Add Pagination utils with tests

src/utils/graphql/pagination.ts

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+import { Op } from '@unocha/hpc-api-core/src/db/util/conditions';
+import { createBrandedValue } from '@unocha/hpc-api-core/src/util/types';
+import { ObjectType, Field } from 'type-graphql';
+
+export interface ItemPaged {
+  cursor: number;
+}
+
+@ObjectType()
+export class PageInfo<TSortFields extends string> {
+  @Field({ nullable: false })
+  hasNextPage: boolean;
+
+  @Field({ nullable: false })
+  hasPreviousPage: boolean;
+
+  @Field({ nullable: false })
+  startCursor: number;
+
+  @Field({ nullable: false })
+  endCursor: number;
+
+  @Field({ nullable: false })
+  pageSize: number;
+
+  @Field(() => String, { nullable: false })
+  sortField: TSortFields;
+
+  @Field({ nullable: false })
+  sortOrder: string;
+
+  @Field({ nullable: false })
+  total: number;
+}
+
+export function prepareConditionFromCursor(
+  sortCondition: { column: string; order: 'asc' | 'desc' },
+  afterCursor?: number,
+  beforeCursor?: number
+): any {
+  if (afterCursor && beforeCursor) {
+    throw new Error('Cannot use before and after cursor at the same time');
+  }
+
+  if (afterCursor || beforeCursor) {
+    const isAscending = sortCondition.order === 'asc';
+    const cursorValue = afterCursor || beforeCursor;
+
+    let op;
+    if (isAscending) {
+      op = afterCursor ? Op.GT : Op.LT;
+    } else {
+      op = beforeCursor ? Op.GT : Op.LT;
+    }
+
+    return {
+      id: {
+        [op]: createBrandedValue(cursorValue),
+      },
+    };
+  }
+
+  return {};
+}

tests/unit/pagination.spec.ts

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+import { Op } from '@unocha/hpc-api-core/src/db/util/conditions';
+import { prepareConditionFromCursor } from '../../src/utils/graphql/pagination';
+
+describe('Based on cursor and order for pagination', () => {
+  describe('Order is asc', () => {
+    const sortCondition = { column: 'id', order: 'asc' as const };
+
+    it("Should return 'GT' when afterCursor is defined", () => {
+      const afterCursor = 1;
+      const beforeCursor = undefined;
+      const result = prepareConditionFromCursor(
+        sortCondition,
+        afterCursor,
+        beforeCursor
+      );
+      expect(result.id).toEqual({ [Op.GT]: afterCursor });
+    });
+
+    it("Should return 'LT' when beforeCursor is defined", () => {
+      const afterCursor = undefined;
+      const beforeCursor = 1;
+      const result = prepareConditionFromCursor(
+        sortCondition,
+        afterCursor,
+        beforeCursor
+      );
+      expect(result.id).toEqual({ [Op.LT]: beforeCursor });
+    });
+
+    it('Should throw an error when both afterCursor and beforeCursor are defined', () => {
+      const afterCursor = 1;
+      const beforeCursor = 2;
+      expect(() =>
+        prepareConditionFromCursor(sortCondition, afterCursor, beforeCursor)
+      ).toThrowError('Cannot use before and after cursor at the same time');
+    });
+  });
+
+  describe("Order is 'desc'", () => {
+    const sortCondition = { column: 'id', order: 'desc' as const };
+
+    it("Should return 'LT' when afterCursor is defined", () => {
+      const afterCursor = 1;
+      const beforeCursor = undefined;
+      const result = prepareConditionFromCursor(
+        sortCondition,
+        afterCursor,
+        beforeCursor
+      );
+      expect(result.id).toEqual({ [Op.LT]: afterCursor });
+    });
+
+    it("Should return 'GT' when beforeCursor is defined", () => {
+      const afterCursor = undefined;
+      const beforeCursor = 1;
+      const result = prepareConditionFromCursor(
+        sortCondition,
+        afterCursor,
+        beforeCursor
+      );
+      expect(result.id).toEqual({ [Op.GT]: beforeCursor });
+    });
+
+    it('Should throw an error when both afterCursor and beforeCursor are defined', () => {
+      const afterCursor = 1;
+      const beforeCursor = 2;
+      expect(() =>
+        prepareConditionFromCursor(sortCondition, afterCursor, beforeCursor)
+      ).toThrowError('Cannot use before and after cursor at the same time');
+    });
+  });
+});