
+    const items = res.hits || [];
+    const itemCount = res.count || 0;
+
+    const result = {
+      ...res,
+      pageInfo: {
+        hasNextPage: itemCount > page * perPage,
+        hasPreviousPage: page > 1,
+        currentPage: page,
+        perPage,
+        pageCount: Math.ceil(itemCount / perPage),
+        itemCount,
+      },
+      items,
+    };
+
+    return result;
+  };
+
+  return resolver;
+}
+
+function getPageInfoTC(opts: mixed = {}): TypeComposer {
+  const name = getTypeName('PaginationInfo', opts);
+
+  return getOrSetType(name, () =>
+    TypeComposer.create(
+      `
+      # Information about pagination.
+      type ${name} {
+        # Current page number
+        currentPage: Int!
+
+        # Number of items per page
+        perPage: Int!
+
+        # Total number of pages
+        pageCount: Int
+
+        # Total number of items
+        itemCount: Int
+
+        # When paginating forwards, are there more items?
+        hasNextPage: Boolean
+
+        # When paginating backwards, are there more items?
+        hasPreviousPage: Boolean
+      }
+    `
+    )
+  );
+}