GraphQL relay connectionFromArraySlice - graphql

Question

There isn't any documentation for how the array meta info (arrayLength and sliceStart) should be implemented using facebook's graphql-relay-js helper library.
https://github.com/graphql/graphql-relay-js/issues/199
I managed to get it to work using the following implemention however I am guessing there is an easier/more correct way to do this.
Retrieve rows and row count from database
function transformRole(role: Role) {
return { ...role, roleId: role.id };
}
async function getRolesSlice({ roleId, after, first, last, before }: any): Promise<[Role[], number]> {
const queryBuilder = repository.createQueryBuilder();
if (roleId !== undefined) {
queryBuilder.where('id = :roleId', { roleId });
}
if (before) {
const beforeId = cursorToOffset(before);
queryBuilder.where('id < :id', { id: beforeId });
}
if (after) {
const afterId = cursorToOffset(after);
queryBuilder.where({
id: MoreThan(Number(afterId))
});
}
if (first === undefined && last === undefined) {
queryBuilder.orderBy('id', 'ASC');
}
if (first) {
queryBuilder.orderBy('id', 'ASC').limit(first);
}
if (last) {
queryBuilder.orderBy('id', 'DESC').limit(last);
}
return Promise.all([
queryBuilder.getMany()
.then(roles => roles.map(transformRole)),
repository.count() // Total number of roles
]);
}
Roles resolver
resolve: (_, args) =>
getRolesSlice(args)
.then(([results, count]) => {
const firstId = results[0] && results[0].roleId;
let sliceStart = 0;
if (args.first) {
sliceStart = firstId;
}
if (args.last) {
sliceStart = Math.max(firstId - args.last, 0);
}
if (args.after && args.last) {
sliceStart += 1;
}
return connectionFromArraySlice(
results,
args,
{
arrayLength: count + 1,
sliceStart
}
);
})
},
Edit:
This is what I came up with which is a little cleaner and seems to be working correctly.
const initialize = () => {
repository = getConnection().getRepository(Role);
}
function transformRole(role: Role) {
return { ...role, roleId: role.id };
}
function getRolesSlice(args: any):
Promise<[
Role[],
any,
{ arrayLength: number; sliceStart: number; }
]> {
if (!repository) initialize();
const { roleId, after, first, last, before } = args;
const queryBuilder = repository.createQueryBuilder();
if (roleId !== undefined) {
queryBuilder.where('id = :roleId', { roleId });
}
if (before !== undefined) {
const beforeId = cursorToOffset(before);
queryBuilder.where({
id: LessThan(beforeId)
});
}
if (after !== undefined) {
const afterId = cursorToOffset(after);
queryBuilder.where({
id: MoreThan(Number(afterId))
});
}
if (first !== undefined) {
queryBuilder.orderBy('id', 'ASC').limit(first);
} else if (last !== undefined) {
queryBuilder.orderBy('id', 'DESC').limit(last);
} else {
queryBuilder.orderBy('id', 'ASC');
}
return Promise.all([
queryBuilder.getMany()
.then(roles => roles.map(transformRole))
.then(roles => last !== undefined ? roles.slice().reverse() : roles),
repository.count()
]).then(([roles, totalCount]) =>
[
roles,
args,
{
arrayLength: totalCount + 1,
sliceStart: roles[0] && roles[0].roleId
}
]
);
}
// Resolver
roles: {
type: rolesConnection,
args: {
...connectionArgs,
roleId: {
type: GraphQLString
}
},
resolve: (_, args) =>
getRolesSlice(args)
.then((slice) => connectionFromArraySlice(...slice))
},