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set.ts
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set.ts
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import { Client } from "../client";
import { Query, fql } from "../query-builder";
import { QueryOptions, QueryValue } from "../wire-protocol";
/**
* A materialized view of a Set.
* @see {@link https://docs.fauna.com/fauna/current/reference/fql_reference/types#set}
*/
export class Page<T extends QueryValue> {
/** A materialized page of data */
readonly data: T[];
/**
* A pagination cursor, used to obtain additional information in the Set.
* If `after` is not provided, then `data` must be present and represents the
* last Page in the Set.
*/
readonly after?: string;
constructor({ data, after }: { data: T[]; after?: string }) {
this.data = data;
this.after = after;
}
}
/**
* A un-materialized Set. Typically received when a materialized Set contains
* another set, the EmbeddedSet does not contain any data to avoid potential
* issues such as self-reference and infinite recursion
* @see {@link https://docs.fauna.com/fauna/current/reference/fql_reference/types#set}
*/
export class EmbeddedSet {
/**
* A pagination cursor, used to obtain additional information in the Set.
*/
readonly after: string;
constructor(after: string) {
this.after = after;
}
}
/**
* A class to provide an iterable API for fetching multiple pages of data, given
* a Fauna Set
*/
export class SetIterator<T extends QueryValue>
implements AsyncGenerator<T[], void, unknown>
{
readonly #generator: AsyncGenerator<T[], void, unknown>;
/**
* Constructs a new {@link SetIterator}.
*
* @remarks Though you can use {@link SetIterator} class directly, it is
* most common to create an instance through the {@link Client.paginate} `paginate`
* method.
*
* @typeParam T - The expected type of the items returned from Fauna on each
* iteration
* @param client - The {@link Client} that will be used to fetch new data on
* each iteration
* @param initial - An existing fauna Set ({@link Page} or
* {@link EmbeddedSet}) or function which returns a promise. If the Promise
* resolves to a {@link Page} or {@link EmbeddedSet} then the iterator will
* use the client to fetch additional pages of data.
* @param options - a {@link QueryOptions} to apply to the queries. Optional.
*/
constructor(
client: Client,
initial: Page<T> | EmbeddedSet | (() => Promise<T | Page<T> | EmbeddedSet>),
options?: QueryOptions
) {
options = options ?? {};
if (initial instanceof Function) {
this.#generator = generateFromThunk(client, initial, options);
} else if (initial instanceof Page || initial instanceof EmbeddedSet) {
this.#generator = generatePages(client, initial, options);
} else {
throw new TypeError(
`Expected 'Page<T> | EmbeddedSet | (() => Promise<T | Page<T> | EmbeddedSet>)', but received ${JSON.stringify(
initial
)}`
);
}
}
/**
* Constructs a new {@link SetIterator} from an {@link Query}
*
* @internal Though you can use {@link SetIterator.fromQuery} directly, it is
* intended as a convenience for use in the {@link Client.paginate} method
*/
static fromQuery<T extends QueryValue>(
client: Client,
query: Query,
options?: QueryOptions
): SetIterator<T> {
return new SetIterator<T>(
client,
async () => {
const response = await client.query<T | Page<T> | EmbeddedSet>(
query,
options
);
return response.data;
},
options
);
}
/**
* Constructs a new {@link SetIterator} from an {@link Page} or
* {@link EmbeddedSet}
*
* @internal Though you can use {@link SetIterator.fromPageable} directly, it
* is intended as a convenience for use in the {@link Client.paginate} method
*/
static fromPageable<T extends QueryValue>(
client: Client,
pageable: Page<T> | EmbeddedSet,
options?: QueryOptions
): SetIterator<T> {
return new SetIterator<T>(client, pageable, options);
}
/**
* Constructs a new {@link FlattenedSetIterator} from the current instance
*
* @returns A new {@link FlattenedSetIterator} from the current instance
*/
flatten(): FlattenedSetIterator<T> {
return new FlattenedSetIterator(this);
}
/** Implement {@link AsyncGenerator.next} */
async next(): Promise<IteratorResult<T[], void>> {
return this.#generator.next();
}
/** Implement {@link AsyncGenerator.return} */
async return(): Promise<IteratorResult<T[], void>> {
return this.#generator.return();
}
/** Implement {@link AsyncGenerator.throw} */
async throw(e: any): Promise<IteratorResult<T[], void>> {
return this.#generator.throw(e);
}
/** Implement {@link AsyncGenerator} */
[Symbol.asyncIterator]() {
return this;
}
}
/**
* A class to provide an iterable API for fetching multiple pages of data, given
* a Fauna Set. This class takes a {@link SetIterator} and flattens the results
* to yield the items directly.
*/
export class FlattenedSetIterator<T extends QueryValue>
implements AsyncGenerator<T, void, unknown>
{
readonly #generator: AsyncGenerator<T, void, unknown>;
/**
* Constructs a new {@link FlattenedSetIterator}.
*
* @remarks Though you can use {@link FlattenedSetIterator} class directly, it
* is most common to create an instance through the
* {@link SetIterator.flatten} method.
*
* @typeParam T - The expected type of the items returned from Fauna on each
* iteration
* @param setIterator - The {@link SetIterator}
*/
constructor(setIterator: SetIterator<T>) {
this.#generator = generateItems(setIterator);
}
/** Implement {@link AsyncGenerator.next} */
async next(): Promise<IteratorResult<T, void>> {
return this.#generator.next();
}
/** Implement {@link AsyncGenerator.return} */
async return(): Promise<IteratorResult<T, void>> {
return this.#generator.return();
}
/** Implement {@link AsyncGenerator.throw} */
async throw(e: any): Promise<IteratorResult<T, void>> {
return this.#generator.throw(e);
}
/** Implement {@link AsyncGenerator} */
[Symbol.asyncIterator]() {
return this;
}
}
/**
* Internal async generator function to use with {@link Page} and
* {@link EmbeddedSet} values
*/
async function* generatePages<T extends QueryValue>(
client: Client,
initial: Page<T> | EmbeddedSet,
options: QueryOptions
): AsyncGenerator<T[], void, unknown> {
let currentPage = initial;
if (currentPage instanceof Page) {
yield currentPage.data;
}
while (currentPage.after) {
// cursor means there is more data to fetch
const query = fql`Set.paginate(${currentPage.after})`;
const response = await client.query<Page<T>>(query, options);
const nextPage = response.data;
currentPage = nextPage;
yield currentPage.data;
}
}
/**
* Internal async generator function to use with a function that returns a
* promise of data. If the promise resolves to a {@link Page} or
* {@link EmbeddedSet} then continue iterating.
*/
async function* generateFromThunk<T extends QueryValue>(
client: Client,
thunk: () => Promise<T | Page<T> | EmbeddedSet>,
options: QueryOptions
): AsyncGenerator<T[], void, unknown> {
const result = await thunk();
if (result instanceof Page || result instanceof EmbeddedSet) {
for await (const page of generatePages(
client,
result as Page<T> | EmbeddedSet,
options
)) {
yield page;
}
return;
}
yield [result];
}
/**
* Internal async generator function that flattens a {@link SetIterator}
*/
async function* generateItems<T extends QueryValue>(
setIterator: SetIterator<T>
) {
for await (const page of setIterator) {
for (const item of page) {
yield item;
}
}
}