item list, paginated

src/items/items.model.ts

@@ -1,4 +1,5 @@
 import { Field, ID, ObjectType } from '@nestjs/graphql';
+import { Paginated } from '../paginated.output';
 
 @ObjectType('Item', {
   description: 'Either the inventored thing or a box containing them',
@@ -28,3 +29,6 @@ export class ItemModel {
   @Field((type) => [ItemModel])
   descendants: ItemModel[];
 }
+
+@ObjectType()
+export class PaginatedItems extends Paginated(ItemModel) {}

src/items/items.resolver.ts

@@ -9,7 +9,7 @@ import {
 } from '@nestjs/graphql';
 import { NewItemInput } from './dto/new-item.input';
 import { EANService } from './ean/ean.service';
-import { ItemModel } from './items.model';
+import { ItemModel, PaginatedItems } from './items.model';
 import { ItemsService } from './items.service';
 
 @Resolver((of) => ItemModel)
@@ -21,6 +21,13 @@ export class ItemsResolver {
     return this.itemsService.getItem(id);
   }
 
+  @Query((returns) => PaginatedItems)
+  async itemList(
+    @Args('cursor', { type: () => ID, nullable: true }) cursor?: string,
+  ) {
+    return this.itemsService.getItemList(cursor ? parseInt(cursor, 10) : 0);
+  }
+
   @ResolveField()
   ean13(@Parent() item: ItemModel) {
     return this.eans.fromID(item.id);

src/items/items.service.ts

@@ -4,7 +4,7 @@ import { EntityManager, Repository, TreeRepository } from 'typeorm';
 import { NewItemInput } from './dto/new-item.input';
 import { EANService } from './ean/ean.service';
 import { Item } from './items.entity';
-import { ItemModel } from './items.model';
+import { ItemModel, PaginatedItems } from './items.model';
 
 @Injectable()
 export class ItemsService {
@@ -63,6 +63,19 @@ export class ItemsService {
     return (await this.treeRepository.findDescendants(parentItem)).slice(1);
   }
 
+  async getItemList(cursor: number = 0): Promise<PaginatedItems> {
+    const [items, count] = await this.itemRepository.findAndCount({
+      take: 25,
+      skip: cursor,
+    });
+    return {
+      nodes: items,
+      cursor: cursor + items.length,
+      totalCount: count,
+      hasNextPage: count > cursor + items.length,
+    };
+  }
+
   async createItem(input: NewItemInput): Promise<Item> {
     // must use Repository.save() for the closure table to work,
     // so we have to check whether the provided ID exists in the first place

src/paginated.output.ts

@@ -0,0 +1,20 @@
+import { Field, ObjectType, Int, ID } from '@nestjs/graphql';
+import { Type } from '@nestjs/common';
+
+export function Paginated<T>(classRef: Type<T>): any {
+  @ObjectType({ isAbstract: true })
+  abstract class PaginatedType {
+    @Field((type) => [classRef])
+    nodes: T[];
+
+    @Field((type) => ID, { nullable: true })
+    cursor?: number;
+
+    @Field((type) => Int)
+    totalCount: number;
+
+    @Field()
+    hasNextPage: boolean;
+  }
+  return PaginatedType;
+}